Ionospheric storm effects of disturbed electric fields

Sunday, August 12, 2012

A comprehensive modeling investigation of ionospheric and thermospheric variations during a prompt penetration electric field on 9 November 2004.

Altitude distributions of electron density image
Altitude distributions of electron density at selected UT times on 9 November 2004 show the super-fountain effect associated with the prompt penetration electric fields. The white lines indicate the geomagnetic field lines.

Using the Thermosphere-Ionosphere-Mesosphere Electrodynamic General Circulation Model (TIMEGCM). The simulation results reveal complex latitudinal and longitudinal/local-time variations in vertical ion drift in the middle- and low-latitude regions owing to the competing influences of electric fields and neutral winds. It is found that electric fields are the dominant driver of vertical ion drift at the magnetic equator; at midlatitudes, however, vertical ion drift driven by disturbance meridional winds exceeds that driven by electric fields. The temporal evolution of the UT-latitude electron density profile from the simulation depicts clearly a super-fountain effect caused by the PPEF, including the initial slow-rise of the equatorial F-layer peak height, the split of the F-layer peak density, and the subsequent downward diffusion of the density peaks along magnetic field lines. Correspondingly, low-latitude total electron content (TEC) becomes bifurcated around the magnetic equator. The O/N2 column density ratio, on the other hand, shows very little variations during this PPEF event, excluding composition change as a potential mechanism for the TEC variations. By using realistic, time-dependent, high-latitude electric potential and auroral precipitation patterns to drive the TIMEGCM, the model is able to successfully reproduce the large vertical ion drift of ~120 m/s over the Jicamarca incoherent radar (IS) in Peru, which is the largest daytime ion drift ever recorded by the radar.

Reference: Lu, G., L. Goncharenko, M. J. Nicolls, A. Maute, A. Coster, and L. J. Paxton (2012), Ionospheric and thermospheric variations associated with prompt penetration electric fields, J. Geophys. Res., 117, A08312, doi:10.1029/2012JA017769.