Radio and EUV observations of a coronal hole

Abstract

We present observations of a coronal hole made with the EUV spectroheliometer of the Harvard College aboard Skylab and with ‘high resolution’ (2–4′) radio telescopes at Culgoora and Fleurs Australia and Bonn, West Germany. We attempt to derive the density and temperature distributions in the transition region and inner corona from the combined observations. No one ‘standard’ model can explain both sets of observations; characteristically, models based on EUV data yield higher radio brightnesses than are observed, while models based on radio data yield lower EUV line intensities than are observed. The discrepancy is essentially that the electron density inferred from the EUV data is about three times that inferred from the radio data.