On the correlation of coronal green-line intensity and solar wind velocity

Recurrent Forbush decreases and recurrent geomagnetic disturbances have been attributed to the solar M regions, which are sources of high‐velocity solar plasma streams. A study of recurrent Forbush decreases for the period 1966‐1975 has been made to examine any possible relationship of M regions with solar active regions. It is shown that at the onset of the recurrent Forbush decrease at the earth there is a high probability of encountering a class of active regions at the central meridian of the sun which give rise to flares of importance ≥2B/3N. These active regions are found to be long lasting and to have large areas as well as high Hα intensities. Other active regions, producing flares of lower importance, are distributed randomly on the sun with respect to the onset of a recurrent Forbush decrease. By using the quasi‐radial hypervelocity approximation the base of the leading edge of the high‐velocity stream at the onset of a recurrent Forbush decrease at the earth is traced to the solar longitude about 40° west of the central meridian. From these results it is deduced that M regions are located preferentially to the west of long‐lasting magnetically complex active regions. Earlier studies of the identification of the M regions on the sun have been reexamined and shown to conform to this positional relationship. A possible mechanism of the development of an M region to the west of the long‐lasting magnetically complex active region is also discussed.

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Coronal density and the solar wind speed at all latitudes

Sime¹,

Rickett²

1981

J. Geophys. Res.

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Data from essentially all heliographic latitudes (50øS to 60øN) are used to demonstrate directly the anticorrelation between the solar wind speed and the coronal density to which it maps. The data, coronameter observations of density and interplanetary scintillation measurements of wind speed, are well suited for comparison, since they have similar selection effects, both responding most accurately to large-scale structures. Their relationship is demonstrated on time scales from 2 days to 1 year for the years 1972-1975, during which the structures were corotating or slowling evolving. This study makes a quantitative point-by-point comparison of coronal density and solar wind velocity, in contrast to earlier comparisons where holes were parameterized by their area and streams by their maximum speed. Trans. AGU, 54, 1190, 1973. Broussard, R. J., N. R. Sheeley, Jr., R. Tousey, and J. H. Underwood, A survey of coronal holes and their solar wind associations throughout sunspot cycle 20, Solar Phys., 56, 161, 1978. Coles, W. A., and J. J. Kaufman, Solar wind velocities estimation from multi-station IPS, Radio Sci., 13, 591, 1978. Coles, W. A., and S. Maagoe, Solar wind velocity from IPS observations, J. Geophys. Res., 77, 5622, 1972. Coles, W. A., and B. J. Rickett, IPS observations of the solar wind speed out of the ecliptic, J. Geophys. Res., 81, 4797, 1976. IPS, ESS

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On the correlation of coronal green-line intensity and solar wind velocity

Cited by 5 publications

References 37 publications

Solar-Terrestrial Relations and Magnetospheric Substorms

Solar-Terrestrial Relations and Magnetospheric Substorms

Recurrent Forbush decreases and the relationship between active regions and M regions

Coronal density and the solar wind speed at all latitudes

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