The Chinese Hα Solar Explorer (CHASE) was successfully launched on 14 October 2021 as the first solar space mission of China National Space Administration (CNSA). The scientific payload of the CHASE satellite is the Hα Imaging Spectrograph (HIS). The CHASE/HIS acquires seeing-free spectroscopic observations of the whole solar disk at three spectral lines of Si I (6560.6 Å), Hα (6562.8 Å) and Fe I (6569.2 Å) which are formed at different heights of the photosphere and chromosphere. A full-Sun scanning takes only 46 seconds, with a spectral sampling of 0.024 Å and a spatial resolution of 1.2 arcsec. Since its launch and in-orbit calibrations, the performance of the CHASE mission is excellent and meets the pre-launch expectations. The FITS formatted science data are now available to the community through the Solar Science Data Center of Nanjing University (SSDC-NJU, https://ssdc.nju.edu.cn). Here we introduce the CHASE science data and the calibration procedures. The first series of scientific studies of the CHASE mission are also presented.

How to cite: Li, C., Fang, C., Ding, M., Chen, P., and Li, Z.: First results of the Chinese Ha Solar Explorer - CHASE mission, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3035, https://doi.org/10.5194/egusphere-egu23-3035, 2023.

The emergence of magnetic flux in the Sun can lead to the formation of active regions with highly complex magnetic fields, evident by δ-spots, filaments, and sigmoids. These regions are often the sources of major flares and coronal mass ejections (CMEs) and monitoring their evolution is crucial for a deeper understanding of these phenomena as well as space weather applications. To this end, high-quality observations of the photospheric magnetic field are routinely used to derive parameters and physical magnitudes, and quantify the magnetic complexity of active regions. Thus, we know that eruptive active regions are associated with highly non-potential magnetic field configurations, with strong electric currents and huge amounts of free magnetic energy and helicity. This talk reviews recent efforts to parameterize this non-potentiality of active regions and discusses ongoing and future work on developing new and improved parameters suitable for flare and CME prediction. It further focuses on the evolution of net electric currents in active regions, from their emergence to eruption. The significance of net electric currents on flare and CME prediction and new ways to utilize them in order to produce improved eruptivity parameters and understand solar eruptions will be discussed.

How to cite: Kontogiannis, I.: Parameterizing the evolution of active regions from emergence to eruption. Recent results and future work., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5436, https://doi.org/10.5194/egusphere-egu23-5436, 2023.

Impulsive solar energetic particle (SEP) events are distinguished from shock-accelerated gradual SEP events especially in terms of their abundance enriched in ³He and heavy ions. Historically, ³He-rich  have been known to be accompanied by type III radio bursts and energetic electrons. For more than 15 years in the past it has often been proclaimed that coronal jets are responsible for ³He-rich SEP events. We revisit the link of ³He-rich SEP events with coronal jets in a series of ³He-rich SEP events that was observed by Solar Orbiter in May 2021 at a radial distance of 0.95 AU. An isolated active region AR 12824 was likely the ultimate source of these SEP events.  The period of the enhanced flux of ³He was also a period of frequent type III bursts in the  decametric-hectometric range, confirming their close relationship. As in past studies, we try to find the solar activities possibly responsible for ³He-rich SEP events, using the type III bursts close to the particle injection times estimated from the velocity dispersion. But this exercise is not as straightforward as in many of the past studies since the region produced many more type III bursts and jet-like eruptions than the SEP injections.  We may generalize the solar activities for the ³He-rich SEP events in question as coronal jets, but their appearances do not necessarily conform to classic jets that consist of a footpoint and a spire. Conversely, such jets often did not accompany type III bursts. The areas that produced jet-like eruptions changed within the active region from the first to the second set of ³He-rich SEP events, which may be related to the extended coronal mass ejection that launched stealthily, involving both the leading and trailing polarity areas of AR 12824.

How to cite: Nitta, N., Bucik, R., Mason, G., Ho, G., Cohen, C., Gomez-Herrero, R., Wang, L., and Balmaceda, L.: Solar Activities Associated with 3He-rich Solar Energetic Particle Events Observed by Solar Orbiter, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16814, https://doi.org/10.5194/egusphere-egu23-16814, 2023.

Prediction of sunspots has been an everlasting interest in the space science community since the discovery of the sunspot cycle. The sunspot number is an indirect indicator of many different solar phenomena, e.g., total and spectral solar radiation, coronal mass ejections, solar flares and magnetic active regions. Its cyclic variation can even be used as a pacemaker to time different aspects of solar activity, solar wind and resulting geomagnetic variations. Therefore, there is considerable practical interest in predicting the evolution of future sunspot cycle(s). This is especially true in today’s technological society where space hazards pose a significant threat, e.g., to satellites, communications and electric grids on ground have been recognized. Another interest to predicting sunspots arises from the relatively recently recognized influences of variable solar radiation and solar wind activity on Earth’s climate system.

There are a variety of methods developed for predicting sunspots ranging from statistical methods to intensive physical simulations. Some of the most successful, yet relatively simple, methods are based on finding precursors that serve as indicators for the strength of the coming solar cycle. These methods are often based on statistics of all past solar cycles. However, most of these methods do not typically take into account the 22-year Hale cycle of solar magnetism, which is well known in different solar and geomagnetic phenomena.

Here we study the prediction of even and odd numbered sunspot cycles separately, thereby taking into account the Hale cyclicity of solar magnetism. We first show that the temporal evolution and shape of all sunspot cycles are extremely well described by a simple parameterized mathematical expression. We find that the parameters describing even sunspot cycles can be predicted quite accurately using the sunspot number 41 months prior to sunspot minimum as a precursor. The parameters of the odd cycles can be best predicted with geomagnetic maximum geomagnetic aa index close to fall equinox within a 3-year window preceding the sunspot minimum. Cross-validated hindcasts indicate that our method has a very good prediction accuracy. For the coming sunspot cycle 25 we predict an amplitude of 171 +/- 23 and the end of the cycle in September 2029 +/- 1.9 years. We are also able to make a rough prediction for cycle 26 based on the predicted cycle 25. While the uncertainty for the cycle amplitude is large we estimate that the cycle 26 will likely be stronger than cycle 25. These results suggest an increasing trend in solar activity for the next two decades.

How to cite: Asikainen, T. and Mantere, J.: Prediction of even and odd sunspot cycles: implications for cycles 25 and 26, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8849, https://doi.org/10.5194/egusphere-egu23-8849, 2023.

The dynamics of small (few hundred nm) charged interstellar dust particles entering the heliosphere is affected by the heliospheric magnetic field and in particular by the heliospheric current sheet. To estimate the flux distribution of the dust particles inside the heliosphere we simulate numerically the trajectories of moderately large samples (10^4 particles) of small charged dust grains with starting points outside the heliopause. The simulations are repeated for different choices of the initial time. We use the semi-analytical model of the heliosphere that combines a simplified time-stationary description of the plasma flow in the heliosphere and the outer heliosheath with the time-dependent magnetic field carried passively by the flow. The form of the heliospheric current sheet is determined by our choice of the time-dependent magnetic polarity structure at the surface of the rotating Sun. 

How to cite: Mann, I. and Czechowski, A.: Interstellar dust in the model heliosphere: effects of  time-dependent heliospheric current sheet, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2860, https://doi.org/10.5194/egusphere-egu23-2860, 2023.

This talk provides an overview of the Interstellar Mapping and Acceleration Probe (IMAP), what we hope and expect to learn from it, and where we are in the development of the mission. IMAP is currently in Phase C and is slated to launch in early 2025. IMAP simultaneously investigates two of the most important and intimately coupled research areas in Heliophysics today: 1) the acceleration of energetic particles and 2) the interaction of the solar wind with the local interstellar medium. IMAP’s ten instruments provide a complete set of observations to simultaneously examine the particle injection and acceleration processes at 1 AU while remotely dissecting the global heliospheric interaction and its response to particle populations generated through these processes. For more information about IMAP, see McComas, D.J. et al., Interstellar mapping and acceleration Probe (IMAP): A New NASA Mission, Space Science Review, 214:116, doi:10.1007/s11214-018-0550-1, 2018.

How to cite: McComas, D.: Update on the Interstellar Mapping and Acceleration Probe (IMAP) Mission, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2100, https://doi.org/10.5194/egusphere-egu23-2100, 2023.

Neutral atoms from the interstellar medium around the Sun enter the heliosphere unimpeded by the electromagnetic fields. They bring information about the properties of our interstellar neighborhood, processes at the boundary between the solar and interstellar media, and the direction of the Sun’s motion in the Galaxy. The interstellar neutral atoms of hydrogen, deuterium, helium, neon, and oxygen reach close distances to the Sun where they are probed either by direct detection or remote sensing methods. Here we focus on a direct measurement technique for interstellar neutral atoms of energies from 10 eV to 1 keV on an example of the instruments onboard the Interstellar Boundary Explorer (IBEX) and the follow-up mission the Interstellar Mapping and Acceleration Probe (IMAP, to be launched in 2025). IBEX continuously collects interstellar neutral atom data from the beginning of its operation in 2008 providing a survey over the Solar Cycle 24 despite its observation season being limited during the year. IMAP tracks the beam of interstellar neutrals in the sky throughout the year, which significantly expands scientific opportunities for probing interstellar neutrals from close distances to the Sun. We present the greatest accomplishments of interstellar neutral atom research enabled by IBEX and discuss the science goals in this area for IMAP.

The results are presented in collaboration with scientists and researchers at Southwest Research Institute, the University of Bern, the University of New Hampshire, and Princeton University.

How to cite: Sokol, J. M.: Interstellar Neutral Atom Measurements with IBEX and IMAP, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1427, https://doi.org/10.5194/egusphere-egu23-1427, 2023.

Turbulence in plasmas involves a complex cross-scale coupling of fields and distortions of particle velocity distributions, with the generation of non-thermal features. How the energy contained in the large-scale fluctuations cascades all the way down to the kinetic scales, and how such turbulence interacts with particles, remains one of the major unsolved problems in plasma physics. Moreover, solar wind turbulence is not homogeneous but is highly space-localized and the degree of non-homogeneity increases as the spatial/time scales decrease (intermittency). Such an intermittent nature has also been found to evolve with distance from the Sun, possible due to the emergence of strong non-homogeneities over a broad range of scales.

Here, by means of new measurements by both Solar Orbiter and Parker Solar Probe, the radial evolution of a homogeneous recurrent fast wind, coming from the same source on the Sun (namely a coronal hole), has been studied from global properties and large-scale features to kinetic structures as it expands in the inner heliosphere from 0.1 out to 1 AU [Perrone et al., 2022]. In particular, the nature of the turbulent magnetic fluctuations around ion scales during the expansion of the wind, has been investigated and the observed coherent events both close to the Sun and to the Earth are statistically studied. The ion scales appear to be characterized by the presence of non-compressive coherent structures, such as current sheets, vortex-like structures, and wave packets identified as ion cyclotron modes, responsible for solar wind intermittency and strongly related to the energy dissipation. Particle energization, temperature anisotropy, and strong deviation from Maxwellian, have been observed in and near coherent structures, both in in-situ data and numerical simulations. Understanding the physical mechanisms that produce coherent structures and how they contribute to dissipation in collisionless plasma will provide key insights into the general problem of solar wind heating.

Perrone, D., et al. (2022) Astronomy & Astrophysics (Special Issue: Solar Orbiter First Results – Nominal Mission Phase) 668, A189

How to cite: Perrone, D.: Turbulence evolution of coronal hole solar wind in the inner heliosphere: Solar Orbiter and Parker Solar Probe combined observations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11253, https://doi.org/10.5194/egusphere-egu23-11253, 2023.

The solar wind is an uninterrupted flow of highly ionised plasma that streams from compact sources at or near the Sun, accelerates across the low solar corona, and expands into the whole interplanetary space. The physical properties of any wind streams thus reflect the characteristics of their source regions and those of the extended zones of the corona they cross, and are affected by the time-varying strength and geometry of the global background magnetic field.  The rotational state of the solar corona also plays a fundamental role in a wide range of solar wind phenomena, but is much less well-known than that of the photosphere. In addition, surface dynamics and magnetic field evolution drive perturbations to the corona and wind that can either be transient or long-lasting.
We investigate the geometry and spatial distribution of solar wind sources by means of an extended time series of data-driven 3D simulations that cover nearly 2 activity cycles. We furthermore examine the corresponding solar wind acceleration profiles (radial trends) as a function of source latitude and time, and highlight consequences for the interpretation of Parker Solar Probe (PSP) and Solar Orbiter (SolO) in-situ measurements (especially as the latter moves away from the ecliptic plane). We also highlight impacts on the rotation profile of the solar corona and on the occurrence of regions of enhanced poloidal and toroidal flow shear that can drive plasma instabilities. Finally, we point out directions to assess the effects of surface transient phenomena driven by flux emergence on the properties of the solar wind.

How to cite: Pinto, R., Rouillard, A., and Finley, A.: Steady and transient solar wind sources, acceleration profiles and rotation across the solar activity cycle, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12000, https://doi.org/10.5194/egusphere-egu23-12000, 2023.

The solar magnetic fields emerging from the photosphere are comprised of a combination of “closed” and “open” fields. The closed magnetic field lines are defined as those having both ends rooted in the solar surface and not extending beyond the critical point, while the “open” field lines are those having one end that extends out into interplanetary space with the other end rooted at the Sun’s surface. Of course, there are no truly “open” magnetic field lines, and those that are dragged out into interplanetary space by the solar wind eventually close in the far reaches of the outer heliosphere. Since the early 2000’s, the amount of total unsigned open magnetic flux estimated by coronal models have been in significant disagreement with in situ spacecraft observations, especially during solar maximum, with factors of two or more differences not uncommon. Estimates of total open unsigned magnetic flux using coronal hole observations (e.g., using EUV or He 10830) are in general agreement with the coronal model results and thus are in similar disagreements with in situ observations. Several possible sources producing these discrepancies have been postulated over the years such as problems with the photospheric magnetic field measurements, underestimates of the polar field strengths, coronal mass ejection (CME) magnetic fields that are still closed but counted as open, the time-dependent nature of the magnetic field (i.e., the opening and closing of magnetic fields), and the manner in which in situ observations are used to estimate total open unsigned magnetic flux. This paper provides a brief review of the problem and some of the proposed explanations to account for the discrepancies. It concludes with compelling new evidence that appears to largely resolve the problem.

How to cite: Arge, C., Leisner, A., Wallace, S., and Henney, C.: On the Open Solar Magentic Flux Problem, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3015, https://doi.org/10.5194/egusphere-egu23-3015, 2023.

Models of the Solar Corona, ranging from potential field source surface (PFSS) to magnetohydrodynamic (MHD), typically provide a steady-state representation for a given time period, based on a single photospheric magnetic map.  However, the Sun's magnetic flux is in truth constantly evolving, and these changes in the flux affect the structure and dynamics of the corona and heliosphere.  The dynamics may be crucial to understanding solar wind properties.  A key question in the "Open Flux Problem" is whether the nature of open magnetic flux is adequately captured by steady-state PFSS and MHD models.  We describe an approach to evolutionary models of the corona and solar wind, using time-dependent boundary conditions.  We use the Lockheed Surface Flux Transport (SFT) model to evolve the surface magnetic fields, which in turn drive the coronal evolution.  The simulations are performed with the MAS thermodynamic Wave-Turbulence Driven (WTD) model for a month of simulated time.  We use the simulated observables derived from the simulation to explore the evolution of coronal structure (e.g., coronal hole boundaries).  We investigate the open magnetic flux in the model and contrast the results with MHD solutions using static magnetic flux boundaries at selected times.

How to cite: Linker, J. A., Mason, E., Lionello, R., Downs, C., Caplan, R., Titov, V., Riley, P., and DeRosa, M.: Open Magnetic Flux in the Time-Evolving Corona, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3939, https://doi.org/10.5194/egusphere-egu23-3939, 2023.

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 typically use numerical simulations to estimate the magnetic field lines pattern, and thus help connecting remote-sensing with in-situ observations.

In this study, we will present our 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 effects the tracing of the magnetic field lines. We will also explain how to provide uncertainties with this method. 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.

How to cite: Perri, B., Kennis, S., Brchnelova, M., Baratashvili, T., Kuzma, B., Zhang, F., Lani, A., and Poedts, S.: Magnetic connectivity from the Sun to the Earth: Impact of the magnetic modelling and input magnetic map, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3536, https://doi.org/10.5194/egusphere-egu23-3536, 2023.

As the coronal dynamics is dominated by magnetic forces, the reconstruction of the coronal magnetic field is of major importance when studying the solar corona. Since coronal field measurements are not routinely available, photospheric fields are extrapolated into the corona in order to obtain the 3D coronal magnetic field structure. A nonlinear force-free field approximation is justified because of the low plasma  $\beta$. Previous extrapolation codes excluded high and low latitudes, because of the well know grid convergence problems at the poles. To overcome these limitations, we developed a new code implemented on a Yin-Yang grid, which was tested and verified with the Low and Lou solution as reference. Here we apply our code to synoptic vector magnetograms obtained from SDO/HMI during solar activity maximum and minimum, respectively. We compare our magnetic field models with EUV-observations of the solar corona as a first validation step.

How to cite: Koumtzis, A., Wiegelmann, T., and Madjarska, M.: Computing the global coronal magnetic field during activity maximum and minimum with a newly developed nonlinear force-free Yin-Yang code, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17168, https://doi.org/10.5194/egusphere-egu23-17168, 2023.

Coronal holes are characterized by open magnetic field lines morphology. The strongest solar wind originates exactly from the area of solar coronal holes. From the other hand the solar oscillation is present at every point of the solar surface. Currently the mechanism which is responsible for formation of open coronal regions is still unidentified. We present a novel study of waves propagation and frequency distribution in coronal holes, which can bring a new insights in its origin. We investigate the discrepancies in the in waves propagation inside the coronal hole are and in its surrounding, using multi-channel intensity observations data from Atmospheric Imaging Assembly (AIA) and Dopplergrams from Helioseismic and Magnetic Imager (HMI) on board Solar Dynamics Observatory (SDO) at the level of photosphere, chromosphere and corona. We study power distribution of p-modes (5-minute oscillation) and wave frequencies above the acoustic cut-off frequency ѵ=5.3 mHz, for very fast waves, in the various levels of solar atmosphere, through helioseismic approach of wavelet 2D-spatial maps of the power spectral density estimated for the coronal hole area.

How to cite: Wisniewska, A.: Frequency Distribution of Solar Oscillation Inside The Coronal Hole, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13848, https://doi.org/10.5194/egusphere-egu23-13848, 2023.

The heliosphere surrounding our solar system is formed by the interaction between the solar wind and the local interstellar medium as the Sun moves through interstellar space. With dimensions on the order of hundreds to potentially thousands of au, it is difficult to determine the 3D structure of the heliosphere and the properties of the plasma surrounding it. However, observations of energetic neutral atoms (ENAs), which are created as a product of charge exchange between interstellar neutrals and energetic plasma ions, allow us to remotely discern the properties of the distant heliospheric boundaries.

NASA's Interstellar Boundary Explorer (IBEX) mission, a small explorer spacecraft which has been measuring ENA fluxes at ~0.5-6 keV for more than a solar cycle, discovered a “ribbon” of enhanced ENA fluxes forming a narrow, circular band across the sky. While it is generally believed that the ribbon is formed from secondary ENAs from outside the heliopause, a source of ENAs that is separate from the globally distributed flux (GDF) across the sky, it is not clear exactly how the parent ions outside the heliopause evolve over time before they become ribbon ENAs. To help solve this issue, we present recent developments in modeling the evolution of the ribbon over a solar cycle, under different pitch angle scattering assumptions. We hypothesize that simulating the evolution of the ribbon under differing scattering rates may help discern the physical mechanisms responsible for creating the ribbon observed by IBEX. We compare our modeling results to IBEX data where the ribbon was separated from the GDF using spherical harmonic decomposition, analyzing the evolution of the ribbon’s intensity and geometry as a function of ENA energy.

How to cite: Zirnstein, E., Swaczyna, P., Dayeh, M., and Heerikhuisen, J.: Constraints on the IBEX Ribbon's Origin from its Evolution over a Solar Cycle, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2095, https://doi.org/10.5194/egusphere-egu23-2095, 2023.

Energetic particles represent an important component of the plasma in the heliosphere. Spacecraft observations have detected energetic particles accelerated at impulsive events in the solar corona and at interplanetary shocks. Fluctuations in energetic particle fluxes are related to solar activity and to magnetic turbulence in the interplanetary medium. Thanks to in-situ satellite observations, numerical simulations, and theoretical models, our knowledge on the particle acceleration processes involved has advanced significantly in recent years. Here we review new developments on particle acceleration at collisionless shocks, in particular in relation with the transport properties of supra-thermal particles, as inferred from the analysis of particle fluxes, addressing that anomalous, superdiffusive transport is common in the interplanetary medium. A link between the results obtained from the in-situ diagnostic, used for studying energetic particle transport and acceleration, and remote observations of astrophysical shocks will be discussed.

How to cite: Perri, S.: Recent advancements on particle acceleration at collisionless shocks, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2360, https://doi.org/10.5194/egusphere-egu23-2360, 2023.

The mechanisms that produce solar energetic particles (SEPs) are still highly debated but coronal shock waves have been proposed as efficient particle accelerators that may be implicated in the production of SEPs.
An analysis of 32 Coronal Mass Ejections (CMEs) that produced strong pressure waves in the solar corona during their eruption has been done. For each event Kouloumvakos et al. (2019) exploited remote-sensing observations from multiple vantage points to reconstruct their 3-D ellipsoidal shapes. This catalogue of shock waves provides important statistical information on their kinematic evolution that we report in Jarry et al. (2023) together with their relation to X-ray flaring activitiy.
Different SEPs exhibit significant spectral and compositional variability. We looked for links between the composition of SEPs including abundance ratios (such as Fe/O) and shock parameters (Mach number, shock geometry, ..) that typically evolves rapidly along the magnetic field lines connected to the spacecraft recording SEPs.
This work was funded by the H2020 SERPENTINE project.

How to cite: Jarry, M., Rouillard, A., Plotnikov, I., Kouloumvakos, A., and Warmuth, A.: Relations between coronal shock waves properties and acceleration of solar energetic particles, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6946, https://doi.org/10.5194/egusphere-egu23-6946, 2023.

Ion mass-per-charge and shock geometry determine both shock injection and the number of times a charged particle is reflected across a shock. As such, they govern charged particle acceleration and heating at shock. Solar Obiter’s Heavy Ion Sensor (HIS) observed a quasi-parallel CME-driven shock on March 11, 2022. HIS has sufficient time, mass, and charge resolution that it measured individual distributions of iron 8+ through 12+ on the variable timescale of 2 to 5 minutes. Using these 1D velocity distribution functions (VDFs), we report that the thermal portion of the Fe distribution heats across the shock, that this heating increases with Q/M, and the heating increases with distance downstream from the shock.

How to cite: Alterman, B. L., Livi, S., Owen, C., Louarn, P., Bruno, R., D'Amicis, R., Raines, J., Lepri, S., Spitzer, S., Dewey, R. M., Bert, C. M., Kistler, L., Galvin, A., Rivera, Y., Horbury, T., Trotta, D., Hietala, H., Fauchon-Jones, E., Gershkovich, I., and Verscharen, D. and the SWA and MAG Teams: Iron Heating Across a Shock Observed by Solar Orbiter's Heavy Ion Sensor, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7823, https://doi.org/10.5194/egusphere-egu23-7823, 2023.

Collisionless magnetohydrodynamic shocks are ubiquitous in solar wind and in other space plasmas. They serve as natural sites where charged particles can be accelerated to supra-thermal energies via various Fermi acceleration mechanisms. Upstream and downstream fluctuations play a key role in these processes because they can act as scatter centers. Furthermore, the downstream turbulent plasma of strong shocks driven by coronal mass ejections can enhance the coupling of this plasma with the Earth’s magnetosphere. Understanding of how the fluctuations are transmitted across the shocks can provide an invaluable insight into many shock related studies.

In this paper, we investigate the interaction of fast forward (FF) shocks with magnetic island/flux rope mode fluctuations. We employ a recently developed framework of the Zank et al. (2021) transmission model. We analyze 378 FF shocks observed by the Wind spacecraft with varying upstream conditions and Mach numbers. We estimate upstream and downstream power spectra within one-hour intervals adjacent to the shock front and we calculate theoretically predicted downstream power spectrum. We analyze closely the difference between the observed and theoretically predicted spectra. On average, the model predicts the spectra with very good accuracy. We argue that large statistical spread of this difference is given mainly by the statistical uncertainties in the shock compression ratio, upstream power spectrum and by the turbulent evolution of fluctuations in the downstream region. Finally, our findings also suggest that Zank et al. (2021) model may estimate the downstream levels of fluctuations accurately even for a wider range of shocks than it was originally meant for.

How to cite: Pitna, A., Zank, G., Nakanotani, M., Zhao, L., Adhikari, L., Šafránková, J., and Němeček, Z.: On the Transmission of Turbulence Across Interplanetary Shocks: Observations and Theory, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8250, https://doi.org/10.5194/egusphere-egu23-8250, 2023.

We use the Magnetospheric Multiscale mission to observe electron acceleration events at Earth’s quasi-perpendicular bow shock. Acceleration mechanisms up to mildly relativistic electron energies are investigated in order to provide more insight into the long-standing injection problem. The events are chosen for their diversity in observed high energy electron flux and shock angle, θ_Bn, enabling the Stochastic Shock Drift Acceleration theory to be further tested for different shock parameters. An alternative acceleration mechanism is also presented. The electron acceleration region of this unusual event is associated with a decrease in wave activity, inconsistent with common electron acceleration mechanisms such as Diffusive Shock Acceleration and Stochastic Shock Drift Acceleration. The energetic electron population is shown to have a bi-directional pitch-angle distribution, indicating parallel heating along the magnetic field lines.
We propose a two-step acceleration process where energetic field-aligned electrons originating from the electron foreshock act as a seed population further accelerated by a shrinking magnetic bottle process. Furthermore, we present evidence for electron pitch-angle scattering at the shocks and discuss its importance and different roles for the different electron acceleration mechanisms mentioned above.

How to cite: Lindberg, M., Vaivads, A., Raptis, S., and Karlsson, T.: Electron acceleration mechanisms at Earth’s quasi-perpendicular bow shock, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-375, https://doi.org/10.5194/egusphere-egu23-375, 2023.

In situ and remote observations of the outer regions of the heliosphere and in the local interstellar medium (LISM) by Voyager, New Horizons, and IBEX continue to present new challenging questions, reflecting the complex processes of the solar wind (SW) - local interstellar medium (LISM) interaction. We present a new version of our recent 3-D MHD-plasma/kinetic-neutrals model of the SW-LISM interaction, which self-consistently includes neutral hydrogen and helium atoms. The new model treats electrons as a separate fluid assumed to co-move with the plasma mixture. In addition, it includes the effect of Coulomb collisions between electrons, He+ ions, and protons. The properties of electrons in the distant SW and in the very local interstellar medium (VLISM) are mostly unknown due to the lack of in situ observations. In this study we discuss the implications of using different models for the electron pressure. A common assumption (model 0) in single-ion global models is to assume that electrons have the pressure of the ion mixture. In this case electrons become hot in the distant SW where plasma is energetically dominated by pickup ions. In the proposed new model, electrons in the SW are colder, which leads to a better agreement with New Horizons observations in the supersonic SW. In the VLISM, however, ions and electrons may be almost in thermal equilibrium due to Coulomb collisions. As far as the plasma mixture properties are concerned, the major differences between the models are in the inner heliosheath, where colder electrons result in hotter protons and induce cooling of the plasma mixture due to the increase in the charge exchange frequency. This makes the heliosheath thinner by ~5 AU along the upstream direction and up to 60 AU in the downwind region. The filtration of interstellar H and He atoms is also discussed. At 1 AU, in the model with separate electrons the H density increases by ~2%. However, the fraction of pristine H atoms decreases by ~12%, while that of atoms born in the IHS increases up to ~35%. While the density of He atoms in the SW remains essentially unchanged, the contribution from the warm breeze increases by ~3%.

How to cite: Fraternale, F., Pogorelov, N. V., and Bera, R. K.: The role of electrons and helium atoms in global modeling of the heliosphere, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11714, https://doi.org/10.5194/egusphere-egu23-11714, 2023.