scholarly journals Electron distribution functions in the diffusion region of asymmetric magnetic reconnection

2016 ◽  
Vol 43 (5) ◽  
pp. 1828-1836 ◽  
Author(s):  
N. Bessho ◽  
L.-J. Chen ◽  
M. Hesse
Keyword(s):  
Magnetic Reconnection ◽  
Electron Distribution ◽  
Distribution Functions ◽  
Diffusion Region

Formation of non-thermal electron velocity distribution functions in kinetic magnetic reconnection

2021 ◽  
Author(s):  
Xin Yao ◽  
Patricio A. Muñoz ◽  
Jörg Büchner
Keyword(s):  
Magnetic Field ◽  
Free Energy ◽  
Field Strength ◽  
Magnetic Reconnection ◽  
Electron Beams ◽  
Distribution Functions ◽  
Electron Velocity ◽  
Diffusion Region ◽  
Electron Velocity Distribution ◽  
Velocity Distribution Functions

<div> <div>Magnetic reconnection can convert magnetic energy into non-thermal particle energy in the form of electron beams. Those accelerated electrons can, in turn, cause radio emission in environments such as solar flares. The actual properties of those electron velocity distribution functions (EVDFs) generated by reconnection are still not well understood. In particular the properties that are relevant for the micro-instabilities responsible for radio emission. We aim thus at characterizing the electron distributions functions generated by 3D magnetic reconnection by means of fully kinetic particle-in-cell (PIC) code simulations. Our goal is to characterize the possible sources of free energy of the generated EVDFs in dependence on an external (guide) magnetic field strength. We find that: (1) electron beams with positive gradients in their parallel (to the local magnetic field direction) distribution functions are observed in both diffusion region (parallel crescent-shaped EVDFs) and separatrices (bump-on-tail EVDFs). These non-thermal EVDFs cause counterstreaming and bump-on-tail instabilities. These electrons are adiabatic and preferentially accelerated by a parallel electric field in regions where the magnetic moment is conserved. (2) electron beams with positive gradients in their perpendicular distribution functions are observed in regions with weak magnetic field strength near the current sheet midplane. The characteristic crescent-shaped EVDFs (in perpendicular velocity space) are observed in the diffusion region. These non-thermal EVDFs can cause electron cyclotron maser instabilities. These non-thermal electrons in perpendicular velocity space are mainly non-adiabatic. Their EVDFs are attributed to electrons experiencing an E×B drift and meandering motion. (3) As the guide field strength increases, the number of locations in the current sheet with distributions functions featuring a perpendicular source of free energy significantly decreases.</div> </div>

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.

Observation of non-gyrotropic electron distribution across the electron diffusion region in the magnetotail reconnection

2020 ◽  
Author(s):  
Xinmin Li ◽  
Quanming Lu
Keyword(s):  
Electric Field ◽  
Energy Range ◽  
Electron Distribution ◽  
Distribution Functions ◽  
Diffusion Region ◽  
Electron Diffusion ◽  
Vertical Distance ◽  
Magnetospheric Multiscale ◽  
Magnetotail Reconnection ◽  
First Time

<p>Using measurements by the Magnetospheric Multiscale (MMS) spacecraft in the magnetotail, we studied electron distribution functions across an electron diffusion region. The dependence of the non-gyrotropic distribution on the energy and vertical distance from the EDR mid-plane was revealed for the first time. The non-gyrotropic distribution was observed everywhere except for an extremely narrow layer right at the EDR mid-plane. The energy of the non-gyrotropic distribution increased with growth of the vertical distance from the mid-plane. For the electrons within certain energy range, they exhibited the non-gyrotropic distribution at the distance further away from the mid-plane than that expected from the meandering motion. The correlation between the crescent-shaped distribution with multiple stripes and the large Hall electric field was established. It appears that the measured non-gyrotropic distribution and the crescent-shaped distribution were caused by the meandering motion and the Hall electric field together.</p>

Calculation of spatially inhomogeneous electron distribution functions

1998 ◽  
Vol 08 (PR7) ◽  
pp. Pr7-33-Pr7-42
Author(s):  
L. L. Alves ◽  
G. Gousset ◽  
C. M. Ferreira
Keyword(s):  
Electron Distribution ◽  
Distribution Functions ◽  
Spatially Inhomogeneous

scholarly journals The effects of density inhomogeneities on the radio wave emission in electron beam plasmas

2021 ◽  
Vol 87 (2) ◽  
Author(s):  
Xin Yao ◽  
Patricio A. Muñoz ◽  
Jörg Büchner ◽  
Xiaowei Zhou ◽  
Siming Liu
Keyword(s):  
Magnetic Reconnection ◽  
Radio Wave ◽  
Solar Flares ◽  
Electron Beams ◽  
Distribution Functions ◽  
Plasma Emission ◽  
Langmuir Waves ◽  
Radio Emissions ◽  
Density Inhomogeneities ◽  
Effects Of Density

Type III radio bursts are radio emissions associated with solar flares. They are considered to be caused by electron beams travelling from the solar corona to the solar wind. Magnetic reconnection is a possible accelerator of electron beams in the course of solar flares since it causes unstable distribution functions and density inhomogeneities (cavities). The properties of radio emission by electron beams in an inhomogeneous environment are still poorly understood. We capture the nonlinear kinetic plasma processes of the generation of beam-related radio emissions in inhomogeneous plasmas by utilizing fully kinetic particle-in-cell code numerical simulations. Our model takes into account initial electron velocity distribution functions (EVDFs) as they are supposed to be created by magnetic reconnection. We focus our analysis on low-density regions with strong magnetic fields. The assumed EVDFs allow two distinct mechanisms of radio wave emissions: plasma emission due to wave–wave interactions and so-called electron cyclotron maser emission (ECME) due to direct wave–particle interactions. We investigate the effects of density inhomogeneities on the conversion of free energy from the electron beams into the energy of electrostatic and electromagnetic waves via plasma emission and ECME, as well as the frequency shift of electron resonances caused by perpendicular gradients in the beam EVDFs. Our most important finding is that the number of harmonics of Langmuir waves increases due to the presence of density inhomogeneities. The additional harmonics of Langmuir waves are generated by a coalescence of beam-generated Langmuir waves and their harmonics.

Statistical analysis of non-Maxwellian electron distribution functions measured with angularly resolved Thomson scattering

2021 ◽  
Vol 28 (8) ◽  
pp. 082102
Author(s):  
A. L. Milder ◽  
J. Katz ◽  
R. Boni ◽  
J. P. Palastro ◽  
M. Sherlock ◽  
...  
Keyword(s):  
Statistical Analysis ◽  
Electron Distribution ◽  
Thomson Scattering ◽  
Distribution Functions

scholarly journals Identification of the Electron-Diffusion Region during Magnetic Reconnection in a Laboratory Plasma

2008 ◽  
Vol 101 (8) ◽  
Author(s):  
Yang Ren ◽  
Masaaki Yamada ◽  
Hantao Ji ◽  
Stefan P. Gerhardt ◽  
Russell Kulsrud
Keyword(s):  
Magnetic Reconnection ◽  
Diffusion Region ◽  
Laboratory Plasma ◽  
Electron Diffusion
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