Rapid Movements of the Earth's Bow Shock

28 years of Earth bow shock crossings observed by the IMP 8 spacecraft between 1973 and 2000 have been compiled into a reference database. Each individual shock crossing is tabulated separately, rather than averaged together, allowing the systematic study of the location and motions of the bow shock over more than two solar cycles. The nearly circular IMP 8 orbit kept the observations near the same flank locations on both the dawn and dusk sides allowing meaningful comparisons over the years. The results of our systematic study will be presented showing the variability of the bow shock location as a function of the upstream solar wind parameters and their standard deviations. Moreover, dawn-dusk asymmetries largely due to the average orientation of the interplanetary magnetic field will be demonstrated. Also, wave analysis shows that for the cases when the bow shock was encountered many tens of times, a simple damped traveling wave does not fit the observations suggesting that the bow shock is continuously driven. These results suggest that the bow shock is very rarely in its steady state position, hence discrepancies with steady state model predictions are expected and the development of dynamic models becomes necessary. The upstream particle populations are also expected to be strongly influenced by the moving and accelerating bow shock.