Satgen 428 Solar Warning by GM4IHJ (BID SGEN428) 7 June 97 As mentioned in Satgen 421 , our Sun is under observation 24 hours a day, by the Solar Heliospheric Observatory satellite SOHO . Stationed 1 million miles sunward of the earth, at Langrangian gravity balance point 1, SOHO is providing the best data we have ever had from our highly variable star. SOHO is however just one of about 20 satellites monitoring our sun. Their combined efforts covering most of the electro magnetic spectrum. Particularly useful is YOHKOH the Japanese Xray imager , which tends to see solar activity as it starts , rather that later as is the case with satellites which monitor the visible spectrum. Now for the first time YOHKOH is allowing us to see the active regions on the surface of the sun below the corona, where as on 7th January this year a tightly coiled magnetic filament , short circuited. This released a massive amount of energy causing a very large ejection of coronal material. Which happened to be aimed in our direction. Starting at about 1500 utc on 7th Jan97. This greatly enhanced burst of solar wind reached earth space 90 hours later travelling at one million miles per hour. Its direction of magnetic polarity was such that it could not couple with the earths magnetic field . So there was no terrestrial magnetic storm and hence no major aurora. But satellites in the geostationary orbit 23000 miles out on the sunward side of the earth were suddenly exposed to the full force of this solar blast as it pushed the normally protective earths magnetic field away from the geosats and closer to the earth. The result at one satellite was quite expensive. Telstar 401 , a 150 million pounds sterling TVsat , has not transmitted anything since then and must now be presumed to be completely dead. In the next 4 or 5 year we will experience the slow climb back up to solar cycle activity maximum. Which may be good for HF propagation, but could be bad news for several more satellites. Lets hope Phase 3D is at perigee when ever this happens. PS. As noted last week the 5 new IRIDIUM mobile phone sats were in a less than regular alignment. But in the past week they have been subject to an excellent piece of orbital manoeuvering. Such that the 5 sats are now evenly spaced about 32 degrees of latitude apart, in line ahead, with their footprints overlapping slightly , so that one of them and sometimes two are in range at IHJ continuously for a 5 sat sum total of 50 minutes or more every 100 minutes, for a large part of the day. The conga line is north going over northern hemisphere stations evenly spaced around 1610 approx local mean solar time (not summer/daylight time) afternoon. So Motorola have manged in one month to do something London buses are reported never to have achieved in 100 years.