An upgrade of the UTR-2 radio telescope to a multifrequency radio heliograph

Abstract

We present the broadband heliograph based on the UTR-2 radio telescope for obtaining the solar corona images in the frequency range 8-32 MHz with the frequency resolution 4 kHz, the time resolution up to 1 ms, and under the dynamic range about 90 dB. The instrument provides new possibilities to measure the non-thermal radiation in an unprecedented way for a better understanding of the radio emission processes in solar corona. We describe various aspects of the instrument including its antenna system, receiver front end, digital hardware and the data acquisition. This is the lowest-frequency heliograph operating in the world. It allows us to detect radio emission from solar radio sources in the upper solar corona near frequencies of ionosphere cut-off. The instrument performance is illustrated with source maps of solar radio bursts at low frequencies during the observational campaigns of 2013 and 2015.

Decameter Radio Emission of the Sun

“…These sizes are close to those obtained earlier with the Clark Lake radio telescope (Kundu et al, 1977). At the same time heliograph measurements give slightly larger sizes in both directions (Abranin and Bazelyan, 1986;Stanislavsky et al, 2013). Any discrepancy in size can be caused by its dependence on year and even month of observation as well as on the activity of the Sun.…”

“…and their sizes if the latter are from units to tens of minutes. Such angular sizes are peculiar to the quiet Sun (Aubier et al, 1971;Kundu et al, 1977;Erickson et al, 1977;Bhonsle et al, 1979;Abranin and Bazelyan, 1986;Thejappa and Kundu, 1992;Sastry, 1994;Subramanian, 2004;Ramesh et al, 2006;Brazhenko et al, 2012a;Stanislavsky et al, 2013) as well as to the sources of Type III bursts (Abranin et al, 1976;Chen and Shawhan, 1978;Bhonsle et al, 1979;Abranin et al, 1980b;Suzuki and Dulk, 1985), Type II bursts (Chen and Shawhan, 1978;Bhonsle et al, 1979;Nelson and Melrose, 1985) and Type IV bursts (Gergely and Kundu, 1974;Chen and Shawhan, 1978) from the forties of the last century, mainly in the mm-, cm-, dm-and m-wavelength bands. For the rst time the quiet Sun decameter radio emission was observed by the Arecibo radio telescope (Aubier et al, 1971).…”

PROGRESS IN THE STUDY OF DECAMETER-WAVELENGTH SOLAR RADIO EMISSION WITH UKRAINIAN RADIO TELESCOPES. Part 1. (Invited paper)

“…by taking the best features of the analog part (specifi cally, the signal phasing system of the UTR-2) and profi ting by the latest achievements of computer electronics (like eff ective integrated circuits) [5]. Th e operation of the heliograph is based on a simple principle, namely sequential scanning of the sky area under investigation with the pencil-shaped beam of the UTR-2 [6]. Th e method has advantages and disadvantages alike.…”