Statistical Analysis of Ring Ionospheric Trough Characteristics

Abstract

AbstractIn this study, the statistical characteristics of the ring ionospheric trough (RIT) are determined. The RIT is formed by the decay processes of the magnetospheric ring current; therefore, it is most clearly distinguished from the main ionospheric trough (MIT) during the recovery phase of a geomagnetic storm. The dynamics of both the troughs is considered in the case of geomagnetic disturbances with Kp indices from 4 to 9 during 2000–2003. In total, 830 RIT occurrences were identified in the CHAMP satellite data. The RIT is most often formed in the post‐midnight period, less often in the evening, and never in the daytime between 10 and 14 LT. In the post‐midnight period, the RIT is observed in the belt of 39°–62° geomagnetic latitude (in both hemispheres), with an occurrence maximum at 55° (L‐shell, L = 3). This finding is in good agreement with the observations of stable auroral red (SAR) arcs and a residual magnetospheric ring current. When a storm exhibits a long recovery phase, during which the geomagnetic activity periodically resumes, the RIT can exist for more than two days. The RIT is most often formed at the longitudes of South America, where the geomagnetic field is the weakest. In contrast to the MIT position, the averaged RIT position is not so strongly dependent on the longitude and Kp index. At low Kp values, the plasmapause position is close to the MIT position, while at high Kp values, the plasmapause approaches the RIT position.