Speaker
Description
Waves in the cometary plasma environment occur at almost every activity level of a comet, both far away from the Sun and near its perihelion. They play an important role in the thermalization of the cometary pick-up ions and in the redistribution of energy. Upstream of the nucleus and for several thousands of kilometers downstream the gyrating motion of both the solar wind (SW) plasma and the cometary ions creates highly anisotropic ion velocity distribution functions. These anisotropies can result in a variety of different wave phenomena. In this study we use the 3D hybrid particle simulation code Amitis to simulate a comet magnetosphere at approximately Mars' distance, with an outgassing rate of $Q \approx 10^{27}$ s$^{-1}$.
We find large-scale wave features that reach from far upstream of the comet nucleus to downstream of the bow shock.
The wave signatures are most apparent in the +E hemisphere and near the quasi-parallel bow shock, whereas in the -E hemisphere and at the quasi-parallel bow shock the magnetic field pile-up dominates. In the innermost part of the comet magnetosphere, where the cometary ions are far more dominant than the solar wind ions, the waves are absent. Peaks in the magnetic field strength and the solar wind density are out of phase, while the cometary ion density is approximately correlated with the magnetic field. These characteristics are consistent with slow magnetosonic waves.
The waves create enhancements in the SW density, which in turn result in an increased dynamic pressure. These dynamic pressure enhancements are commonly referred to as magnetosheath jets. We investigate the possibility that the waves contribute to the formation of jets in the cometary magnetosphere.
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