Open AccessOn postmidnight low‐latitude ionospheric irregularities during solar minimum: 2. C/NOFS observations and comparisons with the Equatorial Atmosphere Radar
Author(s) -
Yokoyama T.,
Pfaff R. F.,
Roddy P. A.,
Yamamoto M.,
Otsuka Y.
Publication year - 2011
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2011ja016798
Subject(s) - ionosphere , f region , middle latitudes , geology , thermosphere , atmosphere (unit) , latitude , solar minimum , atmospheric sciences , geophysics , midnight , physics , geodesy , plasma , meteorology , solar cycle , astronomy , solar wind , quantum mechanics
A detailed comparison between the observations of the Communication/Navigation Outage Forecasting System (C/NOFS) satellite and the 47 MHz Equatorial Atmosphere Radar (EAR) in West Sumatra, Indonesia (10.36°S dip latitude) on the postmidnight irregularities is presented. The zonal and meridional E × B drift velocities measured by the vector electric field instrument on the C/NOFS are consistent with the westward propagation of backscatter echoes and the line‐of‐sight Doppler velocities observed with the EAR, respectively. The plasma density depletions are observed in the postmidnight sector for several consecutive orbits, which suggests the depletions grow slowly during the premidnight period and reach the spacecraft altitude around local midnight. The convergence of the equatorward wind which could be responsible for the midnight temperature maximum may produce a preferable condition for the growth of the Rayleigh‐Taylor instability around midnight. Electric field fluctuations of medium‐scale traveling ionospheric disturbances may play an important role in seeding the instability. Both equatorial and midlatitude‐type plasma instabilities could be operational at the EAR latitude sector, which together would foster a high occurrence of postmidnight irregularities during solar minimum.