An ionospheric storm during the period of a very strong magnetic storm in March 1989

The morphology and its variations of an ionospheric storm related with a very strong magnetic storm on 12(th) similar to 16(th) March, 1989 are examined, using the ionosonde data obtained at stations in European and Asian areas. The strong ionospheric disturbances caused by the significant magnetic storm appeared on the whole world. Since the storm heating intensities at the lower thermosphere resulting from energetic particles precipitated from the magnetosphere are different from area to area, the features of the ionospheric storm are also discrepant in different longitudinal chain regions. As compared with deduction from the theory, there was no "positive" storm period of NmaxF2 (or f(0)F(2)) in Europe, while the developing tendency of the "negative" storm from high-to low-latitudes was consistent well with the result deduced from the thermospheric circulation. Moreover, at the mid-and low-latitude areas there was an evident wavelike process. On the other hand, at the high latitude of the Asian meridian there was a "positive" storm lasted similar to 10 h on March 13(th) in the early stage of the magnetic storm. As to the feature of the "negative" storm, it was similar to that in Europe, but not as distinct as there. Besides, there was no wavelike phenomenon at the Asian area. During the magnetic storm in the mid- and low-latitude areas along a same meridian one can also see the nighttime simultaneous sudden enhancement of h'F. It is proved once more that this is a universal phenomenon during a magnetic storm.