Changes in quasi-periodic variations of solar photospheric fields: precursor to the deep solar minimum in the cycle 23?

Abstract

Using both wavelet and Fourier analysis, a study has been undertaken of the changes in the quasi-periodic variations in solar photospheric fields in the build-up to one of the deepest solar minima experienced in the past 100 years. This unusual and deep solar minimum occurred between solar cycles 23 and 24. The study, carried out using ground based synoptic magnetograms spanning the period 1975.14 to 2009.86, covered solar cycles 21, 22 and 23. A hemispheric asymmetry in periodicities of the photospheric fields was seen only at latitudes above $\pm 45{}^{\circ }$ when the data was divided, based on a wavelet analysis, into two parts: one prior to 1996 and the other after 1996. Furthermore, the hemispheric asymmetry was observed to be confined to the latitude range 45${}^{\circ }$ to 60${}^{\circ }$. This can be attributed to the variations in polar surges that primarily depend on both the emergence of surface magnetic flux and varying solar surface flows. The observed asymmetry when coupled with the fact that both solar fields above $\pm 45{}^{\circ }$ and micro-turbulence levels in the inner-heliosphere have been decreasing since the early to mid nineties (Janardhan et al., 2011) suggests that around this time active changes occurred in the solar dynamo that governs the underlying basic processes in the sun. These changes in turn probably initiated the build-up to the very deep solar minimum at the end of the cycle 23. The decline in fields above $\pm 45{}^{\circ }$ for well over a solar cycle, would imply that weak polar fields have been generated in the past two successive solar cycles \textit{viz.} cycles 22 and 23. A continuation of this declining trend beyond 22 years, if it occurs, will have serious implications on our current understanding of the solar dynamo.

25 pages, 8 Fiures, Accepted for publication in Solar Physics Journal

References in corpus (5)

• Predicting solar cycle 24 with a solar dynamo model
• Solar activity forecast with a dynamo model
• The unusual minimum of sunspot cycle 23 a consequence of Sun's meridional plasma flow variations
• Thinning of the Sun's magnetic layer: the peculiar solar minimum could have been predicted
• Can surface flux transport account for the weak polar field in cycle 23?

Cited by in corpus (11)

• Solar cycle 24: an unusual polar field reversal
• Evidence of Twisted flux-tube Emergence in Active Regions
• Mass Loss via Solar Wind and Coronal Mass Ejections During Solar Cycle 23 and 24
• Amplitude of solar wind density turbulence from 10--45 $R_{\odot }$
• A study of density modulation index in the inner heliospheric solar wind during solar cycle 23
• Another Mini Solar Maximum in the Offing: A Prediction for the Amplitude of Solar Cycle 25
• Variation of Coronal Activity from the Minimum to Maximum of Solar Cycle 24 using Three Dimensional Coronal Electron Density Reconstructions from STEREO/COR1
• On Midrange Periodicities in Solar Radio Flux and Sunspot Areas
• Beyond the mini-solar maximum of solar cycle 24: Declining solar magnetic fields and the response of the terrestrial magnetosphere
• A new tool for predicting the solar cycle: Correlation between flux transport at the equator and the poles
• Wavelet analysis of solar magnetic strength indices