Correlations between sunspot numbers, interplanetary parameters and geomagnetic trends over solar cycles 21–23

• Evaluated a local measure for magnetic activity IΔH, removing solar cycle effects.
• Compared IΔH with Ap, in regard to response to non-solar cycle influences.
• Time varying link between solar parameters and magnetic activity are brought out by wavelet analysis.
• Identified and discussed the influence of non-sunspot activity in magnetic activity of every solar cycle.

We have analysed correlations between sunspot numbers, solar wind, ion density, interplanetary magnetic field vis-à-vis magnetic activity. Planetary geomagnetic index (Ap) and local residual measure of magnetic activity (IΔH) from low-latitude Magnetic Observatory, CSIR-NGRI, Hyderabad (IMO-HYB) spanning solar cycles 21–23 are used for this study.Using correlation coefficients between and wavelet decomposition of sunspot numbers, interplanetary parameters and measures of magnetic activity, the complex and time varying nature of these inter-relationships are brought out. The overall influence of sunspot number could be separated and combined episodic effects of other solar parameters could be distinguished. The demonstrated correlation or lack of it, between measures of magnetic activity (Ap and IΔH), and all the parameters of solar activity, presented here corroborate established mechanisms as well as delineated clearly the relative impact of different solar mechanisms over phases of three solar cycles. The possible role of non-sunspot related activity from high latitude regions of the sun is indicated.