![]() ![]() While wave particle interactions and subsequent wave heating contribute to incorporating the heavy planetary ions into the solar wind flow, the solar wind momentum is not fully deflected around the obstacle and is delivered into the collisional atmosphere. The (Formula presented.) (convective electric field or “ion pickup”) force is weak and highly variable during radial IMF. ![]() The planetary ions above the magnetic barrier are exposed to solar wind flow and subsequent mass-loading. The MAVEN observations are consistent with either an ionopause-like boundary or diamagnetic cavity forming beneath the barrier, as a consequence of the dense cold ionosphere and the absence of significant crustal magnetic fields at this periapsis location. In particular, solar wind protons and alphas are observed to directly penetrate down to periapsis altitudes, while the magnetic barrier forms deep within the dayside ionosphere. We use in-situ plasma measurements made by the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission to identify several prominent features that arise when the IMF is aligned approximately parallel or antiparallel to solar wind flow (conditions known as “radial IMF”). This interaction is highly dependent on the upstream Interplanetary Magnetic Field (IMF) orientation. The solar wind interaction with Mars controls the transfer of energy and momentum from the solar wind into the magnetosphere, ionosphere and atmosphere, driving structure, and dynamics within each. Halekas J, Schwartz SJ, Mazelle C, Chaffin M, Mitchell D, Espley J, Ramstad R, Dong Y, Curry S et al., 2022, A MAVEN Case Study of Radial IMF at Mars: Impacts on the Dayside Ionosphere, Journal of Geophysical Research: Space Physics, Vol: 127, ISSN: 2169-9380 Both populations contribute to the seed population of the shock accelerated ions known as the diffuse ion population. The bow shock transition from the downstream region into the upstream solar wind shows the occasional presence of reflected ions and a population of 90° pitch angle ions in the shock ramp consistent with shock drift accelerated ions. This study discusses distribution functions of protons and alpha particles observed by the HPCA and FPI instruments onboard the MMS satellites during a crossing of the quasi-parallel bow shock. ![]() One of the fundamental outstanding questions of ion acceleration at shocks for which the upstream magnetic field is nearly aligned with the shock normal (i.e., quasi-parallel shocks) is which portion of the incoming solar wind ion distribution ultimately becomes the seed population that is subsequently accelerated to high energies. Shock fronts are an important acceleration site for ions and electrons in collisionless plasmas, and are responsible for much of the particle acceleration in solar, planetary, and astrophysical regions. The terrestrial bow shock is the boundary that slows and diverts the supermagnetosonic solar wind around the terrestrial magnetosphere by converting the kinetic energy of the solar wind into thermal and magnetic energy. ![]() Kucharek H, Burch JL, Ergun RE, Petrinec SM, Madanian H et al., 2023, Ion Acceleration at the Quasi-Parallel Shock: The Source Distributions of the Diffuse Ions, Journal of Geophysical Research: Space Physics, Vol: 128, ISSN: 2169-9380 Furthermore, we discuss how the gradient in velocity-space sheds light on plasma energy conversion mechanisms and wave-particle interactions that occur in fundamental physical processes such as magnetic reconnection and turbulence. We demonstrate how to use single spacecraft measurements to improve the resolution of the electron pressure gradient that supports nonideal parallel electric fields, and we develop a model to intuit the types of kinetic velocity-space signatures that are observed in the Vlasov equation terms. Equipped with these unprecedented spatiotemporal measurements offered by the MMS tetrahedron, we compute each term of the electron Vlasov equation that governs the evolution of collisionless plasmas found throughout the universe. Temporal, spatial, and velocity-space variations of electron phase space density are measured observationally and compared for the first time using the four magnetospheric multiscale (MMS) spacecraft at Earth's magnetopause. Bessho N, Sharma AS, Dorelli JC, Uritsky V, Schwartz SJ, Cassak PA, Denton RE, Chen LJ, Gurram H, Ng J, Burch J, Webster J, Torbert R, Paterson WR, Schiff C, Viñas AF, Avanov LA, Stawarz J, Li TC, Liu YH, Argall MR, Afshari A, Payne DS, Farrugia CJ, Verniero J, Wilder F, Genestreti K, da Silva DE et al., 2023, Temporal, Spatial, and Velocity-Space Variations of Electron Phase Space Density Measurements at the Magnetopause, Journal of Geophysical Research: Space Physics, Vol: 128, ISSN: 2169-9380 ![]()
0 Comments
Leave a Reply. |