He found that EPBs developed in the post-sunset sector, at longitudes where upwellings were observed during the previous orbit, in the pre-sunset sector.
On the contrary, the PPEFs were found to strongly enhance the PRE electric fields in the Indian sector leading to ionospheric irregularities/scintillations in the post-sunset sector.
The yellow shaded areas indicate the local times between ∼ 19 and 02 LT, i.e., the post-sunset sector when GPS scintillation is typically observed.
Abdu et al. (1983) have confirmed that plasma bubble in the post-sunset sector at low-latitude regions could arise from latitudinal extension of plasma bubble generated primarily over the magnetic equator.
The observed differences in SWA and SWB results could be explained by the longitude/LT separation between satellites, as SWB crossed the same post-sunset sector increasingly later than the SWA did.
The observed differences in the SWA and SWB results could be explained by the longitude/LT separation between satellites, as SWB always crossed the same post-sunset sector much later than the SWA did.
An over-shielding electric field associated with a substorm/storm recovery with the Bz turning north has westward polarity in the evening post-sunset sector, that turns eastward after about 22 LT (Fejer et al. 2008).
As shown in Fig. 1, SWA satellite flew in the post-sunset sector earlier than SWB and for the most covered seasons (September 2014 , March 2015 June 2015 and December 2015) SWA provided more observations for 20 23 LT temporal range.
The presence of the enhanced electric fields and, in turn, of the enhanced ExB drift can also be concluded from the observations of fluctuations in the electron density (Figs. 2, 4, rows III IV), which often occur in the post-sunset sector driven by the Rayleigh–Taylor Instability due to the enhanced ExB drift (e.g., Fejer et al. 1999).
PRE causes an enhanced upward E × B drift in the post-sunset sector and thus affects the plasma bubble generation significantly by lifting the ionosphere to higher altitudes, where the growth rate of the RTI is large because of the small ion-neutral collision.
In the equatorial region, the model describes the dayside equatorial ionization anomaly fairly well, but underestimates its depth in the post-sunset local time sector by about 50%.
