Department of Physics
SPACE PHYSICS GROUP

About the Space Physics Group

 

Our research group studies the nature of the upper atmosphere and near-Earth space. We are interested in energy coupling between regions and the inputs from the Sun, lightning, and particles to name a few examples. Recent collaborations have involved researchers from the USA, UK, Japan, Canada, Czech Republic, Hungary, and Australia, some of which are continuing. New projects are now being undertaken with researchers from Finland, France, Hungary, UK, and the USA.

Our research topics include measurements and modelling of atmospheric conductivity, radiation belt variation and losses, solar flares, solar proton events, thunderstorms, lightning properties, red sprites, and the energy inputs of all of these processes on the lower ionosphere. In addition we undertake regular measurements of the plasmasphere, lightning locations, lightning-generated whistlers and the ionospheric D-region.

We use Very Low Frequency (VLF) radio propagation to probe the Earth-ionosphere waveguide, the lower ionosphere, and the plasmasphere, including the regular diurnal, seasonal, and solar-cycle changes. Using these techniques we also monitor the sporadic changes due to events like solar flares and magnetic storms. Generation, propagation, and amplification of plasma waves including wave-particle interactions are investigated as well as precipitation and ionospheric-aeronomy effects such as satellite-observed optical emissions and ground-observed airglow.

Resources

Learn more about our research here:

VLF communications transmitters and Long-range remote sensing of the Upper Atmosphere

Measuring a huge solar flare

Hear the interview with Dr. Craig Rodger on the Australian Broadcasting Corporation's "The Science Show", broadcast across Australia on 10 November 2007.

See the video interview with Dr. Craig Rodger on the Otago University Our People website.

In addition to campaign measurements, we undertake regular measurements of ELF/VLF fields low-noise field station in the hills of Dunedin. In December 2008 some group members travelled to Ross Island, Antarctica, and installed an instrument at Arrival Heights. Some of our Dunedin-based experimental equipment is listed below. Many of these experiments operate as long-term monitors of the environment.

We utilise several OmniPAL, AbsPAL (Phase and Amplitude Logger), and UltraMSK receivers, which log small changes in the phase and amplitude of powerful VLF communications transmitters (~13-30 kHz). The signals from these transmitters are trapped inside the waveguide formed by the Earth and the lower boundary of the ionosphere. By monitoring distant VLF stations (e.g., in the USA) we undertake long-range remote sensing of changes to the waveguide, and particularly the ionosphere. For example, solar flares lead to large changes to the daytime ionosphere, leading to changes in the propagation of the transmitter signals recorded by our instruments. We also study changes caused by electron precipitation from the Van Allan radiation belts, solar eclipses, and red sprites. Recently we have jointly developed a network of long-range ionospheric sensors based on the narrowband measurements of VLF communications transmitters. The core of the network is operated by the University of Otago/British Antarctic Survey and consists of 11 receiving stations. See the AARDDVARK (Antarctic-Arctic Radiation-belt Dynamic Deposition VLF Atmospheric Research Konsortia) homepage for more information.

Our group is also a core member of the growing World Wide Lightning Location Network (WWLLN), which now has more than 60 receiving locations spread across the world. This VLF-based lightning detection and location network sends lightning observations back across the internet to central processing computers in Seattle, USA (University of Washington) and Dunedin, NZ (University of Otago). The WWLLN is unlike any other global scientific lightning detection system in that it operates in real-time, with only a few seconds delay before a lightning location is registered. Working with the PI of the network, we have a growing understanding of the capabilities of the WWLLN. More information on the WWLLN, including realtime lightning maps can we found at webflash.ess.washington.edu.

The VLF Doppler Experiment which monitors whistler-mode signals from VLF transmitters. These signals have penetrated the ionosphere and propagated through the plasmasphere guided along geomagnetic field lines and allow us to monitor the nature of near-Earth space during the night. The group delay times of the whistler mode signals are determined by cross correlating the plasmaspheric signal with the sub ionospheric signal (that which has travelled in the Earth-ionosphere waveguide), accumulating the coefficients for 15 minutes at a time. The L shell has in the past been determined by measuring the difference in group delay time for two different transmitter frequencies travelling in the same duct.

We also host an Eötvös University Automatic Whistler Detector (AWD) system, which has been operating in Dunedin, New Zealand since mid-May 2005. Lightning-generated "Whistlers", the strongly-dispersed radio-wave pulses that have propagated along the Earth's magnetic field from one hemisphere of the Earth to the other, have long been regarded as inexpensive and effective tools for plasmasphere diagnosis.

In addition we also operate a riometer (VHF cosmic radio noise) in the hills of Dunedin.

The group has undertaken research campaigns in the US, Australia, Rarotonga, Antarctica, and the UK. Regular measurement campaigns are undertaken associated with Earth-orbiting satellites, examples being DEMETER, and IMAGE.

Additional facilities include real-time telemetry by microwave from our low-noise field station in the hills of Dunedin, including wideband VLF measurements.

Staff involved: Neil R Thomson, Craig J. Rodger