Letter to the Editor

The infant bow shock: a new frontier at a weak activity comet

¹ Royal Belgian Institute for Space Aeronomy (BIRA-IASB), Avenue Circulaire 3, 1180 Brussels, Belgium
e-mail: herbert.gunell@physics.org
² Department of Physics, Umeå University, 901 87 Umeå, Sweden
³ Institut für Geophysik und extraterrestrische Physik, TU Braunschweig, Mendelssohnstr. 3, 38106 Braunschweig, Germany
e-mail: c.goetz@tu-bs.de
⁴ Department of Physics, University of Oslo, Box 1048 Blindern, 0316 Oslo, Norway
⁵ Swedish Institute of Space Physics, Box 812, 981 28 Kiruna, Sweden
⁶ Southwest Research Institute, 6220 Culebra Rd., San Antonio, TX 78238, USA
⁷ Swedish Institute of Space Physics, Ångström Laboratory, Lägerhyddsvägen 1, 751 21 Uppsala, Sweden

Received: 12 September 2018
Accepted: 15 October 2018

Abstract

The bow shock is the first boundary the solar wind encounters as it approaches planets or comets. The Rosetta spacecraft was able to observe the formation of a bow shock by following comet 67P/Churyumov–Gerasimenko toward the Sun, through perihelion, and back outward again. The spacecraft crossed the newly formed bow shock several times during two periods a few months before and after perihelion; it observed an increase in magnetic field magnitude and oscillation amplitude, electron and proton heating at the shock, and the diminution of the solar wind further downstream. Rosetta observed a cometary bow shock in its infancy, a stage in its development not previously accessible to in situ measurements at comets and planets.