Revealing structures and dynamic phenomena on ground-based coronagraph observations via a multi-resolution approach

FERNANDO MARCELO LÓPEZ; GUILLERMO STENBORG; FRANCILE, CARLOS; LAURA BALMACEDA

Montana

Workshop; Solar Information Processing Workshop VI; 2012

Despite the wealth of space-borne observations of the white light solar corona, ground-based instrumentation has not been yet fully superseded. In particular, the so-called Mirror Coronagraph for Argentina (MICA) has now observed the inner corona (1.05 to 2.0 solar radii) over a whole solar cycle through a narrow band filter centered at 530.3 nm. Its high temporal cadence (1 min in average), relative high spatial resolution (~3.6 arc sec/pixel), proximity of its field-of-view to the solar limb free of vignetting effects, and the use of an specific emission line make it an excellent complement to existent space instrumentation. However, the high variability of the observing conditions at its location (San Juan, Argentina [69.3 W, 31.8 S], at 2400 m altitude) due mainly to atmospheric turbulence, sky brightness variability, and winds, proved to be a major obstacle to allow the full survey and proper analysis of the whole dataset. Only a handful of events have been analyzed to date. We intend to prove that, albeit the inherent constraints that are of common knowledge when observing the emission line corona from ground, we can still take advantage of the instrument to shed light into the kinematical properties of limb events (as observed in white light) during their early stages. In particular, we make use of a technique based on the a-trous wavelet transform to minimize the effects of the fluctuating atmospheric conditions and instrumental jittering while increasing the relative contrast of the dynamic features of interest. The algorithm can be applied straightforwardly on a broad spectrum of similar ground-based instruments. In this work, we introduce the algorithm and present a set of case studies from MICA’s database, which provide different scenarios and hence, allow us to test the helpfulness of the technique. We expect this work to contribute to both scientific and educational aspects since it will open new opportunities for Astronomy undergrad students at the University of San Juan, Argentina, to carry out research projects in Solar Physics.