A statistical study of low latitude F region irregularities at Brazilian longitudinal sector response to geomagnetic storms during post-sunset hours in solar cycle 23

摘要

Effects of intense geomagnetic storms (Dst index < —100) to low latitude F region irregularities in the post-sunset hours are statistically studied by the total electron content (TEC) phase fluctuation observations obtained from the ground-based global positioning system (GPS) receivers in the Brazilian longitude sector during a 7.5-year period of 1 April 1998-31 October 2005. Results show that the low latitude irregularities are significantly suppressed during the main and recovery phases of the intense geomagnetic storms in the months (September—March) that normally have high irregularity activity. In contrast, the post-sunset triggering signatures are pronounced in the low irregularity activity season (April—August) during storms. To further understand the storm-produced behaviors in the low latitude F region irregularity in the post-sunset hours, the relationship between the intensity of GPS phase fluctuations and the occurrence time of the of IMF Bz turnings is examined and discussed.