Abstract:
Relationships between events in the interplanetary magnetic field and the equatorial ionosphere are investigated. Simultaneous data showing sudden northward transitions of the interplanetary magnetic field and nighttime values of the minimum virtual F-region height at the Kodaikanal equatorial station (magnetic latitude 0.6 deg N) are compared for 15 selected events. No significant increase in F-region height is found to be correlated with the sudden interplanetary magnetic field transitions in 13 of the cases, with F-region height increases in the remaining two regions beginning well ahead of the field direction variations, suggesting that they are not related. It is noted that previous investigations have shown the behavior of the height of maximum ionization is similar to that of the F-region height. It is thus concluded that there is no systematic significant effect of northward transitions of the interplanetary magnetic field on the nighttime equatorial ionosphere.
