Conditionally integrated incoherent scatter radar data and flickering aurora

Grydeland, T.1, Gustavsson, B.1, Blixt, E. M.1, Baddeley, L.2 and Lunde, J.3

1 University of Tromsų, Tromsų, Norway
2 Department of Physics and Astronomy, University of Leicester, Leicester, UK
3 currently at Solar-Terrestrial Environment Laboratory, Nagoya University, Nagoya, Japan

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, while the vertical extent is 10-40 km. At times the flickering appears as a whirling motion. Here we use high-speed narrow field-of-view imaging in white light to determine 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 backscatter varies in a way which is correlated with the variation in optical emission intensity. We present the technique and preliminary results of this investigation.