Identification

Title

Constraining non-linear dynamo models using quasi-biennial oscillations from sunspot area data

Abstract

Solar magnetic activity exhibits variations with periods between 1.5 and 4 years, the so-called quasi-biennial oscillations (QBOs), in addition to the well-known 11-year Schwabe cycles. Solar dynamo is thought to be the mechanism responsible for thegeneration of QBOs. In this work, we analyse sunspot areas to investigate the spatial and temporal behaviour of the QBO signal and study the physical mechanisms responsible using simulations from fully non-linear mean-field flux-transport dynamos. We investigated the behaviour of the QBOs in the sunspot area data for the full disk, and the northern and southern hemispheres, using wavelet and Fourier analyses. We also ran solar dynamos with two different approaches to generating a poloidal field from an existing toroidal field, namely Babcock–Leighton and turbulent α mechanisms. We then studied the simulated magnetic field strengths as well as meridional circulation and differential rotation rates using the same methods. Results. The results from the sunspot areas show that the QBOs are present in the full disk and hemispheric sunspot areas. These QBOs show slightly different spatial and temporal behaviours, indicating slightly decoupled solar hemispheres. The QBO signal is generally intermittent and in-phase with the sunspot area data, surfacing when the solar activity is at its maximum. The results from the BLdynamos show that they are neither capable of generating the slightly decoupled behaviour of solar hemispheres nor can they generate QBO-like signals. The turbulent α-dynamos on the other hand generated decoupled hemispheres and some QBO-like shorter cycles. In conclusion, our simulations show that the turbulent α-dynamos with the Lorentz force seem more efficient in generating the observed temporal and spatial behaviour of the QBO signal compared with the BL-dynamos.

Resource type

document

Resource locator

Unique resource identifier

code

http://n2t.net/ark:/85065/d7hm5cjm

codeSpace

Dataset language

eng

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geoscientificInformation

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Text

originating controlled vocabulary

title

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reference date

date type

publication

effective date

2016-01-01T00:00:00Z

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East bounding longitude

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publication

effective date

2019-05-22T00:00:00Z

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Conformity

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None

Responsible organisations

Responsible party

contact position

OpenSky Support

organisation name

UCAR/NCAR - Library

full postal address

PO Box 3000

Boulder

80307-3000

email address

opensky@ucar.edu

web address

http://opensky.ucar.edu/

name: homepage

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pointOfContact

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