Sudden Ionospheric Disturbance Stations (SID) 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.
All SID monitoring stations are homebuilt by the observers. Instructions for constructing the VLF receiver and antenna can be obtained from the AAVSO Solar Division chairman. The receiver design has progressed remarkably as the SID program participants have been inspired to improve signal sensitivity and noise rejection. Recent SID station receivers follow a design developed by SID Technical Coordinator Art Stokes. The Stokes Gyrator receiver can be built and tuned by anyone with simple soldering skills. A small indoor loop antenna captures the radio wave for amplification and rectification by the receiver. The SID station operates unattended until the end of each month. Recordings are then analyzed for the beginning, end, and duration of SID events.
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