Abstract
Extreme-ultraviolet Skylab and ground-based solar magnetic field data have been combined to study the origin and evolution of coronal holes. It is shown that holes exist only within the large-scale unipolar magnetic cells into which the solar surface is divided at any given time. A well-defined boundary zone usually exists between the edge of a hole and the neutral line which marks the edge of its magnetic cell. This boundary zone is the region across which a cell is connected by magnetic arcades with adjacent cells of opposite polarity. Three pieces of observational evidence are offered to support the hypothesis that the magnetic lines of force from a hole are open. Kitt Peak magnetograms are used to show that, at least on a relative scale, the average field strengths within holes are quite variable, but indistinguishable from the field strengths in other quiet parts of the Sun's surface.
Finally it is shown that the large, equatorial holes characteristic of the declining phase of the last solar cycle during Skylab (1973–74) were all formed as a result of the mergence of bipolar magnetic regions (BMR's), confirming an earlier hypothesis by Timothy et al. (1975). Systematic application of this model to the different aspects of the solar cycle correctly predicts the occurrence of both large, equatorial coronal holes (the ‘M-regions’ which cause recurrent geomagnetic storms) and the polar cap holes.
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References
Allen, C. W.: 1963, Astrophysical Quantities, The Athlon Press, London, p. 182.
Altschuler, M. D., Trotter, D. E., and Orrall, F. Q.: 1972, Solar Phys. 26, 354.
Babcock, H. W. and Babcock, H. D.: 1955, Astrophys. J. 121, 349.
Billings, D. E.: 1966, A Guide to the Solar Corona, Academic Press, New York, p. 62.
Bohlin, J. D.: 1976, ‘The Physical Properties of Coronal Holes’, in D. J. Williams (ed.), Proc. of the International Symp. Solar-Terrestrial Physics, Boulder, Colo., June 1976.
Bohlin, J. D.: 1977, Solar Phys. 51, 377.
Bohlin, J. D. and Rubenstein, D. M.: 1975, Report UAG-51, ‘Synoptic Maps of Solar Coronal Hole Boundaries... from the Manned Skylab Missions’, World Data Center A for Solar-Terrestrial Physics, NOAA, Boulder, Colo. (referred to as the NRL Atlas).
Bohlin, J. D., Rubenstein, D. M., and Sheeley, N. R., Jr.: 1975, Bull. Am. Astron. Soc. 7, 457.
Brueckner, G. E. and Bartoe, J.-D. F.: 1974, Solar Phys. 38, 133.
Bumba, V. and Howard, R.: 1965, Astrophys. J. 141, 1502.
Gurman, J. B., Withbroe, G. L., and Harvey, J. W.: 1974, Solar Phys. 34, 105.
Leighton, R. B.: 1964, Astrophys. J. 140, 1547.
Levine, R. H.: 1977, Astrophys. J., 218, 291.
Levine, R. H., Altschuler, M. D., Harvey, J. W., and Jackson, B. V.: 1976, Astrophys. J., 215, 636.
McIntosh, P. S.: 1975, ‘Hα Synoptic Charts of Solar Activity for the Period of Skylab Observations’, World Data Center A for Solar Terrestrial Physics, Report UAG-40, NOAA, Boulder, Colo.
McIntosh, P. S., Krieger, A. S., Nolte, J. T., and Vaiana, G.: 1975, Bull. Am. Astron. Soc. 7, 444.
McIntosh, P. S., Krieger, A. S., Nolte, J. T., and Vaiana, G.: 1976, Solar Phys. 49, 57.
Neupert, W. M. and Pizzo, V.: 1974, J. Geophys. Res. 79, 3701.
Newkirk, G., Jr. and Harvey, J. W.: 1968, Solar Phys. 3, 321.
Nolte, J. T., Krieger, A. S., Timothy, A. F., Gold, R. E., Rolof, E. C., Vaiana, G., Lazarus, A. J., Sullivan, J. D., and McIntosh, P. S.: 1976a, Solar Phys. 46, 303.
Nolte, J. T., Krieger, A. S., Timothy, A. F., Vaiana, G. S., and Zombeck, M. V.: 1976b, Solar Phys. 46, 291.
Saito, K. and Tandberg-Hanssen, E.: 1973, Solar Phys. 31, 105.
Sheeley, N. R., Jr.: 1966, Astrophys. J. 144, 723.
Sheeley, N. R., Jr. and Harvey, J. W., 1977, Trans. Am. Geophys. Union EOS. 58, 768.
Sheeley, N. R., Jr., Harvey, J. W., and Feldman, W. C.: 1976, Solar Phys. 49, 271.
Sheeley, N. R., Jr., Bohlin, J. D., Brueckner, G. E., Purcell, J. D., Scherrer, V. E., and Tousey, R.: 1975, Solar Phys. 40, 103.
Smith, S. M. and Schatten, K. H.: 1970, Nature 226, 1130.
Smith, S. M. and Weinstein, L. M.: 1970; reference communication by S. M. Smith, No. N230-1, and illuslralions A70-1610-5-1, -3, -4, and -5; Ames Research Cenler, Moffel Field, Calif.
Timothy, A. F., Krieger, A. S., and Vaiana, G. S.: 1975, Solar Phys. 42, 135–156.
Withbroe, G. L., Dupree, A. K., Goldberg, L., Huber, M. C. E., Noyes, R. W., Parkinson, W. H., and Reeves, E. M.: 1971, Solar Phys. 21, 272.
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Bohlin, J.D., Sheeley, N.R. Extreme ultraviolet observations of coronal holes. Sol Phys 56, 125–151 (1978). https://doi.org/10.1007/BF00152639
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DOI: https://doi.org/10.1007/BF00152639