on the need of the use of data from small satellites in elucidating ionospheric phenomena during very intense geomagnetic storms

A study to clarify the mechanisms responsible for the pre-storm and main phase ionospheric phenomena during November 20-21, 2003, is presented using heliophysical, interplanetary, geomagnetic, and global ionospheric data. The results show that the ionospheric responses in the main phase do not indicate prompt penetration electric fields as the main ionospheric driver. The results also show that the prestorm phenomena do not originate from a local time effect. The simultaneous occurrence of foF2 enhancements at two widely separated longitudinal zones appeared to suggest a role played by the magnetospheric electric field. However, the analysis of hmF2 at the stations could not confirm the notion that these fields are the main drivers of pre-storm phenomena. An investigation of flare effects on the pre-storm phenomena also revealed that solar flares are not the main drivers. The present results appear to suggest that pre-storm ionospheric phenomena could be a result of some underlying mechanisms that are working together with varying degree of importance. The present results further intend to show that the mechanisms that are responsible for the pre-storm phenomena could only be largely explained by the use of data from small satellites, given that small-satellite missions by filling gaps in time or coverage, can provide valuable measurements that would help answer important outstanding science questions in space weather.

Keywords: geomagnetic storm, solar X-rays, solar wind, shock gas, ionosphere, pre-storm phenomena.