Solar and geomagnetic activity effects on mid-latitude F-region electric fields

Abstract

Abstract. Diurnal patterns of average F-region ionospheric drift (electric field) and their dependence on solar and geomagnetic activity have been defined using digital ionosonde Doppler measurements recorded at a southern mid-latitude station (Bundoora 145.1 • E, 37.7 • S geographic, 49 • S magnetic). A unique database consisting of 300 907 drift velocities was compiled, mostly using one specific mode of operation throughout 1632 days of a 5-year interval (1999)(2000)(2001)(2002)(2003). The velocity magnitudes were generally larger during the night than day, except during the winter months (JuneAugust), when daytime velocities were enhanced. Of all years, the largest drifts tended to occur during the high speed solar wind streams of 2003. Diurnal patterns in the average quiet time (AE<75 nT) meridional drifts (zonal electric field) peaked at up to ∼6 m s −1 poleward (0.3 mV m −1 eastward) at 03:30 LST, reversing in direction at ∼08:30 LST, and gradually reaching ∼10 m s −1 equatorward at ∼13:30 LST. The quiet time zonal drifts (meridional electric fields) displayed a clear diurnal pattern with peak eastward flows of ∼10 m s −1 (0.52 mV m −1 equatorward) at 09:30 LST and peak westward flows around midnight of ∼18 m s −1 (0.95 mV m −1 poleward). As the AE index increased, the westward drifts increased in amplitude and they extended over a greater fraction of the day. The perturbation drifts changed in a similar way with decreasing D st except the daytime equatorward flows strengthened with increasing AE index, whereas they became weak for D st <−60 nT. The responses in all velocity components to changing solar flux values were small, but net poleward perturbations during the day were associated with large solar flux values (>192×10 −22 W m −2 Hz −1 ). These results help to more fully quantify the response of the midlatitude ionosphere to changing solar and geomagnetic conditions, as required to refine empirical and theoretical models of mid-latitude electric fields.Correspondence to:

The effects of thunderstorm-generated atmospheric gravity waves on mid-latitude F-region drifts

“…The control times for the SEA were the times of CG lightning strokes measured by the World Wide Lightning Location Network (WWLLN) (Dowden et al, 2008) from August 2003 to August 2004; the first year WWLLN was fully operational. Parkinson et al (2001) and Kumar et al (2008) previously analysed the geomagnetic effects on the Bundoora database. Later, Kumar et al (2009) investigated the response of the F-region vertical drift due to CG lightning strokes located within 600 km of Bundoora.…”

Thunderstorm-associated responses in the vertical motion of the mid-latitude F-region ionosphere

“…We addressed this problem by creating a statistical model using the 5.5-year F-region database, with the results separated into two representative seasons, the spring-summer months (September-February) and autumn-winter months (MarchAugust). Also, it was found the drift magnitudes were generally larger than usual in the year 2003 (Kumar et al, 2008) due to the high-speed solar wind streams known to re-occur during the declining phase of solar activity (e.g. Cliver et al, 1996).…”

“…The use of a long integration time (40.96-s) and thus high Doppler resolution meant that our estimates of vertical velocity V z were very accurate (Parkinson et al, 2001). Kumar et al (2008) analysed the entire DPS-4 F-region database and found that the velocities exhibited well-defined diurnal and seasonal variations with strong sensitivity to AE. The results were consistent with earlier studies using incoherent scatter radar (e.g.…”

“…In this work, we use part of a 5.5-year (February 1999-August 2004) digital ionosonde (DPS-4) database complied at a southern mid-latitude station, Bundoora, Melbourne (145.11E, 37.71S) (Kumar et al, 2008), 1-min auroral electrojet (AE) index and World Wide Lightning Location Network (WWLLN) (Dowden et al, 2002) data, to determine thunderstorm-associated responses in the overhead ionosphere. The chosen study interval was August 2003-2004, the first year WWLLN was fully operational.…”

Ionospheric response over South Africa to the geomagnetic storm of 11–13 April 2001

“…The F region electric field drifts are believed to be caused by differences in the ionisation (Kelley et al, 1979;Kumar et al, 2008). The study of low latitude ionospheric electric fields and currents by Fejer (2003) using incoherent scatter radar measurements from Arecibo (181N, 671W, dip latitude 301N) and Jicamarca (11.91S, 76.81W, dip latitude 11N) showed that F2 region parameters (e.g.…”