Skip to content Skip to navigation
University of Warwick
  • Study
  • |
  • Research
  • |
  • Business
  • |
  • Alumni
  • |
  • News
  • |
  • About

University of Warwick
Publications service & WRAP

Highlight your research

  • WRAP
    • Home
    • Search WRAP
    • Browse by Warwick Author
    • Browse WRAP by Year
    • Browse WRAP by Subject
    • Browse WRAP by Department
    • Browse WRAP by Funder
    • Browse Theses by Department
  • Publications Service
    • Home
    • Search Publications Service
    • Browse by Warwick Author
    • Browse Publications service by Year
    • Browse Publications service by Subject
    • Browse Publications service by Department
    • Browse Publications service by Funder
  • Help & Advice
University of Warwick

The Library

  • Login
  • Admin

The Sun’s magnetic (Hale) cycle and 27 day recurrences in the aa geomagnetic index

Tools
- Tools
+ Tools

Chapman, Sandra C., McIntosh, S. W., Leamon, R. J. and Watkins, Nicholas W. (2021) The Sun’s magnetic (Hale) cycle and 27 day recurrences in the aa geomagnetic index. Astrophysical Journal, 917 (2). 54. doi:10.3847/1538-4357/ac069e

[img]
Preview
PDF
WRAP-Sun’s-magnetic-(Hale)-cycle-27-day-recurrences-aa-geomagnetic-index-Chapman-2021.pdf - Accepted Version - Requires a PDF viewer.

Download (7Mb) | Preview
Official URL: https://doi.org/10.3847/1538-4357/ac069e

Request Changes to record.

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 yr Hale (magnetic polarity) cycle, using the Hilbert transform of daily sunspot numbers (SSNs) since 1818. The occurrences of solar maxima show almost no discernible Hale cycle dependence, consistent with the clock being synchronized to polarity reversals. We reengineer the Sargent 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.

Item Type: Journal Article
Subjects: Q Science > QB Astronomy
Divisions: Faculty of Science, Engineering and Medicine > Science > Physics
Library of Congress Subject Headings (LCSH): Solar cycle, Solar magnetic fields , Hilbert transform
Journal or Publication Title: Astrophysical Journal
Publisher: IOP Publishing
ISSN: 0004-637X
Official Date: 17 August 2021
Dates:
DateEvent
17 August 2021Published
27 May 2021Accepted
Volume: 917
Number: 2
Article Number: 54
DOI: 10.3847/1538-4357/ac069e
Status: Peer Reviewed
Publication Status: Published
Reuse Statement (publisher, data, author rights): This is an author-created, un-copyedited version of an article accepted for publication/published in Astrophysical Journal. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at https://doi.org/10.3847/1538-4357/ac069e
Access rights to Published version: Restricted or Subscription Access

Request changes or add full text files to a record

Repository staff actions (login required)

View Item View Item

Downloads

Downloads per month over past year

View more statistics

twitter

Email us: wrap@warwick.ac.uk
Contact Details
About Us