Geomagnetic Disturbance, Plasma Wind and Solar Activity

Sarabhai, V.; Pai, G. L.; Patel, D.; Pathak, P. N.

doi:10.5636/jgg.18.157

Cited by 4 publications

(2 citation statements)

References 1 publication

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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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“…For example, Pai and Sarabhai (1963) and Sarabhai et al (1966) have studied the correlations of 2 5303 intensity with cosmic-ray intensity and Kp and have concluded that regions of enhanced 2 5303 intensity are connected with high velocity solar wind. Brandt and Cassinelli (1966) have suggested that coronal condensations above faculae could be the possible regions connected with solar wind streams of high velocity.…”

Section: Introductionmentioning

confidence: 99%

Correlation of solar wind velocity with ? 5303 coronal intensity

Pathak

1971

Sol Phys

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Using solar wind velocity data obtained by Mariner-2 and IMP-1 spacecrafts, an attempt has been made to study its correlation with 25303 coronal intensity. It is shown that the long-lasting regions of enhanced 25303 intensity in the solar corona are well correlated with recurrent streams of solar wind having high velocity. The time-lag between the central meridian passage (CMP) of the coronal features and the detection of the solar wind streams at the spaceclaft is found to be smaller than that implied by a Iadial solar wind. Significant positive correlations for Mariner-2 data are obtained for coronal intensity at heliolatitudes 5 ~ S-10~ with a time-lag of -~ 2 days while for IMP-1 data, high positive correlations are obtained for the southern heliolatitudes (10~176 without any time-lag. It should be noted that the average heliographic latitudes for Mariner-2 and IMP-1 were N 4~ and N 4~ respectively dining the periods covered by the present analysis. The implications of the results are discussed.

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

1975

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Cross-correlation functions have been computed between green-line intensity (Kislovodsk) and Vela solar wind velocity January-June 1967. They are calculated separately for east and west limb observations in 5 ~ latitude increments, and the solar wind velocites are correlated at their estimated emission times by correcting for the plasma Earth-Sun transit time using the observed velocities. The cross-correlation patterns appear to be dominated by two competing effects: a tendency of quasi-stationary green-line emission and solar wind velocity to anti-correlate; and a tendency of transient green-line emission and solar wind velocity enhancements to correlate positively. We also find evidence for simultaneous (same-day) emission brightenings over 2 to 4 limb quadrants. It is therefore recommended that, following a well-known practice in solar terrestrial studies, recurrent and transient events in both solar wind and green-line emissions should be studied separately.

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Geomagnetic Disturbance, Plasma Wind and Solar Activity

Abstract: The authors demonstrate by analysing data for 1960, 1961 and 1962

Cited by 4 publications

References 1 publication

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

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

Correlation of solar wind velocity with ? 5303 coronal intensity

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

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