Periodicity analysis of galactic cosmic rays using Fourier, Hilbert, and higher-order spectral methods
| Autor: | T. E. Girish, V. Vipindas, Sumesh Gopinath |
|---|---|
| Rok vydání: | 2016 |
| Předmět: |
Physics
Neutron monitor 010504 meteorology & atmospheric sciences Astrophysics::High Energy Astrophysical Phenomena Astronomy and Astrophysics Cosmic ray Astrophysics 01 natural sciences Cosmology symbols.namesake Fourier transform Space and Planetary Science Physics::Space Physics 0103 physical sciences symbols Bispectral analysis Spectral method 010303 astronomy & astrophysics Heliosphere 0105 earth and related environmental sciences Hilbert spectrum |
| Zdroj: | Astrophysics and Space Science. 361 |
| ISSN: | 1572-946X 0004-640X |
| DOI: | 10.1007/s10509-016-2719-y |
| Popis: | Galactic cosmic rays (GCRs) that traverse the heliosphere, in the energy range from several 100 MeV to a few GeV, are subjected to heliospheric modulation. GCRs interact with varying fields of the heliosphere to produce fluctuations in cosmic-ray intensity with variations in solar activity. The effects of modulation are continuously measured by the well-established world-wide neutron monitor network. Solar activity indices and cosmic-ray neutron monitor rates (at different cut-off rigidities) have been used to compare Fourier, Hilbert, and higher-order spectral (bispectral) features of GCR intensity variations at six stations for a period of nearly 50 years. The present study reveals that GCRs exhibit a number of short- and long-term periodicities that vary between 9 days and 22 years. The bispectral analysis shows the characteristic features of nonlinear coupling and complex phase relationships between various harmonics present in GCRs and solar activity proxies. We also offer possible explanations for the observed periodicities with the help of the previous findings. |
| Databáze: | OpenAIRE |
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