Auroral plasma-lines at the Søndre Strømfjord radar in Greenland

The Sondrestrom incoherent scatter radar in Kangarlussuaq, Greenland.
The Sondrestrom radar in Greenland is a highly capable incoherent scatter radar. It is also located at a useful high latitude location for studying auroral activity. One of the special characteristics of this radar is its high operating frequency 1290 MHz. Due to this reason, it is very sensitive to supra-thermally enhanced Langmuir waves (electrostatic oscillations of plasma). Plasma-frequency is analytically related with electron density and therefore the observations can be used to obtain accurate high time resolution observations of electron density changes due to auroral energetic particle precipitation. More of the plasma-physics is described in my 2016 GRL paper.

This week, I have been upgrading my plasma-line receiver at Sonde together with folks from SRI International. In addition to adding a new more powerful computer, we have also upgraded to Digital RF 2.0, which was recently released as open source by MIT Haystack Observatory. This allows faster file access and also RAM disk ring buffering. The system now can analyze plasma-lines in realtime and can store over 24 hours of full 25 MHz bandwidth ISR data at any given time! This time, I had no reason to visit Greenland, as SRI provided all of the logistics. Unfortunately, all of the work could be done remotely over the internet. 

Unfortunately, the first observation campaign coincided with the failure of the main generator at Sonde, so only a low duty-cycle mode can be run. Regardless of this, the results are very promising. The first 24 hour run showed plenty of plasma-line enhancements as shown in the figure below. 
Enhanced plasma-lines observed at the Sondrestrom incoherent scatter radar in Greenland on 2017-08-20. The large variations in plasma-frequency correspond to auroral precipitation, which can quickly increase the E-region electron density. Both the up and downshifted plasma lines are shown, in addition to the ion-line in the middle.
Here's a completely unrelated picture from 2014 of some Husky puppies in Kangarlussuaq eating what looks to be a musk ox rump for dinner. 
The equipment that I'm using for plasma-lines is the similar to what I've used at Arecibo and Millstone Hill. A trusty USRP N2x0, recording a wide band IF. Here are some pictures.

The USRP locked to the system 10 MHz and 1 PPS.

A 6 core Intel Xeon used for processing, courtesy of SRI.

Front panel of the computer and some of the control room displays at Sonde. 

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