Meteor Trail Reflection and Sudden Frequency Deviation
The meteor trail reflection system uses high-quality HF general coverage receivers set to SSB and connected to an HF log periodic antenna. The receivers usually are tuned to time services such as WWV and WWVH on 10, 15, 20 and 25 MHz, and frequency offsets usually are about 1 kHz but may vary according to monitoring requirements and conditions.
This system also is used for detection of Sudden Frequency Deviations (SFD) associated with solar flares. The X-ray flux from the flare causes Earth's ionosphere to rapidly change in both electron density and movement, leading to Doppler shift of the monitored carriers.
11 June 2014 at 2056 UTC ~ Solar Flare, X-ray magnitude M3.9
Image from Argo showing a sudden frequency deviation. Time is on the horizontal axis (UTC) and carrier offset on the vertical axis. Full vertical scale is slightly more than 40 Hz. Lower trace is WWV/WWVH at 15 MHz and upper trace is WWV/WWVH at 20 MHz.
Image from R_Metero showing time on horizontal axis (UTC) and carrier offset on vertical axis. Full vertical scale is 50 Hz. Upper trace is WWV/WWVH at 15 MHz and lower trace is WWV/WWVH at 20 MHz. Note: The R_Meteor and Argo displays are mirror images.
Argo Spectra showing meteor trail reflections, bifurcations and other curiosities, click here