Three-dimensional Multispecies Simulation of the Solar Wind Interaction with Mars Under Different Interplanetary Magnetic Field Orientations

Without the intrinsic magnetic field, the solar wind interaction with Mars can be significantly different from the interaction with Earth and other magnetized planets. In this paper, we investigate how a global configuration of the magnetic structures, consisting of the bow shock, the induced magnetosphere, and the magnetotail, is modulated by the interplanetary magnetic field (IMF) orientation. A 3D multispecies numerical model is established to simulate the interaction of solar wind with Mars under different IMF directions. The results show that the shock size including the subsolar distance and the terminator radius increases with Parker spiral angle, as is the same case with the magnetotail radius. The location and shape of the polarity reversal layer and inverse polarity reversal layer in the induced magnetotail are displaced to the y < 0 sector for a nonzero flow-aligned IMF component, consistent with previous analytical solutions and observations. The responses of the Martian global magnetic configuration to the different IMF directions suggest that the external magnetic field plays an important role in the solar wind interaction with unmagnetized planets.

Solar Wind Plasma Properties During Ortho-Parker IMF Conditions and Associated Magnetosheath Mirror Instability Response

The properties of the solar wind fraction that exhibits an Interplanetary Magnetic Field (IMF) orientation orthogonal to the classical Parker spiral (so-called ortho-Parker) are investigated. We make use of a solar wind plasma categorization scheme, using 10 years of OMNI data, and show that the fractions of the different plasma origins (streamer-belt-origin plasma, coronal-hole-origin plasma, sector-reversal-region plasma and ejecta) identified by this scheme are rather constant when expressed as a function of the IMF orientation whereas the Alfvén Mach number significantly depends on this orientation. This has direct implication on the magnetosheath dynamics and, as an example, the stability of the mirror mode in this compressed plasma is studied thanks to Rankine-Hugoniot anisotropic relations. This study sheds light on previously reported, yet unexplained, observations of a larger occurrence of mirror mode in the magnetosheath downstream of ortho-Parker IMF.

Laminar and turbulent plasmoid ejection in a laboratory Parker Spiral current sheet

Quasi-periodic plasmoid formation at the tip of magnetic streamer structures is observed to occur in experiments on the Big Red Ball as well as in simulations of these experiments performed with the extended magnetohydrodynamics code, NIMROD. This plasmoid formation is found to occur on a characteristic time scale dependent on pressure gradients and magnetic curvature in both experiment and simulation. Single mode, or laminar, plasmoids exist when the pressure gradient is modest, but give way to turbulent plasmoid ejection when the system drive is higher, which produces plasmoids of many sizes. However, a critical pressure gradient is also observed, below which plasmoids are never formed. A simple heuristic model of this plasmoid formation process is presented and suggested to be a consequence of a dynamic loss of equilibrium in the high- $\beta$ region of the helmet streamer. This model is capable of explaining the periodicity of plasmoids observed in the experiment and simulations, and produces plasmoid periods of 90 minutes when applied to two-dimensional models of solar streamers with a height of $3R_\odot$ . This is consistent with the location and frequency at which periodic plasma blobs have been observed to form by Large Angle and Spectrometric Coronograph and Sun Earth Connection Coronal and Heliospheric Investigation instruments.

Global coronal and heliospheric magnetic field modelling for Solar Orbiter

&lt;p&gt;Computing the solar coronal magnetic field and plasma&lt;br&gt;environment is an important research topic on it's own right&lt;br&gt;and also important for space missions like Solar Orbiter to&lt;br&gt;guide the analysis of remote sensing and in-situ instruments.&lt;br&gt;In the inner solar corona plasma forces can be neglected and&lt;br&gt;the field is modelled under the assumption of a vanishing&lt;br&gt;Lorentz-force. Further outwards (above about two solar radii)&lt;br&gt;plasma forces and the solar wind flow has to be considered.&lt;br&gt;Finally in the heliosphere one has to consider that the Sun&lt;br&gt;is rotating and the well known Parker-spiral forms.&lt;br&gt;We have developed codes based on optimization principles&lt;br&gt;to solve nonlinear force-free, magneto-hydro-static and&lt;br&gt;stationary MHD-equilibria. In the present work we want to&lt;br&gt;extend these methods by taking the solar rotation into account.&lt;/p&gt;

High Energy Particle Spectrometer for ESA Lagrange mission

&lt;p&gt;The LGR High Energy Particle Spectrometer HEPS for the ESA Lagrange mission belongs to the satellite in-situ instrument suite. The satellite will be placed at the Lagrange point L5 for space weather measurements and real-time observations and alerts. The HEPS instrument with its six detector subsystems will enable the detecting of electrons, protons, and heavy ions at high flux conditions during Solar Energetic Particle Events. The electron and proton detection systems rely on standard telescope techniques covering energy ranges from 100 keV to 15 MeV and 3 MeV to 1 GeV respectively. Two sets of telescopes will be installed facing opposite directions along the Parker spiral. Additional detector with a wide angular range will enable measurements of angular distributions of particles traveling towards the satellite from the Sun. The HEPS heavy-ion telescope HIT represents a new design utilizing a set of scintillators and SiPM light converters. HIT electronics is equipped with a dedicated radiation-tolerant ASIC optimized for low power use and fast signal detections. The first model of HIT was developed and verified for spectroscopic measurements and ion identification. We report on test measurements as well as Monte Carlo simulations of the whole instrument. Results will be discussed and implications on the final design of the instrument provided.&lt;/p&gt;

Why switchbacks may be related to solar granulation

&lt;p&gt;Parker Solar Probe data below 0.3 AU have revealed a near-Sun magnetic field dominated by Alfv&amp;#233;nic structures that display back and forth reversals of the radial magnetic field. They are called magnetic switchbacks, they display no electron strahl variation consistent with magnetic field foldings within the same magnetic sector, and are associated with velocity spikes during an otherwise calmer background. They are thought to originate either at the photosphere through magnetic reconnection processes, or higher up in the corona and solar wind through turbulent processes.&lt;/p&gt;&lt;p&gt;In this work, we analyze the spatial and temporal characteristic scales of these magnetic switchbacks. We define switchbacks as a deviation from the parker spiral direction and detect them automatically through perihelia encounters 1 to 6. We analyze the solid angle between the magnetic field and the parker spiral both over time and space. We perform a fast Fourier transformation to the obtained angle and find a periodical spatial variation with scales consistent with solar granulation. This suggests that switchbacks form near the photosphere and may be caused, or at least modulated, by solar convection.&lt;/p&gt;

Asymmetries in the Earth's dayside magnetosheath: results from global hybrid-Vlasov simulations

Bounded by the bow shock and the magnetopause, the magnetosheath forms the interface between solar wind and magnetospheric plasmas and regulates solar wind–magnetosphere coupling. Previous works have revealed pronounced dawn–dusk asymmetries in the magnetosheath properties. The dependence of these asymmetries on the upstream parameters remains however largely unknown. One of the main sources of these asymmetries is the bow shock configuration, which is typically quasi-parallel on the dawn side and quasi-perpendicular on the dusk side of the terrestrial magnetosheath because of the Parker spiral orientation of the interplanetary magnetic field (IMF) at Earth. Most of these previous studies rely on collections of spacecraft measurements associated with a wide range of upstream conditions which are processed in order to obtain average values of the magnetosheath parameters. In this work, we use a different approach and quantify the magnetosheath asymmetries in global hybrid-Vlasov simulations performed with the Vlasiator model. We concentrate on three parameters: the magnetic field strength, the plasma density, and the flow velocity. We find that the Vlasiator model reproduces the polarity of the asymmetries accurately but that their level tends to be higher than in spacecraft measurements, probably because the magnetosheath parameters are obtained from a single set of upstream conditions in the simulation, making the asymmetries more prominent. A set of three runs with different upstream conditions allows us to investigate for the first time how the asymmetries change when the angle between the IMF and the Sun–Earth line is reduced and when the Alfvén Mach number decreases. We find that a more radial IMF results in a stronger magnetic field asymmetry and a larger variability of the magnetosheath density. In contrast, a lower Alfvén Mach number leads to a reduced magnetic field asymmetry and a decrease in the variability of the magnetosheath density, the latter likely due to weaker foreshock processes. Our results highlight the strong impact of the quasi-parallel shock and its associated foreshock on global magnetosheath properties, in particular on the magnetosheath density, which is extremely sensitive to transient quasi-parallel shock processes, even with the perfectly steady upstream conditions in our simulations. This could explain the large variability of the density asymmetry levels obtained from spacecraft measurements in previous studies.

Numerical simulation and data analysis of the 23 July 2012 SEP event observed by ACE, STEREO-A, and STEREO-B

An extremely powerful, superfast interplanetary coronal mass ejection (ICME) from the Sun on 23 July 2012 was detected by widely separated multiple spacecraft, namely STEREO-A, STEREO-B, and ACE, together with the ICME-driven shock and associated solar energetic particles (SEPs). We use the Parker spiral magnetic field model to analyze the relationship between the propagation of the shock and the SEP flux. Furthermore, we simulate the SEP event by numerically solving the three-dimensional focused transport equation of SEPs considering the shock as the moving source of energetic particles. To deal with the fact that protons and electrons behave completely differently for both parallel and perpendicular diffusion, for simplicity, we use the same diffusion model format for the simulations of protons and electrons but with different parameters. We find that the analysis can qualitatively explain the important features of the SEP flux observed by the multiple spacecraft simultaneously. In addition, the numerical results for both energetic protons and electrons approximately agree with multi-spacecraft observations.