I am a newbie with only 30 flights under my belt and all have been butter smooth till today's.   I have a P3S - and today I had total signal loss with the P3 less then 10 feet away as it was self landing. I live way out in the boonies and had just calibrated prior to this flight, so I am not close to interference sources I am aware of. As it got to about 6 feet above the ground in self landing mode, it started hovering and started making larger and larger circles. I started using the stcks but it was not responding to the sticks. As it was about to hit a building - maybe 5 - 7 seconds after loss of control - I grabbed it mid air and shut down the battery. Log file shows the landing processing as normal and then "Compass Loss - Interference switching to ATTI Mode" but it wasn't acting like it had switched. Could just be my inexperience, as you know these things happen too fast,  but, reading about several crashes the last few weeks, I am wondering if we are in a period of solar flares or GPS testing that are causing some of this?

Funny that you mention the circles - Mine did it yesterday at 5 feet up, and I lost all control.  I was in the middle of nowhere, yet the log says Magnetic Interference.  I turned off the RC and it started the RTH sequence shooting up to 300 feet and then started coming back down.  Once it got to within 10 feet of the ground the RC got signal back and I was able to land it.   I am really hoping that DJI will get the new firmware out soon and address all of these issues.   

Just sounds like it wasn't calibrated, or maybe it was, but lost calibration. What you experienced was the much feared death spiral. Do another calibration and try again. I had this happen to me with anther type of drone, it to was also GPS. I pushed the left stick up and raised the drone fast about 50ft and it came out of it. Then I self landed by coming down as fast as it would allow and slowing for the last few feet to a smooth landing. I came down fast so as not to give it time to get into another spiral. I recalibrated and everything was ok.

What you describe is symptomatic of a compass problem, possibly caused by a bad calibration. The effect of solar flares on GPS reception is vastly over-stated. If the flare was bad enough, the GPS receiver would not be able to establish a valid positional fix and would notify the aircraft system that it was unable to obtain the fix. The aircraft would then enter ATTI mode and you would receive a notification on the screen.

It does not cause the aircraft to fly out of control, and even if it enterted ATTI mode, it woulds simply be carried away in the direction of the wind, it would not fly in circles.

I would examine where you performed the compass calibration to see if it was anywhere near any ferrous metallic material, like concrete with rebar in it, or if there was a car nearby. That will more likely be the reason for what happened.