On the local time dependence of the penetration of solar wind-induced electric fields to the magnetic equator

Abstract

Abstract. For a period of a few hours, the penetration of electric fields of solar wind origin is at its highest efficiency. In November 2003, five days of continuous vertical drift data were obtained at the Jicamarca Radio Observatory. Here we have isolated a range of frequencies centered at a few-hour period for a five-day period and have explored the local time dependence of the penetration, along with the time delay due to magnetospheric effects. We find that the latter ranges from 15 to 25 min.

Electrodynamic coupling processes between the magnetosphere and the equatorial ionosphere during a 5-day HILDCAA event

“…The acronym HILDCAA (Tsurutani and Gonzalez, 1987) stands for High-Intensity Long-Duration Continuous AE Activity and is concerned with a strong energetic coupling process that occurs between the interplanetary medium close to the Earth and the magnetosphere by means of multiple magnetic reconnections due to the existence of Alfvé n waves resulting in very intense, long duration and continuous auroral activity, during the absence of magnetic storms. The coupling between the magnetosphere and the equatorial ionosphere during HILDCAA is an interesting subject of study but it has been rarely studied so far (Sobral et al, 2006;Wei et al, 2008;Kelley and Dao, 2009). We present here for the first time a correlation analysis between the magnitude of the interplanetary electric field at the magnetopause and the perturbed displacement of the F-peak altitude with respect to quiet values (Abdu et al, 1988;Sobral et al, 1997), over an equatorial station, in order to identify prompt penetration-PP drifts during a 5-day HILDCAA event.…”

On the origin of pre-reversal enhancement of the zonal equatorial electric field

“…Although one can quibble with these linear relationships, the two measurements are 85% correlated using this model. The "departure" after 23:00 LT is actually a local time dependence of the penetrating field (Kelley and Dao, 2009). What caught our attention is the fact that, at the time when a normal pre-reversal enhancement was predicted by the quiet time model, the data showed a negative excursion, nearly a mirror image of the normal PRE.…”

Observations of the generation of eastward equatorial electric fields near dawn

“…This allowed them to determine definitively the local time dependence of the penetrating electric fields. Given that the signals discussed in the Kelley and Dao (2009) study displayed a very peaked spectrum at periods of one hour, which is quite a bit lower than the large-scale depletions, we note that the fine structure in the drifts and fields could well be associated with the HSS. Note that the meridional plasma drift is associated with zonal electric fields, and the zonal plasma drift is associated with meridional electric fields.…”

“…The associated and highly variably electric fields in the interplanetary medium are likely due to Alfven waves, which can penetrate to equatorial latitudes (e.g., Tsurutani and Gonzales, 1987;Kikuchi et al, 2008;Kelley, 2009). Kelley and Dao (2009) studied a fortuitous event in which simultaneous data existed from the ACE interplanetary satellite and the Jicamarca radar during such an event. This allowed them to determine definitively the local time dependence of the penetrating electric fields.…”