| Abstrakt: |
In 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. Plain Language Summary: The ring ionospheric trough (RIT) is additional trough that appears equatorward the main ionospheric trough (MIT) during a geomagnetic disturbance. In the recovery phase of a storm, the magnetospheric ring current decays when hot ring‐current ions interact with cold plasmaspheric particles. This process is accompanied by particle precipitation and heat flow into the ionosphere and, subsequently, the formation of an electron temperature (Te) peak, electron density (Ne) trough, and stable auroral red (SAR) arc. Thus, during the recovery phase of a geomagnetic storm, the RIT is associated with the magnetospheric ring current, Te peak, SAR arc, and plasmapause. This article focuses on the study of the statistical characteristics of the RIT based on a large dataset recorded by the CHAMP satellite between 2000 and 2003. The dependence of the RIT position on the local time, latitude, longitude, and geomagnetic activity indices Kp and Dst was investigated. The RIT is most often observed after midnight and at geomagnetic latitudes of 49°–59° (in both hemispheres), at the longitudes of America. Key Points: A total of 840 cases of ring ionospheric trough (RIT) from the CHAMP data during storms in 2000–2002 were recordedThe RIT position dependences on latitude, longitude, local time, and Kp and Dst indices were studiedThe nighttime RIT position is close to position of the SAR arc and plasmapause under high geomagnetic activity [ABSTRACT FROM AUTHOR] |
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