Correlation between Low Frequency AKR and Auroral Structures

K. Pazamickas, J.L. Green, D.L. Gallagher, S. Mende, and H.U. Frey


Auroral Kilometric Radiation (AKR), a radio emission with a broadband frequency
range, has long been associated with auroral activity. Recently we have done a
preliminary study of AKR related very low frequency events (hear after referred
to as LF AKR) and their association to specific auroral structures. LF AKR
events are characterized as a rapid extension of AKR related emissions to 30 kHz
or lower in frequency for typically much less than 10 minutes. We have extended
the previous study to include all instances of LF AKR events during the nearly 4
years of observations from the IMAGE spacecraft's Radio Plasma Imager (RPI)
instrument. We will discuss the possibility of a correlation between low
frequency AKR emissions and the  bifurcation in the aurora by examining images
of the auroral oval from the Far Ultraviolet (FUV) instrument on IMAGE. We will
examine the relationship of LF AKR emissions events and other factors including
dipole tilt, Dst and AE Index . Although  we don't expect LF AKR to be the only
factor in the bifurcated auroral structures, we do expect that this bifurcation
will occur in every instance when LF AKR is observed. The unique character of LF
AKR is a possible indicator of specific processes  sometimes occurring during
storm-time conditions, resulting from narrow field-aligned density cavities
forming at a distance of perhaps 5-6 RE tailward from the Earth.

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Presentation, Fall A.G.U. Meeting, San Francisco, CA, 13-17 December 2004