Transient phenomena in cosmic ray intensity during extreme events |
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Authors: | Rekha Agarwal Rajesh K Mishra |
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Institution: | (1) Department of Physics, Govt. Model Science College (Autonomous), Jabalpur, India;(2) Computer and Information Technology Section, Tropical Forest Research Institute, Jabalpur, India |
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Abstract: | In the present work an analysis has been made of the extreme events occurring during July 2005. Specifically, a rather intense
Forbush decrease was observed at different neutron monitors all over the world during 16 July 2005. An effort has been made
to study the effect of this unusual event on cosmic ray intensity as well as various solar and interplanetary plasma parameters.
It is noteworthy that during 11 to 18 July 2005 the solar activity ranged from low to very active. Especially low levels occurred
on 11, 15, and 17 July whereas high levels took place on 14 and 16 July 2005. The Sun is observed to be active during 11 to
18 July 2005, the interplanetary magnetic field intensity lies within 15 nT, and solar wind velocity was limited to ∼500 kms-1.
The geomagnetic activity during this period remains very quiet, the Kp index did not exceed 5, the disturbance storm time
Dst index remains ∼-70 nT and no sudden storm commencement has been detected during this period. It is noted that for the
majority of the hours, the north/south component of the interplanetary magnetic field, Bz, remains negative, and the cosmic
ray intensity increases and shows good/high correlation with Bz, as the polarity of Bz tends to shift from negative to positive
values, the intensity decreases and shows good/high anti-correlation with Bz. The cosmic ray intensity tends to decrease with
increase of interplanetary magnetic field strength (B) and shows anti-correlation for the majority of the days.
Published in Astrofizika, Vol. 51, No. 2, pp. 255–265 (May 2008). |
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Keywords: | cosmic rays interplanetary magnetic cloud |
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