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The Martian bow shock has been extensively studied through magnetic field and plasma instrument observations from various Mars space missions. However, prior investigations primarily involve statistical analyses based on single spacecraft crossings, leaving the asymmetry of the Martian bow shock unstudied through simultaneous two‐spacecraft observations. In this study, utilizing simultaneous observations from Tianwen‐1 and MAVEN, we examine the instantaneous asymmetry of the Martian bow shock. We present the asymmetry of the Martian bow shock in the Mars‐Solar‐Electric and Mars‐Solar‐Orbital reference frames, possibly influenced by the solar wind motional electric field and Martian crustal magnetic field, respectively. Moreover, we suggest that the bow shock exhibits increased asymmetry under stronger solar wind motional electric field conditions. This study highlights how a two‐point observation approach offers valuable insights into the dynamic behavior of the Martian induced magnetosphere. Plain Language Summary: Scientists have been studying the Martian bow shock, which slows down the solar wind from supersonic to subsonic, using instruments on different Mars missions. But most studies only use data from one spacecraft, so we don't know much about how the bow shock varies in different places at the same time. In this study, we looked at data from two spacecraft, Tianwen‐1 and MAVEN, at the same time to see if we could find any differences. We found that the bow shock is different in the northern and southern parts of Mars in different reference frames, and this might be because of the solar wind electric field and the Martian crustal field. We also noticed that the bow shock is more different when the solar wind electric field is stronger. Such two‐spacecraft observations helps us understand more about how the magnetic environment around Mars works. Key Points: We investigated the asymmetry of Martian bow shock utilizing two‐spacecraft observations at distinct locationsThe dayside Martian crustal field may induce the north‐south asymmetry of the bow shockThe solar wind electric field may cause bow shock asymmetry in the Mars‐Solar‐Electric frame, with stronger fields increasing the effect [ABSTRACT FROM AUTHOR]

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2010.01.009 Byline: Lon L. Hood (a), Keith P. Harrison (b), Benoit Langlais (c)(d), Robert J. Lillis (e), Francois Poulet (f), David A. Williams (g) Keywords: Mars; Magnetic fields; Mars, Interior; Mars, Surface Abstract: The nature of strong martian crustal field sources is investigated by mapping and modeling of Mars Global Surveyor magnetometer data near Apollinaris Patera, a previously proposed volcanic source, supplemented by large-scale correlative studies. Regional mapping yields evidence for positive correlations of orbital anomalies with both Apollinaris Patera and Lucus Planum, a nearby probable extrusive pyroclastic flow deposit that is mapped as part of the Medusae Fossae Formation. Iterative forward modeling of the Apollinaris Patera magnetic anomaly assuming a source model consisting of one or more uniformly magnetized near-surface disks indicates that the source is centered approximately on the construct with a scale size several times larger and comparable to that of the Apollinaris Patera free-air gravity anomaly. A significantly lower rms deviation is obtained using a two-disk model that favors a concentration of magnetization near the construct itself. Estimates for the dipole moment per unit area of the Lucus Planum source together with maximum thicknesses of [approximately equal to]3km based on topographic and radar sounding data lead to an estimated minimum magnetization intensity of [approximately equal to]50A/m within the pyroclastic deposits. Intensities of this magnitude are similar to those obtained experimentally for Fe-rich Mars analog basalts that cooled in an oxidizing (high fO.sub.2) environment in the presence of a strong ([greater than or equal to]10[mu]T) surface field. Further evidence for the need for an oxidizing environment is provided by a broad spatial correlation of the locations of phyllosilicate exposures identified to date using Mars Express OMEGA data with areas containing strong crustal magnetic fields and valley networks in the Noachian-aged southern highlands. This indicates that the presence of liquid water, which is a major crustal oxidant, was an important factor in the formation of strong magnetic sources. The evidence discussed here for magnetic sources associated with relatively young volcanic units suggests that a martian dynamo existed during the late Noachian/early Hesperian, after the last major basin-forming impacts and the formation of the northern lowlands. Author Affiliation: (a) Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA (b) Southwest Research Institute, Boulder, CO 80309, USA (c) Universite de Nantes, Laboratoire de Planetologie et Geodynamique, Nantes F-44000, France (d) CNRS, UMR 6112, Nantes F-44000, France (e) Space Sciences Laboratory, University of California, Berkeley, CA 94720, USA (f) CNRS, Universite Paris-Sud, Orsay, France (g) School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85281, USA Article History: Received 29 January 2009; Revised 10 January 2010; Accepted 12 January 2010

Author(s): Gauthier Hulot (corresponding author) [1]; Céline Eymin [1]; Benoît Langlais [1]; Mioara Mandea [1]; Nils Olsen [2] The 'geodynamo' in the Earth's liquid outer core produces a magnetic field [...]