A Fast Bow Shock Location Predictor-Estimator From 2D and 3D Analytical Models: Application to Mars and the MAVEN Mission

We present fast algorithms to automatically estimate the statistical position of the bow shock from spacecraft data, using existing analytical two-dimensional (2D) and three-dimensional (3D) models of the shock surface. We derive expressions of the standoff distances in 2D and 3D and of the normal to the bow shock at any given point on it. Two simple bow shock detection algorithms are constructed, one solely based on a geometrical predictor from existing models, the other using this predicted position to further refine it with the help of magnetometer data, an instrument flown on many planetary missions. Both empirical techniques are applicable to any planetary environment with a defined shock structure. Applied to the Martian environment and the NASA/MAVEN mission, the predicted shock position is on average within 0.15 planetary radius R p of the bow shock crossing. Using the predictor-corrector algorithm, this estimate is further refined to within a few minutes of the true crossing (≈0.05R p). Between 2014 and 2021, we detect 14,929 clear bow shock crossings, predominantly quasi-perpendicular. Thanks to 2D conic and 3D quadratic fits, we investigate the variability of the shock surface with respect to Mars Years (MY), solar longitude (Ls), and solar EUV flux levels. Although asymmetry in Y and Z Mars Solar Orbital coordinates is on average small, we show that for MY32 and MY35, Ls = [135°-225°] and high solar flux, it can become particularly noticeable, and is superimposed to the usual North-South asymmetry due in part to the presence of crustal magnetic fields.

A new model of the crustal magnetic field of Mars using MGS and MAVEN

While devoid of an active magnetic field today, Mars possesses a remanent magnetic field which may reach several thousand nT locally. The exact origin, and the events which have shaped the crustal magnetization remain largely enigmatic. Three magnetic field datasets from two spacecraft collected over 13 cumulative years have sampled the martian magnetic field over a range of altitudes from 90 km up to 6000 km: a- Mars Global Surveyor (MGS) magnetometer (1997-2006); b- MGS Electron Reflectometer (1999-2006); c- MAVEN magnetometer (2014-today). In this paper we combine these complementary datasets for the first time to build a new model of the martian internal magnetic field. This new model improves upon previous ones in several aspects: comprehensive data coverage; refined data selection scheme; modified modeling scheme; discrete-to-continuous transformation of the model; increased model resolution. The new model has a spatial resolution of ~ 160 km at the surface, corresponding to spherical harmonic degree 134. It shows small scales and well defined features, which can now be associated with geological signatures.

Magnetic Field and Plasma Observations at Mars: Initial Results of the Mars Global Surveyor Mission

The magnetometer and electron reflectometer investigation (MAG/ER) on the Mars Global Surveyor spacecraft has obtained magnetic field and plasma observations throughout the near-Mars environment, from beyond the influence of Mars to just above the surface (at an altitude of approximately 100 kilometers). The solar wind interaction with Mars is in many ways similar to that at Venus and at an active comet, that is, primarily an ionospheric-atmospheric interaction. No significant planetary magnetic field of global scale has been detected to date (<2 x 10(21) Gauss-cubic centimeter), but here the discovery of multiple magnetic anomalies of small spatial scale in the crust of Mars is reported.