Dunedin Aurora

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

2021 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.

Other Experiments

Ambient Radio Frequency

Ambient radio energy is harvested with a rectifying circuit attached to a monopole antenna. This circuit functions just like a crystal set radio, and generates a small DC voltage on the output. An Arduino is used to convert the analogue reading, which is logged by computer. I am curious to see if space weather events affect the ambient RF field.

So far we have observed:

Telluric Current

Telluric currents are a natural voltage gradient that exists in the ground. If two copper electrodes are hammered into the ground some distance apart and wires are attached, then a small voltage can be measured with a standard voltmeter.

Telluric currents are typically induced in the ground by changes in the Earth's magnetic field under the influence of space weather. The equipment to measure these voltages is very simple. Amplifying the signal for measurement is usually accomplished by having a large distance between electrodes, usually in the order of hundreds of meters.

This experiment is a test of equipment at a much smaller, suburban scale. The electrodes are in an E-W line about 20 meters apart. It is likely that there will be some influence from the domestic power network, but hopefully we will see changes due to space weather, natural diurnal variation, etc.

Raw spectrum: less than 1Hz (last 8 hours)

Most geomagnetic phenomena caused by space weather appear at frequencies of less than 1Hz. Frankencoil may be able to detect the imact of these events.