Satellite in-situ electron density observations of the storm enhanced
density and the polar Tongue of Ionization on the noon meridional plane
in the F region during the 20 November 2003 magnetic storm
Abstract
Satellite in-situ electron density observations of the storm enhanced
density 2 and the polar Tongue of Ionization on the noon meridional
plane in the F 3 region during the The first report on satellite
in-situ electron density measurements of the storm enhanced 15 density
at the noon meridian plane 16 The lifecycle of ionospheric storm
enhanced densities is mainly controlled by variations 17 of the dayside
prompt penetration electric fields 18 The key methodologies include a
comparison of TIEGCM modeling with satellite in-situ 19 electron density
observations and a correlation analysis 20 21 22 Abstract 23 Ionospheric
storm enhanced density (SED) has been extensively investigated using
Total 24 Electron Content (TEC) deduced from GPS ground and
satellite-borne receivers. However, in-25 situ electron density
measurements have not been reported for SEDs yet. We report in-situ 26
electron density measurements of a SED event and its associated polar
tongue of ionization 27 (TOI) at the noon meridian plane measured by the
CHAMP polar-orbiting satellite at about 390 28 km altitude during the 20
November 2003 magnetic storm. The measurements provided rare 29 evidence
about the SED’s life cycle at a fixed magnetic local time. CHAMP
detected the SED 30 onset right after the arrival of an interplanetary
coronal mass ejection shock front. The SED 31 electron density
enhancement extended from the equatorial ionization anomaly to the noon
cusp, 32 through which plasmas entered into the polar cap as polar
plasma clouds/TOI. For several 33 satellite-ground conjunction passes,
CHAMP measured the electron density of plasma clouds 34 comparable to
the TOI density measured by the Tromso ISR, establishing that the plasma
clouds 35 were related to the TOI. The SED plume in the NH retreated
gradually to lower latitudes six 36 hours after the SED onset. We
conducted TIEGCM modeling to demonstrate that the SED 37 density
enhancement was likely due to the vertical transport of plasmas. The
observed mid-38 latitude electron density varied with the cross-polar
cap electric fields, suggesting that prompt 39 penetration electric
fields (PPEFs) in the zonal direction played a dominant role. The 40
implication is that variations of the dayside PPEFs largely control the
SED lifecycle. 41 42 Plain Language Summary 43 Ground radar and GPS
stations have frequently detected enhancement of ionospheric electron 44
density at mid-latitudes and in the polar cap during the magnetic storm
recovery phase. We 45 report in-situ satellite observations near 400 km
at the noon meridian plane during an intense 46 magnetic storm. It
provides for the first time clear evidence about the life cycle of
ionospheric 47 electron density enhancement, starting from its onset at
mid-latitudes, entry into the polar cap, 48 and retreat to lower
latitudes. The mid-latitude ionospheric electron density was mainly 49
enhanced in the northern hemisphere, triggered by the passage of a solar
wind dynamic pressure 50 shock front. Global circulation modeling
suggests that the vertical transport of ionospheric 51 plasmas probably
produced the enhancement. The dayside prompt-penetration electric fields
in 52 the zonal direction likely drove the vertical plasma uplift. Thus,
it appears that the SED lifecycle 53 is mainly controlled by variations
of the dayside prompt electric field. 54