Gray Line Propagation

On the lower bands signals are stronger from a station where the sun is just going down or just coming up.  This phenomenon is known as gray line propagation because it follows the gray line between darkness and sunlight as the earth rotates.  A good example to demonstrate how well it works came the weekend of the CQ World Wide DX Contest in November, 2013 on 80 meters.  On the map below notice that the DX stations getting through to North America are on the gray line.  This is a screen snap from Reverse Beacon Network. My station is the green dot.  Red dots are all the stations I was hearing.