Satgen 208 Guide to Satellite/Surface TransPolar HF Propagation 20Mar 93 BID of this msg is SGEN208 Please use that BID if you retransmi this msg Sub Horizon Polar Propagation Calendar Feb/March 93 by GM4IHJ This chart lists the number of RS10 and RS12 satelitte orbits each day , where the satellite's 29 MHz beacon was heard via polar zone HF ionospheric propagation ,for at least 8 minutes ( not necessarily continuously) ,as it either descended to, or , climbed up from ,the GM northern horizon. Events. 7. X 6. X 5. X X X 4. X X X X X 3. XX X X X XX X 2. XX X X XXXX X X 1. XXXX X XXXX X X X ............................................................. 1 6 1 1 2 2 1 6 1 1 2 2 3 1 6 1 6 1 6 1 6 1 February 1993 . March 1993 Explanation :- No polar sub horizon extensions of either RS10 or RS12 beacon were heard in Feb 93 , until 15 Feb , when 4 separate orbits were heard for over 8 minutes on polar tracks, all whilst the satellite was north of the Scottish horizon. On 16th 3 orbits had audible polar extensions, whereas the 17th Feb had only one orbit with a polar extension . The 18th Feb produced 4 orbits with audible extensions over the pole , but 19th Feb had no orbits at all with polar extensions. The 24th Feb saw 7 orbits with polar extensions , and there were 2 , 3 and 5 extensions on the 25th, 26th, and 27th Feb. March has been far less prolific. Only 3 days have produced extensions so far, with records still to come for the period from the 19th to the end of March. Several reports have come in from terrestrial Dxers, mentioning unexpected transpolar HF propagation on 21 and 14MHz, coincident with the RS trans polar events. Timing of propagation events is roughly : single event day circa 1200, 4 event day 1000 to 1400 and 7 event day 0900 to 1600 (all time local) Propagation is believed to occur when a southerly interplanetary magnetic field merges with the earth's magnetic field. Allowing solar wind plasma to ride from the merger, up between the magnetic field lines to the polar cusps and thence down the open field lines into the polar F layer. ( Nature 4th Feb 93 p407 and 424 Merging at the Magnetopause refers ). Charts of this type will be sent out by GM4IHJ at regular intervals , via packet radio addressed to Trace ZL2BS, so that Southern Hemisphere observers can make comparisons with any results they get, from orbits near the South Pole. Records exist in UK for northern events in September and October. So it could happen that Southern observers may see (same season) events in March April 93 . 73 de GM4IHJ @ GB7SAN