The ionospheric currents on Mars play a critical role in governing the movement of charged particles, which is vital for understanding the escape of planetary ions into space. Dr. GAO Jiawei, a postdoctoral researcher at IGGCAS, has demonstrated that these currents are influenced by neutral winds from the lower atmosphere and the solar wind interactions from above, underscoring the complex and dynamic nature of ionospheric systems on unmagnetized planets. This study was recently published in Nature Communications.

Unlike the extensively studied magnetospheric current systems, ionospheric currents driven by solar wind and atmospheric neutral winds on unmagnetized planets like Mars have not been quantitatively analyzed until now. This gap limits our understanding of energy transfer processes between stars and planetary atmospheres. Under the guidance of Prof. RONG Zhaojin and Prof. WEI Yong, Dr. Gao leveraged eight years of data from NASA's Mars Atmosphere and Volatile EvolutioN (MAVEN) mission to map two distinct ionospheric current systems on Mars.

The first current system aligns with the solar wind electric field and exhibits hemispheric asymmetry perpendicular to the direction of the solar wind electric field. This current acts as a load current, driven by electric potential differences generated by charge flow originating from bow shock currents. However, the underlying mechanism for this hemispheric asymmetry remains uncertain. The researchers hypothesize that an additional clockwise current at the Martian terminator might contribute to this phenomenon.

The second current system corresponds to the annual average flow patterns of atmospheric neutral winds. The study suggests that these currents are directly driven by the neutral winds in Mars’s atmosphere. The inferred wind field pattern from the current distribution aligns well in both magnitude and direction with predictions made by the Mars Global Circulation Model (MGCM).

These findings enhance our understanding of energy transfer processes from stellar sources to planetary atmospheres, an essential factor in planetary atmospheric evolution. Additionally, characterizing Martian ionospheric currents provides a framework for understanding current systems on other unmagnetized planets with ionospheres, such as Venus and Titan. This suggests that similar current systems could represent a universal phenomenon in unmagnetized planetary environments.

This research was conducted in collaboration with ETH Zurich, the Swedish Institute of Space Physics in Uppsala, and Boston University, with financial support from the National Natural Science Foundation of China and the China Postdoctoral Science Foundation.

Figure: Illustration of the current systems in the induced magnetosphere. (Image by Dr. GAO Jiawei’s research group)

Contact:

GAO Jiawei

Institute of Geology and Geophysics, Chinese academy of sciences

E-mail: gaojw@mail.iggcas.ac.cn

RONG Zhaojin

Institute of Geology and Geophysics, Chinese Academy of Sciences

Phone: 86-010-82998297
E-mail:  rongzhaojin@mail.iggcas.ac.cn