Persistent global proton aurora caused by high solar wind dynamic pressure

Abstract

[1] Global images of the proton aurora taken with the SI-12 camera onboard the IMAGE satellite reveal a very direct relationship between the solar wind dynamic pressure and the intensity of the global proton aurora. We show that an increase in dynamic pressure leads to an immediate and persistent increase in proton precipitation, also when the increase is slow. When the dynamic pressure decreases, the proton aurora diminishes. Five events during geomagnetic quiet times, with mostly northward IMF, have been selected in order to characterize the proton aurora caused exclusively by high dynamic pressure and establish important criteria that the dynamic pressure-induced precipitation mechanism(s) must satisfy. We also present measurements during southward IMF and show that the combined effect of high solar wind dynamic pressure and southward IMF produces intense global proton aurora. Some of the characteristics are: (1) The aurora is global, with peak intensities at midnight and flanks. (2) A dawn/dusk asymmetry shows that the precipitation originates from magnetospheric protons that have undergone gradient/curvature drift. (3) The time delay between ground magnetic signatures of a change in the solar wind dynamic pressure and a change in global proton aurora is short (À2 minutes). Our observations indicate that the precipitation mechanism(s) behind the proton aurora during high dynamic pressure is directly connected to the compression of the magnetosphere, both at the flanks and nightside.Citation: Laundal, K. M., and N. Østgaard (2008), Persistent global proton aurora caused by high solar wind dynamic pressure,

The Detached Auroras Induced by the Solar Wind Pressure Enhancement in Both Hemispheres From Imaging and In Situ Particle Observations

“…Thus, the loss cone of the protons can be expected to increase significantly and much more protons will get lost into the ionosphere. In addition to the pressure pulse mentioned here, the persisted solar wind pressure enhancement could cause the proton aurora, as have been reported in previous investigations (Laundal & Østgaard, ; Liou et al, ).…”

Earth's collision with a solar filament on 21 January 2005: Overview

“…We now know that high‐density plasma can amplify the damaging effects of magnetic storms [cf. Lyons , ; Zhou and Tsurutani , ; Liou et al ., ; Laundal and Østgaard , ; Weigel , ]. The highest solar wind densities in ICMEs are found in solar filament material [ Crooker et al ., ] and ICMEs are responsible for the most severe types of space weather [cf.…”

Decrease of auroral intensity associated with reversal of plasma convection in response to an interplanetary shock as observed over Zhongshan station in Antarctica

“…Zesta et al [2000] and Boudouridis et al [2003] found that the compression of the magnetosphere by an IP shock led to a global enhancement of the auroral-zone ionospheric currents and increase of the auroral emissions with poleward expansion of the auroral oval. It was also noticed that long-duration high solar wind ram pressure caused increase of the auroral intensity in the flanks of the auroral oval and there is a dawn-dusk asymmetry of the auroral luminosity [Liou et al, 2007;Laundal and Østgaard, 2008].…”

“…The large-scale auroral transient signatures in response to the IP shock (i.e., shock aurora) were analyzed by several authors using satellite observations [e.g., Zhou and Tsurutani, 1999;Sibeck et al, 1999;Zhou et al, 2003;Laundal and Østgaard, 2008]. Shock aurora observed from satellites [e.g., Zhou and Tsurutani, 1999;Tsurutani et al, 2001] show that the aurora immediately brightens near local noon at the time of the shock arrival.…”