Ionospheric ions in the magnetosphere: Important at large and small scales

2020 ◽  
Author(s):  
Mats André ◽  
Sergio Toledo-Redondo ◽  
Andrew W Yau
Keyword(s):  
Electric Field ◽  
Magnetic Reconnection ◽  
Energy Transport ◽  
Small Scale ◽  
Diffusion Region ◽  
Positive Ions ◽  
Small Scales ◽  
Outflow Rate ◽  
Long Time ◽  
Cold Ions

<p><span lang="EN-US">Cold (eV) ions of ionospheric origin dominate the number density of most of the volume of the magnetosphere during most of the time. </span><span lang="EN-US">Supersonic flows of cold positive ions are common and can cause a negatively charged wake behind a positively charged spacecraft. The associated induced electric field can be observed and can be used to study the cold ions. We present observations from the Cluster and MMS spacecraft showing how a charged satellite, and also individual charged wire booms of  an electric field instrument, can be used to investigate cold ion populations. </span><span lang="EN-US">Ionospheric ions affect large scales, including the Alfvén velocity and </span><span lang="EN-US"> </span><span lang="EN-US">thus energy transport with waves and the magnetic reconnection rate. These ions also affect small-scale kinetic plasma physics, including the Hall physics and wave instabilities associated with magnetic reconnection. Concerning large scales, we summarize observations from several spacecraft and show that a typical total outflow rate of ionospheric ions is 10<sup>26</sup> ions/s and that many of these ions stay cold also after a long time in the magnetosphere.  Concerning small scales, we show examples of how cold ions modify the Hall physics of thin current sheets, including magnetic reconnection separatrices. On small kinetic scales the cold ions introduce a new length-scale, a gyro radius between the gyro radii of hot (keV) ions and electrons. </span><span lang="EN-US">The Hall currents carried by electrons can be partially cancelled by the cold ions when electrons and the magnetized cold ions ExB drift together. Also, close to a reconnection X-line an additional diffusion region can be formed (regions associated with hot and cold ions, and with electrons, total of three).</span></p>

scholarly journals ViDA: a Vlasov–DArwin solver for plasma physics at electron scales

2019 ◽  
Vol 85 (5) ◽  
Author(s):  
Oreste Pezzi ◽  
Giulia Cozzani ◽  
Francesco Califano ◽  
Francesco Valentini ◽  
Massimiliano Guarrasi ◽  
...  
Keyword(s):  
Plasma Physics ◽  
Magnetic Reconnection ◽  
Spatial Scales ◽  
Collisionless Plasma ◽  
Low Noise ◽  
Numerical Code ◽  
Small Scale ◽  
Diffusion Region ◽  
Plasma Dynamics ◽  
Algorithm Efficiency

We present a Vlasov–DArwin numerical code (ViDA) specifically designed to address plasma physics problems, where small-scale high accuracy is requested even during the nonlinear regime to guarantee a clean description of the plasma dynamics at fine spatial scales. The algorithm provides a low-noise description of proton and electron kinetic dynamics, by splitting in time the multi-advection Vlasov equation in phase space. Maxwell equations for the electric and magnetic fields are reorganized according to the Darwin approximation to remove light waves. Several numerical tests show that ViDA successfully reproduces the propagation of linear and nonlinear waves and captures the physics of magnetic reconnection. We also discuss preliminary tests of the parallelization algorithm efficiency, performed at CINECA on the Marconi-KNL cluster. ViDA will allow the running of Eulerian simulations of a non-relativistic fully kinetic collisionless plasma and it is expected to provide relevant insights into important problems of plasma astrophysics such as, for instance, the development of the turbulent cascade at electron scales and the structure and dynamics of electron-scale magnetic reconnection, such as the electron diffusion region.

scholarly journals Spatial dimensions of the electron diffusion region in anti-parallel magnetic reconnection

2016 ◽  
Vol 34 (3) ◽  
pp. 357-367 ◽  
Author(s):  
Takuma Nakamura ◽  
Rumi Nakamura ◽  
Hiroshi Haseagwa
Keyword(s):  
Electric Field ◽  
Magnetic Reconnection ◽  
Real Space ◽  
Diffusion Region ◽  
Electron Mass ◽  
Plasma Parameters ◽  
Electron Diffusion ◽  
Background Density ◽  
Spatial Dimensions ◽  
Inner Region

Abstract. Spatial dimensions of the detailed structures of the electron diffusion region in anti-parallel magnetic reconnection were analyzed based on two-dimensional fully kinetic particle-in-cell simulations. The electron diffusion region in this study is defined as the region where the positive reconnection electric field is sustained by the electron inertial and non-gyrotropic pressure components. Past kinetic studies demonstrated that the dimensions of the whole electron diffusion region and the inner non-gyrotropic region are scaled by the electron inertial length de and the width of the electron meandering motion, respectively. In this study, we successfully obtained more precise scalings of the dimensions of these two regions than the previous studies by performing simulations with sufficiently small grid spacing (1∕16–1∕8 de) and a sufficient number of particles (800 particles cell−1 on average) under different conditions changing the ion-to-electron mass ratio, the background density and the electron βe (temperature). The obtained scalings are adequately supported by some theories considering spatial variations of field and plasma parameters within the diffusion region. In the reconnection inflow direction, the dimensions of both regions are proportional to de based on the background density. Both dimensions also depend on βe based on the background values, but the dependence in the inner region ( ∼ 0.375th power) is larger than the whole region (0.125th power) reflecting the orbits of meandering and accelerated electrons within the inner region. In the outflow direction, almost only the non-gyrotropic component sustains the positive reconnection electric field. The dimension of this single-scale diffusion region is proportional to the ion-electron hybrid inertial length (dide)1∕2 based on the background density and weakly depends on the background βe with the 0.25th power. These firm scalings allow us to predict observable dimensions in real space which are indeed in reasonable agreement with past in situ spacecraft observations in the Earth's magnetotail and have important implications for future observations with higher resolutions such as the NASA Magnetospheric Multiscale (MMS) mission.

How does dissipation work in the electron diffusion region of asymmetric magnetic reconnection

2020 ◽  
Author(s):  
Michael Hesse ◽  
Cecilia Norgren ◽  
Paul Tenfjord ◽  
James Burch ◽  
Yi-Hsin Liu ◽  
...  
Keyword(s):  
Electric Field ◽  
Magnetic Reconnection ◽  
Stagnation Point ◽  
Electric Fields ◽  
Current Density ◽  
Electron Flow ◽  
Diffusion Region ◽  
Density Maximum ◽  
Density Peak ◽  
Electron Diffusion

<p>At some level, magnetic reconnection functions by means of a balance between current dissipation, and current maintenance due to the reconnection electric field. While this dissipation is well understood process in symmetric magnetic reconnection, the way nonideal electric fields interact with the current density in asymmetric reconnection is still unclear. In symmetric reconnection, the current density maximum, the X point location, and the nonideal electric field determined by the divergence of the electron pressure tensor usually coincide. In asymmetric reconnection, however, the electric field at the X point can be partly provided by bulk inertia terms, implying that the X point cannot be the dominant location of dissipation. On the other hand, we know that the nongyrotropic pressure-based electric field must dominate at the stagnation point of the in-plane electron flow, and that electron distributions here feature crescents. The further fact that the current density peak is shifted off the position of the X point indicates that there may be a relation between this current density enhancement, the location of the stagnation point, and the electron nongyrotropies. In this presentation we report on further progress investigating the physics of the electron diffusion region in asymmetric reconnection with a focus on how to explain the dissipation operating under these conditions. </p>

scholarly journals Quantification of Cold-Ion Beams in a Magnetic Reconnection Jet

2021 ◽  
Vol 8 ◽  
Author(s):  
Yu-Xuan Li ◽  
Wen-Ya Li ◽  
Bin-Bin Tang ◽  
C. Norgren ◽  
Jian-Sen He ◽  
...  
Keyword(s):  
Magnetic Reconnection ◽  
Plasma Sheet ◽  
Ion Beams ◽  
Distribution Functions ◽  
Diffusion Region ◽  
Hot Plasma ◽  
Order Of Magnitude ◽  
Velocity Distribution Functions ◽  
Cold Ions ◽  
Field Lines

Cold (few eV) ions of ionospheric origin are widely observed in the lobe region of Earth’s magnetotail and can enter the ion jet region after magnetic reconnection is triggered in the magnetotail. Here, we investigate a magnetotail crossing with cold ions in one tailward and two earthward ion jets observed by the Magnetospheric Multiscale (MMS) constellation of spacecraft. Cold ions co-existing with hot plasma-sheet ions form types of ion velocity distribution functions (VDFs) in the three jets. In one earthward jet, MMS observe cold-ion beams with large velocities parallel to the magnetic fields, and we perform quantitative analysis on the ion VDFs in this jet. The cold ions, together with the hot ions, are reconnection outflow ions and are a minor population in terms of number density inside this jet. The average bulk speed of the cold-ion beams is approximately 38% larger than that of the hot plasma-sheet ions. The cold-ion beams inside the explored jet are about one order of magnitude colder than the hot plasma-sheet ions. These cold-ion beams could be accelerated by the Hall electric field in the cold ion diffusion region and the shrinking magnetic field lines through the Fermi effect.

Self-reinforcing process of the reconnection electric field in the electron diffusion region and onset of collisionless magnetic reconnection

2013 ◽  
Vol 55 (8) ◽  
pp. 085019 ◽  
Author(s):  
Quanming Lu ◽  
San Lu ◽  
Can Huang ◽  
Mingyu Wu ◽  
Shui Wang
Keyword(s):  
Electric Field ◽  
Magnetic Reconnection ◽  
Diffusion Region ◽  
Electron Diffusion

Acceleration of cold ions at separatrices of symmetric collisionless magnetic reconnection

2020 ◽  
Author(s):  
Evgeny Gordeev ◽  
Andrey Divin ◽  
Ivan Zaitsev ◽  
Vladimir Semenov ◽  
Yuri Khotyaintsev ◽  
...  
Keyword(s):  
Electric Field ◽  
Magnetic Reconnection ◽  
Electric Fields ◽  
Electrostatic Potential ◽  
Potential Drop ◽  
Local Electron ◽  
One Dimensional ◽  
Particle In Cell ◽  
Background Population ◽  
Cold Ions

<p>Separatrices of magnetic reconnection host intense perpendicular Hall electric fields produced by decoupling of ion and electron components and associated with the in-plane electrostatic potential drop between inflow and outflow regions. The width of these structures is several local electron inertial lengths, which is small enough to demagnetize ions as they cross the layer. We investigate temperature dependence of ion acceleration at separatrices by means of 2D Particle-in-Cell (PIC) simulations of magnetic reconnection with only cold or hot ion background population. The separatrix Hall electric field is balanced by the inertia term in cold background simulations, the effect indicative of the quasi-steady local perpendicular acceleration. The electric field introduces a cross-field beam of unmagnetized particles which makes the temperature strongly non-gyrotropic and susceptible to sub-ion scale instabilities. This acceleration mechanism nearly vanishes for hot ion background simulations. Particle-in-cell simulations are complemented by one-dimensional test particle calculations, which show that the hot ion particles experience scattering in energies after crossing the accelerating layer, whereas cold ions are uniformly energized up to the energies comparable to the electrostatic potential drop between the inflow and outflow regions.</p>

Observations of an Electron-only Magnetic Reconnection within a macroscopic Flux Rope in the Magnetotail

2020 ◽  
Author(s):  
Hengyan Man ◽  
Meng Zhou ◽  
Yongyuan Yi ◽  
Zhihong Zhong ◽  
Xiaohua Deng
Keyword(s):  
Electric Field ◽  
Magnetic Reconnection ◽  
Current Sheet ◽  
Large Scale ◽  
Energy Transport ◽  
Flux Rope ◽  
Space Plasmas ◽  
Positive Energy ◽  
Guide Field ◽  
Flux Ropes

<p>It is widely accepted that flux ropes play important roles in the momentum and energy transport in space plasmas. Recent observations found that magnetic reconnection occurs at the interface between two counter flows around the center of flux ropes. In this presentation, we report a novel observation by MMS that reconnection occurs at the edge of a large-scale flux rope, the cross-section of which was about 2.5 Re. The flux rope was observed at the dusk side in Earth’s magnetotail and was highly oblique with its axis proximity along the X<sub>GSM</sub> direction. We found an electron-scale current sheet near the edge of this flux rope. The Hall magnetic and electric field, super-Alfvénic electron outflow, parallel electric field and positive energy dissipation were observed associated with the current sheet. All the above signatures indicate that MMS detected a reconnecting current sheet in the presence of a large guide field. Interestingly, ions were not coupled in this reconnection, akin to the electron-only reconnection observed in the magnetosheath turbulence. We suggest that the electron-scale current sheet was caused by the strong magnetic field perturbation inside the flux rope. This result will shed new lights for understanding the multi-scale coupling associated with flux ropes in space plasmas.</p>

Effects of local particle acceleration in the solar wind

2020 ◽  
Author(s):  
Olga Khabarova ◽  
Valentina Zharkova ◽  
Qian Xia ◽  
Olga Malandraki
Keyword(s):  
Solar Wind ◽  
Magnetic Reconnection ◽  
Heliospheric Current Sheet ◽  
Small Scale ◽  
Magnetic Islands ◽  
Solar Origin ◽  
Suprathermal Electrons ◽  
Long Time ◽  
The Impact ◽  
Accelerated Particles

<p>Recent observational and theoretical studies have shown that there is an unaccounted population of electrons and protons accelerated locally to suprathermal energies at reconnecting current sheets (RCSs) and 3-D dynamical plasmoids or 2-D magnetic islands (MIs) in the solar wind. The findings can be summarized as following: (i) RCSs are often subject to instabilities breaking those into 3D small-scale plasmoids/blobs or 2D magnetic islands (MIs) with multiple X- and O-nullpoints; (ii) RCSs and dynamical MIs can accelerate particles up to the MeV/nuc energies; (iii) accelerated particles may form clouds expanding far from a reconnecting region; and (iv) bi-directional(or counterstreaming) strahls observed in pitch-angle distributions (PADs) of suprathermal electrons may simply represent a signature of magnetic reconnection occurring at closed IMF structures (e.g., MIs), not necessarily connected to the Sun (Zharkova & Khabarova, 2012, 2015; Zank et al. 2014, 2015; Khabarova et al. 2015, 2016, 2017; 2018; le Roux 2016, 2017, 2018, 2019; Khabarova & Zank, 2017; Adhikari et al. 2019; Xia & Zharkova, 2018, 2020; Malandraki et al. 2019; Mingalev et al. 2019). We will briefly present an overview of the effects of local ion acceleration as observed at different heliocentric distances and focus on the impact of the locally-borne population of suprathermal electrons on typical patterns of PADs. </p><p>Suprathermal electrons with energies of ~70eV and above are observed at 1 AU as dispersionless halo and magnetic field-aligned beams of strahls. For a long time, it has been thought that both populations originate only from the solar corona. This view has consequently impacted interpretation of typical patterns of suprathermal electron PADs observed in the solar wind. We present multi-spacecraft observations of counterstreaming strahls and dropouts in PADs within a previously reported region filled with plasmoids and RCSs, comparing observed PAD features with those predicted by PIC simulations extended to heliospheric conditions. We show typical features of PADs determined by acceleration of the ambient thermal electrons up to suprathermal energies in single RCSs and dynamical plasmoids. Our study suggests that locally-accelerated suprathermal electrons co-exist with those of solar origin. Therefore, some heat flux dropout and bi-directional strahl events observed in the heliosphere can be explained by local dynamical processes involving magnetic reconnection. Possible implications of the results for the interpretation of the strahl/halo relative density change with heliocentric distance and puzzling features of suprathermal electrons observed at crossings of the heliospheric current sheet and cometary comas are also discussed.</p>

Unsteady energy dissipation in the magnetic reconnection diffusion region

2020 ◽  
Author(s):  
Xiangcheng Dong ◽  
Malcolm Dunlop ◽  
Tieyan Wang ◽  
Barbara Giles ◽  
Roy Torbert ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Energy Dissipation ◽  
Magnetic Reconnection ◽  
Energy Transport ◽  
Diffusion Region ◽  
Significant Issue ◽  
Plasma Energy ◽  
2D Structure ◽  
Spacecraft Data ◽  
Current Behavior

<p>Magnetic reconnection is a universal physical process during which energy can be transferred from the electromagnetic field to the plasma. Energy dissipation in the diffusion region has always been a significant issue for understanding this energy transport. Using the four MMS spacecraft data, we investigate a magnetic reconnection diffusion region event at the magnetopause. Similar magnetic field and electric current behavior between each spacecraft indicates the formation of a quasi 2D structure. However, we find that the energy dissipation results of each spacecraft are different. Further analysis indicates that the reconnection electric field, E<sub>M</sub>, plays a key role in this process. Thus, we suggest that the energy dissipation of magnetic reconnection is unsteady on this spatial or temporal scale, even under stable diffusion conditions.</p>

Large‐scale parallel electric field co‐located in an extended electron diffusion region during the magnetosheath magnetic reconnection

2021 ◽  
Author(s):  
Shimou Wang ◽  
Rongsheng Wang ◽  
Quanming Lu ◽  
C. T. Russell ◽  
R. E. Ergun ◽  
...  
Keyword(s):  
Electric Field ◽  
Magnetic Reconnection ◽  
Large Scale ◽  
Diffusion Region ◽  
Parallel Electric Field ◽  
Electron Diffusion
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