Electron Temperature Gradient Scale at Collisionless Shocks

Steven J. Schwartz (1) , Edmund Henley (1) , Jeremy Mitchell (1) , Vladimir Krasnoselskikh (2)

1 Thales Research and Technology [Palaiseau]
2 LPC2E - Laboratoire de Physique et Chimie de l'Environnement et de l'Espace

Shock waves are ubiquitous in space and astrophysics. They transform directed flow energy into thermal energy and accelerate energetic particles. The energy repartition is a multiscale process related to the spatial and temporal structure of the electromagnetic fields within the shock layer. While large scale features of ion heating are known, the electron heating and smaller scale fields remain poorly understood. We determine for the first time the scale of the electron temperature gradient via electron distributions measured in situ by the Cluster spacecraft. Half of the electron heating coincides with a narrow layer several electron inertial lengths (c/ωpe) thick. Consequently, the nonlinear steepening is limited by wave dispersion. The dc electric field must also vary over these small scales, strongly influencing the efficiency of shocks as cosmic ray accelerators.

Keywords: SHOCK waves; ASTROPHYSICS ELECTROMAGNETIC fields; ELECTRON temperature; COSMIC rays

Domains: Astrophysics [astro-ph]

Steven J. Schwartz, Edmund Henley, Jeremy Mitchell, Vladimir Krasnoselskikh. Electron Temperature Gradient Scale at Collisionless Shocks. Physical Review Letters, 2011, 107 (21), pp.215002. ⟨10.1103/PhysRevLett.107.215002⟩. ⟨insu-01310858⟩