COSMIC Observations of TEC Enhancements in Response to moderate disturbances in the solar wind
| Autor: | Pei-Chen Lai, 賴珮晨 |
|---|---|
| Rok vydání: | 2011 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 99 COSMIC (Constellation Observing System for Meteorology, Ionosphere and Climate) satellite data, acquired during five days in November 2007, were analyzed to study the Total Electron Content (TEC) enhancements as a high speed stream (HSS) in the solar wind passed the Earth. In the case of Julian Day 322-326, the HSS arrival was closely preceded by the arrival at the first Lagrange point L1 of an interplanetary coronal mass ejection (ICME). The corotating interaction region (CIR) at the leading edge of the HSS was marked by a sharp increase in plasma density, followed by an intensification and rotation of the interplanetary magnetic field (IMF), inducing a moderate magnetic storm. We calculated the TEC by integrating electron density profiles over altitude and assigned values to the locations of ray-tangent points. The TEC enhancements appeared at mid- to high-magnetic latitudes during the main phase of a magnetic storm driven by the fast stream’s leading edge. Some TEC increases exceeded quiet-time values by a factor of 3 to 4. The Hardy model for distributions of auroral electron precipitation indicated that no source for new plasma creation was present in the range of magnetic latitudes where the TEC enhancements occurred. Thus, the TEC enhancements must reflect transport effects. Neutral winds generated at auroral latitudes should push dayside plasma equatorward, just as opposite to the COSMIC observations. Rather, required transport implies plasma drifts from low to higher latitudes, due to the dawn-to-dusk penetration electric fields. ACE measurements allow estimates of penetration electric field strengths. These are then mapped to the ionosphere and used to calculate plasma transport velocities. We compare empirical solutions of the continuity equation with the TIEGCM predictions. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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