Simultaneous Observations of a Prominence Eruption Followed by a Coronal Arcade Formation in Radio, Soft X-Rays, and Hα

Abstract

Abstract A prominence eruption followed by a coronal brightening was simultaneously observed in radio (17 GHz), soft X-rays, and Ho: on 1992 July 30–31. The observations were performed by newly developed highperformance instruments: the Nobeyama Radioheliograph, the SXT on the Yohkoh satellite, the Flare Monitoring Telescope of the Hida Observatory, and some other Ho: telescopes. This event gives us a much more detailed picture of this type of phenomena than previously observed. The erupting prominence, which occurred in a quiet region and was observed in Hα and radio, ascended with a velocity of about 100 km s–1. The general structure of the erupting prominence seen at 17 GHz is very similar to that at Ho:. While the prominence expanded rapidly, the total radio flux of the erupting prominence did not change very much. Since a prominence consists of fine threads, this fact means that each thread did not expand while the prominence expanded. Consequently, the surface filling factor of the prominence must have decreased during the eruption. The high-resolution pictures of a clear coronal arcade structure were taken in soft X-rays and radio after the prominence eruption; the physical parameters of the arcade were derived from these pictures. The mean temperature was 3.5 × 106 K in the early phase, and decreased to 2.6 × 106 K within seven hours. The total emission measure reached a maximum value of 1.6 × 1048 cm–3 after three hours from the beginning of the arcade brightening, when the electron density at the ridge of the arcade is estimated as 2.4 × 109 cm–3. The temporal and spatial relationship between the erupting prominence and the coronal arcade is shown. It gives an observational restriction to the magnetic field configuration of the models of such events.