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TitleOn solutions of the PFSS model with GONG synoptic maps for 2006-2018
AuthorNikolic, L
SourceSpace Weather vol. 17, 2019 p. 1-19, Open Access logo Open Access
Alt SeriesNatural Resources Canada, Contribution Series 20180441
PublisherAmerican Geophysical Union (AGU)
Mediapaper; on-line; digital
File formatpdf (Adobe® Reader®); html
Subjectsgeophysics; Science and Technology; Nature and Environment; models; solar cycles; solar variations; magnetic field; Global Oscillation Network Group (GONG); Forecasting
Illustrationstime series; sketch maps; geophysical images
ProgramPublic Safety Geoscience Northern Canada Geohazards Project
Released2019 08 01
AbstractThe potential field source surface (PFSS) model is widely used to derive the magnetic field of the solar corona. The only free parameter in the PFSS model is the radius of the so-called source surface, where magnetic field lines are forced to open. The radius of this surface is typically set to 2.5 solar radii in research and operational PFSS numerical models. Here, using Global Oscillation Network Group (GONG) synoptic maps of the photospheric field, solutions of the PFSS model for various heights of the source surface are investigated for 2006-2018. In particular, numerically derived open solar magnetic flux and coronal holes are examined. Solutions of the PFSS model based on GONG synoptic maps are particularly important since they are often used to drive operational space weather forecast models. Comparisons between observations and numerical results in this paper suggest that the radius of the source surface is significantly lower than 2.5 solar radii during the active phase of solar cycle 24. The fact that the source surface location depends on the solar activity suggests that relations which associate solar wind properties with the coronal magnetic field in the PFSS-based solar wind modes should be revisited. Furthermore, although the correction of the polar magnetic field is part of GONG synoptic map production pipeline, the results suggest that better treatment of polar fields is needed to cover observational gaps. The issue with the polar fields in GONG maps is particularly pronounced in recent years.
Summary(Plain Language Summary, not published)
Space weather refers to the dynamic conditions on the Sun and in the space environment, in particular, in the near-Earth environment, that can affect critical infrastructure. NRCan operates the Canadian Space Weather Forecast Centre and conducts research into space weather effects on power systems, pipelines, radio communications and GNSS positioning to help Canadian industry understand and mitigate the effects of space weather. Since the Sun is the source of Space Weather disturbances, numerical modelling of the solar corona plays an important role. This paper investigates a widely used model of the solar corona and the dependence of results on the model parameters.

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