The Mark IV Nançay radioheliograph

Abstract

A multi-frequency capability has been added to the north-south array of the Nançay Radioheliograph, providing observations at up to five frequencies between 150 and 450 MHz with time resolution ≤ 0.1 s. The projected position, brightness and dimension of sources in the solar corona can thus be studied as a function of height. Two-dimensional information is obtained at 164 MHz using the east-west and north-south arrays. In addition, the quiescent corona can be mapped in two dimensions at all observed frequencies by earth rotation synthesis. The paper describes the new aspects of the antennae, the receiver frontend, the data acquisition and the calibration procedure. The performances of the instrument are illustrated with multi-frequency observations of solar fast-drift bursts, continuum emission and maps of the quiet corona.