Can a nightside geomagnetic Delta H observed at the equator manifest a penetration electric field?

Abstract

[1] A prompt penetration electric field (PPEF) usually manifests itself in the form of an equatorial ionospheric electric field being in correlation with a solar wind electric field. Due to the strong Cowling conductivity, a PPEF on the dayside can be inferred from Delta H (ΔH), which is the difference in the magnitudes of the horizontal (H) component between a magnetometer at the magnetic equator and one off the equator. This paper aims to investigate the performance of ΔH in response to a PPEF on the nightside, where the Cowling conductivity is not significant. We first examine the strongest geomagnetically active time during the 20 November 2003 superstorm when the Dst drops to À473 nT and show that the nightside ΔH can indeed manifest a PPEF but with local time dependence and longitude dependence. We then examine a moderately active time by taking advantage of the multiple-penetration event during 11-16 November 2003 when the Dst remains greater than À60 nT. During this event, a series of PPEF pulses recorded in Peru, Japan, and India form a database, allowing us to examine PPEF effects at different local times and longitudes. The results show that (1) the nightside ΔH was caused by attenuation of the effects of the polar electric field with decreasing latitude; (2) the nightside ΔH can manifest a PPEF at least in the midnight-dawn sector (0000-0500 LT), but not always; and (3) the magnitude of the nightside ΔH in the midnight-dawn sector in Peru is on average only 1/18 of that of the dayside ΔH in response to a given PPEF.

Response of the Ionosphere‐Plasmasphere Coupling to the September 2017 Storm: What Erodes the Plasmasphere so Severely?

“…From Figure it can be said that a westward (convection) electric field has penetrated for about 6 hr at least in the nightside ionosphere. The nightside EEJ was an order of magnitude smaller than the dayside EEJ as shown for geomagnetic storms (Tsuji et al, ; Wei et al, ) and substorms (Hashimoto et al, ), which indicates penetration of the electric field to the nightside equatorial ionosphere.…”

Ionospheric Irregularities During Disturbed Geomagnetic Conditions Over Argentinian EIA Region

“…However, several researchers reported PPEF signatures in ΔH on the nightside (Fejer et al, 2007;Galav et al, 2011). Moreover, Wei et al (2013) concluded that nightside ΔH can sometimes manifest a PPEF in the midnight-dawn sector (00-05 LT). We observed that on 28 May, ΔH increased between 2-8 UT (23-5 LT), this may be associated with an eastward penetration electric eld.…”

Electric field penetration into Earth’s ionosphere: a brief review for 2000–2013

“…However, several recent papers reported discernable PPEF signatures in DH on the nightside, where the Cowling conductivity is very weak [25,26]. Based on a multiple penetration event, Wei et al [27] suggested that the nightside DH was caused by the attenuation of the effects of polar electric field with decreasing latitude; the nightside DH can manifest PPEF at least in the midnight-dawn sector, but not always.…”