Planetary Bow Shocks

TL;DR

This paper reviews the properties of planetary bow shocks, categorizing planets by magnetic field presence, and summarizes current in situ knowledge, especially focusing on Earth's bow shock as a physics paradigm.

Contribution

It provides a classification of planetary bow shocks based on magnetic and atmospheric properties and summarizes the limited in situ data available for different celestial objects.

Findings

Earth's bow shock physics well-understood

Limited in situ data for other planets

Classification scheme for planetary bow shocks

Abstract

Our present knowledge of the properties of the various planetary bow shocks is briefly reviewed. We do not follow the astronomical ordering of the planets. We rather distinguish between magnetised and unmagnetised planets which groups Mercury and Earth with the outer giant planets of the solar system, Mars and Moon in a separate group lacking magnetic fields and dense atmospheres, and Venus together with the comets as the atmospheric celestial objects exposed to the solar wind. Asteroids would, in this classification, fall into the group together with the Moon and should behave similarly though being much smaller. Extrasolar planets are not considered as we have only remote information about their behaviour. The presentation is brief in the sense that our in situ knowledge is rather sporadic yet, depending on just a countable number of bow shock crossings from which just some basic conclusions can be drawn about size, stationarity, shape and nature of the respective shock. The only bow shock of which we have sufficient information to deal in sufficient depth with its physics is Earth's bow shock. This has been reviewed in other places in this volume and therefore is mentioned here only as the bow shock paradigm in passing.