Precise Proper-Motion Measurement of Solar Granulation
Abstract
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.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 01, 1988
- Accession Number
- ADA205161
Entities
People
- George W. Simon
- Laurence J. November
Organizations
- Air Force Research Laboratory