Impact of interplanetary shock on the ULF wave activity: A case study of the storm sudden commencement on September 22, 1999

Abstract

We have analyzed short-period geomagnetic pulsations measured by the north-south chain of pulsation magnetometers in Finland in association with the storm sudden commencement (SSC) recorded on September 22, 1999 at 12:22 UT. We observe that structured Pc 1 pulsations with amplitude modulation (modulation period is about 1000 seconds) were excited before the SSC whereas intense wave elements with rising frequency appear soon after SSC. It is concluded that the first effect is due to the interaction of the Earth's magnetosphere with the interplanetary foreshock region. The second one is likely the result of modification of Pc 1 waves due to interaction between the magnetosphere and the shock front structure leading to compression of the magnetosphere during the initial phase of the magnetic storm.

Influence of short-term solar disturbances on the fair weather conduction current

“…Another ground-based method for studying the coupling between the magnetosphere and the mid and low atmosphere is by measurement of Ultra Low Frequency (ULF) magnetic pulsations (Kangas et al 2001;McPherron 2005). They result from the interaction of the solar wind and Earth's magnetosphere, and are a manifestation of ULF plasma waves in the magnetosphere.…”

Pc1 waves in the system of solar–terrestrial relations: New reflections

“…When an interplanetary shock interacts with the Earth's magnetosphere a sharp compression of geomagnetic field is produced (Nishida, 1978). This results in a sudden magnetic impulse (SI) and a short time later in a series of Pc1 pearl waves (Heacock and Hessler, 1965;Kangas et al, 1986Kangas et al, , 2001Kangas et al, , 2005. The corresponding theory is based on the idea of redistribution of the energetic ions in the magnetosphere due to the compression of geomagnetic field by the interplanetary shock wave (Olson and Lee, 1983;Kangas et al, 1998).…”

HF radio propagation through the auroral oval during substorms

“…3. This minimum of the EsMOF and maximum of the F2MOF (that is known as the main effect) is associated with the beginning of the change of the magnetosphere shape due to the influence of the accelerated particles of the solar wind before the To moment (Davies, 1990;Guglielmi et al, 2001;Kangas et al, 2001). Specifically, a compression of the entrance layer and the plasmapause occurs .…”