Shock-crossing data obtained from spacecraft are used to test the shock location models derived by Chapman and Cairns  . Three sets of data are considered: (1) ISEE 1 for 24–25 September 1987, (2) Wind, Geotail, IMP 8, and Interball for the intervals 26–27 April and 10–13 May 1999, and (3) IMP 8, Geotail, Magion-4, and Cluster during the period 1973–2003 from the bow shock database (available at http://nssdc.gsfc.nasa.gov/ftphelper/bowshock.html). Derived from MHD simulations, the two shock models are for angles θIMF = 45° and 90° between the upstream magnetic field BIMF and solar wind velocity vsw. These models have azimuthal asymmetries, and they depend explicitly on the upstream Mach number MA and ram pressure Pram. We also test Cairns et al.'s  rotationally symmetric shock model. The new models perform better on average than the rotationally symmetric model, providing some evidence and support for the shock's shape being strongly dependent upon MA and θIMF. We also compare our analyses here with model/spacecraft comparisons performed by Merka et al. [2003a] and discuss the importance of filtering on the model predictions.
- bow shock shape
- Mach number