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On midrange periodicities in solar radio flux and sunspot areas

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Abstract

Using the Hilbert-Huang transform technique, we investigate the midrange periodicities in solar radio flux at 2800 MHz (F10.7) and sunspot areas (SAs) from February 1, 1947 to September 30, 2016. The following prominent results are found: (1) The quasi-periodic oscillations of both data sets are not identical, such as the rotational cycle, the midrange periodicities, and the Schwabe cycle. In particular, the midrange periodicities ranging from 37.9 days to 297.3 days are related to the magnetic Rossby-type waves; (2) The 1.3-year and 1.7-year fluctuations in solar activity indicators are surface manifestations (from photosphere to corona) of magnetic flux changes generated deep inside the Sun; (3) At the timescale of the Schwabe cycle, the complicated phase relationships in the three intervals (1947–1958, 1959–1988, and 1989–2016) agree with the produced periodicities of the magnetic Rossby-type waves. The findings indicate that the magnetic Rossby-type waves are the possible physical mechanism behind the midrange periodicities of solar activity indicators. Moreover, the significant change in the relationship between photospheric and coronal activity took place after the maximum of solar cycle 22 could be interpreted by the magnetic Rossby-type waves.

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Notes

  1. http://www.spaceweather.gc.ca/solarflux/sx-en.php.

  2. http://www.ngdc.noaa.gov/stp/spaceweather.html.

  3. http://solarscience.msfc.nasa.gov/greenwch.shtml.

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Acknowledgements

We would like to express our deep thanks to the staffs of the websites that provide the data sets and software codes for the public to download. Time series of solar radio flux are available from the Natural Resources Canada and the National Geophysical Data Center. Daily time series of sunspot areas are taken from the Royal Greenwich Observatory (RGO) archive and the Marshall Space Flight Center (MSFC)’s website. This work is supported by the National Key Research and Development Program of China (2016YFE0100300), the Joint Research Fund in Astronomy (No. U1531132, U1631129, U1231205) under cooperative agreement between the National Natural Science Foundation of China (NSFC) and the Chinese Academy of Sciences (CAS), the National Natural Science Foundation of China (No. 11403009, 11773012, 11463003), the open research program of CAS Key Laboratory of Solar Activity (KLSA201807), the Astronomical Big Data Joint Research Center, co-founded by National Astronomical Observatories, Chinese Academy of Sciences and Alibaba Cloud. Last, but not least, the authors wish to express their gratitude to the anonymous referee and the editor for meaningful suggestions and comments that greatly improved the content and presentation of the paper.

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Correspondence to F. Wang.

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Mei, Y., Deng, H. & Wang, F. On midrange periodicities in solar radio flux and sunspot areas. Astrophys Space Sci 363, 84 (2018). https://doi.org/10.1007/s10509-018-3306-1

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  • DOI: https://doi.org/10.1007/s10509-018-3306-1

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