Ionospheric Response to Solar Wind Pressure Pulses Under Northward IMF Conditions

Abstract

Enhancements of aurora and auroral electrojets in response to sudden compression of the magnetosphere by shocks/ pressure pulses are well known and have been attributed by some to compression-enhanced magnetic field reconnection. To examine such a view, we analyze a fortuitous event that is comprised of a series of pressure pulses (< 20 min) on November 8, 2000. These pressure pulses were preceded by a large, northward interplanetary magnetic field (IMF) that lasted more than 15 hours such that effects from reconnection can be minimized. Auroral images acquired by ultraviolet imager on board the Polar satellite clearly show intensifications of the aurora that occurred first near local noon and progressively extended from dayside to nightside. The area-integrated global auroral power reached ~30 gigawatts (GW). It is also found that the global auroral power is well correlated with the solar wind dynamic pressure (correlation coefficient r ~0.90), rather than the change in the solar wind dynamic pressure. In-situ measurements of particle data from the Defense Meteorological Satellite Program satellite indicate that the magnetospheric source for the pressure-enhanced auroras is most likely the central plasma sheet. Other ionospheric parameters such as the auroral electrojet (AE index), magnetic storm index (Sym-H), and the cross polarcap potential drop also show a one-to-one correspondence to the pressure pulses. In one instance the auroral electrojets AE index reached more than 200 nT, the cross polar-cap potential drop (φ pc ) inferred from the SuperDARN radar network ionospheric plasma convection increased to ~60 kV. The observed increases in the auroral emissions, AE, and polar cap potential were not associated with substorms. Our result strongly suggests that solar wind pressure pulses are an important source of geomagnetic activity during northward IMF periods.

Study of a global auroral Pc5 pulsation event with concurrent ULF waves

“…It has also been shown that periodic changes in the solar wind dynamic pressure can also drive auroral Pc5 pulsations at the same frequency in the dawn and dusk flanks [ Liou et al ., ]. Because the response of the auroral intensity to solar wind pressure pulses is prompt and one to one [ Liou et al ., ], compression and decompression of the magnetosphere can cause the auroral intensity to increase and decrease, respectively [ Liou et al ., , ]. However, we do not find any obvious periodic structures in the solar wind at the same frequencies as the pulsations.…”

Characteristics of PMSE associated with the geomagnetic disturbance driven by corotating interaction region and high‐speed solar wind streams in the declining solar cycle 23

“…Electrons can be accelerated by the Pc5 ULF waves, to have high energy (>30 keV), even up to relativistic levels (0.5 MeV), finally precipitating into the atmosphere [Rostoker et al, 1998]. It is well established that dayside aurora can be caused by the solar wind dynamic pressure enhancement [Boudouridis et al, 2007;Zhou and Tsurutani, 1999;Liou et al, 2013;Tsurutani et al, 2006]. As shown in Figure 3a, it is distinctive that the correlation of PMSE with Vsw is higher in solar minimum years than solar maximum years, suggesting that precipitating high-energy particles driven by high-speed solar wind streams and the preceding CIRs likely have an effect on PMSE production.…”