Quiet time meridional (vertical) ion drifts at low and middle latitudes observed by ROCSAT‐1

Abstract

[1] In situ ion drift observations from the ROCSAT-1 satellite, near the 600 km altitude and for the years [1999][2000][2001][2002][2003], are used to describe variations in the local time (LT) distribution of meridional E × B drifts at low and middle latitudes, for different longitudes and seasons. We derive the ion drifts in the direction perpendicular to the magnetic field during quiet times defined by Kp ≤ 3 and Dst > −100 nT. Offsets in the original data are removed by considering separately the northbound and southbound passes in a given volume and by enforcing magnetic conjugacy for the ion drift components perpendicular to the magnetic field. Three major features are identified for which the variations in latitude, longitude, and season allow the major drivers of these features to be indicated: (1) a latitude/magnetic apex height variation in the prereversal (after sunset) enhancement of the vertical drift that is attributed to similar variations in the flux tube-integrated Pedersen conductivity, (2) the daytime meridional drifts that are largely driven by the E region dynamo show significant latitude variations that are attributed to the relative importance of diurnal and semidiurnal wind fields as a function of latitude, and (3) a downward enhancement of the ion drift before sunrise is attributed to a reversal in the F region zonal wind during the nighttime.

The role of zonal winds in the production of a pre‐reversal enhancement in the vertical ion drift in the low latitude ionosphere

“…A maximum in the downward drift of about 30 m s À1 occurs just prior to sunrise. These features in the downward drift are also seen in direct observations made from satellites [Pacheco et al, 2010] and ground-based radar [Fejer et al, 1991].…”

Superrotation of the ionosphere and quiet time zonal ion drifts at low and middle latitudes observed by Republic of China Satellite-1 (ROCSAT-1)

“…This is quite evident at most longitudes where daytime westward drifts are diminished and sometimes turn eastward. It is also seen in the meridional drifts described by Pacheco et al [2010]. Closer to the equator, the daytime peak in the zonal drift is dependent on longitude and season.…”

Statistical Analysis ofTECDistributions Observed Over South and Central America

“…Figure presents the TEC values measured on 19 December 2010, in which the magnetic conditions were quiet ( K p ≤ 1 + ) and the F10.7 solar flux equal to 87.3 × 10 −22 W m −2 Hz −1 . It has been demonstrated before that during the December solstice the electric fields are better developed over the Brazilian sector, where the magnetic meridian aligns more with the terminator than in the Peruvian sector (Fejer et al, ; Pacheco et al, ). This idea is evident in Figure where there exists a marked longitudinal variability in the latitudinal separation of the crests of the anomaly.…”