Magnetic twist: a source and property of space weather

Abstract

We present evidence for finite magnetic helicity density in the heliosphere and numerical models thereof, and relate it to the magnetic field properties of the dynamo in the solar convection zone. We use simulations and solar wind data to compute magnetic helicity either directly from the simulations, or indirectly using time series of the skew-symmetric components of the magnetic correlation tensor. We find that the solar dynamo produces negative magnetic helicity at small scales and positive at large scales. However, in the heliosphere these properties are reversed and the magnetic helicity is now positive at small scales and negative at large scales. We explain this by the fact that a negative diffusive magnetic helicity flux corresponds to a positive gradient of magnetic helicity, which leads to a change of sign from negative to positive values at some radius in the northern hemisphere.

arXiv comment7 pages, 12 Figures, accepted in Journal of Space Weather and Space Climate

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Cited by in corpus (18)

• Advances in mean-field dynamo theory and applications to astrophysical turbulence
• The Global Solar Dynamo
• Convection-driven spherical shell dynamos at varying Prandtl numbers
• Magnetic helicity and energy spectra of a solar active region
• Evolution of Magnetic Helicity and Energy Spectra of Solar Active Regions
• Turbulent processes and mean-field dynamo
• Bipolar region formation in stratified two-layer turbulence
• Bihelical spectrum of solar magnetic helicity and its evolution
• Competition of rotation and stratification in flux concentrations
• Simulations of galactic dynamos
• Magnetic Helicity Reversal in the Corona at Small Plasma Beta
• A global two-scale helicity proxy from $\pi$-ambiguous solar magnetic fields
• Magnetic Helicity from Multipolar Regions on the Solar Surface
• Compensating Faraday depolarization by magnetic helicity in the solar corona
• An analytic mean-field ${\alpha }^2$-dynamo with a force-free corona
• Magnetic field evolution in solar-type stars
• Non-linear and chaotic dynamo regimes
• VIEWPOINT: A New Twist in Simulating Solar Flares