Quasi-periodical small-scale magnetic disturbances in the low-altitude cusp

Satellite data from measurements of thermal plasma and electric and magnetic fields are considered for the low-altitude cusp. Small-scale magnetic disturbances (SSMDs) are studied in relation to other plasma parameters. The SSMDs sometimes have a quasi-periodical structure and probably a compressional component. The analysis of their polarization structure provides grounds to conclude in some cases at least that the SSMDs represent compressional surface MHD waves.