Premium
Unstable Eigenmodes of the Feedback Instability With Collision‐Induced Velocity Shear
Author(s) -
Watanabe T.H.,
Maeyama S.
Publication year - 2018
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 - 10.1029/2018gl079715
Subject(s) - instability , ionosphere , physics , normal mode , collision frequency , geophysics , wavelength , mechanics , harmonics , ion , shear (geology) , magnetic field , magnetosphere , computational physics , geology , optics , quantum mechanics , petrology , voltage , vibration
A linear eigenmode analysis of the magnetosphere‐ionosphere coupling shows that the feedback instability leading to spontaneous formation of auroral arc structures remains unstable even in a case with strong vertical shear of horizontal ion flows induced by ion‐neutral collisions in the E layer. For low‐order Alfvén harmonics, the linear frequency and growth rate obtained by means of a height‐resolved model of the ionosphere are comparable to those resulted from the height‐integrated one, where fine vertical structures of the ionospheric density and magnetic field perturbations are well resolved in the former. The present result confirms validity of the height‐integrated ionosphere model in the long parallel wavelength limit, as assumed in previous studies on the feedback instability.