{
  "bibcode": "2005GCN..2932....1C",
  "body": "P.  Campbell, M. Hill, R. Howe, J.F. Kielkopf, N. Lewis, J.\nMandaville, A. McWilliams, W. Moos, D. Samouce, J. Winkler, G.J.\nFishman, A. Price, D.L. Welch, P. Schnoor, A. Clerkin, and D. Saum\nreport, on behalf of the AAVSO International High Energy Network\nand SID Program, on the detection of the Dec. 27 outburst from SGR\n1806-20 (GCN #2920; Borkowski, et. al) as a sudden ionospheric\ndisturbance (SID) in the Earth's atmosphere.\n\nA disturbance of the Earth's ionosphere was observed coincident\nwith the INTEGRAL detection of a burst from SGR 1806-20. This SID\nwas seen as a change in the signal strength from Very Low Frequency\n(VLF) radio transmitters being monitored by stations around the\nglobe. (Note: This is not a radio detection of SGR 1806-20; this\ndisturbance was caused by the prompt X-rays from SGR 1806-20\nionizing the upper atmosphere and modifying the radio propagation\nproperties of the Earth's ionosphere.)\n\nThe monitoring stations that report detections of the SID are:\n\nObserver     Receiver Location     Transmitter and Location\nMoos         Switzerland           FTA - St. Assie, France \nHill         Massachusetts, USA    NAA - Cutler, ME, USA\nWinkler      Texas, USA            NAA - Cutler, ME, USA\nKielkopf     Kentucky, USA         NAA - Cutler, ME, USA\nCampbell     Alberta, CA           NLK - Jim Creek, WA, USA\nHowe         Colorado, USA         NML - LaMoure, ND, USA\nMc. Williams Minnesota, USA        NML - LaMoure, ND, USA\nSamouce      Montana, USA          NML - LaMoure, ND, USA\nKielkopf     Kentucky, USA         NPM - Lualualei, HI, USA (2nd receiver)\nMandaville   Arizona, USA          NPM - Lualualei, HI, USA\nLewis        California, USA       NPM - Lualualei, HI, USA\nWinkler      Texas, USA            NPM - Lualualei, HI, USA (2nd receiver)\n\nThe observing method employs the monitoring of distant, powerful\nVLF radio transmitters; this is a sensitive monitor of the state\nof the lower ionosphere along the radio propagation path. Due to\nthe sub-burst longitude and latitude and the geographical\ndistribution of LF/VLF beacons and monitoring stations, this burst\nwas not detected by active monitoring stations in Germany,\nAustralia and Canada. However, one monitoring station in\nMassachusetts, USA (separate from Hill) did not detect the SID\nwhile being in a good location to do so.\n\nSeveral plots of the SID detection are available at:\n          \nhttp://www.aavso.org/observing/programs/solar/sid-sgr1806.shtml\n\nAdditional details of the observations are also available at this\nsite, including the raw data of these and future observations as\nthey become available.\n\nPreviously, at least four other transient, high-energy sources have\nproduced detectable ionospheric disturbances, as measured with VLF\nreceivers:  GRB030329 (Price et. al, IBVS #5415, 2003); GRB830801\n(Fishman and Inan, Nature v.331, p.418, 1988); XRF 020427 (GCN\n1394), and the Aug. 27, 1998 super-flare from SGR 1900+14 (Inan, et\nal., Geophys. Res. Lett., v.26, p.3357, 1999).\n\nThe AAVSO is greatful for generous grants from the Curry Foundation\nand NASA for the financial support for the High Energy Workshops\nfor Amateur Astronomers.",
  "circularId": 2932,
  "createdOn": 1104794507000,
  "email": "aavso@aavso.org",
  "subject": "SGR1806: Detection of a Sudden Ionospheric Disturbance",
  "submitter": "AAVSO GRB Network at AAVSO  <aavso@aavso.org>"
}