Topband: Gamma ray bursts

Carl K9LA k9la at
Wed Jan 5 19:08:00 EST 2005

W4ZV's posting about GRBs reminded me of the one back in 1998 that was 
caught on record on a VLF path. Don't know how much it affected 160m, 
but it sure affected VLF.

That GRB passed through our solar system on August 27, 1998. At the time 
the flare hit, the Earth was oriented such that the flare encountered 
the night-time side of the ionosphere. This flare originated from a 
distant star in our own galaxy about 23,000 light years away. As a 
result of this flare, the ionization in the night-time ionosphere 
increased to daytime levels.

Stanford University maintains a network of four VLF transmitters: one in 
Hawaii, one in Washington State, one in Maine, and one in Puerto Rico. 
The signal level of these transmitters is monitored at a site in 
Colorado. The path from Hawaii to Colorado went through that part of the 
night-time ionosphere that was hit by the flare. The quite strong VLF 
signal disappeared for a few mintues around 3:30 AM Colorado local time 
- that's exactly when the gamma ray hit. It didn't last too long, though 
- within 5 minutes or so the normal night-time signal level was back.

Carl K9LA

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