Abstract | Magnetic clouds are among the most geoeffective solar events. They are often preceded by a shock and a sheath, and it is recognized that the sheath could play an important role in the development of geoeffectivity. However, the reasons why sheaths are geoeffective remain poorly understood. In this work, we focus on the fluctuations in the sheaths accompanying Magnetic clouds.
We select a list of single, well-identified events. We investigate their characteristics downstream of the shock and relative to the pristine solar wind. Using data from the Advanced Composition Explorer (ACE) satellite, we compute the power spectra of the magnetic field and of the dynamic pressure. We use these spectra to extract quantities such as the anisotropy of the fluctuations in order to understand the specificity of the sheaths in regard to their accompanying Magnetic clouds and the solar wind they encounter. We examine the role of the characteristics of each shock, such as its Mach number, Beta, or angle between the solar wind’s magnetic field and the shock’s normal. |
