A Spherical Harmonic Martian Crustal Magnetic Field Model Combining Data Sets of MAVEN and MGS

Abstract

From 1997 to 2006, the Mars Global Surveyor (MGS) spacecraft provided magnetic field measurements while orbiting Mars, extensively sampling the magnetic field at an altitude of about 400 km (Acuña et al., 1998) after periapsis was raised upon completion of the aerobraking phase. The MGS mission discovered that Mars possesses many localized remanent magnetic fields, which most likely originate in the Martian lithosphere (Acuña et al., 1999). Remanent magnetic fields, otherwise known as crustal fields or lithospheric magnetic fields, are widely believed to be induced by an ancient core dynamo. Mars currently does not have a global dipole magnetic field as in the case of Earth and Mercury (Langlais et al., 2010). The most intense crustal fields of Mars are located in the Southern Hemisphere. These fields are 1 to 2 orders of magnitude stronger than the crustal fields on Earth (Kother et al., 2015;Voorhies et al., 2002), 3 to 4 orders of magnitude stronger than the crustal fields on Moon (Purucker & Nicholas, 2010) and Mercury (Johnson et al., 2015).

Three‐Dimensional Configuration of Induced Magnetic Fields Around Mars

“…We found 4,179 orbits in total that satisfy the conditions of a steady IMF; the measured magnetic field vectors were transformed into MSE for each orbit. To exclude the direct influence of crustal fields, we only kept magnetic field data points satisfying $${\vert B}_{\mathrm{o}\mathrm{b}\mathrm{s}}\vert \ge 10\vert {B}_{\mathrm{m}\mathrm{o}\mathrm{d}\mathrm{e}\mathrm{l}}\vert $$, where $${\vert B}_{\mathrm{o}\mathrm{b}\mathrm{s}}\vert $$ is the recorded magnetic field strength and $$\vert {B}_{\mathrm{m}\mathrm{o}\mathrm{d}\mathrm{e}\mathrm{l}}\vert $$ is the magnetic field strength predicted by a state‐of‐the‐art crustal fields model (Gao et al., 2021). However, our way to remove the crustal field may not exclude the indirect influence of the crustal field on some processes due to the interaction with solar wind (e.g., reconnection and compression).…”

“…We found 4,179 orbits in total that satisfy the conditions of a steady IMF; the measured magnetic field vectors were transformed into MSE for each orbit. To exclude the direct influence of crustal fields, we only kept magnetic field data points satisfying 𝐴𝐴 |𝐵𝐵obs| ≥ 10|𝐵𝐵model| , where 𝐴𝐴 |𝐵𝐵obs| is the recorded magnetic field strength and 𝐴𝐴 |𝐵𝐵model| is the magnetic field strength predicted by a state-of-the-art crustal fields model (Gao et al, 2021). However, our way to remove the crustal field may not exclude the indirect influence of the crustal field on some processes due to the interaction with solar wind (e.g., reconnection and compression).…”

Mars‐Ward Ion Flows in the Martian Magnetotail: Mars Express Observations

“…There are more observations near the equator region due to the bias of orbit coverage and the IMA's attitude. Figures 3c and 3d show the location of events of Mars‐ward O + and O 2 + in geographic coordinates that overlap with crustal fields at 160 km, which was obtained from a crustal fields model (Gao, Rong, Klinger, et al., 2021), respectively. Figures 3c–3f shows that most events for both O + and O 2 + occurred above magnetic anomalies, especially in the strongest crustal fields region (Latitude ∼ −50, Longitude ∼ 180).…”

A magnetohydrodynamic simulation of the dayside magnetic reconnection between the solar wind and the Martian crustal field

“…On the one hand, this might be due to the irregular crustal field at longitude = 150 • W where it is at the edge of the intense crustal field region. On the other hand, the crustal field model (Arkani-Hamed 2001) may also affect the result that can be improved by a more accurate model with the latest magnetic field data in the future (e.g., Morschhauser et al 2014;Langlais et al 2019;Gao et al 2021). Besides the longitude effect, the latitude information is also important (e.g., Fang et al 2017), as the change of the latitude at the subsolar point would definitely influence the location of the intense crustal field and the magnetic field topology in the north-south direction of the MSO coordinates.…”