Precise Proper-Motion Measurement of Solar Granulation

We describe a powerful cross-correlation technique for the precise measurement of the proper motion of tracers seen on successive images of a time series of solar granulation. The cross correlation is defined as a function of position in the image, within a spatially localized apodization window. Th...

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Bibliographic Details
Main Authors: November, Laurence J, Simon, George W
Format: Report
Language:English
Subjects:
Astrophysics
ATMOSPHERIC MOTION
CROSS CORRELATION
DETERMINATION
DISPLACEMENT
DISTORTION
GEOMETRY
GRANULES
IMAGE PROCESSING
MEASUREMENT
PE61102F
PEAK VALUES
PRECISION
PROPER MOTION MEASUREMENT
REPRINTS
SCALE
SIZES(DIMENSIONS)
SOLAR ATMOSPHERE
SOLAR GRANULATION
SOLAR OBSERVATORIES
SPATIAL DISTRIBUTION
TELESCOPES
TIME SERIES ANALYSIS
TOWERS
VACUUM
VECTOR ANALYSIS
WHITE LIGHT
WINDOWS
WUAFGL2311G326
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Summary:We describe a powerful cross-correlation technique for the precise measurement of the proper motion of tracers seen on successive images of a time series of solar granulation. The cross correlation is defined as a function of position in the image, within a spatially localized apodization window. The time average of the spatially localized cross correlation gives a measure of the displacement that is not biased by atmospheric seeing. The window size and the seeing define the effective resolution of the vector displacement determination. We use this cross-correlation technique to analyze an 80 minute run of white- light observations made at the Sacramento Peak Vacuum Tower Telescope. Even though geometric distortion due to atmospheric seeing is instantaneously at least 10-20 times larger than the observed scale of the large-scale solar displacements, 100-1000 m/s , its net contribution to the 80 minute average of proper motions is RMS 20 m/s. The measured vector displacement clearly show solar mesogranulation and super-granulation flows having spatial scales from 10 min to 40 min. The measured amplitude of these flows is significantly larger than the RMS 100 m/s noise which we attribute principally to solar granulation evolution. Keywords: Solar atmospheric motion. Reprints. Pub. in the Astrophysical Jnl., v333 n1 part 1 p427-442, 1 Oct 1988.