Quasi-adiabaticity in bifurcated current sheets.

Dominique C. Delcourt (1) , H. V. Malova (2) , L. M. Zelenyi (3)

1 CETP - Centre d'étude des environnements terrestre et planétaires
2 SINP - D.V. Skobeltsyn Institute of Nuclear Physics
3 IKI - Space Research Institute of the Russian Academy of Sciences

We examine the non-linear dynamics of charged particles in “bifurcated” (double-humped) current sheets. We show that, when the adiabaticity parameter κ is of the order unity, particles experience a negligible change of magnetic moment. Such a behavior contrasts with the prominent magnetic moment scattering that is achieved in single-humped current sheets at such κ values. It resembles the quasi-adiabatic (Speiser-type) behaviors that is obtained at κ ≪ 1 as a result of resonance between the fast oscillation about the midplane and the slow gyromotion near this plane. We demonstrate that beams of κ ≈ 1 particles may form downstream of bifurcated current sheets, which propagate along the magnetic field lines up to high latitudes. Quasi-adiabaticity and associated beam formation thus occur at significantly larger κ values in double-humped current sheets than in single-humped ones, or equivalently for lower particle energy and/or weaker field reversal.

Domaines: Astrophysique [astro-ph]; Cosmologie et astrophysique extra-galactique [astro-ph.CO]; Physique des plasmas [physics.plasm-ph]

Dominique C. Delcourt, H. V. Malova, L. M. Zelenyi. Quasi-adiabaticity in bifurcated current sheets.. Geophysical Research Letters, 2006, 33 (6), pp.L06106. ⟨10.1029/2005GL025463⟩. ⟨hal-00156435⟩