Predicted times, spatial coordinates of bow shock crossings and shock geometry at Mars from the NASA/MAVEN mission, using spacecraft ephemerides and magnetic field data, with a predictor-corrector algorithm

CHARACTERISTICS
Planet: Mars
Radius: R_M = 3389.5 km (volumetric mean planetary radius)
Spacecraft: NASA/Mars Atmosphere and Volatile Evolution (MAVEN)
Spacecraft coordinates system: Mars Solar Orbital (MSO) equivalent to Sun-State coordinate system:

• +X_MSO points towards the Sun from the planet’s centre,
• +Z_MSO towards Mars’ North pole and perpendicular to the orbital plane defined as the X_MSO–Y_MSO plane passing through the centre of Mars,
• Y_MSO completes the orthogonal system.

Time span: 01/11/2014 to 07/02/2021 (Mars Years 32 to 35 included).
Total number N of candidate bow shock crossings in the database: N = 14929

ORIGINAL DATASETS USED
The original MAVEN/MAG data repository on which these algorithms were applied is available on NASA's Planetary Data System (PDS) at https://doi.org/10.17189/1414178. For this study, 1-Hz magnetic field data was used.

METHOD
To construct this database from the original datasets above, the predictor and predictor-corrector algorithms used are described in:
Simon Wedlund, C., Volwerk, M., Beth, A., Mazelle, C., Möstl, C., Halekas, J., Gruesbeck, J. and Rojas-Castillo, D., (2022), A Fast Bow Shock Location Predictor-Estimator From 2D and 3D Analytical Models: Application to Mars and the MAVEN mission, Journal of Geophysical Research, 127, 1-33, e2021JA029942, https://doi. org/10.1029/2021JA029942. 

Also available at: https://doi.org/10.1002/essoar.10507942.1  and as arXiv e-print: https://doi.org/10.48550/arXiv.2109.04366

These algorithms consist of two consecutive steps: 

1. Predictor geometric algorithm based on J. Gruesbeck's 3D model (Gruesbeck et al. 2018) for prediction of Mars bow shock position
2. Corrector algorithm based on magnetic field measurements (magnitude and fluctuations).

REMARK ON VERSIONS
From Version 3 onwards, we provide also the angle between the average Interplanetary Magnetic Field (IMF) vector upstream of the shock and the shock normal, noted \(\theta_{Bn}\)(ThetaBn). Assuming a smooth shock surface and the 3D model of Gruesbeck et al. (2018, all points), this gives a first indication of the geometry of the shock, so that:

• 45^∘<θ_Bn<135^∘: quasi-perpendicular shock condition
• θ_Bn≤45^∘ and θ_Bn≥135^∘: quasi-parallel shock condition

Uncertainty on these angles is estimated to be ± 5º. 

For details, see Simon Wedlund et al. (2022) above, §2.3 pp. 10-12. Note that due to minor adjustments in the code, some of the ThetaBn angles calculated here for the examples of Fig. 6 in Simon Wedlund et al. (2022) may slightly differ from the values quoted in the paper.

VARIABLES DESCRIPTION
This database contains the following ASCII variables:

• Bow shock times in MAVEN's database (1-s resolution): T_bs
• Mars Solar Orbital coordinates of the shock, in units of Mars radius R_M (R_M = 3389.5 km):
  X_MSO, Y_MSO, Z_MSO and Euclidean distance \(R_{MSO} = \sqrt{X_{MSO}^2 + Y_{MSO}^2 + Z_{MSO}^2}\) (in R_M)
• Solar Zenith angle in degrees: SZA = \(\tan^{-1}{Y_{MSO}^2+Z_{MSO}^2 \over X_{MSO}^2}\) (in º) 
• Angle between average B-field direction and shock normal assuming a smooth shock surface \(\theta_{Bn}\) (ThetaBn, in º)
  • 45 < ThetaBn <  135 deg: quasi-⊥ shock
  • ThetaBn ≤45 deg & ThetaBn ≥ 135 deg: quasi-|| shock
• Crossing sheath \(\longrightarrow\) solar wind, flag = 0.
• solar wind \(\longrightarrow\) sheath, flag = 1.

WARNING
This database is based on an automatic statistical geometrical estimate, further refined by constraints on magnetic field. It is aimed at giving a first approximation of the shock area times in the MAVEN data. It is particularly suited to statistical studies and region identification in the MAVEN datasets. As such, this database should be used as a first indicator of the shock location, and with caution: it CANNOT, and WILL NOT substitute, especially in case studies, for a careful analysis of the full magnetometer and plasma suite bow shock signatures. Moreover, the algorithm is optimised for detecting the first disturbance observed in the magnetic field immediately ahead of the shock's foot (in the foreshock area), and not for the detection of other structures in the shock, such as the shock ramp. The "shock" location is therefore given here with typical uncertainties of about 0.075 R_M (with R_M = 3389.5 km, i.e., about 250 km in the radial direction). Finally, for multiple shock crossings, the algorithm chooses the first occurrence of the shock starting from the undisturbed solar wind.

Current formatting optimised for MATLAB.

ACKNOWLEDGEMENTS
C. Simon Wedlund and M. Volwerk thank the Austrian Science Fund (FWF) project P32035-N36. C. Möstl thanks the Austrian Science Fund FWF projects P31659-N27, P31521-N27. A. Beth thanks the Swedish National Space Agency (SNSA) and its support with the grant 108/18. This database was notably used to add to the Helio4Cast database which monitors solar wind parameters in the solar system (https://doi.org/10.6084/m9.figshare.6356420). Helio4Cast is available at www.helioforecast.space/icmecat and www.helioforecast.space/sircat.     

LICENSE AND RIGHTS
This database is shared under a Creative Commons CC-BY-4.0 license.

Version 1 (c) Cyril Simon Wedlund @ Space Research Institute of Graz (IWF), 
                                                            Austrian Academy of Sciences (ÖAW), 2021-09-08
Version 2 (c) CSW @ ÖAW/IWF, 2021-11-30 -- Addition of R_MSO and SZA
Version 3 (c) CSW @ ÖAW/IWF, 2022-02-09 -- Addition of ThetaBn
Contact email:        cyril.simon.wedlund@gmail.com