• CHANDNI MATHPAL

      Articles written in Journal of Astrophysics and Astronomy

    • Association Between the Solar Wind Speed, Interplanetary Magnetic Field and the Cosmic Ray Intensity for Solar Cycles 23 and 24

      Meena Pokharia Lalan Prasad Chandni Mathpal Chandrasekhar Bhoj Hema Kharayat Rajesh Mathpal

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      The purpose of the present study is to investigate the association of the cosmic ray intensity (CRI) and interplanetary magnetic field (IMF) with high speed solar wind streams (HSSWS) and slow speed solar wind streams (SSSWS) for solar cycle −23 and 24. We have found very interesting and adequate results where CRI provides inverse relationship with the above mentioned streams. Since the correlation coefficient in case of HSSWS is found to be high as compared to SSSWS, it implies that HSSWS are more competent parameters to produce decrease in CRI as compared to SSSWS. Overall analysis of our study shows that CRI, IMF and product of wind speed and IMF (V.B) are poorly correlated with each other for both solar cycles. The year 2016 showed remarkable behavior as there was a drastic increase in the values of interplanetary magnetic field in comparison to the previous years which caused the change in pattern of solar wind streams.

    • A comparative study of geomagnetic storms for solar cycles 23 and 24

      MEENA POKHARIA LALAN PRASAD CHANDRASEKHAR BHOJ CHANDNI MATHPAL

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      The aim of this paper is to investigate the association of the geomagnetic storms with themagnitude of interplanetary magnetic field IMF ($B$), solar wind speed ($V$), product of IMF and wind speed ($V\cdot B$), Ap index and solar wind plasma density ($n_{\rm p}$) for solar cycles 23 and 24. A Chree analysis by the superposed epoch method has been done for the study. The results of the present analysis showed that $V\cdot B$ is more geoeffective when compared to V or B alone. Further the high and equal anti-correlation coefficient is found between Dst and Ap index ($−$0.7) for both the solar cycles. We have also discussed the relationship between solar wind plasma density (np) and Dst and found that both these parameters are weakly correlated with each other. Wehave found that the occurrence of geomagnetic storms happens on the same day when IMF, $V$, Ap and $V\cdot B$ reach their maximum value while 1 day time lag is noticed in case of solar wind plasma density with few exceptions. The study of geomagnetic storms with various solar-interplanetary parameters is useful for the study of space weather phenomenon.

    • Study of the cosmic ray intensity in relation to geomagnetic storms and solar interplanetary parameters for solar cycles 21 and 23

      CHANDRASEKHAR BHOJ LALAN PRASAD MEENA POKHARIA CHANDNI MATHPAL

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      This paper comprises the comparative study of the behavior of CRI with geomagnetic storms, southward component of IMF, i.e. $|Bz|$, IMF $B$, solar wind speed ($V$) and $V \cdot |Bz|$ for two consecutive odd solar cycles 21 (1976–1985) and 23 (1996–2008). Our examination arrived at an interesting result that the strongest decrement in CRI occurs around the same time when Dst achieve their minima. The correlation coefficient of Dst with CRI is observed high for both the solar cycles. We have moreover contrasted the profiles of CRI with$B$, $|Bz|$ and $V$ and came to the resolution that the strongest increment in $B$, $|Bz|$ and $V$ happens on the same day when CRI reaches its minimum peak. During the study of CRI with the solar wind speed, we have observedodd behavior for the year 1977 and 2003 with a time lag of one day. We have also found that CRI is highly anti-correlated with $V\cdot |Bz|$ when contrasted with $V$ or $|Bz|$ alone. The correlation coefficient between CRI and $V · |Bz|$ is found to be high and the same ($−$0.8) for the solar cycles.

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    • Continuous Article Publication

      Posted on January 27, 2016

      Since January 2016, the Journal of Astrophysics and Astronomy has moved to Continuous Article Publishing (CAP) mode. This means that each accepted article is being published immediately online with DOI and article citation ID with starting page number 1. Articles are also visible in Web of Science immediately. All these have helped shorten the publication time and have improved the visibility of the articles.

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      Posted on July 25, 2019

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