scholarly journals Reconstruction of Electron and Ion Distribution Functions in a Magnetotail Reconnection Diffusion Region

2020 ◽  
Vol 125 (7) ◽  
Author(s):  
Jonathan Ng ◽  
Li‐Jen Chen ◽  
Ammar Hakim ◽  
Amitava Bhattacharjee
Keyword(s):  
Distribution Functions ◽  
Diffusion Region ◽  
Ion Distribution ◽  
Magnetotail Reconnection

scholarly journals Ion distribution functions in magnetotail reconnection: global hybrid-Vlasov simulation results

2021 ◽  
Vol 39 (4) ◽  
pp. 599-612
Author(s):  
Andrei Runov ◽  
Maxime Grandin ◽  
Minna Palmroth ◽  
Markus Battarbee ◽  
Urs Ganse ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Time History ◽  
Distribution Functions ◽  
Ion Acceleration ◽  
Meridional Plane ◽  
Ion Distribution ◽  
Velocity Distribution Functions ◽  
History Of ◽  
Simulation Results ◽  
Magnetotail Reconnection

Abstract. We present results of noon–midnight meridional plane global hybrid-Vlasov simulations of the magnetotail ion dynamics under a steady southward interplanetary magnetic field using the Vlasiator model. The simulation results show magnetotail reconnection and formation of earthward and tailward fast plasma outflows. The hybrid-Vlasov approach allows us to study ion velocity distribution functions (VDFs) that are self-consistently formed during the magnetotail evolution. We examine the VDFs collected by virtual detectors placed along the equatorial magnetotail within earthward and tailward outflows and around the quasi-steady X line formed in the magnetotail at X≈-14RE. This allows us to follow the evolution of VDFs during earthward and tailward motion of reconnected flux tubes as well as study signatures of unmagnetized ion motion in the weak magnetic field near the X line. The VDFs indicate actions of Fermi-type and betatron acceleration mechanisms, ion acceleration by the reconnection electric field, and Speiser-type motion of ions near the X line. The simulated VDFs are compared and show good agreement with VDFs observed in the magnetotail by the Time History of Events and Macroscale Interactions during Substorms (THEMIS) and Acceleration, Reconnection, Turbulence and Electrodynamics of Moon's Interaction with the Sun (ARTEMIS) spacecraft. We find that the VDFs become more gyrotropic but retain transverse anisotropy and counterstreaming ion beams when being convected earthward. The presented global hybrid-Vlasov simulation results are valuable for understanding physical processes of ion acceleration during magnetotail reconnection, interpretation of in situ observations, and for future mission development by setting requirements on pitch angle and energy resolution of upcoming instruments.

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>

scholarly journals Ion distribution functions in magnetotail reconnection: Global hybrid-Vlasov simulation results

2021 ◽  
Author(s):  
Andrei Runov ◽  
Maxime Grandin ◽  
Minna Palmroth ◽  
Markus Battarbee ◽  
Urs Ganse ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Time History ◽  
Distribution Functions ◽  
Ion Acceleration ◽  
Meridional Plane ◽  
Ion Distribution ◽  
Velocity Distribution Functions ◽  
History Of ◽  
Simulation Results ◽  
Magnetotail Reconnection

Abstract. We present results of noon–midnight meridional plane global hybrid-Vlasov simulations of the magnetotail ion dynamics under steady southward interplanetary magnetic field using the Vlasiator model. The simulation results show magnetotail reconnection and formation of earthward and tailward fast plasma outflows. The hybrid-Vlasov approach allows us to study ion velocity distribution functions (VDFs) that are self-consistently formed during the magnetotail evolution. We examine the VDFs collected by virtual detectors placed along the equatorial magnetotail within earthward and tailward outflows and around the quasi-steady X-line formed in the magnetotail at X ≈ −14 RE. This allows us to follow the evolution of VDFs during earthward and tailward motion of reconnected flux tubes as well as study signatures of unmagnetized ion motion in the weak magnetic field near the X-line. The VDFs indicate actions of Fermi-type and betatron acceleration mechanisms, ion acceleration by the reconnection electric field, and Speiser-type motion of ions near the X-line. The simulated VDFs are compared and show good agreement with VDFs observed in the magnetotail by the Time History of Events and Macroscale Interactions during Substorms (THEMIS) and Acceleration, Reconnection, Turbulence and Electrodynamics of Moon's Interaction with the Sun (ARTEMIS) spacecraft. We find that the VDFs become more gyrotropic but retain transverse anisotropy and counter-streaming ion beams when being convected earthward. The presented global hybrid-Vlasov simulation results are valuable for understanding physical processes of ion acceleration during magnetotail reconnection, interpretation of in-situ observations, and for future mission development by setting requirements on pitch-angle and energy resolution of upcoming instruments.

The hot hELicon eXperiment (HELIX) and the large experiment on instabilities and anisotropy (LEIA)

2014 ◽  
Vol 81 (1) ◽  
Author(s):  
E. E. Scime ◽  
P. A. Keiter ◽  
M. M. Balkey ◽  
J. L. Kline ◽  
X. Sun ◽  
...  
Keyword(s):  
Double Layer ◽  
Noble Gas ◽  
Velocity Distribution Function ◽  
Plasma Source ◽  
Distribution Functions ◽  
Double Layers ◽  
Driving Frequency ◽  
Ion Temperature ◽  
Temperature Anisotropy ◽  
Ion Distribution

The West Virginia University Hot hELIcon eXperiment (HELIX) provides variable density and ion temperature plasmas, with controllable levels of thermal anisotropy, for space relevant laboratory experiments in the Large Experiment on Instabilities and Anisotropy (LEIA) as well as fundamental studies of helicon source physics in HELIX. Through auxiliary ion heating, the ion temperature anisotropy (T⊥/T∥) is variable from 1 to 20 for parallel plasma beta (β = 8πnkTi∥/B2) values that span the range of 0.0001 to 0.01 in LEIA. The ion velocity distribution function is measured throughout the discharge volume in steady-state and pulsed plasmas with laser induced fluorescence (LIF). The wavelengths of very short wavelength electrostatic fluctuations are measured with a coherent microwave scattering system. Operating at low neutral pressures triggers spontaneous formation of a current-free electric double layer. Ion acceleration through the double layer is detected through LIF. LIF-based velocity space tomography of the accelerated beam provides a two-dimensional mapping of the bulk and beam ion distribution functions. The driving frequency for the m = 1 helical antenna is continuously variable from 8.5 to 16 MHz and frequency dependent variations of the RF coupling to the plasma allow the spontaneously appearing double layers to be turned on and off without modifying the plasma collisionality or magnetic field geometry. Single and multi-species plasmas are created with argon, helium, nitrogen, krypton, and xenon. The noble gas plasmas have steep neutral density gradients, with ionization levels reaching 100% in the core of the plasma source. The large plasma density in the source enables the study of Aflvén waves in the HELIX device.

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>

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