On decreases in ionospheric absorption associated with negative sudden impulses in the geomagnetic field

Decreases in ionospheric absorption at auroral latitudes are found to accompany some negative si's in the geomagnetic field. These decreases are found mainly on the morning side of the magnetosphere, but examples were noted in postmidnight as well as the afternoon hours. The reduction in solar wind pressure on the magnetosphere associated with negative si's apparently reduces the wave turbulence responsible for precipitation of electrons on the dayside and affects electrojet/precipitation regions on the nightside of the magnetosphere.