Summary
The longitudinal proper motion of sunspot groups has been shown to be a function of their size and relative extension in longitude. Two theories are proposed to explain these effects, which theories assume that the wind circulation of the spots and the wind field surrounding the spots are intimately connected, and dynamically interact. The retardation in the motion of large spot groups is hypothesized to be due to the effect of the latitudinal variation of the Coriolis parameter (on a rotating spherical body) and an assumed vortical circulation around the spots. The more rapid longitudinal motion of extended spot groups is suggested to be the result of the preferential occurrence and development of such groups in regions of above-average horizontal wind and wind shear. If these theories are essentially correct, the real solar rotation rate—i.e., the longitude- and time-averaged fluid motion field—should be derived from the motions of small spot groups, and is 1% to 11/2% higher than the usually accepted rate whichNewton andNunn derived.
Similar content being viewed by others
References
M. G. Adam,A New Determination of the Centre to Limb Change in Solar Wave-Lengths, MNRAS119 (1959), 460.
R. J. Boucher andR. J. Newcomb,Synoptic Interpretation of Some TIROS Vortex Patterns: A Preliminary Cyclone Model, J. App. Meteorology1 (1962), 127.
R. E. De Lury,The Law of the Solar Rotation, JRASCXXXIII (1939), 345.
G. E. Hale,Solar Vortices, Astrophysical J.28 (1908), 100.
A. B. Hart,Motions in the Sun at the Photospheric Level. IV.The Equatorial Rotation and Possible Velocity Fields in the Photosphere, MNRAS114 (1954), 17.
A. B. Hart,Motions in the Sun at the Photospheric Level. VI.Large Scale Motions in the Equatorial Region, MNRAS116 (1956), 38.
L. F. Hubert andO. Berg,A Rocket Portrait of a Tropical Storm, Mon. Weather Rev.83 (1955), 119.
A. Kasahara,The Numerical Prediction of Hurricane Movement with the Baratropic Model, J. Meteor.14 (1957), 386.
K. O. Kiepenheuer,Solar Activity, The Sun, edited by G. P. Kuiper, University of Chicago Press (1953), 322.
N. J. Macdonald,Methods of Measuring Solar and Terrestrial Atmospheric Circulations, Tellus18 (1966), 13.
P. Maltey,On the Velocity Field in Sunspots, Astrophysica NorvegicaVIII (1964), 205.
F. R. Miller,An Application of TIROS Cloud Observations in Sparse Data Regions, Mon. Weather Rev.91 (1963), 433.
H. W. Newton andM. L. Nunn,The Sun's Rotation Derived from Sunspots and Additional Results, 1934 to 1944, MNRAS111 (1951), 413.
H. H. Plaskett,Motions in the Sun at the Photospheric Level. I.Methods, MNRAS112 (1952), 414.
H. H. Plaskett,Motions in the Sun at the Photospheric Level. V.Velocities of Granules and of Other Localized Regions, MNRAS114 (1954), 251.
H. H. Plaskett,Motions in the Sun at the Photospheric Level. VIII.Solar Rotation and Photospheric Circulation, MNRAS119 (1959), 197.
H. H. Plaskett,Limb Darkening and Solar Rotation, MNRAS123 (1962), 541.
V. P. Starr andP. A. Gilman,Energetics of the Solar Rotation, Astrophysical J.141 (1965), 1119.
F. Ward,General Circulation of the Solar Atmosphere from Observational Evidence, Pure and Appl. Geophys.58 (1964/II), 157.
F. Ward,The General Circulation of the Solar Atmosphere and the Maintenance of the Equatorial Acceleration, Astrophysical. J.141 (1965), 534.
F. Ward,The Determination of the Solar Rotation Rate from the Motion of Identifiable Features, Astrophysical J.145 (1966), in press.
H. Wexler,Structure of Hurricanes as Determined by Radar, Annals, NYASXLVIII (1947), 821.
W. K. Widger, Jr.,A Synthesis of Interpretations of Extratropical Vortex Patterns as Seen by TIROS, Mon. Weather Rev.92 (1964), 263.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Ward, F. The longitudinal proper motion of sunspots and the solar rotation rate. PAGEOPH 63, 196–204 (1966). https://doi.org/10.1007/BF00875169
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF00875169