The Sun’s Magnetic (Hale) Cycle and 27 Day Recurrences in the aa Geomagnetic Index

Abstract

We construct a new solar cycle phase clock which maps each of the last 18 solar cycles onto a single normalized epoch for the approximately 22 year Hale (magnetic polarity) cycle, using the Hilbert transform of daily sunspot numbers (SSN) since 1818. The occurrences of solar maxima show almost no discernable Hale cycle dependence, consistent with the clock being synchronized to polarity reversals. We re-engineer the Sargent (1985Sargent ( , 2021 R27 index and combine it with our epoch analysis to obtain a high time resolution parameter for 27 day recurrence in aa, acv(27) . This reveals that the transition to recurrence, that is, to an ordered solar wind dominated by high speed streams, is fast, with an upper bound of a few solar rotations. It resolves an extended late declining phase which is approximately twice as long on even Schwabe cycles as odd. Galactic Cosmic Ray flux rises in step with acv(27) but then stays high. Our analysis also identifies a slow timescale trend in SSN that simply tracks the Gleissberg cycle. We find that this trend is in phase with the slow timescale trend in the modulus of sunspot latitudes, and in antiphase with that of the R27 index.

Petsamon magneettinen observatorio polaarivuonna 1932-1933: Varhaisia meteorologisia kokeita suomalaisella radioluotaimella

“…Jälkimmäinen miiri oli valaistu sähkölampulla, joten D-mittaus oli mahdollista tehdä pimeänä kaamosaikanakin, kun aurinko ei noussut horisontin yläpuolelle. (Chapman et al, 2021;Nevanlinna, 2004).…”

Deciphering Solar Magnetic Activity. The Solar Cycle Clock

“…Finally, we note that the above describes a single activity cycle, approximately 11 years long. Chapman et al (2020) also expressed the F10.7 and aa index activity as a clock with an average 11 year cycle; Chapman et al (2021) 8 extend the concept to the difference between 11-and 22-year cycles. The two different (solar polar) polarities that comprise the Hale Cycle affect the inflowing galactic cosmic rays (e.g., Jokipii, Levy, and Hubbard, 1977;Jokipii and Thomas, 1981), but also how solar coronal activity translates into the level of disorder in the solar wind.…”

“…The two different (solar polar) polarities that comprise the Hale Cycle affect the inflowing galactic cosmic rays (e.g., Jokipii, Levy, and Hubbard, 1977;Jokipii and Thomas, 1981), but also how solar coronal activity translates into the level of disorder in the solar wind. The data shown in Figures 2-6 barely span two full Hale cycles, so we do not attempt to generate "clock" figures with a rigid terminator-terminator phase as the "hour hand," and instead refer the interested reader to the companion papers (Chapman et al, 2020(Chapman et al, , 2021.…”

Prediction of even and odd sunspot cycles

“…Toriumi et al, 2017). Its cyclic variation can even be used as a pacemaker to time different aspects of solar activity, solar wind and resulting geomagnetic variations (Chapman et al, 2021;Leamon, McIntosh, and Title, 2022). Therefore, there is considerable practical interest in predicting the evolution of future sunspot cycle(s).…”

“…Gnevyshev and Ohl, 1948;Takalo and Mursula, 2018;Leamon, McIntosh, and Title, 2022) and geomagnetic phenomena (e.g. Chernosky, 1966;Takalo, 2021;Chapman et al, 2021). Here we study the prediction of sunspot cycles accounting for the 22-year Hale cycle by considering the differences in the even and odd numbered sunspot cycles.…”