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Morphology of Nightside Subauroral Ionospheric Convection: Monthly, Seasonal, Kp, and IMF Dependencies
Author(s) -
Maimaiti M.,
Baker J. B. H.,
Ruohoniemi J. M.,
Kunduri B.
Publication year - 2019
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1029/2018ja026268
Subject(s) - ionosphere , dynamo , interplanetary magnetic field , thermosphere , geophysics , atmospheric sciences , local time , convection , magnetosphere , solar wind , physics , noon , geology , magnetic field , meteorology , statistics , mathematics , quantum mechanics
In this study we have used 7 years (2011–2017) of quiet (Kp ≤ 2+) to moderately disturbed (Kp = 3) time nightside line‐of‐sight measurements from six midlatitude Super Dual Auroral Radar Network radars in the U.S. continent to characterize the subauroral convection in terms of magnetic latitude, magnetic local time, month, season, Kp, and the interplanetary magnetic field (IMF) clock angle. Our results show that (1) the quiet time (Kp ≤ 2+) subauroral flows are predominantly westward (20–90 m/s) in all months and become meridional (−20–20 m/s) near dawn and dusk, with the flows being the strongest and most structured in December and January. (2) The Kp dependency is prominent in all seasons such that for higher Kp the premidnight westward flow intensifies and the postmidnight eastward flow starts to emerge. (3) Sorting by IMF clock angle shows Bz+/Bz− features consistent with lower/higher Kp conditions, as expected, but also shows distinct differences that are associated with By sign. (4) There is a pronounced latitudinal variation in the zonal flow speed between 18 and 2 magnetic local time in winter (November to February) that exists under all IMF conditions but is most pronounced under IMF Bz− and higher Kp. Our analysis suggests that the quiet time subauroral flows are due to the combined effects of solar wind/magnetosphere coupling leading to penetration electric field and the neutral wind dynamo with the ionospheric conductivity modulating their relative dominance.