Statistical identification of solar wind origins of magnetic impulse events

{[}1] We have compiled a complete list of magnetic impulse events (MIEs) during the 8-year period of 1995 - 2002 covering solar minimum to solar maximum using fluxgate magnetometer data obtained at the South Pole. Wavelet analysis enables us to detect 825 distinct MIEs automatically with high confidence. Interplanetary magnetic field ( IMF) discontinuities are also detected automatically for the same period from Wind and ACE satellite data. From an examination and comparison of the two lists, we find that monthly and seasonal variations in IMF discontinuity occurrences have a significant correlation (0.4 - 0.5) with those of MIEs. We also find that MIEs tend to occur during intervals of low density, high-speed solar wind streams, and/or radial IMF. No preferences for MIE occurrences are found for solar wind pressure jumps or IMF Bz southward turnings. From detailed minimum variance analysis of 36 IMF discontinuities with one-to-one correspondence to MIEs, similar to70% of the IMF discontinuities are found to be tangential discontinuities. The hot flow anomaly (HFA) mechanism can explain at most similar to50% of the MIEs; bursty reconnection and pressure pulses can explain the production of at most similar to30% and similar to20% of the MIEs, respectively. All of the observations and associations are consistent with HFAs or foreshock cavities being the main cause of MIEs.