Fast Plasma Flows Downstream of the Bow Shock Using MMS: Correlations and Generation Mechanisms

<p>Fast plasma flows (magnetosheath jets) are localized and transient dynamic pressure enhancements found downstream of the Earth’s bow shock, in the magnetosheath region. They can be attributed to density and/or density enhancements and they are an energetic manifestation of the solar wind-magnetosphere coupling. They have been associated to several phenomena such as magnetopause reconnection, direct magnetosphere plasma inflow and the energization of the outer radiation belt electrons.</p><p>In this work, we are investigating the properties of a dataset of 9196 jets found by Magnetospheric Multiscale (MMS) from 09/2015 to 09/2020. These jets are classified into different classes based on their associated bow shock configuration. From the full dataset, about 300 jets are distinguished by being in very close proximity to a bow shock transition.</p><p>This subset of jet is then carefully pre-processed and statistically analyzed, providing information regarding the likelihood of existent (bow shock ripples, SLAMS penetration) and newly proposed (magnetic reconnection, magnetic islands) generation mechanisms for these jets. The initial results of these events support the pre-existing generation mechanism while giving indications to other possible effects that may take place.</p>

Electromagnetic electron hole generation: theory and PIC simulations

<div> <div> <div> <p>Recent MMS observations (<em>e.g.</em> [Holmes et al, 2018, Steinvall et al., 2019]) exploring various regions of the magnetosphere have found solitary potential structures call Electron phase-space Hole (EH). These structures have kinetic scale (dozens of Debye lengths) and persist during long time (dozens of plasma frequency periods). EH are characterized by a bipolar electric field parallel to ambient magnetic field and fastly propagate along this latter (a few tenths of speed light). We have created a 3D Bernstein-Greene-Kruskal (BGK) model (as [Chen et al, 2004]) adapted to various magnetospheric ambient magnetic fields. BGK model results depend on choice of potential shape and passing distribution function at infinity (before EH potential interaction).</p> <p>2D-3V Particle-In-Cell simulations have been developed with the fully kinetic code Smilei [Derouillat et al, 2017], using real magnetosphere plasma parameters. Solitary waves in the magnetotail are three-dimensional potentials which can be generated through nonlinear evolution of an electron beam instability (or bump on tail). The simulated EH are comparable to the EH observed in the magnetosphere with the same parameters.</p> <p>We have also investigated the EH formation with density inhomogeneities using a BGK stability model we have developed. Indeed, density inhomogeneities exist notably in interplanetary plasmas. As a result taking into account the background density inhomogeneities, significantly alters the stability criteria. We have performed 2D-3V PIC simulations with realistic inhomogeneous density background (smaller than 10% of mean density) to understand such a type of EH formation.</p> <p><strong>References:</strong></p> <ul><li>Holmes et al., J. Geophys. Res. Space Phys. 123, 9963, 2018</li> <li>Steinvall et al., Phys. Rev. Lett. 123, 255101, 2019</li> <li>Chen et al., Phys. Rev. E 69, 055401, 2004</li> <li>Derouillat et al., Comput. Phys. Commun. 222, 351, 2017</li> </ul><div> <div> <div> <div> <div> <div> <div> <div> <div> </div> </div> </div> </div> </div> </div> </div> </div> </div> </div> </div> </div>

Multiple transpolar auroral arcs reveal new insight about coupling processes in the Earth’s magnetotail

<p><strong>A distinct class of aurora, called transpolar auroral arc (TPA) (in some cases called “theta” aurora), appears in the extremely high latitude ionosphere of the Earth when interplanetary magnetic field (IMF) is northward. The formation and evolution of TPA offers clues about processes transferring energy and momentum from the solar wind to the magnetosphere and ionosphere during a northward IMF. However, their formation mechanisms remain poorly understood and controversial. We report a new mechanism identified from multiple-instrument observations of unusually bright, multiple TPAs and simulations from a high-resolution three-dimensional global MagnetoHydroDynamics (MHD) model. The observations and simulations show an excellent agreement and reveal that these multiple TPAs are generated by precipitating energetic magnetospheric electrons within field-aligned current (FAC) sheets. These FAC sheets are generated by multiple flow shear sheets in both the magnetospheric boundary produced by Kelvin-Helmholtz instability between super-sonic solar wind flow and magnetosphere plasma, and the plasma sheet generated by the interactions between the enhanced earthward plasma flows from the distant tail (less than -100 R<sub>E</sub>) and the enhanced tailward flows from the near tail (about -20 R<sub>E</sub>). The study offers a new insight into the complex solar wind-magnetosphere-ionosphere coupling processes under a northward IMF condition, and it challenges existing paradigms of the dynamics of the Earth’s magnetosphere.</strong></p>

Monitoring of Ionosphere and Magnetosphere Plasma and High Energy Charge Particle Fluxes in Multi-satellite Measurements in Wide Range of Altitudes

A system for monitoring the radiation parameters of near-Earth space is described. This system is based on the multi-satellite measurements made on spacecraft Meteor, Electro, Arktika launched into orbits with a wide range of altitudes. The main instrument for space radiation monitoring is spectrometer of electrons and protons SKIF. Such instruments operate in all spacecraft of mentioned above series. The results of observations of different events connected with solar and geomagnetic activity in 2017 and 2021 years are presented and discussed.

Multiple transpolar auroral arcs reveal insight about coupling processes in the Earth’s magnetotail

A distinct class of aurora, called transpolar auroral arc (TPA) (in some cases called “theta” aurora), appears in the extremely high-latitude ionosphere of the Earth when interplanetary magnetic field (IMF) is northward. The formation and evolution of TPA offers clues about processes transferring energy and momentum from the solar wind to the magnetosphere and ionosphere during a northward IMF. However, their formation mechanisms remain poorly understood and controversial. We report a mechanism identified from multiple-instrument observations of unusually bright, multiple TPAs and simulations from a high-resolution three-dimensional (3D) global MagnetoHydroDynamics (MHD) model. The observations and simulations show an excellent agreement and reveal that these multiple TPAs are generated by precipitating energetic magnetospheric electrons within field-aligned current (FAC) sheets. These FAC sheets are generated by multiple-flow shear sheets in both the magnetospheric boundary produced by Kelvin–Helmholtz instability between supersonic solar wind flow and magnetosphere plasma, and the plasma sheet generated by the interactions between the enhanced earthward plasma flows from the distant tail (less than −100 RE) and the enhanced tailward flows from the near tail (about −20 RE). The study offers insight into the complex solar wind-magnetosphere-ionosphere coupling processes under a northward IMF condition, and it challenges existing paradigms of the dynamics of the Earth’s magnetosphere.

Differences in inner magnetospheric wave activity, outer Van Allen belt electron dynamics and atmospheric precipitation during CME sheaths and flux ropes

<p>Coronal mass ejection (CME) driven sheath regions are one of the key structures driving strong magnetospheric disturbances, in particular at high latitudes. Sheaths are turbulent and compressed regions that exhibit large-amplitude magnetic field variations and high and variable dynamic pressure. They thus put the magnetosphere under particularly strong solar wind forcing. We show here the results of our recent studies that have investigated the response of inner magnetosphere plasma waves, energy and L-shell resolved outer belt electron variations and precipitation of high-energy electrons to the upper atmosphere during sheath regions. The data come primarily from Van Allen Probes and ground-based riometers. Our results reveal that sheaths drive intense “wave storms” in the inner magnetosphere (ULF, EMIC, chorus, hiss). Lower-energy electron fluxes (source and seed populations) are typically enhanced due to frequent and strong substorms injecting fresh electrons, while relativistic electrons are effectively depleted at wide L-ranges due to scattering by wave-particle interactions and magnetopause shadowing playing in concert. We found that even non-geoeffective sheaths can drive significant wave activity and dramatic changes in the outer belt electron fluxes. The “complex ejecta”, however, that consist of multiple sheaths and distorted CME ejecta can lead to sustained chorus and ULF waves, and as a consequence, effective electron acceleration to high energies. We also report some distinct characteristics in the intensity and Magnetic Local Time distribution of precipitation during sheaths when compared to other large-scale solar wind driver structures. The different precipitation responses likely stem from driver specific characteristics in their ability to excite inner magnetosphere plasma waves.</p><p> </p>

Analysis of Whistlers Registration Data Obtained by Ssan System on Subauroral Station in Yakutsk

Since from November 2017 to August 2018, synchronous registration of atmospherics and whistlers at the radiophysical station “Oibenkyol”, began in the operational mode within the network SSAN/VLF (“Sensor signal analysis network/Very low frequency”). The classification and the characteristics of the registered whistlers are carried out. The correlation analysis of the number of the whistlers registered by the SSAN/VLF with the number of lightning registered by the WWLLN is used to determine the location of lightning sources of whistlers in the opposite hemisphere in the magnetoconjugate point at South of Australia. Thus, the SSAN/VLF make possible the distance monitoring of the dynamics of the various geophysical processes changes. The large number of registered nose whistlers allow performing the statistical analysis of processes occurring in the magnetosphere’ plasma.