The Sun's Sneaky Variability

The Sun is of vital importance to Radio Amateurs since it determines propagation conditions on the HF radio bands.

A NASA report describes work to help us better understand the characteristics of the Sun.

When the sun is active, intense solar Extreme Ultra Violet (EUV) emissions can rise and fall by factors of thousands in just a matter of minutes. These surges heat Earth's upper atmosphere, puffing it up and increasing the drag on satellites.

EUV photons also break apart atoms and molecules, creating a layer of ions in the upper atmosphere that can severely disturb radio signals.

To monitor these energetic photons, NASA is going to launch a sensor named 'EVE', short for EUV Variability Experiment, onboard the Solar Dynamics Observatory as early as this winter.

Read the full NASA report, The Sun's Sneaky Variability, at
http://science.nasa.gov/headlines/y2009/27oct_eve.htm