A perspective on substorm dynamics using 10 years of Auroral Kilometric
Radiation observations from Wind
Abstract
We study 10 years (1995-2004 inclusive) of auroral kilometric radiation
(AKR) radio emission data from the Wind spacecraft to examine the link
between AKR and terrestrial substorms. We use substorm lists based on
parameters including ground magnetometer signatures and geosynchronous
particle injections as a basis for superposed epoch analyses of the AKR
data. The results for each list show a similar, clear response of the
AKR power around substorm onset. For nearly all event lists, the average
response shows that the AKR power begins to increase around 20 minutes
prior to expansion phase onset, as defined by the respective lists. The
analysis of the spectral parameters of AKR bursts show that this
increase in power is due to an extension of the source region to higher
altitudes, which also precedes expansion phase onset by 20 minutes. Our
observations show that the minimum frequency channel that observes AKR
at this time, on average, is 60 kHz. AKR visibility is highly sensitive
to observing spacecraft location, and the biggest radio response to
substorm onset is seen in the 2100 - 0300 hr LT sector.