Solar X-rays:

Geomagnetic Field:

The Grey Line is the band around the Earth that separates day from night. There is always a short period, around one hour, of semi darkness, hence "Grey". On one side of this area the Earth is coming into daylight, and on the other the Earth is darkening to night. Propagation along the Grey Line is usually very good, albeit of short duration. This line generally runs in a north-south direction depending on the time of year and it can have a tilt of as much as 23°.

On the sunset side of the Grey Line, the D Layer disappears quite quickly and on the sunrise side the D Layer takes time to form. During this period propagation is enhanced along the line. The effect is most noticed on the low bands, 1.8MHz to 10MHz. Of course hf yagi antennas are the best to use to take advantage of this propagation, but wire antennas also work well if aligned to take advantage of the Grey Line, especially since below 7MHz yagis are somewhat large!

The current solar cycle, number 23, is now at it's end as the number of sunspots dwindles to zero. The new solar cycle, number 24 is now predicted to be 3 stronger than cycle 23. This is good news for Radio Amateurs! Look forward to a busy time as the cycle peaks between 2010 and 2012. Experts are still out on the exact timing of the peak. In fact some are not predicting a high peak, rather the opposite. As you can see from the picture above, the predicted sunspot values are quite a bit less than the actual values. We shall have to wait and see, however the signs are good and new research using models of the solar "conveyor belt" is suggesting good things are coming. Of course, what might be good for us as Radio Amateurs is not necessarily good for everyone. Power utility companies and owners of space satellites are amongst those who are worried about the effects of a stronger solar maximum. This can cause the earths atmosphere to expand causing drag on satellites in orbit. They will subsequently lose orbital altitude and their life span will be significantly shortened. Power companies worry about the effects of circulating currents in the Earth's ionosphere. Spectacular auroral displays can be accompanied by massive electrical disturbances which are picked up in the power distribution systems, causing widespread blackouts.