Physics – Plasma Physics
Scientific paper
Dec 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010agufmsm43a1898b&link_type=abstract
American Geophysical Union, Fall Meeting 2010, abstract #SM43A-1898
Physics
Plasma Physics
[2407] Ionosphere / Auroral Ionosphere, [2487] Ionosphere / Wave Propagation, [6924] Radio Science / Interferometry
Scientific paper
The auroral zone is the source of multiple kinds of radio emissions that can be observed on the ground. The study of radio emissions offers a way to remotely sense space plasma processes and, in the case of auroral emissions, to use the auroral ionosphere as a large-scale plasma physics laboratory. Medium frequency (MF) burst is an impulsive radio emission at 1.5-4.5 MHz observed on the ground. Its generation mechanism is unknown, and it is often associated with the onset of substorms. Auroral hiss is an impulsive emission observed on the ground at frequencies up to 1 MHz and is also associated with substorm onset. LaBelle et al. [1997] reported a temporal relationship between MF burst and auroral hiss. Multiple impulses of both MF burst and auroral hiss occurred simultaneously over a time period that in certain cases lasted tens of minutes. While the temporal relationship on the timescale of seconds is well established, the spatial relationship between MF burst and auroral hiss has yet to be investigated. Dartmouth College currently operates a broadband (0-5 MHz) four-element radio interferometer at Toolik Field Station in Alaska (68° 38' N, 149° 36' W, 68.5° magnetic latitude) in order to study the direction of arrival (DOA) of radio emissions. Since the antenna spacing is 50 meters, the interferometer is optimized for DOA measurements of MF bursts. However, in certain cases, it can provide the DOA for the high-frequency portion of impulsive auroral hiss. We present two case studies that represent the first simultaneous DOA measurements of impulsive auroral hiss and MF burst. On March 4, 2010, the DOA of MF burst was predominantly from 30 degrees south of east, an observation consistent with the statistical work performed by Bunch et al. [2009]. Simultaneous DOA measurements of the high-frequency portion of auroral hiss also showed the DOA as approximately 30 degrees south of east but with greater scatter in the data. The second case study, which involved an event on April 5, 2010, also showed both emissions coming from approximately the same part of the sky. These observations are consistent with a spatial correlation between MF burst and auroral hiss. Further investigation of this correlation could contribute significantly to understanding the complex space plasma processes that give rise to radio emissions.
Broughton M.
Labelle James W.
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