The solar wind pressure variations are associated either with tangential discontinuities or interplanetary shocks, which are intrinsic to the solar wind, or with foreshock pressure pulses generated at the bow shock (Korotova and Sibeck, 1994). The pressure pulses have an important role in the solar wind - magnetosphere - ionosphere coupling. They
- compress the magnetopause,
- enhance magnetospheric magnetic field strength, and
- excite resonant azimuthal magnetic field oscillations
The ground-based signatures of the pressure pulses are divided into two groups:
- low-latitude magnetometers record sudden impulse/sudden storm commencement (SI/SSC) signatures as simple step function increases (or decreases) in the H component.
- high-latitude magnetometers record bipolar signatures in the H component (traveling convection vortices)
- Korotova, G. I., D. G. Sibeck, Generation of ULF magnetic pulsations in response to sudden variations in solar wind dynamic pressure, in Solar Wind Sources of Magnetospheric Ultra-Low-Frequency Waves, Geophysical Monograph 81, 265-271, 1994.