The Astrophysical Journal · 1975 · 350 citations · 0 references
Natural SciencesAstronomyPhysicsAstrophysicsElectromagnetismSolar AstronomyMagnetohydrodynamicsPlanetary MagnetospheresSolar DynamoSolar Magnetic FieldsSolar RotationMagnetic FluxMagnetic Flux EmergenceMagnetic Flux TransportSolar Dynamo ProcessesSolar Dynamo TheorySolar Magnetic ActivitySolar Magnetohydrodynamics
Magnetic fields in astrophysical bodies, such as the Sun, arise from azimuthal fields of roughly 100 G beneath the surface, with amplification times of about 10 years due to differential rotation. The study seeks to determine where the azimuthal magnetic field can be retained long enough to be amplified despite rapid buoyant rise through the convective zone. The authors find that while magnetic fields can persist in the stable radiative zone beneath the convective zone, the solar dynamo must operate in the lowest convective layers (depths >150,000 km, density 0.1 g cm⁻³) where fields are limited to ~50 G. Published in The Astrophysical Journal (May 1975), DOI 10.1086/153593.
view Abstract Citations (354) References (30) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The generation of magnetic fields in astrophysical bodies. X. Magnetic buoyancy and the solar dynamo. Parker, E. N. Abstract The magnetic field appearing as bipolar magnetic regions at the surface of the sun represents the lines of force from a general azimuthal field of the order of 100 gauss somewhere beneath the surface. The amplification time, as a consequence of the nonuniform rotation, is of the order of 10 years. But magnetic buoyancy brings the azimuthal field up through much of the convective zone in a time rather less than 10 years, raising the question of where the azimuthal field can be retained long enough to be amplified. We show that magnetic fields can be retained for long periods of time in the stable radiative region beneath the convective zone, but unfortunately the solar dynamo cannot function there because turbulent diffusion is an essential part of its operation. The only possible conclusion appears to be that the dynamo operates principally in the very lowest levels of the convective zone at depths of 150,000 km or more, where the gas density is 0.1 g/cu cm, and the fields are limited to 50 gauss. Publication: The Astrophysical Journal Pub Date: May 1975 DOI: 10.1086/153593 Bibcode: 1975ApJ...198..205P Keywords: Atmospheric Stratification; Dynamo Theory; Magnetic Field Configurations; Magnetic Stars; Solar Magnetic Field; Stellar Rotation; Azimuth; Buoyancy; Convective Flow; Lines Of Force; Magnetic Flux; Solar Activity; Temperature Gradients; Solar Physics full text sources ADS | Related Materials (10) Part 1: 1970ApJ...162..665P Part 2: 1971ApJ...163..255P Part 3: 1971ApJ...163..279P Part 4: 1971ApJ...164..491P Part 5: 1971ApJ...165..139P Part 6: 1971ApJ...166..295P Part 7: 1971ApJ...168..231L Part 8: 1971ApJ...168..239P Part 9: 1972ApJ...176..213L Part 11: 1977ApJ...215..370P