Three decades of bow shock observations by IMP 8 and model predictions

During almost three decades of operation, the IMP 8 satellite collected an extensive amount of both plasma and magnetic field measurements. The entire data set has been searched for all Earthʹs bow shock crossings observed by IMP 8. We have recorded total 11,455 single and multiple bow shock crossings and for 5870 of the crossings complete upstream interplanetary magnetic field and solar wind parameters, measured by the same spacecraft, were available allowing us to test empirical models predicting the bow shock position as a function of upstream parameters. The chosen models were F79, NS91, FR94, CL95, P95 and V01 (Planet. Space Sci. 27(9) (1979) 1151; J. Atmos. Terr. Phys. 53 (1991) 1049; J. Geophys. Res. 99(A9) (1994) 17,681; J. Geophys. Res. 100(A9) (1995) 17,173; J. Geophys. Res. 100(A5) (1995) 7907; Earth Planets Space 53 (2001) 1001). This study investigates these models’ accuracy not only for average upstream conditions but also for unusual conditions and as a result points out some deficiencies of these models. We demonstrate that most of the models underestimate bow shock distance for low Mach numbers and/or high magnitudes of IMF components.