This page will be about propagation and the ionosphere and solar wind and other neat stuff... Here is a sample of what will go on here... mainly a discussion about things that affect the medium through which we send and receive radio waves... The Ether....
My goal is to make these discussions as close to plain English as the topic will allow... let me know what you think and what topics you want discussed on this page..... Send comments to KE3VV
A Note about X-ray Flares
Note: the D-layer is usually fairly inactive during the daytime because normal solar radiation (sunlight... duh!) ionizes the upper layers (F1 and F2). But the x-rays from a big solar flare can bang on through the F and E layers and ionize the D layer. The effect is not the noise or interference generally associated with geomagnetic storming, but is more of an "absorption" phenomenon, caused by a tremendous (up to 10 times) increase in the electron density of the daytime D layer. The temporary daytime photo-ionization of the D layer simply sucks up most (if not all) of the energy in the radio waves we are trying to exchange.
By the way, the effect of X-flare radiation and the accompanying absorption is greater the closer you get to the equator. This occurs because X-rays are straight-line radiation and there is greater intensity at low solar zenith angles where the x-ray flux is greater. Shortwave fadeout is also greater at lower HF frequencies. Fadeout only happens during daylight hours and only lasts as long as the flare is active.
A Note about Geomagnetic Storms
While the Earth may experience some shortwave fading from an X-flare, the real impact usually occurs 2-3 days later when the proton stream and plasma cloud get here. Unlike the "speed-of-light" sunshine and X-rays, protons and plasma travel at about 0.8 lightspeed and it takes them longer to reach earth.
Most geomagnetic disturbances are caused by the large number of protons ejected from and plasma clouds associated with solar flares and coronal holes. There are tons of protons tossed out into space during events called Coronal Mass Ejections or CME's. When the protons and associated plasma cloud (plasma is just ionized gas... the solar wind is plasma...) arrive they will generate some disturbances in Earth's geomagnetic field (magnetosphere) that will affect the ionosphere. That is a geomagnetic storm.
A Note about Auroras
There is normally a lot of geomagnetic activity near the Earth's magnetic poles. It is what causes the aurora. Sometimes, when there are severe or very severe geomagnetic storms, the activity near the poles increases and moves southward, displaying the aurora borealis southward into the mid latitudes.
Oddly enough, if you were in Alaska at this time of year, where the aurora is normally visible, you could not really enjoy it because the sun never really sets at those latitudes around the solstice (mid-June)... sort of "permanent" twilight! Thus it does not get dark enough to get a good look at the aurora. Moonless, dark nights are best.... usually the hours before dawn (before morning twilight).
Get the latest aurora visibility information at http://www.spacew.com/www/aurora.html
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