Ionospheric effects observed throughout East Asia of the large magnetic storm of 13-15 March 1989

Abstract

The ionospheric effects in East Asia of the large magnetic storm of 13-15 March 1989 have been investigated. Commencing after local sunset on 13 March, extending throughout the second day until the morning of the third day, depletions of up to 5-8 MHz in f{hook}oF2 were recorded over a latitude range 14.7-60.0°N. The corresponding large decreases of electron density are attributed to increases in loss rate/decreases of production rate due to increases in the local N2 O atmospheric composition ratio, produced by atmospheric circulation from an (extended) disturbed polar region. There is evidence that the equatorial ionospheric anomaly (EIA) process was still active during the most disturbed day of 14 March, implying that the composition changes did not extend to near the magnetic equator. Large crests of ionisation (f{hook}oF2 ~ 5 MHz) observed to move northwards between 0200 and 1000 LST (120°E) on 14 March seem to have been, indirectly, caused by the ionospheric disturbance dynamo producing eastward electric fields before sunrise and westward electric fields in the early morning, at low latitudes. Also, an eastward electric field induced at low latitudes by the changing magnetic field, due to the rapid formation of an Earth-ring current during the evening of 13 March, is thought to have caused elevation of the ionosphere, resulting in a large momentary drop in total electron content. Throughout both nights of 13 and 14 March atmospheric gravity waves were observed (via h′F variations) propagating southward from the disturbed polar region. Magnetic declination variations in anti-phase seem to indicate corresponding field-aligned currents. © 1993.