The ionospheric F2-region at low geomagnetic latitudes during the geomagnetic storms of 22–26 April 1990: Comparison of observed and modeled response

Anomalous night-time peaks in diurnal variations of NmF2 close to the geomagnetic equator: A statistical study

“…We found that during the studied time periods (see Table 1) the largest number of the first ANNPs was It follows from the model simulations that the post-sunset enhanced NmF2 cannot be caused by changes in neutral densities and temperature Pavlov and Fukao, 2007). Anomalous night-time increases in NmF2 cannot be explained in terms of traveling ionospheric disturbances since these disturbances would have to be extremely large to produce the night-time electron density observed (Young et al, 1970).…”

“…The resulting effect of the E Â B drift on NmF2 depends on the competition between an electron density enhancement caused by a plasma inflow and an electron density depletion due to an increase in the loss rate of O + ( 4 S) ions owing to a NmF2 peak layer lowering. The model simulations show that the reduction in NmF2 at night over Manila caused by the increase in the loss rate of O + ( 4 S) ions is stronger than the NmF2 enhancement caused by the plasma outflow during the quiet and geomagnetic storm periods of 17-22 March 1990and 22-26 April 1990Pavlov and Fukao, 2007). As a result, Pavlov et al (2006) and Pavlov and Fukao (2007) found that the value of the night-time vertical equatorial plasma drift velocity given by the empirical model of Scherliess (1997) (or Scherliess andFejer, 1999) after the pre-reversal increase of the E Â B drift is excessively strengthened for the studied time periods, preventing NmF2 from the development of the post-sunset enhancements in NmF2.…”

“…The model simulations show that the reduction in NmF2 at night over Manila caused by the increase in the loss rate of O + ( 4 S) ions is stronger than the NmF2 enhancement caused by the plasma outflow during the quiet and geomagnetic storm periods of 17-22 March 1990and 22-26 April 1990Pavlov and Fukao, 2007). As a result, Pavlov et al (2006) and Pavlov and Fukao (2007) found that the value of the night-time vertical equatorial plasma drift velocity given by the empirical model of Scherliess (1997) (or Scherliess andFejer, 1999) after the pre-reversal increase of the E Â B drift is excessively strengthened for the studied time periods, preventing NmF2 from the development of the post-sunset enhancements in NmF2. If the meridional component of the nighttime E Â B drift velocity produced by the empirical model of Scherliess (1997) (or Scherliess andFejer, 1999) is weakened then it causes an increase in the F2 layer peak altitude, hmF2, resulting in a decrease in the loss rate of O + ( 4 S) ions at hmF2 and leads to an increase in NmF2 at night over the Manila sounder.…”

Analysis of ionospheric electron parameters versus geomagnetic index Dst from RO data of FORMOSAT-3/COSMIC

“…The response of the ionospheric F2-layer to geomagnetic activities has received much research interests (Prölss et al 1991;Buonsanto 1995;Field and Rishbeth 1997;Rishbeth and Mendillo 2001;Kumar 2005;Pavlov and Fukao 2007). Most of the research has focused on case studies of geomagnetic storm events from ground-station measurements with limited spatial ranges.…”

The zonal E×B plasma drift effects on the low latitude ionosphere electron density at solar minimum near equinox

“…Anderson (1981) has found that the F2-layer peak electron densities calculated over the geomagnetic equator at 20:00 LT and at 24:00 LT for high solar activity conditions do not differ significantly from those obtained when the zonal E Â B drift is omitted. As a result of the model calculations given by Anderson (1981), effects of the zonal E Â B plasma drift on electron and ion densities and temperatures were not taken into account in the previous model studies (e.g., Anderson et al, 1996;Bailey and Balan, 1996;Millward et al, 1996;Roble, 1996;Schunk and Sojka, 1996;Huba et al, 2000;Maruyama et al, 2003;Pavlov, 2003;Pavlov et al, 2004a, b, 2006, Pavlov and Fukao, 2007, except of Pavlov (2006). The influence of the zonal E Â B plasma drift on the low latitude ionosphere was reinvestigated by Pavlov (2006) for high solar activity conditions near equinox.…”