Satellite In Situ Electron Density Observations of the Midlatitude Storm Enhanced Density on the Noon Meridional Plane in the F Region During the 20 November 2003 Magnetic Storm

Ionospheric storm enhanced density (SED) has been extensively investigated using total electron content deduced from GPS ground and satellite-borne receivers. However, dayside in situ electron density measurements have not been analyzed in detail for SEDs yet. We report in situ electron density measurements of a SED event in the Northern Hemisphere (NH) at the noon meridian plane measured by the Challenging Minisatellite Payload (CHAMP) polar-orbiting satellite at about 390 km altitude during the 20 November 2003 magnetic storm. The CHAMP satellite measurements render rare documentation about the dayside SED's life cycle at a fixed magnetic local time (MLT) through multiple passes. Solar wind drivers triggered the SED onset and controlled its lifecycle through its growth and retreat phases. The SED electron density enhancement extended from the equatorial ionization anomaly to the noon cusp. The midlatitude electron density increased to a maximum at the end of the growth phase. Afterward, the dayside SED region retreated gradually to lower magnetic latitudes. The observations showed a hemisphere asymmetry, with the NH electron density exhibiting a more significant enhancement. The simulations using the Thermosphere Ionosphere Electrodynamic General Circulation model show a good agreement with the CHAMP observations. The simulations indicate that the dayside midlatitude electron density enhancement has a complicated dependence on vertical ion drift, neutral wind, magnetic latitude, MLT, and the height of the F2 layer. Finally, we discuss the notion of using the mean cross-polar cap electric field as a proxy for assessing the effects of solar wind drivers on producing midlatitude electron density enhancement.