It's not due to a solar flare, however a flare at the time could make it more intense.
It affects the sat downlinks, just as carndt said. I remember February and October, and sure enough, you will get it. Usually 15 minutes in the (somewhat) late morning West coast (DirecTV), and early afternoon for
Dish. That would change with daylight savings time and location a bit, so take it as a general idea. Or to be more exact, look it up
HERE.
That's your direct downlink. Remember that the uplink centers (uplinks are not affected) receive many of their services by C-Band and other satellite bands. Since these services are downlinks too, they are just as vulnerable and it can occur at a different time on different channels, depending on what satellite they receive the signal and of course if the sun is behind that one..
If DirecTV's particular programming source is the same as Dish's, an outage affecting their programming receiver (not yours) wouldn't be at the same instance as Dish's. DirecTV's uplink center is primarily in El Segundo CA and Dish's is in Cheyenne WY. (There are other uplink centers elsewhere too).
If you suspect an outage, look where your dish points (horizontally, it's offset vertically). Is the sun there? (Don't stare at it!)
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XM could however the vehicle's antenna's gain is much less than a fixed-station parabolic (dish). As well, XM's satellite's transponders are much higher powered than their TV counterparts. The reason for that is so one doesn't need a mobile tracking system to receive it. So there is a higher level of signal than the solar noise, by comparison.
Sirius' sat's do figure-8's over your head, so if one happened to orient itself between you and the sun, the outage would only be brief, if at all. Sirius is at a much lower orbit than XM or the TV sat's are.
HTH!
