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

¹ Institute of Space Weather, School of Atmospheric Physics, Nanjing University of Information Science and Technology, Nanjing, PR China
² State Key Laboratory of Lunar and Planetary Sciences, Macau University of Science and Technology, Taipa 999078 Macao, PR China
e-mail: xjxu@must.edu.mo; louclee@earth.sinica.edu.tw
³ CNSA Macau Center for Space Exploration and Science, Taipa 999078 Macao, PR China
⁴ Institute of Earth Sciences, Academia Sinica, Taipei, Taiwan
e-mail: louclee@earth.sinica.edu.tw
⁵ State Key Laboratory of Space Weather, National Space Science Center, Chinese Academy of Sciences, Beijing, PR China
⁶ Joint Research and Development Center of Chinese Science Academy and Shen county, Shandong, PR China
⁷ Planetary Environmental and Astrobiological Research Laboratory (PEARL), School of Atmospheric Sciences, Sun Yatsen University, Zhuhai, PR China
⁸ Institute of Space Science and Applied Technology, Harbin Institute of Technology, Shenzhen, PR China

Received: 14 February 2022
Accepted: 15 September 2022

Abstract

Using a three-dimensional multispecies magnetohydrodynamic model, we study the effects of the orientation of the interplanetary magnetic field (IMF), solar wind dynamic pressure (P_d), and the location of the intense crustal field, on the dayside magnetic reconnection between the solar wind and the Martian crustal field. Our main results are as follows: (1) Different IMF orientations result in different magnetic field configurations and reconnection conditions on the Martian dayside. When the intense crustal field is located on the dayside, the dayside magnetic reconnection tends to occur in the region with solar zenith angles (SZA) ≈45° in the southern hemisphere for the IMF with a southward component. When the IMF has a northward component, the magnetic field lines are piled up in the same place and the Martian magnetic pileup boundary (MPB) appears as a local bulged “mini-magnetopause”. Under the pure radial IMF, the magnetic reconnection is absent, which might be due to the presence of additional outward magnetic tension and kinetic effects. (2) Dayside reconnection can change the shape of the Martian MPB, while the bow shock is weakly affected. When the IMF has a southward component, the dayside magnetic reconnection happens and the MPB is located closer to Mars with a “cusp” shape. When the IMF has a northward component, the Martian MPB expands with a local bulged “mini-magnetopause”. For the pure radial IMF condition, the subsolar region of the MPB is located closer to Mars than that under other IMF directions. The influence of the IMF cone angles on the Martian bow shock is much less than that on the MPB, and the bow shock locations are very close to the model results of another author found in the literature. (3) With increasing P_d, the size of the crustal field region decreases and the draped fields correspondingly move to lower altitudes where the IMF and crustal field have the same direction. When the IMF has a southward component and the magnetic reconnection occurs at SZA ≈ 45°, the reconnection site, the region of the closed topology of the crustal field, and the draped IMF, do not change much with increasing P_d. We suggest that the multipolar crustal magnetic fields can protect the solar wind IMF from further reconnecting with the crustal field to a lower altitude when P_d is enhanced.