THEMIS observations of the magnetopause electron diffusion region and magnetospheric separatrix: Large amplitude waves and heated particles

We present the first observations of large amplitude waves in a well-defined electron diffusion region based on the criteria described by Scudder et al. [2012] at the subsolar magnetopause [Tang et al., 2013] as well as near the magnetospheric separatrix using data from the THEMIS satellites. A wide range of wave modes identified as whistler mode waves, electrostatic solitary waves, lower hybrid waves, electrostatic electron cyclotron waves and electrostatic ion harmonic waves are often simultaneously observed in association with signatures of active magnetic reconnection. The large amplitude waves in the electron diffusion region are coincident with abrupt increases in electron parallel temperature suggesting strong wave heating. Evidence of perpendicular ion heating (< 100 eV) by the electrostatic ion harmonic waves has been found near the magnetospheric separatrix. The whistler mode waves, which are at the electron scale and enable us to probe electron dynamics in the diffusion region were analyzed in detail. The energetic electrons (∼30 keV) within the electron diffusion region have anisotropic distributions with Te⊥/Te∥ > 1 that may provide the free energy for the whistler mode waves. The energetic anisotropic electrons may be produced during the reconnection process. The whistler mode waves propagate away from the center of the 'X-line' along magnetic field lines, suggesting that the electron diffusion region is a possible source region of the whistler mode waves.