On the occurrence of mirror modes at Mercury and their comparison with magnetic holes and ion cyclotron waves

Abstract The MESSENGER magnetometer data for the years 2011 through 2015 are used to study the presence of mirror modes in Mercury’s environment. Using magnetic-field-only-detection of these structures, 13,691 intervals of 20 s and longer are found in the solar wind, and in the magnetosheath and magnetosphere of Mercury. The distribution of mirror modes around the planet is similar to that found at Venus and Mars, however, the occurrence rate of $$\sim \, 1.0\, \times \,10^{-4}$$ ∼ 1.0 × 10 - 4 per second is up to 2 orders of magnitude smaller than at the other two planets. The mirror modes are more prone to be excited near Mercury’s aphelion. A comparison shows that mirror modes and magnetic holes have a similar behaviour around Mercury, and that about 40% of the mirror modes can also be identified as magnetic holes. As ion cyclotron waves can be generated by the same temperature anisotropy, they are also compared with the mirror modes. It is found that the ion cyclotron waves show a lesser dependence on the true anomaly angle. Graphical Abstract Occurrence rate of mirror modes around Mercury for the whole MESSENGER mission