>> I'm curious as to how the Solar activity affects "Line of sight" transmissions.
If you are referring to high band - or higher - frequencies, solar activity rarely has an affect.
Solar activity, which generally takes place in the ionosphere and upper levels of the Earth's atmosphere, has the greatest affect on longer wave lengths (lower frequencies). from below the AM broadcast band through the 6-meter ham band (50-54 MHz).
High band VHF and above frequencies are generally affected by weather conditions occuring between ground level and the Troposphere, which begins several thousand feet up.
Conditions on high band and above can be enhanced anytime the atmosphere in your region has an inversion. Under normal conditions, the air temperature is higher and the moisture level is lower at ground level than at high altitudes, but, during an inversion, the reverse occurs.
To some extent, inversions occur almost daily around sunrise and / or sunset ... which is
part of the reason why reception can be so good in the early morning, but fade out by mid-morning.
You can also experience enhanced conditions when the troposphere supports ducting. With ducting, a signal reaching the Troposphere does not pass through it. Instead, it bends to ride within the Tropo layer until it evenually exits back toward ground.
Tropo ducting can occur when a stable high pressure system parks itself over a part of the country. Shorter-term ducting can occur along a weather front.
Although Tropospheric-related enhancements generally affect high frequencies than Ionospheric "skip," there is some overlap. Under the right circumstances, either condition can affect 6-meter, the FM broadcast band and the civilian aero band. DXing the FM radio band and the lower TV channels (2 through 6) is a popular pastime for many hobbyists.
For more information on tropo and related subjects, check out:
http://www.radioreference.com/forums/forumdisplay.php?f=96
http://www.dxinfocentre.com/tropo.html