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Sudden Ionispheric Disturbances (SIDs)

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.

The Gyrator III VLF Receiver

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).


Circuit diagrams and wiring for the Gyrator III are available here in Microsoft Word and PDF formats: .doc, .pdf

AAVSO Sudden Ionospheric Disturbance Program Observers

Active Observers (Data submitted within the last year)

OBS ID Observer Name Station Location
A-94 Al McWilliams St Cloud, MN
A-96 Roberto Battaiola Milan, Italy
A-97 Jon Wallace Torrington, CT
A-118 Lionel Loudet Muret, France
A-120 Bob Terrill Ballarat, Victoria, Australia
A-121

SID Database

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.

SID Monitoring Group FAQ

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.

VLF Station List

VERY LOW FREQUENCY (VLF) RADIO STATIONS
                                     
           Station            Station     Frequency        Radiated
             Site               ID          (kHz)            Power
                                                             (kW)
  U.S. Navy                     
       Cutler, ME                NAA          24.0            1000
       Jim Creek, WA             NLK          24.8             250
       Lualualei, HI             NPM          21.4             566
       LaMoure, ND               NML          25.2             500

Solar Program, Reducing Data and Email Format

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

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:

Photos of Danie Overbeek

 

Click any image to enlarge.

SID Program - Reducing Data and Email Format

Reducing Data Gathered by VLF Monitoring Systems

(Extracted from SID Technical Bulletin Vol. 3, Number 4, Oct. 1992)

The reduction process is quite simple, and consists of the steps which follow. First, the universal time for each of three event-phases must be measured for each SID. Examples are indicated on the recording at the end of this report.

Pages

AAVSO 49 Bay State Rd. Cambridge, MA 02138 aavso@aavso.org 617-354-0484