Modelling the evolution of the Sun's open and total magnetic flux

Abstract

Solar activity in all its varied manifestations is driven by the magnetic field. Particularly important for many purposes are two global quantities, the Sun's total and open magnetic flux, which can be computed from sunspot number records using models. Such sunspot-driven models, however, do not take into account the presence of magnetic flux during grand minima, such as the Maunder minimum. Here we present a major update of a widely used simple model, which now takes into account the observation that the distribution of all magnetic features on the Sun follows a single power law. The exponent of the power law changes over the solar cycle. This allows for the emergence of small-scale magnetic flux even when no sunspots are present for multiple decades and leads to non-zero total and open magnetic flux also in the deepest grand minima, such as the Maunder minimum, thus overcoming a major shortcoming of the earlier models. The results of the updated model compare well with the available observations and reconstructions of the solar total and open magnetic flux. This opens up the possibility of improved reconstructions of sunspot number from time series of cosmogenic isotope production rate.

References in corpus (8)

• Evolution of the solar irradiance during the Holocene
• Numerical simulations of quiet Sun magnetism: On the contribution from a small-scale dynamo
• A solar surface dynamo
• The Sun is less active than other solar-like stars
• Solar cyclic activity over the last millennium reconstructed from annual 14C data
• Level and length of cyclic solar activity during the Maunder minimum as deduced from the active day statistics
• The Dimmest State of the Sun
• Statistical evolution of quiet-Sun small scale magnetic features using Sunrise observations

Cited by in corpus (7)

• Solar cyclic activity over the last millennium reconstructed from annual 14C data
• Re-calibration of the Sunspot Number: Status Report
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• Long-term forcing of Sun's coronal field, open flux and cosmic ray modulation potential during grand minima, maxima and regular activity phases by the solar dynamo mechanism
• Forward modelling of brightness variations in Sun-like stars -- II. Light curves and variability
• Reconstruction of annual solar irradiance over the last three millennia
• Solar Irradiance Reconstruction over the Telescopic Era Using a Revised Photospheric Magnetic Field Model