Formation of reflected electron bursts by the nonstationarity and nonuniformity of a collisionless shock front

2002 ◽  
Vol 107 (A3) ◽  
Author(s):  
B. Lembège
Keyword(s):  
Shock Front ◽  
Collisionless Shock

scholarly journals Density jump for parallel and perpendicular collisionless shocks

2020 ◽  
Vol 38 (2) ◽  
pp. 114-120 ◽  
Author(s):  
Antoine Bret ◽  
Ramesh Narayan
Keyword(s):  
Shock Front ◽  
Vlasov Equation ◽  
Jump Conditions ◽  
Collisionless Shock ◽  
Density Jump ◽  
Collisionless Shocks ◽  
Binary Collisions ◽  
Parallel Case ◽  
Relativistic Pair

AbstractIn a collisionless shock, there are no binary collisions to isotropize the flow. It is therefore reasonable to ask to which extent the magnetohydrodynamics (MHD) jump conditions apply. Following up on recent works which found a significant departure from MHD in the case of parallel collisionless shocks, we here present a model allowing to compute the density jump for collisionless shocks. Because the departure from MHD eventually stems from a sustained downstream anisotropy that the Vlasov equation alone cannot specify, we hypothesize a kinetic history for the plasma, as it crosses the shock front. For simplicity, we deal with non-relativistic pair plasmas. We treat the cases of parallel and perpendicular shocks. Non-MHD behavior is more pronounced for the parallel case where, according to MHD, the field should not affect the shock at all.

DYNAMICS OF HIGH ENERGY IONS AT A STRUCTURED COLLISIONLESS SHOCK FRONT

2016 ◽  
Vol 825 (2) ◽  
pp. 149 ◽  
Author(s):  
M. Gedalin ◽  
W. Dröge ◽  
Y. Y. Kartavykh
Keyword(s):  
Shock Front ◽  
High Energy ◽  
Collisionless Shock ◽  
High Energy Ions

scholarly journals Under and over-adiabatic electrons through a perpendicular collisionless shock: theory versus simulations

2005 ◽  
Vol 23 (12) ◽  
pp. 3685-3698 ◽  
Author(s):  
P. Savoini ◽  
B. Lembège ◽  
V. Krasnosselskhik ◽  
Y. Kuramitsu
Keyword(s):  
Shock Front ◽  
Lower Percentage ◽  
Collisionless Shock ◽  
The Core ◽  
High Injection ◽  
Theory Versus ◽  
Particle Simulations ◽  
Core Part ◽  
The Magnetic Field

Abstract. Test particle simulations are performed in order to analyze in detail the dynamics of transmitted electrons through a supercritical, strictly perpendicular, collisionless shock. In addition to adiabatic particles, two distinct nonadiabatic populations are observed surprisingly: (i) first, an over-adiabatic population characterized by an increase in the gyrating velocity higher than that expected from the conservation of the magnetic moment µ, and (ii) second, an under-adiabatic population characterized by a decrease in this velocity. Results show that both nonadiabatic populations have their pitch angle more aligned along the magnetic field than the adiabatic one at the time these hit the shock front. The formation of "under" and "over-adiabatic" particles strongly depends on their local injection conditions through the large amplitude cross-shock potential present within the shock front. A simplified theoretical model validates these results and points out the important role of the electric field as seen by the electrons. A classification shows that both nonadiabatic electrons are issued from the core part of the upstream distributionÊ function. In contrast, suprathermal and tail electrons only contribute to the adiabatic population; nevertheless, the core part of the upstream distribution contributes at a lower percentage to the adiabatic electrons. Under-adiabatic electrons are characterized by small injection angles θinj≤90°, whereas "over-adiabatic" particles have high injection angles θinj>90° (where θinj is the angle between the local gyrating velocity vector and the shock normal).

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