CD7 – All about the solar wind
(click “Online content” to show online material)
Talks
CD7.1 Tue 5/11 14:15-15:15, room C2D – Almedina
Author(s): Steph Yardley
Northumbria University
Abstract: One of the main goals of the joint ESA/NASA Solar Orbiter and NASA’s Parker Solar Probe missions is to determine the sources and drivers of the solar wind. Solar Orbiter’s unique orbit and extensive suite of instruments are now being utilised to answer open questions regarding the origin and formation of the solar wind, and how it is released and accelerated into the heliosphere. In order to link solar wind measurements in the inner heliosphere together with high-resolution remote sensing observations of their sources in the solar corona, observations need to be coordinated in advance through Solar Orbiter Observing Plans (SOOPs). The results presented here are from the Slow Solar Wind Connection Science SOOP designed to capture in situ measurements of slow solar wind plasma originating from open-closed magnetic field boundaries. We show through the combination of high-resolution observations and measurements taken at 0.5au, coupled with magnetic field modelling and spectroscopic techniques that the solar wind variability is driven by spatio-temporal changes in the magnetic connectivity across a coronal hole-active region complex. Where the magnetic topology is also changing due to interchange reconnection between the closed core and open field of the active regions. The Slow Wind SOOP, despite presenting many challenges, was very successful and provides a blueprint for planning other campaigns, such as the Fast Wind SOOP, that also rely on the magnetic connectivity of Solar Orbiter.
Author(s): Jean-Baptiste Dakeyo, Alexis Rouillard, Victor Réville, Pascal Démoulin, Milan Maksomovic, Alice Chapiron, Rui Pinto, Philippe Louarn
IRAP – CNRS; IRAP – CNRS; IRAP – CNRS; LESIA; LESIA; IRAP; IRAP; IRAP
Abstract: The properties of the solar wind measured in situ in the heliosphere are largely controlled by energy deposition in the solar corona which in turn is closely related to the properties of the coronal magnetic field. Previous studies have shown that long duration and large scale magnetic structures show an inverse relation between the solar wind velocity measured in situ near 1 au and the expansion factor of the magnetic flux tubes in the solar atmosphere. The advent of the SolO mission offers a new opportunity to analyse the relation between solar wind properties measured in situ in the inner heliosphere and the coronal magnetic field. We exploit this new data in conjunction with models of the coronal magnetic field and the solar wind to evaluate the flux expansion factor – speed relation. We use a Parker-like solar wind model, the “isopoly” model presented in previous works, to describe the motion of the solar wind plasma in the radial
direction, and model the tangential plasma motion due to solar rotation with the Weber & Davis equations. Both radial and tangential velocities are used to compute the plasma trajectory and streamline from SolO location sunward to the solar ’source surface’ at rss. We then employ a Potential Field Source Surface (PFSS) model to reconstruct the coronal magnetic field below rss to connect wind parcels mapped back to the photosphere. We find a statistically weak anti-correlation between in situ bulk velocity and coronal expansion factor for about 20 months
of in situ and solar data. Classification of the data by source latitude reveals different levels of anticorrelation, which is typically higher when SolO magnetically connects to high latitude structures than when it connects to low latitude structures. We show the
existence of fast solar wind that originates in strong magnetic field regions at low latitudes and undergoes large expansion factor. We provide evidence that such winds become supersonic during the super radial expansion (below rss), and are theoretically governed by
a positive correlation v-f. We find that faster winds on average have a flux tube expansion at a larger radius than slower winds. An anticorrelation between solar wind speed and expansion factor is present for solar winds originating in high latitude
structures in solar minimum activity, typically associated with coronal hole-like structures, but this cannot be generalized to lower latitude sources. We have found extended time intervals of fast solar wind associated with both large expansion factors and strong
photospheric magnetic fields. Therefore, the value of the expansion factor alone cannot be used to predict the solar wind speed. Other
parameters, such as the height at which the expansion gradient is the strongest must also be taken into account.
Author(s): Denise Perrone, Silvia Perri, Adriana Settino, Rossana De Marco, Raffaella D’Amicis, Roberto Bruno
ASI – Italian Space Agency, Rome, Italy; Dipartimento di Fisica, Università della Calabria, Rende, Italy; Space Research Institute, Austrian Academy of Sciences, Graz, Austria; INAF- IAPS, Rome, Italy; INAF- IAPS, Rome, Italy; INAF- IAPS, Rome, Italy
Abstract: We statistically study magnetic switchbacks, large deflections of the magnetic field which occur simultaneously with a sudden increase in the radial solar wind velocity, in the first stream of slow Alfvénic wind observed by Solar Orbiter at a heliocentric distance of 0.64 au. We investigate how ions, both protons and alpha particles, kinetically react to the presence of these strong deflections in the magnetic field. Beyond the expected correlation between magnetic deflections and the increase in the ion velocity, related to the Alfvénic nature of the switchbacks, we find a certain correlation between switchbacks and both proton and alpha particle densities, which suggests wave activity. Related to the kinetic physics of protons and alpha particles, very interestingly we observe a clear correlation between switchbacks and alpha particle temperature, but not with proton temperature, suggesting a role of magnetic field deflections in preferentially heating heavy ions. We use ion data from an innovative method based on the statistical technique of clustering applied directly to the full three-dimensional VDFs measured by the Proton and Alpha Sensor to separate the core and beam for both protons and alphas.
CD7.2 Tue 5/11 17:30-18:30, room C2D – Almedina
Author(s): Jon Linker
Predictive Science Inc.
Abstract: The ambient solar corona and solar wind plays an essential role in space weather at Earth and throughout the solar system. Coronal mass ejections (CMEs) propagate and interact with the ambient solar wind; their geoeffectiveness is affected by this interaction. The connection of the ambient interplanetary magnetic field to CME-related shocks and impulsive solar flares determines where solar energetic particles propagate. The partitioning of the ambient solar wind into fast and slow streams drives recurrent geomagnetic activity. The magnetic field is a key aspect of describing the solar wind ambient state, and solar wind properties are closely tied to magnetic structure. The field is most readily measured in the photosphere, so models must extrapolate this field out into the solar wind. In this presentation, I will describe different approaches to modeling the solar wind’s ambient state, their strengths and weaknesses, and how they can help us to explore open questions about the origins of the solar wind as well as be improved for space weather forecasts and applications.
Research supported by NASA and NSF.
Author(s): Tinatin Baratashvili, Stefaan Poedts
Centre for Mathematical Plasma Astrophysics, Dept. of Mathematics, KU Leuven, 3001 Leuven, Belgium; Centre for Mathematical Plasma Astrophysics, Dept. of Mathematics, KU Leuven, 3001 Leuven, Belgium, Institute of Physics, University of Maria Curie-Skłodowska, Pl. M. Curie-Skłodowska 5, 20-031 Lublin, Poland
Abstract: Space weather, a field that studies the conditions in the solar atmosphere and their effects on the heliosphere, is of paramount importance, particularly in understanding the space environment of the Earth. The main drivers of interplanetary shocks and space weather disturbances are Coronal Mass Ejections (CMEs). The internal magnetic configuration of the CME is a key parameter that determines the geo-effectiveness of the CME impact. The potential impact of strong CMEs directed towards Earth is severe, and their prediction is crucial in mitigating possible damages. This underscores the necessity of efficient space weather prediction tools, which can produce timely forecasts for the CME arrival at Earth and their strength (shock, momentum density, magnetic field, etc.) upon arrival.
The novel heliospheric model Icarus (Verbeke et al. 2022, Baratashvili et al. 2023), a product of the MPI-AMRVAC framework (Xia et al. 2018), revolutionizes our ability to model the heliospheric solar wind and real CME events. By solving the MHD equations in the co-rotating reference frame with the Sun, we achieve a stationary solution after obtaining the relaxed solar wind in the domain for a particular magnetogram. This paves the way for injecting different CME models on top of this stationary background solar wind. To enhance the simulations, we’ve implemented advanced techniques, such as adaptive mesh refinement and gradual radial grid stretching.
In this work, we present the effect of upgrading inner boundary conditions dynamically, where magnetograms are upgraded hourly. This way, the solar wind is no longer stationary in the domain as new information propagates from the inner boundary. Additionally, CMEs are injected on top of the varying solar wind. We compare the results with the simulations with fixed boundary simulations to quantify the effect of the updated magnetograms for heliospheric modelling. The results are also compared to the observational data.
Furthermore, we also introduce coupling to the MHD coronal model COCONUT, where the output of the coronal model is dynamically coupled to Icarus.
The upgraded time-dependent boundary treatment of the heliospheric model, with updated magnetograms, ensures accurate space weather modelling. The solar wind is a more accurate representation of the actual wind than the stationary wind model, which has an important effect on the propagation and impact of the CMEs.
TB acknowledges support from the projects C14/19/089 (C1 project Internal Funds KU Leuven), G0B5823N and G002523N (WEAVE) (FWO-Vlaanderen), 4000134474 (SIDC Data Exploitation, ESA Prodex-12), and Belspo project B2/191/P1/SWiM.
Author(s): Mathew Owens
University of Reading
Abstract: The solar wind is a highly driven system, meaning the accuracy of solar-wind models and forecasts is primarily determined by the inner-boundary conditions. These are are typically provided by a coronal model, itself constrained by the observed magnetic at the photosphere. While coronal models generally provide steady-state (SS) “snapshots” of the near-Sun solar-wind conditions, those snapshots are regularly updated as new photospheric observations become available, producing indirect information about time evolution. However, at present, independent SS solar-wind solutions are generated for each coronal-model snapshot, discarding all time-history information. In this study, we use one year of daily-updated coronal-model solutions to compare SS and fully time-dependent (TD) approaches to solar-wind modelling. We demonstrate how the SS approach misrepresents the accuracy of coronal models. We attribute three key problems with current space-weather forecasting directly to the SS approach. These are: (1) the somewhat paradoxical situation that forecasts based on observations from 3-days previous are more accurate than forecasts based on the most recent observations; (2) high inconsistency, with forecasts for a given day jumping significantly as new observations become available, which is a barrier to acting on a forecast; and (3) insufficient variability in the heliospheric magnetic field connection to Earth, which control solar energetic particle (SEP) propagation. We show the TD approach, applied to the exact same inner-boundary conditions, alleviates all three issues.
CD7.3 Thu 7/11 17:30-18:30, room Auditorium
Author(s): Nicholeen M. Viall, Natalia Zambrana Prado, Irena Gershkovich, Peter Young, Terry A. Kucera, Sue Lepri, Charles N. Arge
NASA/GSFC; MSSL; University of Michigan; NASA/GSFC; NASA/GSFC; University of Michigan; NASA/GSFC
Abstract: The solar wind originates from 3 types of coronal magnetic fields – the continuously open fields that form coronal holes (CHs), or from either active region (AR) or quiet Sun (QS) at the magnetic open-closed boundary. Relating in situ solar wind observations to their source at the Sun is a critical step to understanding how the solar wind is formed, because the source determines the plasma temperature, its elemental composition, and the possible mechanisms involved in its release and acceleration. We present recent work from two studies in which we use the Wang-Sheeley-Arge (WSA) model driven by Air Force Data Assimilative Photospheric Flux Transport (ADAPT) time-dependent photospheric field maps to connect the in situ observed solar wind at L1 and Solar Orbiter, with its source region observed remotely. In the first study, we classify the L1-observed solar wind based on source (AR, QS, or CH) using model parameters derived for the magnetic field lines connected to each source (e.g. source region distance from magnetic open-closed boundary), and the corresponding photospheric field measurements at the source. We characterize the in situ properties of the solar wind observed at ACE (e.g. speed, proton density, nA/nP, Fe/O, carbon and oxygen charge state ratios) that originate from each source, in order to investigate whether the source region as defined here ultimately determines the plasma properties observed in situ. We use this methodology to investigate 5 Carrington rotations, three near solar maximum and two near solar minimum. In the second study, we use the ADAPT-WSA model to connect mesoscale solar wind structures observed in SolO/HIS and ACE solar wind composition measurements, during a period where the two spacecraft are radially aligned, to that observed remotely in the corona by SolO/SPICE, to investigate how these structures were formed at the Sun. We discuss our findings from both investigations in the context of how the source region determines or influences the solar wind properties observed in situ.
Author(s): Tatiana Podladchikova, Astrid M. Veronig, Manuela Temmer, Stefan J. Hofmeister
Skolkovo Institute of Science and Technology; University of Graz, Institute of Physics, University of Graz, Kanzelhöhe Observatory for Solar and Environmental Research; University of Graz, Institute of Physics, University of Graz; Columbia University
Abstract: Accurate solar wind modeling is important for predicting the arrival and geomagnetic response of high-speed solar wind streams as well as for modeling the transit of coronal mass ejections
in interplanetary space and their impact at Earth. In this study, we show how data from an additional “L5” viewpoint (future Vigil mission) improves the predicted solar wind velocity at “L1”.
For simulating an L5–L1 set-up we use available archive data from STEREO-B, STEREO-A, and Earth. For the L5–L1 solar wind forecast, we developed a prediction algorithm including three steps.
First, we perform initial predictions using separation angle between “L5” and “L1” and accounting for the distance from “L5” and “L1” to the Sun. Second, we show for the first time, that the latitude of a coronal hole (CH, primarily with a small fractional area) associated with high-speed solar wind stream (HSS) is responsible for differences in SW velocity at “L5” and “L1”. Finally, we introduce a predictive indicator to estimate the level of overestimation/underestimation and produce corrected SW predictions. Our findings demonstrate that “L5” suggests a great potential for solar wind predictions at “L1” with relatively high accuracy and large lead times, enhancing space weather forecasting and applications.
Author(s): Alexandros Koukras, Daniel W. Savin, Michael Hahn
Columbia University; Columbia University; Columbia University
Abstract: The fast solar wind originates from regions of open magnetic field on the Sun, which are called coronal holes; but the source regions of the slow solar wind are still not well understood. The in-situ measured elemental abundances of the slow solar wind suggest that it originates from initially closed field lines. Consequently, several theories propose that the boundaries of coronal holes are the source region of the slow solar wind through magnetic reconnection of quiet Sun loops with the open field lines of coronal holes. This process could also explain the apparent rigid rotation of coronal holes.
Our aim is to quantify the relative abundances of different elements at the boundaries of coronal holes. Reconnection is expected to modulate these abundances through the First Ionization Potential (FIP) effect. We have measured the FIP effect across coronal hole boundaries (CHBs), both on the leading and trailing edges and quantified any difference. For our analysis we used spectroscopic data from EIS on Hinode and from SPICE on Solar Orbiter. To account for the temperature structure of the observed region we computed the differential emission measure (DEM), based on the observed line intensities of low-FIP elements, such as iron and silicon. Then, the DEM was used to predict the intensity of high-FIP elements, such as sulfur. Comparing the modeled to observed intensities enabled us to infer the FIP bias between the coronal and photospheric abundances. By examining the variation of the FIP bias moving from the quiet Sun to the coronal hole, we have been able to constrain models of interchange reconnection. The FIP bias variation at CHBs has an approximate width of 30-50 Mm, comparable to the size of supergranules.
Due to interchange reconnection some amount of open flux is rooted in the boundary region of coronal holes. Using the properties of the FIP bias variation in that region we can derive an estimate for that amout of open flux and its relationship with the amount measured in situ in the interplanetary space.
Lastly, we examined the connenctivity of the in-situ measured solar wind and identified the portion of the solar wind that originated from the coronal hole boundaries. This enabled us to correlate remote sensing and in-situ measurements of elemental abundances for the same region.
Author(s): Evangelia Samara, Charles N. Arge, Elena Provornikova, Samantha Wallace, Viacheslav G. Merkin
NASA/GSFC; NASA/GSFC; APL, Johns Hopkins University; Embry-Riddle Aeronautical University; APL, Johns Hopkins University
Abstract: Realistic modeling of the solar wind in the heliosphere is a complex task subject to many limitations related to the currently available solar observations and the capabilities of models per se. A major limitation, for example, is the lack of observations at the limbs, poles and back side of the Sun that does not allow the creation of trustworthy magnetograms which are the necessary drivers for coronal and heliospheric models. Other limitations arise from the models’ restricted capabilities to describe known physics because of numerical and computational complexity. Moreover, several ad hoc assumptions are frequently adopted by various models to reconstruct the solar corona magnetic field and forecast the solar wind in the heliosphere. The extent at which these assumptions affect the final predictions is still not very well understood. In this work, we address the aforementioned limitations with state-of-the-art time dependent solar wind simulations which represent a critical step towards more realistic solar wind modeling. However, we ask the question, how far can we go with them and what else is needed to go forward? Our goal is not to (only) show nice solar wind predictions compared to observations at different spacecraft locations (PSP, Solar Orbiter, STEREO A, Earth), but to discuss why major discrepancies with observations occur and how/if we can overcome them. By using two models, the semi-empirical ADAPT-WSA coronal model and the MHD GAMERA inner heliosphere model, we explain solar wind predictions from their magnetic connectivity to the solar origins, and discuss how the emergence of active regions on the invisible side of the Sun can affect this connectivity and the overall forecast. If time allows, we will further show how we can constrain the boundary conditions of our models based on PSP and Solar Orbiter observations and discuss how far we can get in improving solar wind forecasting based on them.
Posters
Posters I Display Tue 5/11 – Wed 6/11, room C1A – Aeminium
Authors in attendance: Tue 5/11 10:15–11:30, 15:15-16:15; Wed 6/11 10:15–11:30
Author(s): Silke Kennis, Marian Lazar, S. M. Shaaban, Viviane Pierrard, Stefaan Poedts
KULeuven; KuLeuven; Qatar University; BIRA; KuLeuven
Abstract: The properties of electrons in heliospheric plasma are subjected to a multitude of factors, beginning with the expansion of the bi-modal slow/fast solar wind, and continuing with the physical mechanisms of acceleration and energy exchange with plasma waves and turbulence. The recent excursions of the Parker Solar Probe and Solar Orbiter missions motivate further research for a comprehensive connection of the new data from the young solar wind with previous in-situ data from heliocentric distances extending up to 1 AU and beyond. We still need to explain the dual nature of the solar wind electrons, as shown by the velocity (or energy) distributions that indicate two major components, namely, the core and suprathermal populations.
Here we reveal for the first time a series of categories of correlations between the core and halo populations of electrons in the solar wind, by exploiting electron data measured at different distances in the ecliptic by three different missions Helios I, Cluster II and Ulysses (Stverak et al. 2008, Pierrard et al. 2016). Of particular interest are their kinetic properties, such as temperature anisotropy and the beta parameter, crucial for the description of kinetic energy transfer processes, governed by wave fluctuations and kinetic instabilities. Surprising is the linear correlation shown by the temperature anisotropies of the core and halo populations. Observations in the slow solar wind (with a minimal effect of the Strahl component) showing that over 90% (more precisely 97.75%) of the total events (over 100000) are moderately correlated, 78.22% are highly correlated, and 43.75% are very high correlated.
The beta parameters corresponding to the two populations also show a clear trend of correlation, for which we also estimate a simplified linear regression model. These correlations allow us to realistically evaluate the properties of the instabilities generated by the temperature anisotropy, in particular their thresholds given by the anisotropy as a function of the beta parameter. The comparison with the anisotropy limits for the same set of events thus becomes consistent, for each component in part, and can thus clarify if the self-generated instabilities constrain the temperature anisotropy in the collisionless space plasma.
Author(s): Charles Arge
NASA Goddard Space Flight Center
Abstract: The solar magnetic fields emerging from the photosphere into the chromosphere and corona are comprised of a combination of “closed” (field lines with both ends rooted at the Sun) and “open” (field lines with only one end at the Sun) fields. This open flux is especially important for understanding and predicting space weather, because all solar disturbances must propagate along this flux to reach the Earth. Since the early 2000’s, the magnitude of total unsigned open magnetic flux estimated by coronal models has been in significant disagreement with in situ spacecraft observations, especially during solar maximum. Recent results using the WSA model suggest that the missing flux emerges from the dynamical region at the open-closed boundary of coronal holes. In particular, strong magnetic fields in close proximity of active regions and residing near the boundaries of mid-latitude coronal holes are the primary source of the missing open flux. When the magnetic fields within these dynamical boundaries are accounted for, excellent overall agreement between the WSA model and in situ observations are obtained spanning several decades. In this talk, we briefly review the long-standing problem of the missing open magnetic flux and present results which seem to reconcile the discrepancies between observed and modeled total open unsigned magnetic flux. Furthermore, assuming proper recalibration of the ADAPT HMI maps occurs in time, we extend our open flux estimates to the present to determine if they continue to agree with in situ observations. We discuss the implications of our results for modeling space weather.
Author(s): Harriet Turner, Mathew Owens, Matthew Lang, Luke Barnard
University of Reading; University of Reading; British Antarctic Survey; University of Reading
Abstract: Accurate space weather forecasting requires knowledge of the solar wind conditions. Current forecasting methods are initialised with photospheric magnetic field observations but typically contain no information from observations of the solar wind. Data assimilation (DA) methods aim to combine a model of a system with observations to find an optimum estimation of reality. DA has led to large forecast improvements in terrestrial weather forecasting but has been underused is space weather forecasting, especially in the solar wind. In this talk I will outline the methods behind using DA in the solar wind and the most recent findings within the field.
Author(s): Suresh Karuppiah, Mateja Dumbovic, Karmen Martinic, Manuela Temmer, Stephan G. Heinemann, Bojan Vrsnak
Hvar Obs, Faculty of Geodesy, University of Zagreb; Hvar Obs., Faculty of Geodesy, University of Zagreb; Hvar Obs., Faculty of Geodesy, University of Zagreb; University of Graz; Department of Physics, University of Helsinki; Hvar Obs., Faculty of Geodesy, University of Zagreb
Abstract: We investigate the deflection and rotational behaviour of 49 Earth-directed coronal mass ejections (CMEs) spanning the period from 2010 to 2020. We aim to understand the possible influence of coronal holes (CHs) on their trajectories. Our analysis incorporates data from coronagraphic observations taken from multiple vantage points. In addition we use extreme ultraviolet observations to identify associated low coronal signatures, such as solar flares, filament eruptions and dimmings. For each CME, we perform a 3D reconstruction using the Graduated Cylindrical Shell (GCS) model. We perform the GCS reconstruction in several time steps, from the time the CME enters the field of view (FOV) of the coronagraphs to the time it exits. We analyse the difference in the longitude, latitude, and inclination between the first and last GCS reconstruction as possible signs of deflection/rotation. In addition, we investigate the presence of nearby CHs at the time of eruption. We use the Collection of Analysis Tools for Coronal Holes (CATCH) to estimate relevant CH parameters: magnetic field strength, centre of mass and area. To assess the potential influence of CHs on the deflection and rotation of CMEs, we calculate the so-called Coronal Hole Influence Parameter (CHIP) for each event and analyse its relation to their trajectories. CHIP is related to the ability of the CH to influence the trajectory of the CME and it is larger for CH with strong magneticfield closer to the CME. A statistically significant difference is observed between the CHIP and the overall change in the direction of a CME in the lower corona, but not higher up. This indicates that CH in the lower corona have a significant influence on the overall change in the direction of Earth-directed CMEs. However, the further outward the CME evolves, the less effective the influence of the CH becomes. We also found a negative correlation between the deflection rate of CMEs and their velocity, suggesting that higher velocities are associated with lower deflection rates, as expected.
Author(s): Ehsan Tavabi, Rayhaneh Sadeghi
PNU; PNU
Abstract: Solar plasma flow, consisting of ionized energetic particles, continuously emanates from the solar atmosphere as fast and slow solar winds. A research study proposes using machine learning and the Hough transform algorithm to analyze the torsional motions of solar spicules, small jets exhibiting twisting motion at the base. These spicules play a crucial role in providing and replenishing energetic particles in the corona, potentially serving as sources for the fast solar wind (Sadeghi & Tavabi, 2022; Riedl et al. 2021;).
The study finds that rotational spicules are more prevalent in polar regions compared to equatorial regions, which are known as primary locations for the generation and sustenance of fast solar winds. The proportion of twisted spicules is significantly higher at the poles (20%) compared to the equator (4%). This suggests a potential correlation between twisted spicules and the generation and acceleration of fast solar winds, providing novel insights into the origin and production mechanisms of the solar wind. Additionally, the research reveals regional disparities in spicule distribution. The number of observed spicules is 39% higher in polar areas compared to equatorial regions. There is also a difference in spicule numbers between the western and eastern sides of the Sun, with a 2% decrease on the western side. These disparities may be influenced by the effects of solar rotation speed. The study highlights that the fast solar wind originates from open magnetic polar plumes in coronal holes, which are primarily unipolar magnetic regions. The abundance of rotational spicules near the poles and in coronal hole regions is attributed to the rupture of mini-loops, which possess magnetic helicity. These observations provide insights into the origins and mechanisms of the fast solar wind. However, uncertainties remain regarding the exact coronal origins of both the fast and slow solar winds. The distinction between open and closed magnetic field lines in coronal holes and quiet regions remains unclear. The research also acknowledges the limitations of previous observations, particularly in terms of spatial and spectral resolution, which hinder a comprehensive understanding of fast solar wind origins and mini-loops. The study emphasizes the need for more systematic and detailed observations of the low-coronal region, coordinated with outer corona observations, to address these questions. Future missions such as the Solar Orbiter aim to provide remote sensing and in situ observation capabilities to further investigate the origins of the fast solar wind and mini-loops (Tavabi & Sadeghi, 2024a; Tavabi & Sadeghi, 2024b; Tavabi et al, 2014; Tavabi et al, 2014;).
In concultion, the research focuses on the torsional motions of solar spicules and their potential connection to the generation and acceleration of fast solar winds. It utilizes machine learning and data from the IRIS and Hinode missions to gain insights into the statistical properties and variations of spicules and their role in the solar wind. The findings highlight the prevalence of rotational spicules in polar regions and their association with fast solar wind generation, contributing to our understanding of solar plasma flow dynamics.
Author(s): Christos Katsavrias, Georgios Nicolaou, Simone Di Matteo, Larry Kepko, Nicholeen Viall-Kepko, Sigiava Aminalragia-Giamini, George Livadiotis
NASA GSFC; MSSL, UCL; NASA GSFC; NASA GSFC; NASA GSFC; SPARC; Princeton University
Abstract: In recent years, mesoscales have gained scientific interest because they have been determined to be important in a broad range of phenomena throughout heliophysics. The solar wind mesoscale structures include periodic density structures (PDSs), which
are quasi-periodic increases in the density of the solar wind that range from a few minutes to a few hours. These structures have been extensively observed in remote-sensing observations of the solar corona and in in-situ observations out to 1 AU, where they manifest as radial length scales greater than or equal to the size of the Earth’s dayside magnetosphere, that is, from tens to hundreds of Earth radii. While the precise mechanisms that form PDSs are still debated, recent studies confirmed that most PDSs are of solar origin and do not form through dynamics during the solar wind’s propagation in the interplanetary space. Here, we investigate further the origin of PDSs by exploring the thermodynamic signature of these structures. To do this, we estimate the values of the effective polytropic index (γ) and the entropy of protons, which in turn are compared with the corresponding values found for the solar wind. We used an extensive list of PDS events spanning more than two solar cycles of Wind measurements (the entire Wind dataset from 1995 to 2022), to investigate the thermodynamic signatures of PDSs. With the use of wavelet methods, we classified these PDSs as coherent or incoherent, based on the shared periodic behavior between proton density and alpha-to-proton ratio, and we derive the proton polytropic index. Our results indicate that the coherent PDSs exhibit lower polytropic index values (γ~1.54) on average and a higher entropy than the values in the entire Wind dataset (γ~1.79). A similar behavior was observed for the magnetic cloud of an interplanetary coronal mass ejection, which further suggest that PDSs with a composition signature form at the Sun with a mechanism involving magnetic reconnection and the emission of flux ropes. In contrast, incoherent PDSs exhibit the same values as those of the entire Wind dataset making plausible both their formation at the Sun or in situ.
.
Author(s): Silke Kennis, Stefaan Poedts
KU Leuven; KU Leuven
Abstract: Connectivity between our star and our planet is a huge but necessary challenge. Indeed, remote-sensing instruments allow us to observe with great details the surface of the Sun, while in-situ measurements let us see the consequences at Earth. However, it it not always easy to understand the link between the two, thus preventing us from understanding the propagation of physical effects. One way to chase this connection is to use the magnetic field: although not visible, open magnetic field bathes the entire heliosphere, and has a major influence on plasma and particle events such as CMEs or flares. We can use models to estimate this connectivity like the two-step ballistic mapping, however most method rely on many free parameters that can greatly affect the final result.
In this study, we will present our self-consistent computation of the magnetic connectivity through the heliosphere by coupling the MHD codes COCONUT for the solar corona and EUHFORIA for the inner heliosphere. MHD codes are usually too slow to compute connectivity on a near-real time cadence, but this chain of model can be optimised to run in less than 6 hours, which allows refined tracking within a single day. We will explain how the coupling between the code operates, as it affects the tracing of the magnetic field lines. We will also explain how to provide uncertainties with this method (both temporal and spatial). We will first show the validation of our method by comparison with PFSS and wind ballistic mapping, for both polar and equatorial open coronal holes, on several test cases that were already used in previous studies. This will allow us to discuss the impact of the magnetic modelling on the connectivity estimation. Finally, we will also discuss the impact of the input magnetic map by comparing 20 different runs for the same Carrington rotation at minimum of activity, based on various maps from different providers.
Author(s): Maximilien Péters de Bonhome, Viviane Pierrard, Fabio Bacchini
Center for mathematical Plasma Astrophysics, Department of Mathematics, Katholieke Universiteit Leuven, Celestijnenlaan 200B, B-3001 Leuven, Belgium; Solar-Terrestrial Center of Excellence and Space Physics, Royal Belgian Institute for Space Aeronomy, B-1180 Brussels, Belgium; Center for mathematical Plasma Astrophysics, Department of Mathematics, Katholieke Universiteit Leuven, Celestijnenlaan 200B, B-3001 Leuven, Belgium
Abstract: The solar wind, the continuous outflow of material from the solar surface, is mainly composed of protons and electrons that are accelerated throughout the heliosphere up to a few hundred km/s. Although many theoretical models have been developed since the first solar wind observations in the sixties, we still do not completely comprehend the mechanism behind the acceleration of the solar wind. In particular, the origin of the observed high-energy electrons is not understood. The aim of this presentation is to investigate the mechanisms responsible for this acceleration by using the new Parker Solar Probe (PSP) observations combined with kinetic models. Fits of the observed velocity distributions from PSP with kappa distributions functions have already shown that high-energy particles are observed even below 20 solar radii [1]. Moreover, through constraining a kinetic exospheric model based on observational data and incorporating the impact of high-energy electrons, it was demonstrated that the model effectively replicated the observed average profiles of solar wind speeds relative to distance from the Sun [1]. Therefore, the kinetic exospheric model can explain at least part of the solar wind acceleration while further improvements are needed to explain the faster winds. In fact, the solar wind comprises two distinct modes: one characterized by high speed (typically exceeding 500 km/s) and another by lower speed (typically below 400 km/s) coming from specific regions of the Sun’s surface. PSP reaches distances where the solar wind has a significant remaining acceleration inducing difficulties to discriminate between fast and slow winds by using only the bulk velocities. This discrimination is critical in constraining the models. Recently, a new way of differentiating the data of slow and fast winds has been found for the observations of PSP using the apparent strong correlation between bulk velocity and temperature of protons [2]. Furthermore, the impact of simulating the diffusion of particles on the acceleration of the solar wind unveiled the ability of considering much more realistic modeled velocity distribution functions for our kinetic exospheric model. This further reinforces the importance of diffusion mechanisms such as wave-particle interaction on the global acceleration of the solar wind. This presentation aims at describing how those results are crucial in explaining the acceleration of the solar wind.
References[1] V. Pierrard, M. Péters de Bonhome, J. Halekas, C. Audoor, P. Whittlesey, R. Livi, “Exospheric solar wind model based on regularized Kappa distributions for the electrons constrained by Parker Solar Probe observations”, Plasma, vol. 6, pp. 518-540, 2023.[2] V. Pierrard and M. Péters de Bonhome, “Acceleration of the Solar Wind by Ambipolar Electric Field”, in Proceedings of the Conference Solar wind 16, 2024, arXiv:2401.13308. (Under Review)
Author(s): Valentina Zharkova
Northumbria University, Newcastle, NE1 8ST, UK
Abstract: Aims. This research aims to explore variations of electron pitch-angle distribution (PAD) during spacecraft cross recon- necting current sheets (RCSs) with magnetic islands. The results can benchmark the sampled characteristic features with realistic PADs derived from in-situ observations.
Methods. Particle motion is simulated in 2.5D Harris-type RCSs using particle-in-cell (PIC) method considering the plasma feedback to electromagnetic fields. We evaluate particle energy gains and PADs in different locations and under the different directions of passing the current sheet by a virtual spacecraft. The RCS parameters are comparable to heliosphere and solar wind conditions.
Results. The energy gains and the PADs of particles would change depending on the specific topology of magnetic fields. Besides, the observed PADs also depend on the crossing paths of the spacecraft. When the guiding field is weak, the bi-directional electron beams (strahls) are mainly present inside the islands and located closely above/below the X-nullpoints in the inflow regions. The magnetic field relaxation near X-nullpoint converts the PADs towards 90◦. As the guiding field becomes larger, the regions with bi-directional strahls are compressed towards small areas in the exhausts of RCSs. Mono-directional strahls are quasi-parallel to the magnetic field lines near the X-nullpoint due to the dominant Fermi-type magnetic curvature drift acceleration. Meanwhile, the high-energy electrons confined inside magnetic islands create PADs about 90◦.
Conclusions. Our results link the electron PADs to local magnetic structures and directions of spacecraft crossings. This can help explain a variety of the PAD features reported in the recent observations in the solar wind and the Earth’s magnetosphere.
Author(s): Guifre Molera Calves, Jasper Edwards, Oliver White, Pradyumna Kummamuru, Giuseppe Cimo, Dominic Dirkx, Masdiana Noor Said
University of Tasmania; University of Tasmania; University of Tasmania; University of Tasmania; JIVE; TU Delft; JIVE
Abstract: The Planetary Radio Interferometry and Doppler Experiment is a multi-purpose experimental technique aimed at enhancing the science return of planetary missions. The technique exploits spacecraft radio signals and Very Long Baseline Interferometry (VLBI) radio telescopes on Earth to explore the Solar System. To achieve ultimate precision in the scientific campaigns: orbital determination, gravitational measurements, or planetary atmospheric profiles, it is necessary to understand well the medium through which radio waves propagate. Thus, we have been working on models of the solar wind and transient detections over the past 15 years with planetary missions.
Studies began with the European Space Agency Venus Express (VEX) mission producing a detailed solar wind model for missions based on phase scintillation measurements along the line-of-sight (Molera Calvés et al. 2014). Work continued with the Mars Express (MEX) probe between 2014-2023, during which solar wind model were developed along three Martian orbits at different solar elongations from the phase scintillation (Kummamuru et al. 2023, Edwards et al. 2024, submitted). Currently, the PRIDE experiment is one of the primary experiments of the European Space Agency Jupiter Icy moons Explorer (JUICE), opening new opportunities to study space weather in detail.
Detections of interplanetary coronal mass ejections (Molera Calvés et al. 2017) and solar events in the solar corona (Maoli et al. 2022, Maoli et al. 2023) have been demonstrated using this technique with radio telescopes. The capability to utilize multiple line-of-sights and an increased number of operational spacecraft allows us to build a powerful method for studying and forecasting space weather. These tools range from assessing the intensity of solar transients, studying the interior of coronal mass ejections and its 2-dimensional propagation, understanding co-rotating interaction regions (CIR) structure, to analysing Faraday rotation of plasma structures using multi-polarised spacecraft/antennas.
In this presentation, I will discuss past missions and achievements as well as the synergies between space weather research and next-generation space missions.
Author(s): Silvia Perri, Federica Chiappetta, Denise Perrone
Università della Calabria; Università della Calabria; Italian Space Agency (ASI)
Abstract: By analyzing the first stream of slow Alfvènic wind observed by Solar Orbiter at a heliocentric distance of 0.64 au and an Alfvènic high-speed stream observed by Solar Orbiter on September 2022 at a distance of 0.58 au from the Sun, we detected switchbacks, large deflections of the magnetic field associated to rapid increases in the radial solar wind speed, occurring both as isolated, well defined structures, and as group of structures embedded in the flow.
Applying the Dudok de Wit et al. 2020 definition to pick up rotations in the magnetic field, we investigated turbulence properties around and within switchbacks. In particular, we computed the structure functions, the level of magnetic field intermittency under the assumption of a p-model of the turbulent cascade, and we carried out a coherence analysis in order to capture wave-like activity at the boundaries of switchbacks. We found that such structures are characterized by a high coherence over a certain range of time scales. In particular, the coherence reaches almost maximum values in the leading and trailing regions of switchbacks.
Studying the properties of magnetic switchbacks in the solar wind has implications also on the propagation of solar energetic particles, since particle dynamics is affected by the ratio between particle gyroradius and the size of the switchbacks (see Malara et al., 2023).
Author(s): Nicholas Wynn Watkins
CSDA, University of Warwick, UK
Abstract: A key assumption behind the widespread use of Fourier and wavelet power spectra in space physics is the “ergodic” one-that an operation (like the FFT) performed on only one measured time series can nonetheless estimate a property (like the power spectral density) that is only defined for an ensemble.
In a still little known 1967 paper, however, Mandelbrot dealt with systems where the ergodic assumption is broken, using as an example a two level system switched at random intervals, where the times between switching had a power law distribution. This was an alternative model for 1/f spectra to his much better known fractional Brownian motion, and yet is much closer to his subsequent work on multifractals and turbulence. The model has recently been applied to in physical systems like the quantum dots which received the Nobel Prize in Chemistry in 2023, and my presentation will argue that this “old” work is both timeless and timely for solar wind physics problems such as switchbacks, for which power spectra have been an important diagnostic.
See also Watkins, On the Continuing relevance of Mandelbrot’s non-ergodic fractional renewal models of 1963 to 1967. The European Physical Journal B. 90(12), 241. DOI:10.1140/epjb/e2017-80357-3 and Watkins, Mandelbrot’s stochastic time series models. Earth and Space Science. 6(11), 2044-2056. DOI:10.1029/2019EA000598.
CD7-p13 Effects of changing source surface height parameter in solar wind simulations using EUHFORIA
Author(s): Senthamizh Pavai Valliappan, Jasmina Magdalenic
Royal Observatory of Belgium; Royal Observatory of Belgium & Katholieke Universiteit Leuven, Belgium
Abstract: The solar wind modelling study using the 3D MHD model EUHFORIA (EUropean Heliospheric FORecasting Information Asset, Pomoell & Poedts, 2018) at near the Sun distances show a large discrepancy between modelling results and in situ observations by Parker Solar Probe (PSP). The default coronal model used in EUHFORIA consists of the potential field source surface extrapolation (PFSS), Schatten current sheet (SCS) model and semi-empirical WSA model, which simulate the plasma and magnetic conditions at the inner boundary (0.1 AU). The outer boundary of the PFSS model, known as the source surface height parameter (RSS), and the inner boundary of the SCS model are among the free parameters in the coronal model that determine the area of modelled coronal holes, which in turn influences the area of open flux. In EUHFORIA, a default value of RSS = 2.6 R⊙ as suggested by McGregor et al. (2008) is used in the solar wind modelling at short radial distances. It is reported that lower RSS value in coronal models better captures the area of coronal holes (Asvestari et al., 2019), reconstructs small-scale features (Badman et. al., 2020), and represents coronal magnetic field topologies during different phases of solar cycles (Lee et al. 2011; Arden et al. 2014).
In this study, we employ different values for the outer boundary of the PFSS model and inner boundary of the SCS model, while keeping default values for other parameters. We then compare the solar wind modelling results with varying RSS parameters to those obtained using all default parameters in the coronal model, by evaluating their agreement with the in situ observations from PSP for its first ten perihelion encounters.
Author(s): John Morgan
CSIRO
Abstract: A major challenge in Space Weather is probing the region between that covered by white-light coronagraphs (out to a few solar radii), and in-situ observations made at L1. This region, comprising almost all of the volume of the heliosphere within 1 AU, remains only sparsely sampled by in-situ observations with few exceptions.
Radio propagation observations is one approach to probing this volume. Compact, as well as polarised and/or pulsating astrophysical radio sources provide a dense network of sightlines. Propagation through the soslar wind causes group delay, scintillation (IPS, similar to stars twinkling) as well as Faraday rotation. Measurement of these signatures provide proxies for solar wind density and velocity (integrated along the line of sight), as well as information on the intervening magnetic field. For example, observations from established IPS observatories have been shown to improve forecasts of solar wind density and velocity at L1, both for ambient solar wind and Coronal Mass Ejections (CMEs).
In this presentation I will focus on the use of a new generation of radio telescopes for these observations. With their unprecedented combination of sensitivity, wide field of view, and snapshot imaging capability, these instruments can measure hundreds of sources in parallel, providing a resolution sufficient to reveal the existence of smaller-scale structures in interplanetary space, as well as map the morphology of interplanetary CMEs.
I will describe how a broad range of ground-based radio observations here in Australia are providing information that is complementary both to more conventional measurements and similar work being carried out using European instruments such as Lofar. I will discuss the prospects for integrating these measurements into simulations and other 3D reconstructions. I will also provide an overview of the exciting prospects for making even more extensive observations with future instruments that are under construction.
Author(s): Satabdwa Majumdar, Martin Reiss, Karin Muglach, Shibaji Chakrabory
Austrian Space Weather Office, GeoSphere Austria, Graz, Austria; Community Coordinated Modelling Center, NASA Goddard Space Flight Center, Greenbelt, USA; NASA Goddard Space Flight Center, Greenbelt, MD, USA; Center for Space Science and Engineering Research, Virginia Tech, Blacksburg, VA, USA
Abstract: With a highly technology dependent modern life, understanding and predicting space weather has become a necessity, and in this aspect, a good understanding of the solar wind plays a crucial role. For the last two decades, the Wang-Sheeley-Arge (WSA) model has been widely used for predicting solar wind conditions at L1 and specifying physical conditions at the inner boundary of heliospheric MHD codes such as Enlil and MAS. While many studies have evaluated the WSA model‘s ability to simulate solar wind conditions at L1 by comparing simulation results to in-situ spacecraft measurements, little attention has been given to understanding the causes of erroneous predictions on an event-by-event basis. This study presents a comprehensive analysis of events where the Wang-Sheeley-Arge (WSA) model succeeds and fails. Specifically, we study the large-scale coronal magnetic field and how magnetic structures at the coronal hole boundaries affect the WSA model results. To do so, we study a catalog of 29 full-disk images of coronal holes from Reiss et al. (2024) that were taken by the AIA instrument onboard the SDO spacecraft. Using models hosted at NASA’s Community Coordinated Modeling Center (CCMC), we model the large-scale structure of the corona, including streamers and pseudo-streamers, and compare the simulation results to the coronal hole observations in the extreme ultraviolet regime and in-situ measurements at L1. Through this approach, we aim to understand the effect of different magnetic structures at the coronal hole boundaries on large-scale models of the corona and solar wind. In this presentation, we present our findings on the connection between coronal magnetic structures and solar wind profiles, and discuss opportunities for using these findings to improve solar wind predictions at L1.
Author(s): Inmaculada F. Albert, S. Toledo-Redondo, V. Montagud-Camps, A. Castilla, N. Fargette, B. Lavraud, P. Louarn, C. Owen, I. Zouganelis
University of Murcia; University of Murcia; University of Murcia; University of Murcia; Blackett Laboratory, Imperial College; Laboratoire d’astrophysique de Bordeaux, Univ. Bordeaux, CNR; Institut de Recherche en Astrophysique et Planétologie, CNRS; University College London, Mullard Space Science Laboratory; uropean Space Agency (ESA), European Space Astronomy Centre (ESAC)
Abstract: Properties of turbulence in the interplanetary medium affect propagation of geomagnetic storm drivers such as CMEs. Magnetic reconnection in turbulent plasmas, specially at small scales, is relevant in the process of cross-scale energy transfer and energy dissipation in turbulence. Magnetic reconnection is a process in which magnetic energy dissipates, turning into kinetic and thermal energy, through the reconfiguration of the magnetic field topology. It has been observed throughout the solar wind at multiple spatial scales and Sun distances.
The study of magnetic reconnection in large- and medium-scale structures has received closer attention than ion-scale magnetic reconnection, due to instrumental limitations. Thanks to the high cadence Solar Orbiter data, and in particular the Proton-Alpha Sensor (PAS) from the Solar Wind Analyzer (SWA) instrument, we can now resolve ion velocity distribution functions inside current sheets of thicknesses in the range of few proton gyroradii. Thus, it is now possible to search for magnetic reconnection at scales near the ion spectral break of the turbulent cascade.
We introduce an algorithm that automatically identifies reconnecting current sheets near the ion spectral break in the solar wind, and assesses the presence of associated reconnection exhausts. The uncertainty associated to ion bulk velocity measurements constrains the Alfvén velocities that can be resolved with the available data, resulting in a lower threshold for the detectable reconnecting component of the magnetic field.
A catalog of small-scale current sheets in the solar wind is presented. We show the prevalence of reconnecting versus alfvenic current sheets near ion-scales, study their properties, and discuss the relevance of small-scale magnetic reconnection for energy dissipation in solar wind turbulence.
Author(s): Alexandre Matthieu
IRAP
Abstract: We present an on-going effort to develop a public infrastructure to support research in
heliophysics as well as space-weather forecasting. STORMS combines a wide range of
observation and in situ measurements with heliospheric models to study and model the
influence of solar activity on the near-Earth environment. Supporting operations of space
missions, such as Solar Orbiter, is an important goal for this service.
The Magnetic Connectivity Tool helps with deciding the pointing of remote-sensing instruments by exploiting real-time data and forecasts based on numerical simulations. It finds regions of the solar surface that may be connected with a spacecraft in a near future. It is operational since 2020 and is
currently used for Solar Orbiter mission. Predicting solar wind properties is achieved by
combining coronal and heliospheric models (Multi-VP, Pluto, 1D-MHD). Analysis of multi-point
imaging to derive the 3-D structure of solar wind structures such as Coronal Mass Ejections
(CMEs) and Corotating Interaction Regions (CIRs) is also performed (Shock Tool).
Daily forecasts provides prediction to the scientific community and end users. As a community
service, STORMS allows « run on request » simulations for users, helping them in studying a
particular event. This is available through the VSWMC Virtual Space Weather Modelling Center
and can be coupled with other models (EUHFORIA). Further STORMS services will integrate
runs-on-demand of the new multi-species IRAP Solar Atmosphere Model (ISAM) and a full
database of 3-D MHD simulations.
Author(s): Indurain Mikel
IRAP
Abstract: As part of the Solar Terrestrial ObseRvations and Modeling Service
(STORMS), an important development axis is the production of
heliospheric magnetohydrodynamic (MHD) simulations for monitoring
and studying solar activity in the heliosphere and the near-Earth
environment.
Starting from observations on the photosphere, 1D MHD model Multi-
VP and 3D MHD model Heliocast give a physical and consistant
description of the solar wind. The creation of synthetic imagery make
it possible to compare the results with observations like coronagraph.
A part of these simulations are available through the VSWMC Virtual
Space Weather Modelling Center and can be coupled with other
models (EUHFORIA). A « run on request » mode for users can help
user in studying a particular event.
Author(s): Sergio Dasso, Gutierrez Christian, Demoulin Pascal, Janvier Miho
IAFE; IAFE; Observatory of Paris; ESTEC – European Space Agency
Abstract: Plasma coming from different solar regions can create different interplanetary conditions when access to the heliosphere.
The interior of coronal holes (CHs) are sources for fast solar wind, which typically is preceded by slow solar wind, creating stream interaction regions (SIRs). SIRs can have several consequences in the medium, such as producing shock waves; accelerating particles; changing the direction of the interplanetary magnetic field; increasing its modulus as well as the plasma density and temperature, mainly as consequence of the plasma compression. SIRs also change the conditions for propagation of galactic cosmic rays (GCRs) in the heliosphere, causing Forbush decreases (FDs).
A detailed analysis of the structure of SIRs and of consequente FDs, applying an original normalized superposed epoch technique to a large samples of events, will be shown here. Finally, for getting insight of most relevant physical processes, we will make a compararive analysis between FDs produced by SIRs respect to the ones produced by interplanetary coronal mass ejections.
Author(s): Guifre Molera Calvés, Pradyumna Kummamuru, Jasper Edwards, Giuseppe Cimo’
University of Tasmania; University of Tasmania; University of Tasmania; Joint Institute for VLBI ERIC (JIVE)
Abstract: Ground-based observations of spacecraft signals provide crucial insights into space weather, but single-spacecraft’s signal measurements from Earth are limited in their ability to distinguish between spatial and temporal variations in the solar plasma. To address this challenge and enhance our understanding of interplanetary scintillation, we conducted simultaneous observations of radio signals transmitted by two co-orbiting spacecraft: ESA’s Mars Express (MEX) and the Chinese National Space Administration’s Tianwen-1 (TIW-1). These observations were carried out from April to November 2021 using the University of Tasmania’s VLBI radio telescopes operating at 8.4 GHz.
We obtained topocentric Doppler measurements and residual phase data of the carrier signals by employing the Planetary Radio Interferometer and Doppler Experiment (PRIDE) technique. These measurements enabled us to quantify phase fluctuations in the spacecraft signals induced by solar wind and hydrodynamic turbulence in the interplanetary medium.
The use of simultaneous observations of these two co-orbiting spacecraft not only allows us to perform RFI characterization and data comparison, which are critical for distinguishing between outliers and unique features caused by solar activity, but also enables us to differentiate spatial and temporal variations measured from two different points in the vicinity of Mars. These advancements point out the value of simultaneous multi-spacecraft measurements in improving our understanding of solar plasma dynamics and enhancing the accuracy of space weather predictions.
Author(s): Curt A de Koning, Chris J Scott, Luke A Barnard, Craig E DeForest
University of Colorado, CIRES; University of Reading; University of Reading; Southwest Research Institute
Abstract: Permutation entropy was introduced by Bandt&Pompe in 2002. They found that this entropy measure was simple, quick to calculate, robust, invariant with respect to nonlinear monotonous transformations, and was particularly useful in the presence of dynamical or observational noise. Their definition directly applies to arbitrary real-world time series and has been used on biomedical data, such as EEG recordings and heartbeat time series, financial time series, music genres, and space physics time series. However, it has only been within the last decade that efforts have been made to apply permutation entropy to two-dimensional image data. Here, for the first time, we present the permutation entropy, plotted in the entropy-complexity plane, for coronagraph and heliospheric imager observations.
Author(s): Jean-Baptiste DAKEYO, Samuel Badman, Alexis Rouillard, Milan Maksimovic, Pascal Démoulin, Philippe Louarn
IRAP – LESIA; CFA – Harvard; IRAP; LESIA; LESIA; IRAP
Abstract: One of the fundamental models in heliophysics is the Parker solution, which describes the hydrodynamic equilibrium of the solar corona, producing an outwardly propagating solar wind throughout the heliosphere (Parker, 1958, 1960). One of the recent refinements of Parker’s equations, the two-thermal regime Isopoly model embedding an isothermal until the radius Riso, followed by a polytropic evolution (Dakeyo, 2022, 2024), provides a simple modeling consistent with the observed bulk velocity while accounting for in-situ temperature observations (i.e., interplanetary heating). Although the underlying physics and equations are well described and already used by the space weather community, the determination of the radial evolution of the solar wind properties (velocity, temperature, density) requires numerical solution and an appropriate treatment of the equations through the sonic point to ensure a transonic wind. This implies a non-trivial task of writing a solver, it is therefore useful to provide open source code to facilitate this process.
This is the purpose of IsopolySolarWind, an open source Python code that provides a simple solver for 1D isopoly solar wind solutions with plotting capabilities. A primary version of isopoly solutions has already been released within the ParkerSolarWind open source code (https://github.com/STBadman/ParkerSolarWind), and models a solar wind bifluid evolution for which protons and electrons share the isothermal radius Riso. We present here a detailed complementary version with new features (https://github.com/jbdakeyo/Isopoly), exclusively dedicated to isopoly modeling, which embeds a two-fluid modeling (protons and electrons), with fully separated thermal behavior contribution and radial evolution (i.e. thermal pressure), and the modeling of the super-radial expansion region via the expansion factor parameter. This complement significantly increases the number of wind solutions that can be obtained.
Author(s): Griselda Baron-Martinez, Ernesto Aguilar-Rodríguez, J. C. Mejía-Ambriz, O. Chang, J.A. Gonzalez-Esparza, P. Villanueva, E. Andrade
Institute of Geophysics-UNAM; Institute of Geophysics-UNAM; CONAHCYT, Institute of Geophysics-UNAM; RAL Space, United Kingdom Research and Innovation – Science & Technology Facilities Council; Institute of Geophysics-UNAM; Institute of Geophysics-UNAM; Institute of Geophysics-UNAM
Abstract: The flux intensity of a compact radio source (<1 arcsec) fluctuates randomly when its signal passes through the inhomogeneous solar wind. This phenomenon is known as Interplanetary Scintillation (IPS). The Mexican Array Radio Telescope (MEXART) is specifically designed to observe IPS. MEXART consists of a 64×64 dipole array and operates at a center frequency of 139.65 MHz with a bandwidth of 12.5 MHz. Its primary goal is to monitor large-scale solar wind disturbances moving between the Sun and the Earth. In this work, we implemented an algorithm to address the noise from certain frequency channels. Additionally, we have updated a catalog of radio sources observed with an IPS signature recorded by MEXART from June 2020 to June 2022. The catalog contains information on the declination, right ascension, and an estimated flux at 140 MHz for each source. It is a primary reference for estimating solar wind values and monitoring large-scale interplanetary disturbances for space weather analysis.
Author(s): Francesco Carella, Giovanni Lapenta, Alessandro Bemporad, Maria Elena Innocenti, Sophia Köhne, Stefan Eriksson, Jasmina Magdalenic
KU Leuven; KU Leuven; INAF-Osservatorio Astrofisico di Torino; Institut für Theoretische Physik, Ruhr-Universität Bochum; Institut für Theoretische Physik, Ruhr-Universität Bochum; Laboratory for Atmospheric and Space Physics, University of Colorado; Royal Observatory of Belgium / KU Leuven
Abstract: Studying the solar wind is crucial for understanding the behavior of plasma within the solar system. At 1 AU, where the solar wind interacts with Earth’s magnetosphere, we can observe various transient phenomena, such as Interplanetary Coronal Mass Ejections (ICMEs) and Corotating Interaction Regions (CIRs), which may lead to magnetic reconnection. In this research, we employ Self Organizing Maps (SOMs) [1], an unsupervised learning technique that uses neural networks for dimensionality reduction, to convert time series data from the WIND spacecraft (including proton density, proton temperature, solar wind speed, and magnetic field strength) into visual representations. We then apply clustering methods to these maps to classify the solar wind. Finally, using a reconnection exhaust catalog by Eriksson et al. 2022 [2], we investigate the occurrence of magnetic reconnection within the identified clusters and we provide a possible physical interpretation of those clusters.[1] T. Kohonen, ‘Self-organized formation of topologically correct feature maps’, Biol. Cybern., vol. 43, no. 1, pp. 59–69, Jan. 1982, doi: 10.1007/BF00337288.[2] S. Eriksson et al., ‘Characteristics of Multi-scale Current Sheets in the Solar Wind at 1 au Associated with Magnetic Reconnection and the Case for a Heliospheric Current Sheet Avalanche’, ApJ, vol. 933, no. 2, p. 181, Jul. 2022, doi: 10.3847/1538-4357/ac73f6.
Author(s): Eliza Teodorescu, Marius Echim
Institute of Space Science – subsidiary of INFPLPR; Institute of Space Science – subsidiary of INFPLPR
Abstract: Complex dynamic interactions of various sized coherent structures in stochastic media result in intermittent fluctuating events. We evaluated the intermittency level of the turbulent magnetic field measured by the Parker Solar Probe (PSP) in the slow solar wind in the proximity of the Sun during the probe’s first close encounter using the flatness parameter. We calculated the flatness of the magnetic field data collected by the PSP between 1 and 9 November 2018. We observed high variability of the intermittency level when dividing the data into contiguous time intervals of various lengths, ranging from 3 to 24 hours. Through an elaborate statistical test based on data surrogates, we determined that the non-stationarity of the time series strongly influences the flatness of both the data and the surrogates. By appropriately choosing a null-hypothesis, the test allows us to determine whether the source of the observed intermittency is the underlying nonlinear process or the amplitude distribution. Further, we analyzed the scale-dependent self-similarity of intermittent events through a relatively new method, ROMA (rank-ordered multifractal analysis), that combines the idea of one-parameter scaling which implies self-similar topology at all scales (i.e. mono-fractality) with the classical structure function analysis. Different physical phenomena taking place at kinetic or MHD scales further require the division of the domain of scales into regimes. This is accomplished through a global multi-order simultaneous fit of the structure functions, that further revealed a decrease in flatness at scales smaller than a few seconds: intermittency is reduced in this scale range. This behavior was mirrored by the spectral analysis, which was suggestive of an acceleration of the energy cascade at the high frequency end of the inertial regime. ROMA results in spectra of scaling indices that collapse the Probability Density Functions (PDFs) of fluctuating fields onto single master-curves for selected ranges of scales.