LAUSR

This paper comprises the comparative study of the behavior of CRI with geomagnetic storms, southward component of IMF, i.e. $${\vert }{} { Bz}{\vert }$$|Bz|, IMF B, solar wind speed (V) and $$V\cdot {\vert }{} { Bz}{\vert }$$V·|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,$${\vert }{} { Bz}{\vert }$$|Bz| and V and came to the resolution that the strongest increment in B, $${\vert }{} { Bz}{\vert }$$|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 observed odd 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 $$V\cdot {\vert }{ Bz}{\vert }$$V·|Bz| when contrasted with V or $${\vert }{} { Bz}{\vert }$$|Bz| alone. The correlation coefficient between CRI and $$V\cdot {\vert }{} { Bz}{\vert }$$V·|Bz| is found to be high and the same ($$-\,0.8$$-0.8) for the solar cycles.