Harmonics of high-amplitude wave trains in cosmic ray intensity

Mishra, Rajesh K.; Mishra, Rekha Agarwal

doi:10.1016/j.pss.2005.02.001

Cited by 1 publication

(2 citation statements)

References 28 publications

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“…From these values we see that the DAs are different, but the average phases are consistent with the corotational direction of 18 hr LT (although in the T sector there was a larger spread). This is in contrast with the results reported by Mavromichalaki (1989) and Mishra & Mishra (2005) for GCR at lower energy.…”

Section: Carrington Rotation 2070 and 2071contrasting

confidence: 99%

“…They reported diurnal amplitudes observed by neutron monitors that were enhanced during the period of decline of the HSS, which might be associated with the recovery of the cosmic ray intensity. -1994, Mishra & Mishra (2005 have studied the highamplitude anisotropic wave train events and found that the phase of the diurnal variations for a majority of events shifted toward later hours, whereas it remained at the corotational hour for some events. Mavromichalaki (1989) investigated neutron monitor data of [1970][1971][1972][1973][1974][1975][1976][1977] and found that the phase shifted toward earlier hours, perhaps in association with variation of the size of the polar CHs, an effect in agreement with the drift motions of cosmic ray particles in the IMF.…”

Section: Introductionmentioning

confidence: 99%

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Corotating Solar Wind Structures and Recurrent Trains of Enhanced Diurnal Variation in Galactic Cosmic Rays

Yeeram

Ruffolo

Sáiz

et al. 2014

ApJ

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Data from the Princess Sirindhorn Neutron Monitor at Doi Inthanon, Thailand, with a vertical cutoff rigidity of 16.8 GV, were utilized to determine the diurnal anisotropy (DA) of Galactic cosmic rays (GCRs) near Earth during solar minimum conditions between 2007 November and 2010 November. We identified trains of enhanced DA over several days, which often recur after a solar rotation period (∼27 days). By investigating solar coronal holes as identified from synoptic maps and solar wind parameters, we found that the intensity and anisotropy of cosmic rays are associated with the high-speed streams (HSSs) in the solar wind, which are in turn related to the structure and evolution of coronal holes. An enhanced DA was observed after the onset of some, but not all, HSSs. During time periods of recurrent trains, the DA was often enhanced or suppressed according to the sign of the interplanetary magnetic field B, which suggests a contribution from a mechanism involving a southward gradient in the GCR density, n, and a gradient anisotropy along B × ∇n. In one non-recurrent and one recurrent sequence, an HSS from an equatorial coronal hole was merged with that from a trailing mid-latitude extension of a polar coronal hole, and the slanted HSS structure in space with suppressed GCR density can account for the southward GCR gradient. We conclude that the gradient anisotropy is a source of temporary changes in the GCR DA under solar minimum conditions, and that the latitudinal GCR gradient can sometimes be explained by the coronal hole morphology.

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Section: Carrington Rotation 2070 and 2071contrasting

confidence: 99%

Section: Introductionmentioning

confidence: 99%