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Session 13 - Image Processing, Chromosphere.
Oral session, Monday, June 30
Ballroom A, Chair: Thomas Metcalf
In this paper we present a new fast spectral scan method to study Halpha jets, which are more energetic than regular spicules. The observations achieved high two-dimensional spatial resolution, temporal resolution and spectral resolution simultaneously. We used the Coude spectrograph in the Big Bear Solar Observatory for the Halpha data acquisition. The procedure starts with fast spectral scans across the solar surface (600" by 300") at the vicinity of the solar disk center. The guiding system is turned off allowing the Sun to drift smoothly relative to the spectrograph system. A total number of 600 spectral images at 6563A are recorded per scan on an optical disk recorder at a rate of 30 frames/sec. Tracking re-position the system to point to the same initial coordinates on the Sun for new scans. The process repeats every 30 seconds until 60 scans are completed. The stored images are digitized for off-line data analysis. A number of different image processing techniques are used to improve the image quality. These include off-line correlation tracking and running average among various constructed images. From the four-dimensional (x,y,t,wavelength) Halpha data arrays, we can reconstruct spectroheliograms (600 by 240 pixels) at different wavelengths. We calculate velocities of jets by measuring Doppler shifts of the Halpha absorption line, where we used an optically thin jet model. Velocities of 30 to 50 km/sec for jets are derived. Velocity maps are constructed thereafter for the scanned region, and are compiled as movies. We measure the lifetime and size of the jets from these movies. Lifetimes of a few minutes are observed. Further approximations are made to find out temperature and density of jets by fitting the Halpha absorption line profile. The results will enable us to estimate the total mechanical energy released by the jets.
Program listing for Monday