The propagation of radio signals in the medium frequency band (MF: 300kHz-3MHz), the high frequency band (HF: 3MHz-30MHz) and even the very high frequency band (VHF: 30MHz-300MHz) is largely influenced by the condition of our sun and, through the emissions of our sun, also the earth magnetic field that captures these. Because of its importance for certain radio communications, a number of observatories continuously monitor the condition of the sun and the geomagnetic field. Follow the steps outlined in this section to get an instant view on how propagation conditions are right now. If you are completely new to the topic of shortwave propagation, then have a look at AE4RV's HF Radio Propagation Primer (Flash movie!).
Current Solar-Geophysical Data Dashboard
Terminology
You are eager to learn more about the terms that are used in solar-geophysical reports?
If you are in a hurry to learn, have a quick look at this Glossary of Solar Terrestrial Terms of NOAA's Space Weather Prediction Center, formerly known as the Space Environment Center (SEC).
For those who have more time to read: David A. Rosenthal compiled a very instructive and more comprehensive primer, published by Radio Netherlands, that helps us to understand solar-geophysical alert broadcasts.
Preface
Geophysical Alert Broadcasts
The Broadcasts Explained (1)
The Broadcasts Explained (2)
Further Information
Summary of Solar-Geophysical Effects on HF Propagation
In general, the augmented electromagnetical solar flux originating from sunspots has a positive effect on HF propagation by improving the ionisation of the ionosphere and thereby increasing the maximum useable frequency (MUF) of the ionospheric layers, as well as their respective hop distances.
However, sunspots may exhibit a propensity to produce giant solar flares or prominences, staying for minutes to hours. The X-rays and particles originating from these flares are capable of causing sudden shortwave radio fadeouts on sunlit paths due to increased D-layer absorption starting at the lower bands and moving up with flare intensity. In the case of an 
, an 
or a 
be sure to monitor the absorption curve on SEC's D-region absorption chart. During quiet episodes of solar activity, this graph will remain void.
In an other, slightly more delayed mechanism, particles escaping from the Sun's Coronal Holes (CHs) or freed during Coronal Mass Ejections (CMEs) travel at high speed through space along the Sun's interplanetary magnetic field. This is called the solar wind. CH particles need 5 days to reach Earth, CME particles only 4. When they get trapped by the Earth's geomagnetic field they cause aurora upon entering the Earth's atmosphere at the magnetic poles. The effect is more pronounced when the z-component of the interplanetary magnetic filed Bz is pointing south relative to the Earth's magnetic poles (see leftmost dial). On 160m, signals paths crossing an aurora zone are often completely lost or severly skewed.
Geomagnetic disturbances 
, reflected in higher A- and K-indices, might bring good DX to the VHF enthusiasts among us, but will have detrimental effects for propagation starting at the lower bands (≤10MHz).
An explanation by the experts: The Earth's magnetic field causes the ionosphere to become anisotropic. Hence, incident plane waves entering the ionosphere will split in an ordinary and an extraordinary wave. Upon exiting the ionosphere, both modes would normally recombine into a single plane wave, if it were not for the polarisation changes caused by the geomagnetic disturbances. This results in signal loss. The effect is called Faraday rotation.
Music extract: Sunny by Bobby Hebb
Some people like to hear music on web pages, others just hate it. Or, you may have your computer's soundcard connected to your transceiver to generate digimode modulation. In order to prevent Internet Explorer from playing any sounds, click on the toolbar Tools > Internet Options... Then select the Advanced tab. Scroll down to Multimedia and deselect Play sounds in web pages. That should do it. Hopefully everybody is happy now!