Monday 19 May 2014

Further investigations on the strange solar ripple

We've been following the progress on trying to understand a strange ripple in some recent solar observations.

As each antenna has two polarisations, we plot first the X-polarisation and the Y-polarisation. They are done separately, to avoid a strong flickering effect (which is due to the different responses to the event between the two polarisations).

The "RCU" number is the Reciever Unit number. The even RCUs are for the X-polarisation and the odd ones are for the Y-polarisation. Three RCUs have been omitted (68,69, and 70) as these were offline at the time the observations were made.

Actually, we noticed that they oscillate. The oscillation is small to start with and then it increases. The movement is small, but those fringes waver with RCU number.

RCU number is a function of the antenna number.

   RCU 0,1 = LBA #L00
   RCU 2,3 = LBA #L01  
   RCU 94,95 = LBA #L47

And, if you look at the map of the array, and join the dots in numeric order, you get this:

So, then what I did was to look for where the minimum fringes and maximum fringes occur. In other words, as the pattern moves up and down, what are the local min/max points in that oscillation.

I noted the RCU numbers, determined the antenna numbers and plotted them. I also note the direction of the sun during this time (roughly).

This tells as that the fringe pattern is associated with distance from the sun. Well, it is not likely to be that directly, but because there is a mound with the LBAs, there will be more flat ground between #L43 and the sun than #L35. This snow/ground could be causing reflections.

What these results tell us, though, is that the original hypothesis of a reflection off the reindeer fence or gate is actually pretty unlikely.

So there are now two likes of thought. One is that this is a snow effect and some modelling is going on to investigate this.

The other is that it is an ionospheric refraction effect.

Neither idea is firm yet and investigations remain ongoing.

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