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Excitation of banded whistler waves in the magnetosphere
Author(s) -
Liu Kaijun,
Gary S. Peter,
Winske Dan
Publication year - 2011
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2011gl048375
Subject(s) - whistler , magnetosphere , excitation , physics , geophysics , computational physics , atomic physics , plasma , nuclear physics , quantum mechanics
Linear kinetic dispersion analysis and a two‐dimensional electromagnetic particle‐in‐cell simulation are performed to demonstrate a possible excitation mechanism of banded whistler waves in the magnetosphere outside of the plasmapause. Whistler waves in the lower and the upper bands can be generated simultaneously by the whistler anisotropy instability driven by two bi‐Maxwellian electron components with T ⊥ / T ∥ > 1 at different T ∥ , independently, where ∥ and ⊥ denote directions relative to the background geomagnetic field. Given ω e /Ω e , the ratio of the electron plasma frequency to the electron cyclotron frequency, T ∥ of each electron component determines the properties of the excited waves. For the typical magnetospheric condition of 1 < ω e /Ω e < 5 in regions associated with strong chorus emissions, the present study suggests that upper‐band waves can be excited by anisotropic electrons below ∼1 keV, while lower‐band waves are excited by anisotropic electrons above ∼10 keV. The resultant lower‐band waves are generally field‐aligned and substantially electromagnetic. However, the excited upper‐band waves generally propagate obliquely to the background geomagnetic field with quasi‐electrostatic fluctuating electric fields.