The 22-Year Hale Cycle in Cosmic Ray Flux – Evidence for Direct Heliospheric Modulation

Thomas, S. R.; Owens, M. J.; Lockwood, M.
January 2014
Solar Physics;Jan2014, Vol. 289 Issue 1, p407
Academic Journal
The ability to predict times of greater galactic cosmic ray (GCR) fluxes is important for reducing the hazards caused by these particles to satellite communications, aviation, or astronauts. The 11-year solar-cycle variation in cosmic rays is highly correlated with the strength of the heliospheric magnetic field. Differences in GCR flux during alternate solar cycles yield a 22-year cycle, known as the Hale Cycle, which is thought to be due to different particle drift patterns when the northern solar pole has predominantly positive (denoted as qA>0 cycle) or negative ( qA<0) polarities. This results in the onset of the peak cosmic-ray flux at Earth occurring earlier during qA>0 cycles than for qA<0 cycles, which in turn causes the peak to be more dome-shaped for qA>0 and more sharply peaked for qA<0. In this study, we demonstrate that properties of the large-scale heliospheric magnetic field are different during the declining phase of the qA<0 and qA>0 solar cycles, when the difference in GCR flux is most apparent. This suggests that particle drifts may not be the sole mechanism responsible for the Hale Cycle in GCR flux at Earth. However, we also demonstrate that these polarity-dependent heliospheric differences are evident during the space-age but are much less clear in earlier data: using geomagnetic reconstructions, we show that for the period of 1905 – 1965, alternate polarities do not give as significant a difference during the declining phase of the solar cycle. Thus we suggest that the 22-year cycle in cosmic-ray flux is at least partly the result of direct modulation by the heliospheric magnetic field and that this effect may be primarily limited to the grand solar maximum of the space-age.


Related Articles

  • Is the Highest Cosmic-Ray Flux Yet to Come? Strauss, R.; Potgieter, M. // Solar Physics;Aug2014, Vol. 289 Issue 8, p3197 

    The recent 2009 solar-minimum period was characterized by a record-setting high Galactic cosmic-ray flux observed at Earth. This, along with the unexpected low heliospheric magnetic-field magnitude, caused this period to be characterized as unusual compared with previous minimum epochs. In this...

  • The character of the solar magnetic field restructuring and its effect on the modulation depth of galactic cosmic rays in the heliosphere. Alexeev, V.; Ustinova, G. // Doklady Physics;May2013, Vol. 58 Issue 5, p200 

    The article focuses on a study which analyzed the character of the solar magnetic field restructuring, as well as its effect on the modulation depth of galactic cosmic rays (GCR) in the heliosphere. It notes on the correlations between the GCR gradients and solar activity (SA). It illustrates...

  • Solar Modulation of Cosmic Rays during the Declining and Minimum Phases of Solar Cycle 23: Comparison with Past Three Solar Cycles. Aslam, O.; Badruddin // Solar Physics;Sep2012, Vol. 279 Issue 1, p269 

    We study solar modulation of galactic cosmic rays (GCRs) during the deep solar minimum, including the declining phase, of solar cycle 23 and compare the results of this unusual period with the results obtained during similar phases of the previous solar cycles 20, 21, and 22. These periods...

  • 27-day variations of the galactic cosmic ray intensity and anisotropy. Alania, M. V.; Gil, A.; Modzelewska, R. // Astrophysics & Space Sciences Transactions (ASTRA);May2008, Vol. 4 Issue 1, p31 

    We study the 27-day variations of the galactic cosmic ray (GCR) intensity and three dimensional (3-D) anisotropy in different polarity periods of the solar magnetic cycle. We found that the larger amplitudes of the 27-day variations of the galactic cosmic ray anisotropy and intensity in the...

  • Modeling the Relationship Between Neutron Counting Rates and Sunspot Numbers Using the Hysteresis Effect. Inceoglu, F.; Knudsen, M. F.; Karoff, C.; Olsen, J. // Solar Physics;Apr2014, Vol. 289 Issue 4, p1387 

    Several studies show that temporal variations in the Galactic cosmic ray (GCR) intensity display a distinct 11-year periodicity due to solar modulation of the galactic cosmic rays in the heliosphere. The 11-year periodicity of GCRs is inversely proportional to, but out of phase with, the 11-year...

  • Coronal Holes in Solar Cycles 21 to 23. Tlatov, A.; Tavastsherna, K.; Vasil’eva, V. // Solar Physics;Apr2014, Vol. 289 Issue 4, p1349 

    We present identifications of coronal holes (CHs) from observations in the He  i 10 830 Å line made at Kitt Peak Observatory (from 1975 to 2003) and in the EUV 195 Å wavelength with SOHO/EIT (from 1996 to 2012). To determine whether a feature is a CH we have developed...

  • On recovery of anomalous oxygen intensity on the decay phase of solar cycle at negative polarity of the magnetic field of the sun. Zhuravlev, D. A.; Kondratyeva, M. A.; Tretyakova, Ch. A. // Cosmic Research;May2007, Vol. 45 Issue 3, p257 

    The article presents a study which focuses on the recovery of anomalous oxygen intensity on the decay phase of solar cycle at negative polarity of the magnetic field of the sun. It has been found that the delay in the recovery of the intensity of oxygen ions took place in relation to galactic...

  • On periodicities in long term climatic variations near 68º N, 30º E. Kasatkina, E. A.; Shumilov, O. I.; Krapiec, M. // Advances in Geosciences;2007, Vol. 13, p25 

    It is generally believed that the low-frequency variability of climatic parameters seems to be connected to solar cycles. The principal periodicities are: 11-year (Schwabe), 22-year (Hale), 33-year (Bruckner) and 80-100-year (Gleissberg) cycles. The main heliophysical factors acting on climate,...

  • Heliospheric Modulation of Galactic Cosmic Rays During Solar Cycle 23. Chowdhury, Partha; Kudela, K.; Dwivedi, B. // Solar Physics;Sep2013, Vol. 286 Issue 2, p577 

    Galactic cosmic rays (GCRs) encounter an outward-moving solar wind with cyclic magnetic-field fluctuation and turbulence. This causes convection and diffusion in the heliosphere. The GCR counts from the ground-based neutron monitor stations show intensity changes that are anti-correlated with...


Read the Article


Sorry, but this item is not currently available from your library.

Try another library?
Sign out of this library

Other Topics