Open AccessAverage characteristics and activity dependence of the subauroral polarization stream
Author(s) -
Foster J. C.,
Vo H. B.
Publication year - 2002
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 - 10.1029/2002ja009409
Subject(s) - millstone hill , convection , ionosphere , geophysics , geology , latitude , convection cell , amplitude , middle latitudes , incoherent scatter , f region , atmospheric sciences , physics , meteorology , geodesy , optics , combined forced and natural convection , natural convection
Data from the Millstone Hill incoherent scatter radar taken over two solar cycles (1979–2000) are examined to determine the average characteristics of the disturbance convection electric field in the midlatitude ionosphere. Radar azimuth scans provide a regular database of ionospheric plasma convection observations spanning auroral and subauroral latitudes, and these scans have been examined for all local times and activity conditions.We examine the occurrence and characteristics of a persistent secondary westward convection peak which lies equatorward of the auroral two‐cell convection. Individual scans and average patterns of plasma flow identify and characterize this latitudinally broad and persistent subauroral polarization stream (SAPS), which spans the nightside from dusk to the early morning sector for all Kp greater than 4. Premidnight, the SAPS westward convection lies equatorward of L = 4 (60° invariant latitude, Λ), spans 3°–5° of latitude, and has an average peak amplitude of >900 m/s. In the predawn sector, SAPS is seen as a region of antisunward convection equatorward of L = 3 (55° Λ), spanning ∼3° of latitude, with an average peak amplitude of 400 m/s.