Search for Rapid Changes in the Visible-Light Corona during the 21 June 2001 Total Solar Eclipse

TL;DR

This study analyzed high-quality solar corona images during the 2001 total eclipse to search for rapid intensity oscillations, finding no significant periodic fluctuations that could support MHD wave-based coronal heating theories.

Contribution

It provides the first detailed wavelet analysis of high-cadence eclipse images, setting constraints on coronal oscillations related to heating mechanisms.

Findings

No significant periodic intensity fluctuations found in the 0.1-17 second range.

Results suggest MHD wave dissipation may not produce observable intensity oscillations.

Enhanced image stability improved detection capabilities compared to previous eclipse observations.

Abstract

Some 8000 images obtained with the SECIS fast-frame CCD camera instrument located at Lusaka, Zambia, during the total eclipse of 21 June 2001 have been analyzed to search for short-period oscillations in intensity that could be a signature of solar coronal heating mechanisms by MHD wave dissipation. Images were taken in white- light and Fe XIV green-line (5303 A) channels over 205 seconds (frame rate 39 s-1), approximately the length of eclipse totality at this location, with a pixel size of four arcseconds square. The data are of considerably better quality than were obtained during the 11 August 1999 total eclipse, observed by us (Rudawy et al.: Astron. Astrophys. 416, 1179, 2004), in that the images are much better exposed and enhancements in the drive system of the heliostat used gave a much improved image stability. Classical Fourier and wavelet techniques have been used to analyze the emission at 29518 locations, of which 10714 had emission at reasonably high levels, searching for periodic fluctuations with periods in the range 0.1-17 seconds (frequencies 0.06-10 Hz). While a number of possible periodicities were apparent in the wavelet analysis, none of the spatially and time-limited periodicities in the local brightness curves was found to be physically important. This implies that the pervasive Alfven wave-like phenomena (Tomczyk et al.: Science 317, 1192, 2007) using polarimetric observations with the CoMP instrument do not give rise to significant oscillatory intensity fluctuations.