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Terrestrial lion roars and non‐Maxwellian distribution
Author(s) -
Qureshi M. N. S.,
Nasir Warda,
Masood W.,
Yoon P. H.,
Shah H. A.,
Schwartz S. J.
Publication year - 2014
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2014ja020476
Subject(s) - distribution (mathematics) , astrobiology , physics , mathematics , mathematical analysis
Lion roars are low‐frequency (∼100 Hz) whistler waves frequently observed in the Earth's magnetosheath. By analyzing both wave and electron data from the Cluster spacecraft, and comparing with linear Vlasov kinetic theory, Masood et al. (2006) investigated the underlying cause of the lion roar generation. However, the analysis based upon the bi‐Maxwellian distribution function did not adequately explain the observations qualitatively as well as quantitatively. This outstanding problem is revisited in the present paper, and a resolution is put forth in which, the flat‐top non‐Maxwellian distribution function with a velocity power law energetic tail, known as the ( r , q ) distribution, or the generalized kappa distribution is employed. Upon carrying out the linear stability analysis of the ( r , q ) distribution against the whistler wave perturbation, and upon comparison with the Cluster data, good qualitative and quantitative agreements are found between theory and data.