The ionospheric response to ¯ux transfer events: the ®rst few minutes
Abstract. We utilise high-time resolution measurements from the PACE HF radar at Halley, Antarctica to explore the evolution of the ionospheric response during the ®rst few minutes after enhanced reconnection occurs at the magnetopause. We show that the plasma velocity increases associated with ¯ux...
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| Format: | Text |
| Language: | English |
| Published: |
1997
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.371.9340 http://hal.archives-ouvertes.fr/docs/00/31/62/66/PDF/angeo-15-685-1997.pdf |
| Summary: | Abstract. We utilise high-time resolution measurements from the PACE HF radar at Halley, Antarctica to explore the evolution of the ionospheric response during the ®rst few minutes after enhanced reconnection occurs at the magnetopause. We show that the plasma velocity increases associated with ¯ux transfer events (FTEs) occur ®rst 100±200 km equatorward of the region to which magnetosheath (cusp) precipitation maps to the ionosphere. We suggest that these velocity variations start near the ionospheric footprint of the boundary between open and closed magnetic ®eld lines. We show that these velocity variations have rise times 100 s and fall times of 10 s. When these velocity transients reach the latitude of the cusp precipitation, sometimes the equatorward boundary of the precipitation begins to move equatorward, the expected and previously reported ionospheric signature of enhanced reconnection. A hypothesis is proposed to explain the velocity variations. It involves the rapid out¯ow of magnetospheric electrons into the magnetosheath along the most recently reconnected ®eld lines. Several predictions are made arising from the proposed explanation which could be tested with ground-based and space-based observations. 1 |
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