Penetration electric fields: A Volland–Stern approach

Abstract

This paper reformulates the Volland–Stern model, separating contributions from corotation and convection to predict electric field penetration of the inner magnetosphere using data from the Advanced Composition Explorer (ACE) satellite. In the absence of shielding, the model electric field is E VS= Φ PC/2 L Y R E, where Φ PC is the polar cap potential and 2 L Y R E is the width of the magnetosphere along the dawn–dusk meridian. Φ PC is estimated from the interplanetary electric field (IEF) and the dynamic pressure of the solar wind ( P SW); values of L Y were approximated using P SW and simple force-balance considerations. ACE measurements on 16–17 April 2002 were then used to calculate E VS for comparison with the eastward electric field component ( E Jφ ) detected by the incoherent scatter radar at Jicamarca, Peru. While the interplanetary magnetic field (IMF) was southward, the model predicted observed ratios of E VS/IEF. During intervals of northward IMF, E Jφ turned westward suggesting that a northward IMF B Z system of field-aligned currents affected the electrodynamics of the dayside ionosphere on rapid time scales.