A relationship between polar magnetic substorms, ionospheric height rises and the occurrence of spread- F

Abstract

Statistical analyses performed for ionosonde stations (at mid- and low-latitudes) in a longitude zone near the 75°W (geographic) meridian, suggest that increases in the ionospheric parameter h′ F are related to polar-magnetic-substorm onset times as recorded by a magnetogram station in the same longitude zone as the ionosonde stations. The height increases are recorded for several hours after the substorm onset times, and seem to trigger the onset of ionospheric spread- F. One individual event which was analyzed, showed a variation with latitude of the time of onset of the height increase suggesting the propagation towards the equator of an ionospheric disturbance with a speed of about 740 m s −1. On this particular occasion the onset of spread- F followed the height-rise onset at most of the stations used in the analysis. These effects were clearly discernable at the geomagnetic equator.