Relation between coronal lambda 5303 intensity, recurrent geomagnetic storms, and solar sector structure

Summary. A correlation is demonstrated between recurrent geomagnetic storms and longitudinal zones of low coronal λ 5303 intensity, called L zones. The onset of a storm occurs about 2 days after the central meridian passage of an L zone. The L zones partly coincide with regions of low brightness temperature at the 9.1-cm microwave emission. Comparison with data of the interplanetary sector structure suggests that an L zone is located to the east of a solar magnetic sector boundary.