The Forming Mechanism of the Induced Global Looping Magnetic Fields on Mars and Venus

The magnetic fields inconsistent with the draped IMF and the crustal field have been observed on Mars. Considering the discovered feature on Venus, a global looping magnetic field around the magnetotail, and the similarities in the solar wind interactions with Mars and Venus, the investigation of the global looping magnetic field on Mars could help in understanding the magnetic environment of Mars and the looping field's forming mechanism. The MAVEN observations of the magnetic field and plasma have made such investigation possible. Both the case studies and the statistical analysis prove that the global looping magnetic field found on Venus also exists on Mars, and therefore is a common feature of unmagnetized planet bodies with ionospheres. The comparison of looping fields on Mars and Venus shows that while the magnetotail is much weaker the looping field is stronger on Mars. A forming mechanism of the global looping magnetic field is proposed based on the observation of the solar wind flows around the magnetotail on Mars and the 3-D hybrid simulation results. The possible effects of the global looping magnetic field on ion escape process and nightside ionosphere production are discussed.