Preprints
https://doi.org/10.5194/angeo-2020-84
https://doi.org/10.5194/angeo-2020-84

  14 Dec 2020

14 Dec 2020

Review status: a revised version of this preprint was accepted for the journal ANGEO and is expected to appear here in due course.

Steepening of magnetosonic waves in the inner coma of comet 67P/Churyumov-Gerasimenko

Katharina Ostaszewski1, Karl-Heinz Glassmeier1,2, Charlotte Goetz3, Philip Heinisch1, Pierre Henri4,5, Hendrik Ranocha6, Ingo Richter1, Martin Rubin7, and Bruce Tsurutani8 Katharina Ostaszewski et al.
  • 1Institut für Geophysik und extraterrestrische Physik, Technische Universität Braunschweig, Mendelssohnstr. 3, 38106 Braunschweig, Germany
  • 2Max-Planck-Institut fur Sonnensystemforschung, Justus-von-Liebig-Weg 3, D-37077 Göttingen, Germany
  • 3ESTEC, European Space Agency, Keplerlaan 1, 2201AZ Noordwijk, The Netherlands
  • 4Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), UMR7328 CNRS/Université d'Orléans/CNES, Orléans, France
  • 5Laboratoire Lagrange, OCA, UCA, CNRS, Nice, France
  • 6Computer Electrical and Mathematical Science and Engineering Division (CEMSE), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
  • 7Physikalisches Institut, University of Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland
  • 8Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA

Abstract. We present a statistical survey of large amplitude, asymmetric plasma, and magnetic field enhancements at comet 67P/Churyumov-Gerasimenko from December 2014 to June 2016. The aim is to provide a general overview of these structures' properties over the mission duration. At comets, nonlinear wave evolution plays an integral part in the development of turbulence and in particular facilitates the transfer of energy and momentum. As the first mission of its kind, the ESA Rosetta mission was able to study the plasma properties of the inner coma for a prolonged time and during different stages of activity. This enables us to study the temporal evolution of steepened waves and their characteristics. In total, we identified ~70000 events in the magnetic field data by means of machine learning. We observe that the occurrence of wave events is linked to the activity of the comet, where events are primarily observed at high outgassing rates. No clear indications of a relationship between the occurrence rate and solar wind conditions were found. The waves are found to propagate predominantly perpendicular to the background magnetic field, which indicates their compressive nature. Characteristics like amplitude, skewness, and width of the waves were extracted by fitting a skew normal distribution to the magnetic field magnitude of individual events. With increasing massloading the average amplitude of steepened waves decreases while the skewness increases. Using a modified 1D MHD model it was possible to show that such solitary structures can be described by the combination of nonlinear, dispersive, and dissipative effects. By combining the model with observations of amplitude, width, and skewness we obtain an estimate of the effective plasma viscosity in the comet-solar wind interaction region. At 67P/Churyumov-Gerasimenko steepened waves are of particular importance as they dominate the innermost interaction region for intermediate to high activity.

Katharina Ostaszewski et al.

 
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Status: closed
Status: closed
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Printer-friendly Version - Printer-friendly version Supplement - Supplement

Katharina Ostaszewski et al.

Katharina Ostaszewski et al.

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Short summary
Plasma waves are an integral part of cometary physics, as they facilitate the transfer of energy and momentum. From intermediate to strong activity nonlinear asymmetric plasma and magnetic field enhancements dominate the inner coma of 67P/CG. We present a statistical survey of these structures from December 2014 to June 2016, facilitated by Rosetta's unprecedented long mission duration. Using a 1D-MHD model we show that they can be described as a combination of nonlinear and dissipative effects.