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Parameter optimization for surface flux transport models

Whitbread, T.; Yeates, A.R.; Muñoz-Jaramillo, A.; Petrie, G.J.D.

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T. Whitbread

A. Muñoz-Jaramillo

G.J.D. Petrie


Accurate prediction of solar activity calls for precise calibration of solar cycle models. Consequently we aim to find optimal parameters for models which describe the physical processes on the solar surface, which in turn act as proxies for what occurs in the interior and provide source terms for coronal models. We use a genetic algorithm to optimize surface flux transport models using National Solar Observatory (NSO) magnetogram data for Solar Cycle 23. This is applied to both a 1D model that inserts new magnetic flux in the form of idealized bipolar magnetic regions, and also to a 2D model that assimilates specific shapes of real active regions. The genetic algorithm searches for parameter sets (meridional flow speed and profile, supergranular diffusivity, initial magnetic field, and radial decay time) that produce the best fit between observed and simulated butterfly diagrams, weighted by a latitude-dependent error structure which reflects uncertainty in observations. Due to the easily adaptable nature of the 2D model, the optimization process is repeated for Cycles 21, 22, and 24 in order to analyse cycle-to-cycle variation of the optimal solution. We find that the ranges and optimal solutions for the various regimes are in reasonable agreement with results from the literature, both theoretical and observational. The optimal meridional flow profiles for each regime are almost entirely within observational bounds determined by magnetic feature tracking, with the 2D model being able to accommodate the mean observed profile more successfully. Differences between models appear to be important in deciding values for the diffusive and decay terms. In like fashion, differences in the behaviours of different solar cycles lead to contrasts in parameters defining the meridional flow and initial field strength.


Whitbread, T., Yeates, A., Muñoz-Jaramillo, A., & Petrie, G. (2017). Parameter optimization for surface flux transport models. Astronomy & Astrophysics, 607, Article A76.

Journal Article Type Article
Acceptance Date Jul 28, 2017
Online Publication Date Nov 17, 2017
Publication Date Nov 17, 2017
Deposit Date Aug 4, 2017
Publicly Available Date Aug 7, 2017
Journal Astronomy and astrophysics.
Print ISSN 0004-6361
Electronic ISSN 1432-0746
Publisher EDP Sciences
Peer Reviewed Peer Reviewed
Volume 607
Article Number A76
Related Public URLs


Accepted Journal Article (2 Mb)

Copyright Statement
Reproduced with permission from Astronomy & Astrophysics, © ESO 2017

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