Interferometric imaging of Stimulated Electromagnetic Emissions

Here's an update on the SEE campaign. We've managed to make images of stimulated electromagnetic emissions using the eight antenna interferometer we built in Skibotn. The aperture synthesis imaging technique that we are using is essentially the same as is used for radio astronomy, but with some filtering in place to exclude radio emissions that are caused by radio interference and radio emissions that are not O-mode polarized.

Here's an animation I made yesterday. The images of HF emissions from the ionosphere are shown on the left hand side. The color indicates the frequency shift of the emissions. These colors are mixed together to make a false color image of the emissions. The x is the location of the field aligned direction at 200 km altitude, the star is the location of zenith of Ramfjordmoen at 200 km, and the "o" is the zenith of Skibotn. The frequencies are HF, and the emissions occur near the reflection altitude, where the plasma frequency is the same as the radio wave frequency. Due to this reason, there is a lot of ray bending, which distorts the image.

Thanks again for everyone who participated in the campaign, especially Markus Floer, who spent the last two summers building the interferometer antennas. We've earlier covered the build of the interferometer (01), and the campaign (2, 3, 4).

We're not the first ones to do interferometry on SEE. There are three publications on this topic (5,6,7).