Correlation of radio dropouts with solar electron flux density

Radio users will be familiar with dropouts in HF and VHF radio signals, which vary with time of day and solar activity.

The basic process:

• Electrons stream continuously from the Sun; but the flux density varies with solar activity
• From a point on Earth, electron flux density also has diurnal variation (maximum when facing the sun at midday, minimum at midnight)
• Electrons impacting the upper atmosphere produces ionisation which builds during the day and dissipates overnight
• HF and some VHF radio waves are absorbed in the ionised layers
• Consequently earth-side radio flux in the HF and lower VHF bands is attenuated in proportion to electron flux

Time variation of radio flux data from the Radio Spectroscope reflects this phenomenon and correlates to the flux density of electrons as measured from the GOES 13 satellite.

Data inputs:

• One week's radio flux data from a radio-quiet VHF band (57-62MHz)
• Electron flux data from GOES 13 satellite