High‐latitude ionospheric response to a sudden impulse event during northward IMF conditions

Abstract

A high‐density structure under northward interplanetary magnetic field BZ conditions is identified at the Wind and IMP 8 satellites, both in the solar wind on August 22, 1995. A compression of the magnetosphere is observed by the GOES 7 magnetometer within a few minutes of the pressure increase encountering the magnetopause. The response of the high‐latitude ionosphere is analyzed on the basis of ground‐based magnetometer data. A comprehensive description of this response in the Northern Hemisphere is provided by more than 70 ground magnetometers. This data set is interpreted in terms of high‐latitude ionospheric potential patterns by means of the assimilative mapping of ionospheric electrodynamics technique. Convection cells in the polar cap are formed and disappear on minute timescales in accordance with previous results. However, the high‐latitude ionospheric ground magnetic signature does not match the interpretation as events of traveling convection vortices, as has been suggested by past studies.

The response of the magnetosphere-ionosphere system to a sudden dynamic pressure enhancement under southward IMF conditions

“…Engebretson et al (1999) showed equivalent convection patterns calculated from all available magnetometer data for the preliminary impulse and revealed traveling convection vortices (TCV). Moretto et al (2000) interpreted the response measured by ground-based magnetometers to a compression of the magnetosphere on 22 August 1995 in terms of potential patterns by means of the assimilative mapping of ionospheric electrodynamics (AMIE) technique (Richmond and Kamide, 1988). Slinker et al (1999) studied the ionospheric response to a density pulse in the solar wind using a global 3-D MHD model.…”

“…While some studies mentioned above did not account for the IMF orientation (e.g., Lysak and Lee, 1992;Engebretson et al, 1999), some studies specifically focused on pressure changes when the IMF was northward (e.g., Russell and Ginskey, 1995;Slinker et al, 1999;Moretto et al, 2000;Fujita et al, 2003a,b). Using the University of Michigan MHD code, we have investigated the response of the magnetosphere-ionosphere system to a sudden pressure enhancement under northward IMF conditions and found the same responses as those reported by Slinker et al (1999), Keller et al (2002), Fujita et al (2003a), Fujita et al (2003b).…”

“…Engebretson et al (1999) suggested the first short-lived set of FACs results in charge imbalances, which, when unloading, could help to enhance the effect of the second set of FACs. Araki (1994), Moretto et al (2000) explained the first response as a result of a dusk-to-dawn inductive electric field launched by a compressional wave that is caused by the sudden change in magnetic field at the dayside magnetopause due to the compression induced by the pressure enhancement. While Araki (1994) attributed the second response to enhanced convection electric fields, Moretto et al (2000) inferred it as a generic feature of the magnetospheric and ionospheric response to the pressure increase, but did not determine the physical mechanism.…”

“…Araki (1994), Moretto et al (2000) explained the first response as a result of a dusk-to-dawn inductive electric field launched by a compressional wave that is caused by the sudden change in magnetic field at the dayside magnetopause due to the compression induced by the pressure enhancement. While Araki (1994) attributed the second response to enhanced convection electric fields, Moretto et al (2000) inferred it as a generic feature of the magnetospheric and ionospheric response to the pressure increase, but did not determine the physical mechanism. Keller et al (2002) concluded that the first response is consistent with the theory of Kivelson and Southwood (1991) who proposed that Alfvén waves driven by a pressure perturbation near the magnetopause generates the FACs.…”

Daytime geomagnetic disturbances at high latitudes during a strong magnetic storm of June 21–23, 2015: The storm initial phase

“…It is known (e.g., (Moretto et al, 2000;Lukianova, 2004)) that the approach of the solar wind dynamic pres sure jumps to the Earth's magnetosphere affects the dis tribution of large scale ionospheric plasma convection at high latitudes. The data of the SuperDARN ground radar system (http://vt.superdarn.org/tiki index.php?page= Conv+map+overview), including the polar convec tion maps obtained by synthesizing the incoherent scatter radar observations and the known statistical models (e.g., (Cousins and Shepherd, 2010)), were used to consider variations in high latitude convection caused by dynamic pressure (Psw) jumps.…”