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Large-Scale Periodic Solar Velocities LARGE-SCALE PERIODIC SOLAR VELOCITIES: AN OBSERVATIONAL STUDY (NASA-CR-153256) LARGE-SCALE PERIODIC SOLAR N77-26056 ElOCITIeS: AN OBSERVATIONAL STUDY Stanford Univ.) 211 p HC,A10/F A01 CSCL 03B Unclas G3/92 35416 by Phil Howard Dittmer Office of Naval Research Contract N00014-76-C-0207 National Aeronautics and Space Administration Grant NGR 05-020-559 National Science Foundation Grant ATM74-19007 Grant DES75-15664 and The Max C.Fleischmann Foundation SUIPR Report No. 686 T'A kj, JUN 1977 > March 1977 RECEIVED NASA STI FACILITY This document has been approved for public INPUT B N release and sale; its distribution isunlimited. 4 ,. INSTITUTE FOR PLASMA RESEARCH STANFORD UNIVERSITY, STANFORD, CALIFORNIA UNCLASSIFIED SECURITY CLASSIFICATION OF THIS PAGE (When Data Entered) DREAD INSTRUCTIONS REPORT DOCUMENTATION PAGE BEFORE COMPLETING FORM I- REPORT NUMBER 2 GOVT ACCESSION NO. 3. RECIPIENT'S CATALOG NUMBER SUIPR Report No. 686 4. TITLE (and Subtitle) 5 TYPE OF REPORT & PERIOD COVERED Large-Scale Periodic Solar Velocities: Scientific, Technical An Observational Study 6. PERFORMING ORG. REPORT NUMBER 7. AUTHOR(s) 8 CONTRACT OR GRANT NUMBER(s) Phil Howard Dittmer N00014-76-C-0207 S PERFORMING ORGANIZATION NAME AND ADDRESS 10. PROGRAM ELEMENT, PROJECT, TASK Institute for Plasma Research AREA & WORK UNIT NUMBERS Stanford University Stanford, California 94305 12. REPORT DATE . 13. NO. OF PAGES 11. CONTROLLING OFFICE NAME AND ADDRESS March 1977 211 Office of Naval Research Electronics Program Office 15. SECURITY CLASS. (of-this report) Arlington, Virginia 22217 Unclassified 14. MONITORING AGENCY NAME & ADDRESS (if diff. from Controlling Office) 15a. DECLASSIFICATION/DOWNGRADING SCHEDULE 16. DISTRIBUTION STATEMENT (of this report) This document has been approved for public release and sale; its distribution is unlimited. 17. DISTRIBUTION STATEMENT (of the abstract entered in Block 20, if different from report) 18. SUPPLEMENTARY NOTES TECH: OTHER 19 KEY WORDS (Continue on reverse side if necessary and identify by block number) solar pulsations five-minute oscillations large-scale solar velocities 20. ABSTRACT (Continue on reverse side if necessary and identify by block number) Observations of large-scale solar velocities have been made using the mean field telescope and Babcock magnetograph of the Stanford Solar Observatory. Observations were made in the magnetically insensitive iron line at 5124 A, with light from the center (limb) of the disk right (left) circularly polarized, so that the.magnetograph measures the difference in wavelength between center and limb. Computer calculations are made of the wavelength difference produced by global pulsations for spherical harmonics up to second order, Computations are also made of the signal produced by displacing the solar image relative DD 1 731473 UNCLASSIFIED EDITION OF 1 NOV 65 IS OBSOLETE SECURITY CLASSIFICATION OF THIS PAGE (When Data Entered) UNCLASSIFIED SECURITY CLASSIFICATION OF THIS PAGE (When Data Entered) 19. KEY 'WORDS (Continued) 20 ABSTRACT (Continued) to polarizing optics or diffraction grating. Such displacements are the probable source of slow drifts in the observed signal. Individual observations clearly show the five-minute oscillations. From power spectra, the amplitude is '2.0meters/second, and the period is 312.9 ± ,0.9 seconds. The amplitude gives evidence for a horizontal wavelength greater than 20000 kilometers, and the period is larger than reported for smaller apertures. Six months of almost daily observations have been examined for changes in. oscillatory power'or period that might be'associated with large-scale coronalahd solar-wind strdctures as identified by solar sector boundaries, thb amplitude of the mean magnetic field, or the C9 index- No'evidence for large-scale organization of the oscillations -hasbeen found. -The average power spectrum has no statistically significant features at periods between seven and seventy minutes. Independent calculations support Hill's claim that the presence of a large portion of the downward propagating solution would give his technique added sensitivity at these periods. However, this explanation is unlikely to explain differences between Hill's observations and those presently reported beacuse (1) radiative damping greatly 'reduces the downward propagating solution, (2) the observed increase in five-minute amplitude with height is too small, and (3) the observed ratio of fivez to ten­ minute power is too large. Questions are also raised concerning the statistical significance of the peaks in the power spectra of Hill -andBrown. Using analysis similar to that used in the Crimea, no 160 minute oscillation is observed. Calculations show that the absence of signal cannot be explained by vignetting, different polarization dimensions, incorrect choice of period, or subtraction of a parabolic fit. As a result of a data exchange with the Crimea, it was found that (1) twelve-hou period drifts in the -Stanford data can produce a signal at 160 minutes, (2) integer fractions of a day other than 160 minutes are favored in the Crimea data, and (3)-editing can produce a 160 minute signal in the Stanford data, though it is of small amplitude and present only in the final one-third of the data. DDI FORM jft7'_(BACK) JAN 0314, UNCLASSIFIED. EDITION OF 1 -NOV 65 'IS OBSOLETE SECURITY CLASSIFICATION OF THIS PAGE (When Data Entered) LARGE-SCALE PERIODIC SOLAR VELOCITIES: AN OBSERVATIONAL STUDY by Phil Howard Dittmer Office of Naval Research Contract N00014-76-C-0207 National Aeronautics and Space Administration Grant NGR 05-020-559 National Science Foundation Grant ATM74-19007 Grant DES75-15664 and The Max C. Fleischmann Foundation SUIPR Report No. 686 March 1977 Institute for Plasma Research Stanford University Stanford, California Ph.D. Dissertation March 1977 ACKNOWLEDGMENTS The author would first like to thank those most responsible for the length and breadth of this study. His adviser, John M. Wilcox, first directed his interest to the area of periodic solar velocities. He made available financial support and the use.of telescope and computer facilities which enabled this study to be undertaken. His careful and thorough approach to research has extended the time and effort required to obtain the results obtained herein, but with greater confidence therefore justified in these results. This study could not have been conducted without the velocity subtraction technique developed by Valeri A. Kotov. He and A. B. Severny are also thanked for exchanging data and for causing this investigation to be extended to the two-hour forty-minute range. The work of Henry A. Hill and collaborators has led to a much more thorough investigation of oscillations at periods from five to seventy minutes than would otherwise have been undertaken. Financial support for this investigation has been provided by the Office of Naval Research through Contract N00014-76-C-0207, by the National Aeronautics and Space Administration through Grant NGR 05-020-559, by the National Science Foundation through Grant ATM74-19007 and Grant DES75-15664, and by the Max C. Fleishman Foundation. Appreciation should next be expressed to those who aided in the accomplishment of this study. The assistance of Philip H. Scherrer has been conspicuous at all stages of this investigation, from putting the iii telescope into operation and keeping it operating to data analysis and interpretation. He read the entire manuscript and gave many helpful suggestions, especially on the second chapter. John M. Wilcox, A. B. C. Walker, Jr., and Peter A. Sturrock are also thanked as readers of the dissertation. Eric K. Gustafson, assisted by Steven D. Bryan, performed most of the actual observations. Thomas L. Duvail, Jr. helped improve operation of the telescope, and he, Eric Fossat, Robert Howard, and Leif Svalgaard provided helpful discussions. George A. Kotler'help6d prepare optics and Gerard H. Dewerk helped machine mounts for the polarizing aperture. Marguerite F. Dearborn did an excellent job of typing the final manuscript. Last, but not least, the author wishes to thank those "whose contributions were more personal than scientific. 'He thanks his wife and sweetheart, Janet, for her constant love, her insistent encourage­ ment, and her efforts yhtch succeeded in making the author's residence a home. She also did an excellent job of proof-reading the second and final ,drafts of the manuscript. The author thanks his parents for love and support,, for planting the seed of this project in his initials, and for encouraging attitudes toward education and work which enabled the 'seed to bear fruit. He also 'thanks his boys, Andrew and Peter, for being ever loyal but totally unimpressed with this accomplishment. iv TABLE OF CONTENTS Page ACKNOWLEDGMENTS iii ABSTRACT vii Chapter I. INTRODUCTION AND HISTORICAL BACKGROUND 1 Five-Minute Oscillations 5 Observational techniques 5 Observed characteristics 9 Theories 20 Longer-Period Oscillations 30 Theory 31 Observations 39 II. THE INSTRUMENT 49 Velocity Measurements Using the Servo Encoder 64 Velocity Measurements Using the Kotov Subtractive Technique 69 III. OBSERVATIONS AND ANALYSIS 93 General Procedures 93 Five-Minute Oscillations 100 Average characteristics 101 The search for large-scale organization Ill Periods from Five to Seventy Minutes 119 Calculations of the sensitivity of the FFTD 126 Difficulties in reconciling results with those of Hill 144 Statistical significance of the SCLERA peaks 151 The Two-Hour Forty-Minute Oscillation 156 Instrumental
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