Foreshock Cavities at Venus and Mars. Issue 8 (14th August 2020)

• Record Type: Journal Article
• Authors: Collinson, Glyn; Sibeck, David; Omidi, Nick; Frahm, Rudy; Zhang, Tielong; Mitchell, David; Halekas, Jasper; Espley, Jared; Futaana, Yoshifumi; Jakosky, Bruce
• Is Part Of: Journal of geophysical research. Volume 125:Issue 8(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-08-14
• Subjects: foreshock -- cavity -- solar wind -- Venus -- Mars -- ULF waves; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1029/2020JA028023
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: "Foreshock cavities" are regions of turbulent and heated solar wind plasma that form upstream of Earth's bow shock. Despite being common at Earth, none have yet been reported at other planets. Here we present a survey of events encountered by the ESA Venus Express spacecraft consistent with foreshock cavities at Venus and a case study of a foreshock cavity encountered at Mars by NASA's MAVEN orbiter. Cavities appear to be common at Venus, and their properties appear to be very similar to those at Earth. Foreshock cavities appear to be observed preferentially in fast solar wind and when the interplanetary magnetic field is "radial" (parallel to the Sun‐planet line). Our collected observations are consistent with the hypothesis that "foreshock cavities" are simply the result of a transient encounter with a planetary foreshock. We posit foreshock cavities represent one of the following two possibilities: (1) a spacecraft encountering a traveling foreshock formed by a finite bundle of interplanetary magnetic field lines connecting to a shock or (2) the transient temporary motion of the foreshock over the spacecraft. Key Points: We report the first observations of foreshock cavities at Venus and Mars They are common and have properties similar to those at Earth They are an observational effect resulting from transient encounters with a planetary ion foreshock