Sundkvist, D; Vaivads, A; Bogdanova, YV; Krasnoselskikh, VV; Fazakerley, A; Decreau, PME; (2006) Shell-instability generated waves by low energy electrons on converging magnetic field lines. Geophysical Research Letters , 33 (3) , Article L03103. 10.1029/2005GL024388.

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Abstract

Wave emissions at electron cyclotron harmonics and at frequencies above the local plasma frequency are commonly observed in different magnetospheric regions. We show that such emissions when observed in the cusp, mantle or polar cap can be generated by shell-type electron distributions. We present an example of observations of such shell type distributions having positive slope in velocity space at low energies, about 10 eV. Numerical calculations of wave growth rate based on the observed particle distributions show that the shell-instability can generate electrostatic and electromagnetic wave modes: whistler waves, electron cyclotron harmonics, upper-hybrid as well as the RX mode. Local wave spectra observations are consistent with the presence of all those wave modes in data. A possible connection between low and high frequency waves is discussed. Our results clearly show the importance of detailed studies of the lowest energy electrons.

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