Turbulent heating and cross-field transport near the magnetopause from THEMIS

C. Chaston (1) , J. Bonnell (1) , J. Mcfadden (1) , C. Carlson (1) , C. Cully (2) , O. Le Contel (3) , A. Roux (3) , H. Auster (4) , K. Glassmeier (4) , V. Angelopoulos (5) , C. Russell (5)

1 SSL - Space Sciences Laboratory [Berkeley]
2 LASP - Laboratory for Atmospheric and Space Physics [Boulder]
3 CETP - Centre d'étude des environnements terrestre et planétaires
4 Technische Universität Braunschweig = Technical University of Braunschweig [Braunschweig]
5 IGPP - Institute of Geophysics and Planetary Physics [Los Angeles]

We demonstrate that the low frequency broadband magnetic fluctuations observed during THEMIS spacecraft traversals near the Earth's magnetopause may be described as a turbulent spectrum of Doppler shifted kinetic Alfvén waves (KAWs). These waves are most intense along reconnected flux-tubes in the magnetosheath just outside the magnetopause. We identify distinct power-law scalings of wave spectral energy density in wavenumber and show that Landau (LD) and transit time damping (TD) on ions and electrons is largest at the wavenumber where the power-law index changes. The threshold amplitude for stochastic ion scattering/acceleration is also exceeded by these waves. These acceleration processes are manifest in observations of field-aligned and transverse heating of electrons and ions respectively. From integration over the range of observed wavenumbers we show that, if the wave-normal angles are sufficiently large, these waves can provide diffusive transport of magnetosheath plasmas across the magnetopause at up to the Bohm rate.

Domaines: Planétologie et astrophysique de la terre [astro-ph.EP]

C. Chaston, J. Bonnell, J. Mcfadden, C. Carlson, C. Cully, et al.. Turbulent heating and cross-field transport near the magnetopause from THEMIS. Geophysical Research Letters, 2008, 35 (17), pp.L17S08. ⟨10.1029/2008GL033601⟩. ⟨hal-03086703⟩