On Jan 20, 11:10*am, dave wrote:
On 01/19/2011 11:06 PM, wrote:

On Jan 18, 8:36 am, *wrote:
On 01/18/2011 04:30 AM, Keith wrote:

* *The sun spots are very low right now which effects the ionosphere.
Here is a short article on the concept:

http://hamchatforum.lefora.com/2009/11/13/hf-radio-propagation-and-su...

Here's a shorter one:

In order for signals to refract (be bent back toward the Earth) the
ionosphere needs ions. These are produced when UV radiation interacts
with the atmosphere. UV radiation comes from Sunspots.

And nobody can figure out what causes the sunspots. Unknown.

Although the details of sunspot generation are still a matter of
research, it appears that sunspots are the visible counterparts of
magnetic flux tubes in the Sun's convective zone that get "wound up" by
differential rotation. If the stress on the tubes reaches a certain
limit, they curl up like a rubber band and puncture the Sun's surface.
Convection is inhibited at the puncture points; the energy flux from the
Sun's interior decreases; and with it surface temperature.http://en.wikipedia.org/wiki/Sunspot

Yes,it is a scientific research,still in progress !