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Detailed Reference Information |
Farrugia, C.J., Sandholt, P.E., Moen, J. and Arnoldy, R.L. (1998). Unusual features of the January 1997 magnetic cloud and their effect on optical dayside auroral signatures. Geophysical Research Letters 25: doi: 10.1029/98GL01226. issn: 0094-8276. |
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We study features of the January 1997 magnetic cloud and their effect on the optical aurora at 0630--0930 magnetic local time (MLT). WIND data suggest a thin plasma depletion layer (PDL) preceding the cloud, at whose outer edge the magnetic field rotates southwards, the proton temperature has a local maximum, and the dynamic pressure drops by a factor of 2. At the cloud's front boundary there is a further dynamic pressure drop, another localized temperature rise, and a ~30¿ field shear. Prior to arrival of the southward rotation at Earth, the ~08 MLT aurora is dominated by forms with intense 557.7 nm emission, presumably of boundary plasma sheet origin, located south of zenith (~75¿ MLAT) and moving eastward. Minutes after the southward rotation reaches Earth, this emission is replaced by an auroral form which encroaches into the field-of-view at ~73¿ MLAT, expands southward to ~70¿ MLAT and westward, approaching ~0800 MLT at 0600 UT. Its latitudinal positions satisfy a known relation between cusp latitude and interplanetary Bz, and its morphological and spectral properties are similar to those previously associated with an energy-latitude dispersion signature attributed to plasma transfer at an open low latitude boundary layer. We argue that this auroral precipitation at such far off-noon MLTs may be due to enhanced reconnection occasioned by the strongly southward field in the PDL/cloud. A POLAR pass across the open/closed field line boundary at 66¿ invariant latitude is consistent with these inferences. ¿ 1998 American Geophysical Union |
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BACKGROUND DATA FILES |
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Abstract |
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Keywords
Magnetospheric Physics, Magnetopause, cusp, and boundary layers, Ionosphere, Auroral ionosphere, Interplanetary Physics, Ejecta, driver gases, and magnetic clouds, Ionosphere, Particle precipitation |
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Publisher
American Geophysical Union 2000 Florida Avenue N.W. Washington, D.C. 20009-1277 USA 1-202-462-6900 1-202-328-0566 service@agu.org |
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