Two types of mirror mode waves in the Kronian magnetosheath

Abstract

A mirror mode wave is a fundamental magnetic structure in the planetary space environment that is persistently compressed by solar wind, especially in the magnetosheath. Mirror modes have been widely identified in the magnetosheaths of the Earth and other planets in the solar system, yet the understanding of mirror mode waves on extraterrestrial planets is not as comprehensive as that on the Earth. Using magnetic field data collected by the Cassini spacecraft, we found peak and dip types according to the magnetic morphology (i.e., structures with higher or lower magnetic strengths than the background field). Moreover, mirror mode waves and electromagnetic ion cyclotron waves were found one after the other, implying that the two wave modes may evolve into one another in the Kronian magnetosheath. The results indicate that many fundamental plasma processes associated with the mirror mode structure exist in the Kronian magnetosheath. The energy conversion in Saturn’s magnetosheath may provide key insights that will aid in understanding giant planetary magnetospheric processes.