Correlation of solar wind velocity with ? 5303 coronal intensity

Pathak, P. N.

doi:10.1007/bf00159779

Cited by 15 publications

(1 citation statement)

References 20 publications

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“…M regions are the quasi-permanent regions on the sun, devoid of any visible features, to which the 27-day recurrent phenomenon in geomagnetic disturbances has been attributed [Bartels, 1932]. The earlier study of a possible association between the recurrent disturbances and the various characteristic features of active regions in the photosphere, the chromosphere, and the corona led to the controversy as to whether M regions are located in active regions [Mustel, 1964;Sarabhai et al, 1966;Couturier and Leblanc, 1970;Pathak, 1971 ] or tend to avoid them [Saemundsson, 1962;Allen, 1964;Obayashi, 1964;Basler, 1966]. From satellite observations it is now becoming evident that M regions indeed tend to avoid active regions.…”

Section: Introductionmentioning

confidence: 99%

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

Shah¹,

Kaul²,

Razdan³

et al. 1978

J. Geophys. Res.

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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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Section: Introductionmentioning

confidence: 99%

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

Shah¹,

Kaul²,

Razdan³

et al. 1978

J. Geophys. Res.

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Asymmetric variations of the coronal green line intensity

1988

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The analysis of the daily measurements of the coronal green line intensity, which have been extensively tested for homogeneity and freedom of trends observed at the Pic-du-Midi observatory during the period 1944-1974, has revealed some characteristic asymmetric variations. A north-south asymmetry of the green line intensity is the main feature of the period 1949-1971 while a south-north one is obvious within 1972-1974 and the minor statistical significance span 1944-1948. On the other hand a significant W-E asymmetry has been confirmed in the whole period 1944-1974. It is noteworthy that the period 1949-1971, where the N-S asymmetry takes place consists a 22-yr solar cycle which starts from the epoch of the solar magnetic field inversion of the solar cycle No. 18 and terminates in the relevant epoch of the cycle No. 20.The combination of N-S and S-N asymmetry with a W-E one makes the NW solar-quarter to appear as the most active of all in the 22-yr cycle 1949-1971, while in the periods 1944-1948 and 1972-1974 the SW quarter is the most active. Finally, from the polar distribution of the green line intensity has been derived that the maximum values of the asymmetries occur in heliocentric sectors _+ 10~ ~ far from the solar equator on both sides of the central meridian.Physical mechanisms which could contribute to the creation of both N-S and E-W asymmetries of the solar activity and the green line intensity as an accompanied event, like different starting time of an 11-yr solar cycle in the two solar hemispheres, the motion of the Sun towards the Apex, and short-lived 'active' solar longitudes formed by temporal clustering of solar active centers, have been discussed.

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A coronal hole and its identification as the source of a high velocity solar wind stream

Krieger¹,

Timothy²,

1973

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X-ray images of the solar corona, taken on November 24, 1970, showed a magnetically open structure in the low corona which extended from N20W20 to the south pole. Analysis of the measured X-ray intensities shows the density scale heighl within the structure to be typically a factor of two less than that in the surrounding large scale magnetically closed regions. The structure is identified as a coronal hole.Since there have been several predictions that such a region should be the source of a high velocity stream in the solar wind, wind measurements for the appropriate period were traced back to the Sun by the method of instantaneous ideal spirals. A striking agreement was found between the Carrington longitude of the solar source of a recurrent high velocity solar wind stream and the position of the hole. Solar wind bulk velocity and photospheric magnetic field data from the period 1962-1970 indicate the possible extension of the result to the interpretation of long term variations in the wind pattern.

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Correlation of solar wind velocity with ? 5303 coronal intensity

Cited by 15 publications

References 20 publications

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

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

Asymmetric variations of the coronal green line intensity

A coronal hole and its identification as the source of a high velocity solar wind stream

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