Mars and Venus are the only unmagnetized planets in the solar system. Thus, instead of an intrinsic magnetosphere as a result of an internal dipole field, an induced magnetosphere forms around these planets. Significant progress has been made in understanding the physics in these plasma environments, but most of the studies targeting the two planets only examine them individually. We propose a project through this ISSI team, that would address the following overarching science question and three sub-questions:
1. What are the physical processes that drive the magnetotail structure and dynamics within unmagnetized and hybrid magnetospheres?
- How do the structure and dynamics of the near Venusian and Martian magnetotail regions differ; what processes drive the observed structure and variability; how do the near magnetotail regions facilitate the flow of energy back towards the nightsides of the planets and away from them downstream?
- What are the structure and dynamics of the far Venusian and Martian magnetotail regions?
- How do the Venusian and Martian magnetotail regions respond to solar driving, and what processes control these responses?
Our study will focus on the induced magnetotails of Venus and Mars, leveraging the uniqueness of each system to achieve these goals. To address our science questions, we will investigate the following topics: 1. Plasma structures on the nightside of both planets at high altitudes and their response to changing solar wind conditions through particle and field observations from Mars Express (MEX), Mars Atmosphere and Volatile EvolutioN (MAVEN) and Venus Express (VEX). What are the differences between the two planets? 2. Features in the far magnetotails of Mars and Venus, through Rosetta’s Mars flyby, the recent Venus flybys from Solar Orbiter (SolO), BepiColombo and Parker Solar Probe (PSP) and simulations. What can we learn about the far magnetotails of unmagnetized planets? How far do the magnetotails extend? 3. The response of the induced magnetotails to space weather events such as interplanetary coronal mass ejections (ICMEs). How long does it take for a disturbance to propagate through the magnetotail? How different is this for the two planets? How long does it take for the tails to return to the nominal state? By answering these questions, we will improve our understanding of the physical processes occurring in the induced magnetotails, not only of Mars and Venus, but also of other unmagnetized solar system bodies such as comets and Titan as well as unmagnetized or weakly magnetized exoplanets.