Other
Scientific paper
Dec 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007agufmsm14a..02m&link_type=abstract
American Geophysical Union, Fall Meeting 2007, abstract #SM14A-02
Other
2720 Energetic Particles: Trapped, 2724 Magnetopause And Boundary Layers, 2728 Magnetosheath, 2748 Magnetotail Boundary Layers, 2778 Ring Current
Scientific paper
To monitor substorm associated auroras 20 THEMIS Ground Based Observatories (GBO-s), were deployed to provide near contiguous coverage over North America each with an all sky imagers (ASI) and a magnetometer. The network of imagers takes global scale image collages (mosaics) with 3 second cadence providing hitherto unprecedented spatial and temporal resolution. The GBO magnetometer data are sampled at 2 samples per second. The THEMIS GBOs provide a global perspective with unprecedented temporal and spatial resolution and sensitivity. The ASI network recorded substorm signatures of the 23rd of March 2007 substorm which was also the first substorm observed by the THEMIS satellite instruments. The GBO array was able to pinpoint the location and time of occurrence of the auroral break up associated with this substorm. To investigate the possible role of Alfven wave accelerated electrons in substorm aurora a special purpose camera was also constructed and fielded at Poker Flats, Alaska. This camera also observed the initial brightening of the onset of the 23rd of March substorm. The special purpose camera was designed to record band component ratios of the N2+ first negative band at 427.8 nm with the objective of estimating of the N2 rotational temperature of the emitting region. Since the rotational temperature varies substantially with altitude this method provides information regarding the altitude of the auroral emissions and thus about the energy of the precipitating particles. The ultimate goal of this instrument is to develop a ground based technique for discriminating soft, wave accelerated electron auroras of energy <2 keV from the conventional inverted V auroras of energy that is regularly > 4keV and to investigate whether initial onset arc brightening is caused by soft Alfven wave accelerated electrons. In dynamic conditions this technique has several advantages over other methods of estimating auroral electron energy based on comparisons of two different spectral features of differing color and quenching lifetime. On the 23rd of March the auroral break up arc was captured overhead with this instrument and it showed that the emission from the arc brightening had the characteristics of colder atmospheres namely that the aurora was produced by higher energy electrons. A mosaic presentation of the GBO all sky imager data from the GBO stations Kiana , Ft Yukon and Inuvik showed that the major onset brightening and break up occurred originally within the Kiana field of view and then it propagated mainly eastward to Ft Yukon and Poker Flats. Therefore the brightening seen at Poker Flats was not part of the original onset brightening. It is also noteworthy that the initial onset arc that brightened at Kiana appeared as a new feature located between two pre-existing arcs.
Angelopoulos Vassilis
Donovan Eric F.
Frey Harald U.
Greffen Mike
Harris Shirley E.
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