Power of magnetopause low-frequency waves: A statistical study

摘要

ULF fluctuations at the Earth magnetopause have been the subject of a long-standing interest because of their noticeable amplitude and their potential role in plasma penetration through the magnetosphere boundary. Some information on the nature of these fluctuations has already been provided thanks to GEOS and ISEE, and more recently Cluster, case studies and from a few statistical studies on magnetopause crossings. Here we present a new statistical study concerning the power of the ultralow frequency fluctuations based on the data of the Cluster-STAFF experiment. New insight in the properties of turbulence is obtained, because of the orbit of the Cluster spacecraft, which gives access to regions far from the subsolar point. The correlation of the wave power with solar wind and magnetosheath properties indicates that these fluctuations are controlled and possibly driven by external sources. Its correlation with the magnetopause properties (namely the magnetic shear angle) provides an indication of an amplification process at the boundary.