Ionospheric Monitoring and Solar Flare/CME Detection

The ionosphere is high outer layer of the Earth's atmosphere, charged (ionised) by solar radiation. This charging allows radio signals to bounce off the ionosphere and propagate over long distance. The ionosphere is also sensitive to the impact of space weather, and when this happens we should see changes in the signal strength of radio transmissions. There are also signature markers for solar flare x-ray events, which are usually correlated with coronal mass ejections (CMEs).

At Dunedin Aurora we monitor:

• The amplitude of the signal from an Australia VLF naval transmitter (Station NWC in Western Australia). VLF radio is especially senstitive to change in the ionosphere.
• The signal to noise ratio of GPS satellite transmission to a common GPS module.

VLF Monitor - Last 24 Hours

The VLF antenna is a wire loop with approx 50 turns of wire. The signal is passed through a "SuperSID" filter and processed with Spectrum Lab software and custom software. Reception of long distance stations shows a diurnal variation in signal strength. This signal can be altered by space weather and x-rays generated by solar flares.

GPS Data

Signals from GPS satellites are affected by disturbances in the ionosphere, in the same way radio signals are. GPS recievers usually store data about changes in signal strength and phase, etc

We are able to crunch this data to provide a guide of how turbulent or frothy the ionosphere is. One of these measurements is called the S4 index, and can be calculated from the data that a very simple GPS receiver provides.

Disturbance Plot [open in new tab]

The position in the sky (altitude and azimuth) of ionospheric disturbances for the last hour. Larger circles mean bigger disturbance.

Broad field S4 index [open in new tab]

This plot is the median value of the S4 indices for each minute from the GPS (USA) and Glosnass (Russia) constellations. This gives us a broadband value of ionospheric activity

S4 data - spread of values [open in new tab]

S4 values for every visible GPS satellite. From the ground, GPS satellites appear rise, cross the sky, and set in a few hours. As they do their signal strength also improves, peaks and wanes. This scatter plot shows the spread of S4 values. The clustering of values about 11% can fade - presumably in response to ionospheric changes.

Signal to Noise Ratio - All Satellites [open in new tab]

The signal to noise readings for all GPS satellites for the past 24 hours. Lower readings are noisier.