Flickering Aurora: Optical and Incoherent Scatter Radar Observations
Dr Björn Gustvasson, from the University of Tromsö
Abstract:
Flickering aurora is characterized by optical emissions varying in intensity with frequencies typically between 5 and 20 Hz.
The horizontal scale size of flickering columns are typically 1--10 km. Here we use high-speed narrow field-of-view imaging in white
light to determine the spatial motion of intensity variations in the 15 by 11 degrees field-of-view centered around magnetic zenith.
The temporal variation of the spatial structures are compared with theoretical predictions based on interference between
electromagnetic ion-cyclotron waves (Sakanoi et al. 2005). The intensity variation in the field aligned direction,
which is also the direction of the beam of the EISCAT Svalbard Radar (ESR).
Incoherent scatter radar data is noise-like, and must be integrated over multiple pulses to reduce the variance
to useful levels, even for high signal to noise ratios. Usually, this means integrating over several seconds
to some tens of seconds of observation, which is not very useful with respect to flickering aurora.
In the experiment presented here, we have taken data at the voltage level, before any integration.
By doing so, we are free to define integrations which are not necessarily contiguous in time.
We have used the intensity variation of flickering aurora within the area of the radar beam to define local temporal origins,
and have integrated together pulses at the same time offset from the nearest origin to investigate
whether radar back-scatter varies in a way which is correlated with the variation in optical emission intensity.
This way we can determine the ionospheric response to the temporal variation of the electron precipitation at time-scales of 0.01 s.
