Mars is a planet which does not possess a global magnetic field. But it has weak local crustal magnetic fields in its southern hemisphere. Using nearly 8 years of MAVEN (Mars Atmosphere and Volatile EvolutioN) satellite in situ data, IIG scientists  investigated how the crustal magnetic fields affect the Martian ionosphere. It is found that crustal field effects are much stronger during day-time but almost non-existent during night-time. Also the daytime crustal field effects remained unaffected by seasons or Sun-Mars distance. The Indian Institute of Geomagnetism (IIG) is an autonomous research institute under the Department of Science and technology which has been actively involved in research exploring the Earth’s magnetic field and its plasma environment. In recent years, IIG has forayed into planetary space plasma as well. In this particular study, IIG scientists have conducted an in-depth investigation into how the weak crustal magnetic field of Mars controls its ionosphere. 
For more details see  
Nayak, C., Yiğit, E., Remya, B., Bulusu, J., Devanandhan, S., Singh, S., et al. (2024). Role of Martian crustal fields in ionospheric electron density distribution and subsequent south-north asymmetry: Insights from multi-year MAVEN observations during (MYs 33–36). Journal of Geophysical Research: Space Physics, 129, e2024JA032760. https://doi.org/10.1029/2024JA032760