Rocket-coronagraph photometry of the 7 March, 1970 corona from 3 to 8.5 R _s

Abstract

A rocket-borne coronagraph utilizing external occulting disks was used to photograph the solar corona from 3 to 9 R _s at 1931 UT on 7 March, 1970. Comparison of the rocket and ground-based observations shows a one-to-one correspondence between major streamers from the inner to the outer corona. In particular streamers over the poles are clearly visible against the background corona from 3 to ≳ 8 R _s. These rocket data had a scattered light level of ∼1.2 × 10⁻¹⁰ B _s. The derived quiet equatorial and polar K + F corona was within 10% of the absolute brightness of standard coronal models and displayed identical radial gradients to those models. The photometric profiles of the NE limb streamer were analyzed assuming a model in which the core density follows a Gaussian distribution in directions perpendicular to the radius vector. This streamer was assumed to be rooted on the visible disk at 55 to 60° from the plane-of-the-sky as based on K-coronameter and XUV data. An uncertainty of as much as a factor of three still remains for the value of the axis density owing to uncertainty in the line-of-sight dimension of the streamer.