Roles of electrons and ions in formation of the current in mirror mode structures in the terrestrial plasma sheet: MMS observations

Abstract. Currents are believed to exist in mirror mode structures and to be self-consistent with the magnetic field depression. Here, we investigate a train of mirror mode structures in the terrestrial plasma sheet on 11 August 2017 measured by the Magnetospheric Multiscale mission data. We find that a bipolar current exists in the cross-section of two hole-like mirror mode structures, referred to as magnetic dips. The bipolar current in the magnetic dip with a size of ~ 3 ρi (the ion gyro radius) is mainly contributed by an electron bipolar velocity, which is mainly formed by the magnetic gradient-curvature drift. For another magnetic dip with a size of ~ 6.67 ρi, the bipolar current is mainly caused by an ion bipolar velocity, which can be explained by the ion diamagnetic drift. These observations suggest that the electrons and ions play different roles in the formation of currents in magnetic dips with different sizes.

Download Full-text

Roles of electrons and ions in formation of the current in mirror mode structures in the terrestrial plasma sheet: MMS observations

10.5194/egusphere-egu2020-4003 ◽

2020 ◽

Author(s):

Guoqiang Wang ◽

Tielong Zhang ◽

Mingyu Wu ◽

Daniel Schmid ◽

Yufei Hao ◽

...

Keyword(s):

Plasma Sheet ◽

Electron Velocity ◽

Collective Behaviors ◽

Ion Drift ◽

Magnetospheric Multiscale ◽

Electrons And Ions ◽

Current Densities ◽

Mirror Mode ◽

Magnetospheric Multiscale Mission ◽

The Magnetic Field

Currents are believed to exist in mirror mode structures and to be self-consistent with the magnetic field depression. Here, we investigate a train of mirror mode structures in the terrestrial plasma sheet on 11 August 2017 measured by the Magnetospheric Multiscale mission. We find that bipolar current densities exist in the cross-section of two hole-like mirror mode structures, referred to as magnetic dips. The bipolar current in the magnetic dip with a size of ~2.2 &#961;i (the ion gyro radius) is mainly contributed by variations of the electron velocity, which is mainly formed by the magnetic gradient-curvature drift. For another magnetic dip with a size of ~6.6 &#961;i, the bipolar current is mainly caused by an ion bipolar velocity, which can be explained by the collective behaviors of the ion drift motions. These observations suggest that the electrons and ions play different roles in the formation of currents in magnetic dips with different sizes.

Download Full-text

Roles of electrons and ions in formation of the current in mirror-mode structures in the terrestrial plasma sheet: Magnetospheric Multiscale observations

Annales Geophysicae ◽

10.5194/angeo-38-309-2020 ◽

2020 ◽

Vol 38 (2) ◽

pp. 309-318 ◽

Cited By ~ 3

Author(s):

Guoqiang Wang ◽

Tielong Zhang ◽

Mingyu Wu ◽

Daniel Schmid ◽

Yufei Hao ◽

...

Keyword(s):

Current Density ◽

Plasma Sheet ◽

Electron Velocity ◽

Collective Behaviors ◽

Ion Drift ◽

Magnetospheric Multiscale ◽

Electrons And Ions ◽

Current Densities ◽

Mirror Mode ◽

Magnetospheric Multiscale Mission

Abstract. Mirror-mode structures widely exist in various space plasma environments. Here, we investigate a train of mirror-mode structures in the terrestrial plasma sheet on 11 August 2017 based on the Magnetospheric Multiscale mission. We find that bipolar current densities exist in the cross section of two hole-like mirror-mode structures, referred to as magnetic dips. The bipolar current density in the magnetic dip with a size of ∼2.2 ρi (the ion gyro radius) is mainly contributed by variations of the electron velocity, which is mainly formed by the magnetic gradient–curvature drift. For another magnetic dip with a size of ∼6.6 ρi, the bipolar current density is mainly caused by an ion bipolar velocity, which can be explained by the collective behaviors of the ion drift motions. The current density inside the mirror dip contributes to the maintenance of the hole-like structure's stable. Our observations suggest that the electrons and ions play different roles in the formation of currents in magnetic dips with different sizes.

Download Full-text

The Properties of Lion Roars and Electron Dynamics in Mirror Mode Waves Observed by the Magnetospheric MultiScale Mission

Journal of Geophysical Research Space Physics ◽

10.1002/2017ja024551 ◽

2018 ◽

Vol 123 (1) ◽

pp. 93-103 ◽

Cited By ~ 7

Author(s):

H. Breuillard ◽

O. Le Contel ◽

T. Chust ◽

M. Berthomier ◽

A. Retino ◽

...

Keyword(s):

Electron Dynamics ◽

Magnetospheric Multiscale ◽

Mirror Mode ◽

Magnetospheric Multiscale Mission

Download Full-text

Observational Evidence of Magnetic Reconnection in the Terrestrial Foreshock Region

The Astrophysical Journal ◽

10.3847/1538-4357/ac2500 ◽

2021 ◽

Vol 922 (1) ◽

pp. 56

Author(s):

K. Jiang ◽

S. Y. Huang ◽

H. S. Fu ◽

Z. G. Yuan ◽

X. H. Deng ◽

...

Keyword(s):

Magnetic Reconnection ◽

Direct Evidence ◽

Bow Shock ◽

Shock Acceleration ◽

Diffusive Shock Acceleration ◽

Strong Energy ◽

Magnetospheric Multiscale ◽

Electron Distributions ◽

Magnetospheric Multiscale Mission ◽

The Magnetic Field

Abstract Electron heating/acceleration in the foreshock, by which electrons may be energized beyond thermal energies prior to encountering the bow shock, is very important for the bow shock dynamics. And then these electrons would be more easily injected into a process like diffusive shock acceleration. Many mechanisms have been proposed to explain electrons heating/acceleration in the foreshock. Magnetic reconnection is one possible candidate. Taking advantage of the Magnetospheric Multiscale mission, we present two magnetic reconnection events in the dawnside and duskside ion foreshock region, respectively. Super-Alfvénic electron outflow, demagnetization of the electrons and the ions, and crescent electron distributions in the plane perpendicular to the magnetic field are observed in the sub-ion-scale current sheets. Moreover, strong energy conversion from the fields to the plasmas and significant electron temperature enhancement are observed. Our observations provide direct evidence that magnetic reconnection could occur in the foreshock region and heat/accelerate the electrons therein.

Download Full-text

Statistical study of linear magnetic hole structures near Earth

Annales Geophysicae ◽

10.5194/angeo-39-239-2021 ◽

2021 ◽

Vol 39 (1) ◽

pp. 239-253

Author(s):

Martin Volwerk ◽

David Mautner ◽

Cyril Simon Wedlund ◽

Charlotte Goetz ◽

Ferdinand Plaschke ◽

...

Keyword(s):

Magnetic Field ◽

Occurrence Rate ◽

Ion Temperature ◽

Pressure Balance ◽

Magnetospheric Multiscale ◽

Background Magnetic Field ◽

Earth’S Bow Shock ◽

Mirror Mode ◽

Magnetospheric Multiscale Mission ◽

Upstream Solar Wind

Abstract. The Magnetospheric Multiscale mission (MMS1) data for 8 months in the winter periods of 2017–2018 and 2018–2019, when MMS had its apogee in the upstream solar wind of the Earth's bow shock, are used to study linear magnetic holes (LMHs). These LMHs are characterized by a magnetic depression of more than 50 % and a rotation of the background magnetic field of less then 10∘. A total of 406 LMHs are found and, based on their magnetoplasma characteristics, are split into three categories: cold (increase in density, little change in ion temperature), hot (increase in ion temperature, decrease in density) and sign change (at least one magnetic field component changes sign). The occurrence rate of LMHs is 2.3 per day. All LMHs are basically in pressure balance with the ambient plasma. Most of the linear magnetic holes are found in ambient plasmas that are stable against the mirror-mode generation, but only half of the holes are mirror-mode-stable inside.

Download Full-text

In situ irradiation effects studies in medium- and high-voltage TEM

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100137549 ◽

1995 ◽

Vol 53 ◽

pp. 234-235

Author(s):

Charles W. Allen

Keyword(s):

Cross Section ◽

Particle Flux ◽

Threshold Value ◽

High Energy ◽

Irradiation Damage ◽

Defect Complexes ◽

Lattice Position ◽

Electrons And Ions ◽

The Masses

With respect to structural consequences within a material, energetic electrons, above a threshold value of energy characteristic of a particular material, produce vacancy-interstial pairs (Frenkel pairs) by displacement of individual atoms, as illustrated for several materials in Table 1. Ion projectiles produce cascades of Frenkel pairs. Such displacement cascades result from high energy primary knock-on atoms which produce many secondary defects. These defects rearrange to form a variety of defect complexes on the time scale of tens of picoseconds following the primary displacement. A convenient measure of the extent of irradiation damage, both for electrons and ions, is the number of displacements per atom (dpa). 1 dpa means, on average, each atom in the irradiated region of material has been displaced once from its original lattice position. Displacement rate (dpa/s) is proportional to particle flux (cm-2s-1), the proportionality factor being the “displacement cross-section” σD (cm2). The cross-section σD depends mainly on the masses of target and projectile and on the kinetic energy of the projectile particle.

Download Full-text

Simulating Solar Global Magnetism in 3-D

Proceedings of the International Astronomical Union ◽

10.1017/s1743921314004736 ◽

2012 ◽

Vol 10 (H16) ◽

pp. 101-103

Author(s):

A. S. Brun ◽

A. Strugarek

Keyword(s):

Magnetic Field ◽

Recent Progress ◽

Convection Zone ◽

Thermal Structure ◽

Solar Convection ◽

Self Consistent ◽

The Mean ◽

The Magnetic Field

AbstractWe briefly present recent progress using the ASH code to model in 3-D the solar convection, dynamo and its coupling to the deep radiative interior. We show how the presence of a self-consistent tachocline influences greatly the organization of the magnetic field and modifies the thermal structure of the convection zone leading to realistic profiles of the mean flows as deduced by helioseismology.

Download Full-text