Comparison of Global 3D Bow Shock Models with Different Controlling Parameters

Abstract:

Interaction of the supersonic solar wind with Earth’s magnetosphere creates fast mode magnetosonic waves that travel back upstream, combine and steepen to form the bow shock wave. The bow shock wave has been studied for more than four decades but existing models are still often inaccurate.
Previous studies established that bow shock shape and position are primarily controlled by solar wind pressure, upstream Mach numbers, interplanetary magnetic field orientation and magnetopause shape and position.

We have collected a total of 28,287 bow shock crossings identified in observations from the Cluster 1-4, Geotail, IMP-8, Interball-1, MAGION-4, THEMIS A-E and WIND spacecraft and use this database to predict bow shock position as a function of solar wind parameters.

The database of bow shock crossings is fitted using a method similar to Peredo et al. [1995] which presumes a general 3D second-order bow shock shape parameterized by the upstream dynamic pressure and Alfven Mach number values. The use of a prescribed shock shape results in a model that provides accurate predictions for Alfven Mach numbers as low as 2 and can be used with confidence up to 40 Re along the magnetotail. For comparison, we apply the same method to create additional global 3D bow shock models parameterized by various parameters such as interplanetary magnetic field magnitude, solar wind proton density, bulk speed, etc. The best model is sought that would be most accurate for a wide range of upstream conditions.