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

Abstract

Some 8000 images obtained with the Solar Eclipse Coronal Imaging System (SECIS) fast-frame CCD camera instrument located at Lusaka, Zambia, during the total eclipse of 21 June 2001 have been analysed 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 Å) 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 those that we obtained during the 11 August 1999 total eclipse (Rudawy et al.: Astron. Astrophys. 416, 1179, 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 analyse the emission at 29 518 locations, of which 10 714 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-

Detection of High-Frequency Oscillations and Damping from Multi-slit Spectroscopic Observations of the Corona

“…The power and period distribution of intensity, Doppler velocity and width variations (Figure 9, 10 and 11) reveal that they have a slight tendency to occur preferentially close to the boundaries of the structures where intensity gradients are relatively high. This result confirms earlier observations O'Shea and Doyle, 2009;Rudawy et al, 2010), although they were limited to intensity only. O'Shea and Doyle (2009) reported a variation of wave mode with frequency and location.…”

“…Hence we are not able to conclude further on the statistics. We have also noticed that the oscillations at periods less than 12 s are barely present in A and B but more frequent in the extended structure C. It has been pointed out O'Shea and Doyle, 2009;Rudawy et al, 2010) that the intensity oscillations are significantly prevalent at the edges of bright coronal loops.…”

“…Using the Solar Eclipse Coronal Imaging System (SECIS) instrument (Phillips et al, 2000) during the total solar eclipse in 1999, Williams et al (2001Williams et al ( , 2002 and Katsiyannis et al (2003) reported the presence of propagating fast magnetoacoustic modes in coronal loops dominated by 6 s intensity oscillation. From the same instrument, Rudawy et al (2010) found periodic fluctuations with periods in the range 0.1 to 17 s. Observational detection of these short period waves using SECIS instrument complements the theoretical work by Cooper, Nakariakov, and Williams (2003). In the numerical work, Porter, Klimchuk, and Sturrock (1994b,a) explored the processes of coronal heating by damping of the slow and fast mode "high-frequency MHD waves".…”

High time resolution observations of solar Hαflares

“…The CCD cameras form part of the Solar Eclipse Coronal Imaging System (SECIS: Phillips et al 2000;Rudawy et al 2004Rudawy et al , 2010, used during solar eclipses. Our objective was to compare Hα flare observations with those of the X-ray emission made with RHESSI.…”

“…The other Table 1. CCD camera is used to record the precise time from the DCF77 long-wavelength transmitter (the signal of which is generated by a caesium clock). The two SECIS cameras have 512 × 512 pixel 2 CCD image sensors (the photometric characteristics of the cameras were discussed by Rudawy et al 2010) with an image scale ∼1 arcsec per pixel. Up to 10 000 images can be taken and stored using a specially adapted computer with proprietary software.…”