E-Print Archive

There are 4571 abstracts currently viewable.


Advanced Search
Main Page Add New E-Print Submitter
News Help/FAQ About Preferences
Manage Key Phrase
Magnetic flux concentrations from turbulent stratified convection View all abstracts by submitter

Axel Brandenburg   Submitted: 2016-06-30 07:39

Context: The mechanisms that cause the formation of sunspots are still unclear. Aims: We study the self-organisation of initially uniform sub-equipartition magnetic fields by highly stratified turbulent convection. Methods: We perform simulations of magnetoconvection in Cartesian domains that are 8.5-24 Mm deep and 34-96 Mm wide. We impose either a vertical or a horizontal uniform magnetic field in a convection-driven turbulent flow. Results: We find that super-equipartition magnetic flux concentrations are formed near the surface with domain depths of 12.5 and 24 Mm. The size of the concentrations increases as the box size increases and the largest structures (20 Mm horizontally) are obtained in the 24 Mm deep models. The field strength in the concentrations is in the range of 3-5 kG. The concentrations grow approximately linearly in time. The effective magnetic pressure measured in the simulations is positive near the surface and negative in the bulk of the convection zone. Its derivative with respect to the mean magnetic field, however, is positive in the majority of the domain, which is unfavourable for the negative effective magnetic pressure instability (NEMPI). Furthermore, we find that magnetic flux is concentrated in regions of converging flow corresponding to large-scale supergranulation convection pattern. Conclusions: The linear growth of large-scale flux concentrations implies that their dominant formation process is tangling of the large-scale field rather than an instability. One plausible mechanism explaining both the linear growth and the concentrate on of the flux in the regions of converging flow pattern is flux expulsion. Possible reasons for the absence of NEMPI are that the derivative of the effective magnetic pressure with respect to the mean magnetic field has an unfavourable sign and that there may not be sufficient scale separation.

Authors: P. J. Käpylä, A. Brandenburg, N. Kleeorin, M. J. Käpylä, I. Rogachevskii
Projects: None

Publication Status: A&A 588, A150 (2016)
Last Modified: 2016-07-06 10:37
Go to main E-Print page  How did a Major Confined Flare Occur in Super Solar Active Region 12192?   Stellar Evidence that the Solar Dynamo may be in Transition  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Go to main E-Print pageGo to main E-Print page.
Previous AbstractPrevious Abstract.
Next AbstractNext Abstract.
Download PreprintDownload Preprint.
Submitter's HomepageSubmitters Homepage.
Edit EntryEdit Entry.
View All Abstracts By SubmitterView all abstracts by submitter.
Delete AbstractDelete abstract.

Latest Entries
Solar Radio Spikes and Type IIIb Striae Manifestations of Sub-second Electron Acceleration Triggered by a Coronal Mass Ejection
Statistical study of Type III bursts and associated HXR emissions
On orbit performance of the solar flare trigger for the Hinode EUV Imaging Spectrometer
Plasma Composition Measurements in an Active Region from Solar Orbiter/SPICE and Hinode/EIS
Modulation of cosmic ray anti-protons in the heliosphere: simulations for a solar cycle
Temporal and spatial association between microwaves and type III bursts in the upper corona
Prospective Implications of EUV Coronal Plumes for Magnetic-network Genesis of Coronal Heating, Coronal-hole Solar Wind, and Solar-wind Magnetic-field Switchbacks
Solar Energetic Particle Events with Short and Long Onset Times
The mechanism of magnetic flux rope rotation during solar eruption
Quantification of the Writhe Number Evolution of Solar Filament Axes
Starspot mapping with adaptive parallel tempering. II. Application to TESS data for M-dwarf flare stars, AU Microscopii, YZ Canis Minoris, and EV Lacertae
A Superflare on YZ Canis Minoris Observed by Seimei Telescope and TESS: Red Asymmetry of Hα Emission Associated with White-Light Emission
The frequency ratio and time delay of solar radio emissions with fundamental and harmonic components
Prospects of Detecting Non-thermal Protons in Solar Flares via Lyman Line Spectroscopy: Revisiting the Orrall-Zirker Effect
Rapid Rotation of an Erupting Prominence and the Associated Coronal Mass Ejection on 13 May 2013
Spectral and Imaging Diagnostics of Spatially-Extended Turbulent Electron Acceleration and Transport in Solar Flares
Detection of a high-velocity prominence eruption leading to a CME associated with a superflare on the RS CVn-type star V1355 Orionis
Magnetohydrodynamics Instabilities of Double Magnetic Bands in a Shallow-water Tachocline Model: I Cross-equatorial Interactions of Bands
Stability of slow magnetoacoustic and entropy waves in the solar coronal plasma with thermal misbalance
The chromosphere underneath a Coronal Bright Point

Related Pages
MSU Solar Physics.
Max Millennium Science Mail Archive.
Max Millennium Message of the Day Mail Archive.
Max Millennium Flare Catalog

Archive Maintainer
Alisdair Davey

© 2000-2020 Solar Physics Group - Montana State University