Dynamics of Main and Ring Ionospheric Troughs at the Recovery Phase of Storms/Substorms

This study explores the dynamics of the main ionospheric trough (MIT) and ring ionospheric trough (RIT) during geomagnetic disturbances. The RIT is formed by a decay process of the magnetospheric ring current during the recovery phase of a geomagnetic storm/substorm. As a result, it is usually observed within the latitude belt 48 degrees-60 degrees GMLat, that is, the RIT is a midlatitude trough in contrast to the subauroral MIT. To explore the mutual dynamics of the MIT and RIT, 120 geomagnetic disturbances with Kp > 4, according to Kosmos-1809, Kosmos-900, Interkosmos-19, and CHAMP satellites, are considered. At night, the RIT is almost always formed at the recovery phase of geomagnetic disturbances. The RIT occurs most frequently in the morning and less often before midnight. The dynamics of the MIT and RIT during geomagnetic disturbances is quite complex: both troughs can be observed either separately or simultaneously, the MIT can transform abruptly into RIT and vice versa. The position of the RIT depends on Kp and longitude, but not always as distinctly as the position of the MIT. The RIT can be observed for 1.5 days during the recovery phase of a geomagnetic disturbance. The RIT can be observed simultaneously in both hemispheres at close conjugate latitudes.