Herein we have examined the relationships between the wave power on the ground and the upstream solar wind conditions by using a full 2 years of ground-based and solar wind data under all solar wind conditions that occurred during the period. The frequency range 4-64 mHz is divided into four bands in order to study the differences among them. We find a distinct difference in solar wind control of pulsation power between low-frequency (4-8 mHz) events and high-frequency (32-64 mHz) events.
For the high-frequency events that correspond to Pc3 waves, we confirm the existing model that their major energy source is the upstream waves in the foreshock region. They occur predominantly at low IMF cone angles and at the IMF magnitude (mHz)/6 nT. We further test the cusp entry hypothesis of Pc3 wave energy [Engebretson et al., 1991] by examining the high-frequency (32-64 mHz) wave power under different IMF orientations. However, our results show that the cusp entry does not appear to be important for the low-latitude Pc3 waves.
This study also reveals the relationships between the low-latitude Pc5 and the interplanetary parameters. Our observations show that both the occurrence and the amplitude of those wave events are greater during southward IMF. This suggests that the major energy source is likely to be related to substorms or the reconnection on the dayside magnetopause.
P. J. C. is grateful to M. G. Kivelson and R. J. Strangeway at IGPP, UCLA, for their helpful comments. This work is supported by the National Science Foundation under research grant ATM 94-13081.
The Editor thanks L. J. Lanzerotti and K. Yumoto for their assistance in evaluating this paper.