A fast bow shock location predictor-estimator from 2D and 3D analytical
models: Application to Mars and the MAVEN mission
Abstract
We present general empirical analytical equations of bow shock
structures historically used at Mars, and show how to estimate
automatically the statistical position of the bow shock with respect to
spacecraft data from 2D polar and 3D quadratic fits. Analytical
expressions of bow shock normal in 2D and 3D are given for any point on
the shock’s surface. This empirical technique is applicable to any
planetary environment with a defined shock structure. Applied to the
Martian environment and the NASA/MAVEN mission, the predicted bow shock
location from ephemerides data is on average within 0.15 planetary
radius Rp of the actual shock crossing as seen from
magnetometer data. Using a simple predictor-corrector algorithm based on
the absolute median deviation of the total magnetic field and the
general form of quasi-perpendicular shock structures, this estimate is
further refined to within a few minutes of the true crossing (≈0.05
Rp). With the refined algorithm, 14,929 bow shock
crossings, predominantly quasi-perpendicular, are detected between 2014
and 2021. Analytical 2D conic and 3D quadratic surface fits, as well as
standoff distances, are successively given for Martian years 32 to 35,
for several (seasonal) solar longitude ranges and for two solar EUV flux
levels. Although asymmetry in Y and Z Mars Solar Orbital
coordinates is on average small, it is shown that for Mars years 32 and
35, Ls = [135-225] degrees and high solar flux, it can become
particularly noticeable and is superimposed to the usual North-South
asymmetry due to the presence of crustal magnetic fields.