Supergranulation and the dynamics of gas and magnetic field below the solar photosphere

Journal Article · Thu Dec 01 04:00:00 EST 1977 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/155707· OSTI ID:5331683

Foukal, P

We suggest that the scale of supergranular flow may simply reflect the depth dapprox. =1.5 x 10/sup 4/ km below the photosphere over which the magnetic field occupies a relatively small volume and the nonmagnetic fluid is allowed to convect and rotate freely. If magnetic buoyancy is important in bringing flux to the photosphere from a deep region of either primordial or dynamo field, then a sharp increase of magnetic flux inward below the photosphere is required to satisfy a simple continuity argument. It is remarkable that the angular velocity of the nonmagnetic fluid seems to increase with depth over this supergranular layer at the rate expected if angular momentum per unit mass is conserved in radial convection. From this rotation law in the supergranular layer, we suggest that the effective eddy viscosity ..nu.. at this scale exceeds 10/sup 11/ cm/sup 2/ s/sup -1/. This means that large values of viscosity in the range ..nu..> or approx. =10/sup 13/ cm/sup 2/ s/sup -1/ may be reasonable in dynamical models of deep (d> or =10/sup 5/ km) convection on the Sun. We demonstrate that the radial gradient of the rotation velocity in the nonmagnetic gas is capable of bending flux tubes that extend upward through this supergranular layer through an angle which agrees closely with that inferred from observations by Howard. If this inferred tilt of the photospheric fields were ascribed to the torque of the interplanetary field, it would imply a rate of loss of angular momentum from the Sun exceeding by two orders of magnitude the value estimated from the rate of mass loss in the solar wind at the present epoch.

• Research Organization: Center for Astrophysics, Harvard College Observatory
• OSTI ID: 5331683
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 218:2; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640104* -- Astrophysics & Cosmology-- Solar Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ANGULAR VELOCITY
ATMOSPHERES
CONVECTION
ENERGY TRANSFER
FLUID FLOW
GAS FLOW
HEAT TRANSFER
MAGNETIC FIELDS
MOTION
PHOTOSPHERE
PLASMA
ROTATION
SOLAR ACTIVITY
SOLAR ATMOSPHERE
SOLAR GRANULATION
SUNSPOTS
VELOCITY
VISCOSITY