Wavelet analysis of long-term variations in neutron monitor, sunspot number and interplanetary magnetic field data

We use wavelet analysis to investigate the characteristic timescales appearing in neutron monitor data and their solar drivers. Wavelet analysis of Oulu NM data shows the well-known roughly 11-year variation in inten- sity, but with a period contracting during solar cycle 22. This is also seen in the wavelet analysis of the interpla- netary magnetic field magnitude data. However, this varying period is not shown in the wavelet analysis of daily estimated sunspot numbers, a proxy for solar magnetic field strength. The time at which the wavelet transform is found to be similar for both NM and sunspot number, but not for the interplanetary magnetic field magnitude. This further highlights a complex relationship between cosmic rays, the heliosphere, and Earth.

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