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Published byDayna Stevenson Modified over 5 years ago
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1IGPP/UCLA, 2SSL/UCB, 3LASP, 4Univ. Calgary, 5TUB, 6UNH
FAST/THEMIS observations of the westward traveling surge field-aligned currents and their relationship to the substorm current wedge R. J. Strangeway1, V. Angelopoulos1, C. W. Carlson2, J. P. McFadden2, R. E. Ergun3, S. B. Mende2, H. U. Frey2, D. Larson2, E. Donovan4, C. T. Russell1, K.-H. Glassmeier5, H.-U Auster5, J. Raeder6, D. J. Larson6 1IGPP/UCLA, 2SSL/UCB, 3LASP, 4Univ. Calgary, 5TUB, 6UNH ST2-1TU4O-005 EGU2007-A-10726
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Introduction The March 23rd 1007 event – THEMIS/FAST conjunction
THEMIS observations – dipolarization and passage of western substorm currrent wedge field-aligned current FAST observations of a flow channel and FAC pair MHD simulations – relationship between FACs and Westward Traveling Surge MHD model validation Conclusion: the upward current of the substorm current wedge is more complex than a single field-aligned current. Is this also the case for the downward current? ST2-1TU4O-005 EGU2007-A-10726
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THEMIS – FAST Conjunction
March 23rd, 2007 FAST and THEMIS in same local time sector ~ 21 MLT THEMIS footprint in the south FAST footprint in the north ST2-1TU4O-005 EGU2007-A-10726
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THEMIS Observations ST2-1TU4O-005 EGU2007-A-10726
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FAST Observations ST2-1TU4O-005 EGU2007-A-10726
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Westward Traveling Surge – MHD Simulation
ST2-1TU4O-005 EGU2007-A-10726
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MHD FAC and Precipitation
ST2-1TU4O-005 EGU2007-A-10726
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WTS and Substorm Current Wedge
THEMIS observed pair of field-aligned currents, with net current out of the ionosphere, resulting in dipolarization – western leg of substorm current wedge. FAST observed pair of FACs and a flow channel. Dominant signature, But there is a small net outward current. MHD simulations show that the paired FACs are also associated with a rapid westward motion of the region of electron precipitation, the WTS? Implication: The upward current for the substorm current wedge is not a single FAC, but is more complex. ST2-1TU4O-005 EGU2007-A-10726
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MHD Validation ST2-1TU4O-005 EGU2007-A-10726
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Another WTS Example ST2-1TU4O-005 EGU2007-A-10726
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Eastward Traveling Surge?
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Conclusions Combination of THEMIS, FAST and MHD simulations is a powerful tool for understanding current system dynamics The upward current for the substorm current wedge is not a single FAC, but is more complex Is this also the case for the downward current? Possibly … Validation of MHD-derived delta-B’s with FAST data show very good agreement. ST2-1TU4O-005 EGU2007-A-10726
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