2021 Eclipse

There will be a polar annular solar eclipse tomorrow (Thursday 2021-06-10 08:00-13:30 UTC). The maximum eclipse is going to be experienced in Tromsø around 11:15 UTC, with about 50 % of the solar disc eclipsed by the Moon. 

The fraction of the sun visible at 300 km altitude. The red line indicates the great circle path between HAARP and Skibotn Norway, which is sounded by a 100 W 2-20 MHz ionosonde setup by Naval Research Laboratories.

 

This event presents a serendipitous observation opportunity for studying how a solar eclipse affects trans-polar HF radio propagation, as Paul Bernhardt and colleagues from the Naval Research Laboratories have setup a FMCW chirp sounder (ionosonde) at HAARP, Alaska. Northern Norway happens to be nearly perfectly situated on the other side of the geographic North pole. This allows us to listen to oblique ionograms that will probe the ionosphere through the eclipsed region. The path of the radio wave and the eclipsed fraction of the Sun is shown in the figure above. 

Example oblique ionogram HAARP-Skibotn

The ionosonde is operating with a regular schedule every 6 minutes and it can be observed using the GNU Chirp Sounder program that I have written. The plot shown above is an example ionogram observed in Skibotn today.  Note that the propagation distance between Alaska and Northern Norway is 5000-6000 km, which means that the oblique ionogram will be very blurry. It will be very interesting to see what effects we'll have tomorrow. 

I've tried to make real-time plots of the HAARP-Skitbotn path ionogram here:

Latest HAARP-Skibotn oblique ionogram

 

I am also recording another path, which is the Sodankylä-Skibotn path. This won't be as much affected by the eclipse. 

Latest Sodankylä-Skibotn oblique ionogram

The EISCAT Tromsø and Svalbard radars are also observing the eclipse. You can follow the analysis for the EISCAT UHF and Svalbard radars.