Radio Astronomy

Participants: Dr G Woan, Mr R Dupuis, Mr M Hewitson

We carry out a varied program of observational and theoretical research, loosely based around radio astronomy at low frequencies, radio propagation through turbulent media and weak signal detection.

Interplanetary scintillation

An important feature of low frequency radio astronomy is the effect of the interstellar and interplanetary media on wave propagation. By combining scintillation ('twinkling') measurements of distant quasars and radiogalaxies with models of plasma dynamics we can infer much about the nature of both. The Glasgow group maintains the 'Cambridge IPS database' -- data collected with the 3.6 hectare array at Lords Bridge in Cambridge. The antenna itself is now no longer maintained and is unable to make further observations, so this database represents a unique view of the inner heliosphere throughout the early 1990s. Recent analysis of these data by Noelle Daly has identified a new single-station velocity mapping technique and has compared IPS-based parameters of the solar wind derived over this period with in situ measurements (from IMP-8, SAMPEX and GOES) and from other ground-based facilities. She has also demonstrated the usefulness of large-scale heliospheric density mapping for geomagnetic storm prediction.

This research brings together problems in both theoretical plasma physics and interplanetary and galactic astronomy. Research in low frequency radio propagation has also lead to work on the design of a radio telescope on the far side of the Moon for the European Space Agency and to a recent MIDEX proposal to NASA (in collaboration with JPL and other groups) for a free-flying constellation of radio telescopes to carry out very low frequency interferometry in Earth orbit.

Radio exoplanet detection

There are good reasons to believe that, at decametric wavelengths, the auroral emission from some 'hot jupiter' exoplanets will outshine their host star. In a collaboration with a number of groups, including Meudon, MPIAe and PRAO, we are using the UTR-2 radio telescope in the Ukraine to search for such emission from nearby exoplanets. These are some of the most sensitive broad-band observations made with the world's largest telescope, and have already produced some unique high-sensitivity pulsar observations in the 20-30 MHz band.

Compact object astronomy

In collaboration with the Institute for Gravitational Research, we are extending ideas of radio pulsar searches to the detection of quasi-sinusoidal gravitational wave emission from asymmetric neutron stars and similar sources. The search involves long-period integrations (1-2 yr) on the GEO600 detector in Hannover, and a similar analysis of data from LIGO as part of the LIGO Science Collaboration (LSC),

Further theoretical work by Rejean Dupuis concentrates on the dynamics of core collapse supernovae, and the possible mechanisms for gravitational radiation from the resulting neutron star.

The collaborations extend to more general data analysis issues connected with GEO and the commissioning of the GEO data acquisition system.

Low frequency array technology

Radio telescope designers have always made strong demands on the technology of the day, most recently in the construction of low-noise millimetre-wave receivers. At lower frequencies, (below 500 MHz) radical design innovations are now possible using digital signal processing techniques. A research programme has recently begun to investigate the feasibility of constructing very broad-band, multi-beam telescopes for use in scintillation and pulsar astronomy. Future developments in this programme will be in support of the SKA and LOFAR proposals.