Dunedin Aurora

A citizen science magnetic observatory in suburban Dunedin, New Zealand.

2020 Edition

Experimental Prototypes

This page is for prototype data, instruments, and software. Usually I'm just testing that gadgets are recording and displaying whatever data they're receiving. While this is happening, I'm also looking to see if there are any common trends appearing, especially during space weather events.

Induction Coil Experiments

Frankencoil 2 being constructed.
Frankencoil 2 on location.

Frankencoil 2 is an prototype air-core induction magnetometer. The idea is that a large coil with a high number of turns will generate a voltage in a changing magnetic field. In theory geomagnetic disturbances caused by space weather should be detected.

Frankencoil is made from 4 boxes of network cable, wound into a loop three metres in diameter. All of the wires in the network cables are soldered together to create a single giant scramble-wound coil of about 1000 turns. This coil is then wrapped in an earthed skin of aluminium mesh which dampens the sensitivity to radio-frequency signals, but allows the changing magnetic field to be recieved. Frankencoil has an effective area of 7200m2.Because Frankencoil lays on the ground, it is most sensitive to the vertical component of the Earth's magnetic field.

The signal from Frankencoil can then be fed into simple electronics to filter out noise, amplify the signal etc, before being fed into the Mic-in of a computers sound card. We use a free signal processing software package called Spectrum Lab to filter and display the data and to generate CSV files which we process with custom software to create the following graphs and plots.

The biggest challenge with using a device like this is the amount of electromagnetic pollution from domestic power. A rural location would be much quieter, but in the meantime I am interested to see if there is anything that can be detected with Frankencoil that can be linked to space weather.

In most of the experiments that follow, I try to find ways to bypass or use the problem of electromagnetic pollution.

H Component (Last 24 hours)

Activity from a standard magnetometer. Look for spikes in the experiments that co-incide with magnetometer activity.

Sferics (Last 24 hours)

Raw broadband count of sferic noise. Most of this is lightning strikes within a 1000km or so. There is a possibility that the rate of sferics is affected by space weather events, so this experiment is designed to see if our 1000 turn shielded coil can detect this.


This is a measure of background noise in two broad bands - 4.8kHz and 8kHz. This chart zooms in the y-axis only, to allow you to exaggerate the variations in the curve over the course of a day.

Powerline Harmonics (Last 24 hours)

The idea here is that if we can't track the direct effects of space weather on the magnetic field, maybe we can observes it's effects by proxy, on the noise in the power network. Geomagnetically Induced Current is usually monitored directly in substation transformers. I want to see if any of this "leaks out" into the domestic power grid. Results have been ambivalent so far!

Ambient Radio Frequency

Ambient radio energy is harvested with a "rectenna" circuit attached to a monopole antenna. This circuit functions just like a crystal set radio, and so far has been seen to generate anything between 0.4 to 1.3 volts. I am curious to see if the ambient RF field can be influenced by space weather.

Raw spectrum: 1 - 100Hz (last 8 hours)

This is a spectrum of VLF noise from zero to 100 hertz. In theory, low frequency magnetic noise that occurs during space weather events should be visible. In practice, the urban location of Dunedin Aurora means that domestic mains noise drowns out everything. However this is a chance that during strong CME and solar wind events, something could be visible above the hum. Look for dark, diffuse blobs and patches in the spectrum under 50Hz, that are not mirrored above 50hz.

It is also possible that harmonic noise may increase during a space weather event due to induced voltages in the local power grid. This may appear as addition dark horizonal lines at certain frequencies that appear at the onset of a magnetic storm, or CME.