Premium
High frequency drift waves with wavelengths below the ion gyroradius in equatorial spread F
Author(s) -
Huba J. D.,
Chaturvedi P. K.,
Ossakow S. L.,
Towle D. M.
Publication year - 1978
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/gl005i008p00695
Subject(s) - gyroradius , physics , ion , wavelength , atomic physics , lower hybrid oscillation , collision frequency , instability , wavenumber , ionosphere , frequency drift , stochastic drift , cyclotron , f region , computational physics , geophysics , optics , statistics , phase locked loop , mathematics , quantum mechanics , mechanics , phase noise
Evidence is given for intense VHF and UHF radar backscatter during equatorial Spread F resulting from irregularities of 1 meter and 36 cm, respectively. The linear theory for high frequency (ω ≳ Ω i , where Ω i is the ion gyrofrequency) drift waves, generated by the drift‐cyclotron and lower‐hybrid‐drift instabilities, is presented. This linear theory is set forth as a possible explanation for the occurrence of these irregularities below the ion gyroradius. The maximum growth for these instabilities occurs for kr e ∼ 1, where k is the wavenumber perpendicular to the magnetic field and r e is the electron gyroradius. For these instabilities, the growth rate is γ ≳ (m e /m i ) ¼ Ω i and results in growth times less than a second. For typical equatorial Spread F ionospheric parameters, where (ν ii /Ω i ) (kr i )² ≳ 1 (ν ii is the ion‐ion collision frequency, r I is the ion gyroradius), the lower‐hybrid‐drift instability is dominant.