Decametre

Abstract: THE high-resolution dynamic spectra of Jupiter's decameter radio emission exhibit structures consisting of repeated tilted ridges1. The frequency–time slope of these ‘diagonal patterns’ also referred to as modulation lanes varies from 50 to 300 kHz s−1. The slope is a function of the System III central meridian longitude of Jupiter and it may be either positive or negative2,3. Recent observations of modulation lanes are described by Ellis4,5 and Lecacheux6. Here I report a study of polarisation diversity in the spectra of modulation lanes.

Abstract: In this paper properties of decameter spikes observed by radio telescope UTR-2 in July-August 2002 are considered. These bursts are placed chaotically on dynamic spectrum. They have duration about 1 s and frequency bandwidth 50-70 kHz. The bandwidth is increased linear with frequency. A model for decameter spikes is proposed.

Abstract: The Nancay Decameter Array, operating in the 10-80 MHz frequency range, consists in two phased antenna arrays in opposite senses of circular polarisation - with a 4000 m 2 effective aperture each -, and a series of powerful spectrum analysers allowing for wide band, high resolution and sensitive spectroscopy of Jovian and Solar Corona radio emissions. Coupled with spacecraft observations (Voyager, Ulysses, Wind, Galileo, SOHO) or working alone, it has provided some key information on radiation processes in Solar System magnetised objects. The used antenna concept and the newly developed, digital receiver system are described. Both have demonstrated their ability to solve some of the main difficulties in ground-based observing at decametre wavelengths: struggling against man made radio frequency interference, perturbations from terrestrial ionosphere, low signal to noise ratio inherent to the high sky brightness. Some ideas for future giant decameter radio telescope projects (10 6 m 2 effective area at least) are proposed.