Satgen 205 The Sun and Radio Communications by GM4IHJ 27th Feb 93 BID of this msg is SGEN205 Please use this BID if you retransmit the msg The Sun is a giant ball of ionised gas held together for the most part by its own gravity and self generated magnetic fields. But the containment is not complete. Plasma (electrified/ionised gas) is constantly escaping from the Sun , in several different ways. There is a constant stream of escaping material from Coronal Holes - locations on the Sun where the magnetic field is unable to hold in the energetic plasma, and , there are Solar Flares, massive explosive releases of plasma which leave the Sun at very high speed. The Earth sits inside the protection of its own magnetic field, sheltered almost completely from solar bombardment, but just above our heads, the upper atmosphere and ionosphere are not so well protected, and can be heavily affected by the bombarding plasma which we call the "SOLAR WIND" How does the plasma penetrate the Earth's Magnetic Field ? Firstly as a steady stream washing over the sunward side of the magnetic field, then penetrating down the open magnetic field lines over the poles. This constant dribble forms the Polar Auroral Ovals and fills up the Van Allen radiation belts - where the Earth's magnetic field acts as a magnetic bottle containing and restraining the plasma. The second type of penetration results from the energetic events in the Solar Wind , produced by Solar Flares. Here the plasma shock wave flows over and around the Earth into the Magneto Tail behind the Earth. There it rearranges the Earth's field causing it to fire bolts of plasma back into the Earth's polar regions where they cause major auroras. Only recently has it been realised that there is a simpler less energetic way that Solar wind plasma can get into the ionosphere near the poles. What happens relies on the fact that the Solar Wind - a moving cloud of electrified gas, is a very powerful "Electric Current", carrying with it, its own self generated magnetic field. This field is highly variable because the solar wind is variable , and it spreads throughout the solar system as a collection of different discrete field elements we call the Interplanetary Magnetic Field IMF. So the Earth sees the IMF as a field changing in both magnitude and polarisation as it encounters succeeding "patches" of solar wind plasma. When the IMF encountering the Earth has a Northerly polarity , its field and that of the Earth oppose one another , but when the IMF is southerly it can " merge" with the outer layers of the Earth's field opening up a hole in the protective sheath around the Earth high above the Sub Solar Point. Solar Wind plasma can enter this opening . It is then constrained by the magnetic field. Like cattle between two long electric fences across a field. It can only move up or down between the field lines, it cannot cross them . So it moves up in latitude to the polar regions and enters down the open field lines providing relatively steady patches of plasma in the upper F layer of the ionosphere, where it is quite capable of oblique incidence propagating HF radio communications across the pole . Giving us both NM7M's Trans Polar Winter Satellite signals and even better , excellent HF links trans polar aand beyond at 14 , 21 and 28 MHz for terrestrial users , including W2RS in New Jersey who seems to have used this route on 14 MHz for his first North Korean contact. EXTRA My thanks to Brian VK4BBS . I hope VK4TEC got copies of Satgens he required from VK4CXX or perhaps VK4WIA BBS. If not, I can supply. 73 from GM4IHJ @ GB7SAN