Fine Structure of the Magnetic Chromosphere: Near-Limb Imaging, Data Processing and Analysis of Spicules and Mottles

Abstract

The origin and the dynamical evolution of spicules and mottles continue to be a highly interesting research subject. Using high-resolution Hα observations obtained with the Dunn Solar Telescope of the Sacramento Peak Observatory and an image processing technique for the enhancement of near-limb solar images, we study the dynamics of spicules and mottles as well as their relation. Our image-processing technique is based on the correction for the limb darkening and the use of a directionally sensitive operator, the `MadMax'. The temporal evolution of characteristic cases of spicules, dark and bright mottles, indicates an association between them and supports the suggestion that the magnetic field and probably related forces play a fundamental role in their generation and dynamics. We present characteristic cases of fine bright mottles, observable in the Hα far wings, that appear in close juxtaposition to dark mottles. The phenomenon appears to be common, suggesting that the velocities derived from marginal resolution spectroscopic observations could be underestimated. Typical examples of individual mottles crossing the solar limb further support the association between spicules and mottles. Finally we show images of arch-shaped mottles above the limb and especially on the disk, confirming the existence of chromospheric small loops. Our image-processing method substantially enhances near-limb observations and permits an insight into the studies of the very fine chromospheric structures.