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Bremen, KS | As I understand it, there are two parts of a solar flare/coronal mass ejection (CME). The flare is the visible part we see about eight minutes after it happens and in itself isn't the disrupting phenomenon. The CME is the part that causes the disruption and can take a day or more to reach earth. It is composed of charged particles that interact with the earth's geomagnetic field and the ionosphere to create the northern and southern lights and disturb/distort radio signals. As the CME hits the geomagnetic field the particles are spread around the earth rather quickly so there really isn't a time of day that is less prone to its effects than another. The effects last as long as the stream of particles passes through our orbit.
Keep in mind the earth is orbiting the sun and the sun is rotating. Both of these motions determine whether a CME will impact earth or not. Most CMEs do not, in fact it is a bit rare that they do as probably thousands of CMEs occur during a solar cycle (this is Cycle 25 we're in right now) but almost all are directed away from us or only a glancing impact. What made the recent CMEs unique as the one two weeks ago is that it was a large CME and it was directed almost straight on toward earth as was the one in June. As a result the northern lights could be seen at much lower latitudes than usual. Keep in mind that the sun is always sending particles our way as aurora always exists around the Arctic Circle.
I'm no expert but this seems to jibe with what I've learned of HF radio propagation. | |
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