Density, Temperature and Magnetic Field Structure of High Latitude Corona

Abstract

This paper explores the physical and morphological characteristics of the large-scale coronal structures such as polar coronal rays and high latitude streamers as seen in white-light and relates these structures to observations in soft X-ray (3–45 A), red (6374 A Fe X) and green (5303 A Fe XIV) line emissions to estimate their densities and temperatures. Analysis shows that polar rays can be characterized by at least two temperature classes. Cool (0.7–1.3 106 K) rays are a dominant feature of the polar corona during the quiescent phase of the solar cycle. The hot (1.8–2.6 106 K) rays when present form a small subset of the array of rays seen in white-light. Hot rays seem to emerge from the boundary of the polar coronal hole (polar crown filament belt). The location of the cool rays on the other hand can be on the boundary or inside the coronal hole. We do not always find a one to one correspondence between the polar rays observed in white-light versus those observed in XUV and visible emission lines. We find the emission line-ratio temperature to be high in the high latitude (> 45° N,S) coronal streamers with enhanced white-light emission. These streamers are located along a neutral line which separates the weak old cycle polar field from the weak new cycle high-latitude magnetic field of opposite polarity (Ap J (Letters), 471, 1, L69). This paper is an extended abstract for the Ap J Letters paper.