The long-term modulation of cosmic ray intensity (CRI) by different solar activity (SA) parameter... more The long-term modulation of cosmic ray intensity (CRI) by different solar activity (SA) parameters and an inverse correlation between individual SA parameter and CRI is well known. Earlier, it has been suggested that the concept of multi-parametric modulation of CRI may play an important role in the study of long-term modulation of CRI. In the present study, we have tried to investigate the combined effect of a set of two SA parameters in the long-term modulation of CRI. For this purpose, we have used a new statistical technique called "Running multiple correlation method", based on the "Running cross correlation method". The running multiple correlation functions among different sets of two SA parameters (e.g., sunspot numbers and solar flux, sunspot numbers and coronal index, sunspot numbers and grouped solar flares, etc.) and CRI have been correlated separately. It is found that the strength of multiple correlation (among two SA parameters and CRI) and cross correlation (between individual SA parameter and CRI) is almost similar throughout the period of investigation . It is also found that the multiple correlations among various SA parameters and CRI is stronger during ascending and descending phases of the solar cycles and it becomes weaker during maxima and minima of the solar cycles, which is in accordance with the linear relationship between SA parameters and CRI. The values of multiple correlation functions among different sets of SA parameters and CRI fall well within the 95% confidence interval. In the view of odd-even hypothesis of solar cycles, the strange behaviour of present cycle 23 (odd cycle), as this is characterized by many peculiarities with double peaks and many quiet periods (Gnevyshev gaps) interrupted the solar activity (for example April 2001, October-November 2003 and January 2005), leads us to speculate that the solar cycle 24 (even cycle) might be of exceptional nature.
Abstract: A minimum between solar cycle 22 and 23 has been defined earlier on the basis of type-I... more Abstract: A minimum between solar cycle 22 and 23 has been defined earlier on the basis of type-I radio burst only. In the present paper a re-visit to the occurrence of type-I radio bursts in relation to general level of solar activity (sunspot number) is made covering the minima ...
We have performed a correlative analysis to study the relationship of sunspot numbers (SSN) and t... more We have performed a correlative analysis to study the relationship of sunspot numbers (SSN) and tilt angle with cosmic ray intensity (CRI) observed by the neutron monitor stations having different cut-off rigidity for the period 1976 to 2005 covering solar cycles 21, 22 and 23. It is found that tilt angle and sunspot numbers are positively correlated with each other and have inverse correlation with cosmic ray intensity. The time-lag analysis has been performed by the method of 'minimizing correlation coefficient' and it is found that time-lag is larger for odd solar cycles and smaller for even solar cycles. We have also calculated 'running cross correlation coefficient' between cosmic ray intensity and tilt angle and observed that the correlation is positive during the maxima of odd cycles 21 and 23. The 22-year variational pattern is clearly apparent in the different types of analysis based on tilt angle observations; it has been noticed that the behaviour of cycle 23 in declining phase is different than of cycle 21 and 22.
A detailed correlative analysis between sunspot numbers (SSN) and tilt angle (TA) with cosmic ray... more A detailed correlative analysis between sunspot numbers (SSN) and tilt angle (TA) with cosmic ray intensity (CRI) in the neutron monitor energy range has been performed for the solar cycles 21, 22 and 23. It is found that solar activity parameters (SSN and TA) are highly (positive) correlated with each other and have inverse correlation with cosmic ray intensity (CRI). The 'running cross correlation coefficient' between cosmic ray intensity and tilt angle has also been calculated and it is found that the correlation is positive during the maxima of odd cycles 21 and 23. Moreover, the time lag analysis between CRI and SSN, and between CRI and TA has also been performed and is supported by hysteresis curves, which are wide for odd cycles and narrow for even cycles.
From the monthly data of cosmic ray intensity (CRI), sunspot numbers (SSN) and solar flare index ... more From the monthly data of cosmic ray intensity (CRI), sunspot numbers (SSN) and solar flare index (SFI), an attempt has been made to study the relationship between CRI and solar activity (SA) parameters SSN and SFI. The correlation between SA parameters and CRI for different neutron monitoring stations having low, middle and high cutoff rigidity has been investigated. The anti-correlation between SA and CRI is found to exist with some time lag. Based on the method of minimizing correlation coefficient and time-delayed component method, the observed time-lag between SA parameters (SSN and SFI) and CRI has been found to be large for odd solar cycles in comparison to even solar cycles. The results of time-lag analysis between CRI and SSN and between CRI-SFI have also been compared. The findings of correlative study between CRI and SSN are in agreement with earlier results, while the CRI-SFI relationship provides new insights to understand the solar modulation of cosmic rays.
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Papers by V.K Mishra