The solar wind interaction with the topside ionospheres of Venus and Mars: A multi-instrument study

• Applicant: Dr. Kerstin Peter
• Subject Area: Astrophysics and Astronomy
• Term: from 2021 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 458148472

While the solar wind interaction with Earth is dominated by the presence of an intrinsic magnetic field, the atmospheres of Venus and Mars are directly exposed to the solar wind flow. In-situ observations of the Pioneer Venus Orbiter spacecraft (1978-1992) during a strong solar maximum led to the discovery of the Venus ionopause (a sharp boundary between the planetary ionosphere and the solar wind regime which does not exist at Earth). Despite this discovery, many questions about the solar wind interaction with globally unmagnetized planets remain unanswered today. This proposal combines observations from the Venus Express (2006–2014), Mars Express (2003–today) and the MAVEN spacecraft (2014–today) with global 3-D modeling to improve our current understanding of the solar wind interaction with Mars and Venus.1.) In addition to the main planetary plasma regions of both planets several sub-regions/plasma boundaries have been identified due to individual spacecraft instrument capabilities. It is currently under discussion, which observations describe different physical features of the same region and which observations describe completely different boundaries. The compilation of a data base containing the characteristics of the in-situ observed potential plasma regions/boundaries of Venus and Mars is proposed to analyze and clarify the relation between the individual plasma regions for changing environmental and space weather conditions.2.) In-situ observations are constrained by the orbit of the spacecraft, making it impossible to resolve horizontal and vertical changes of the observed parameters simultaneously. The high altitude resolution of the almost vertical ionospheric electron density profiles makes radio occultations a valuable but currently unused resource for the investigation of the planetary solar wind interaction. Because of geometrical reasons, radio science observations can never be performed simultaneously with same-time and same-location in-situ measurements. Proposed are the statistical and the orbit-by-orbit comparison of the ionospheric radio occultation observations with the plasma boundary data base proposed in (1) to determine the origin of the ionospheric topside variability and the strong electron density gradient feature (pot. ionopause) seen in radio occultation observations. Radio occultation observations are also assessed as a tool for the remote investigation of the planetary solar wind interaction.3.) The proposed work will result in a thorough analysis of the plasma boundaries at Venus and Mars. It will provide new evidence for/against the presence of the ionopause during changing space weather conditions. The intercomparison of the derived data sets in combination with 3-D MHD/hybrid + local electron density modeling for Venus and Mars will result in a better understanding of the solar wind interaction with globally unmagnetized terrestrial planets.

• DFG Programme: Research Grants