The AAVSO SID Program consists of solar observers who monitor very low frequency (VLF) radio stations for sudden enhancements of their signals. Earth's ionosphere reacts to the intense X-ray and ultraviolet radiation released during a solar flare. The ionospheric disturbance enhances VLF radio propagation. By monitoring the signal strength of a distant VLF transmitter, sudden ionospheric disturbances (SIDs) are recorded and indicate a recent solar flare event.
About the SID Database
The Sudden Ionospheric Disturbance (SID) Database lists all events identified in the AAVSO Solar Bulletin. These results are provided monthly by the worldwide network of SID observers in the AAVSO Solar Division. Individual results are correlated with other observers' reports and reduced to a list of events with high definiteness ratings.
The latest version of the Gyrator series of VLF receivers (first developed in the 1990s) is the Gyrator III, a revision of Arthur Stokes' Gyrator II by Guglielmo Di Filippo (observer A-93).
Active Observers (Data submitted within the last year)
|OBS ID||Observer Name||Station Location|
|A-94||Al McWilliams||St Cloud, MN, USA|
|A-96||Roberto Battaiola||Milan, Italy|
|A-97||Jon Wallace||Torrington, CT, USA|
|A-118||Lionel Loudet||Muret, France|
When the ultraviolet rays from the Sun hit the Earths atmosphere the energy they possess work to knock electrons off of the atoms and molecules that the atmosphere is made up of. These free electrons make up a region of the atmosphere known as the Ionosphere. The region is strongest on the daytime side of the earth since it is dependant on the energy from the solar ultra violet rays.
VERY LOW FREQUENCY (VLF) RADIO STATIONS Station Station Frequency Radiated Site ID (kHz) Power (kW) U.S.
Solar Program, Reducing Data and Email Format
Reducing Data Gathered by VLF Monitoring Systems
(Extracted from SID Technical Bulletin Vol. 3, Number 4, Oct. 1992)
SID Monitoring Overview
AAVSO SID Program
Rodney Howe, Solar Section chair & SID leader
So, what are we looking for? Here are a couple references of SID events and their influence on the ionosphere:
Click any image to enlarge.