Michael S. Stix

Magnetic Field Generation in Fully Convective Rotating Spheres

Magnetohydrodynamic simulations of fully convective, rotating spheres with volume heating near the center and cooling at the surface are presented. The dynamo-generated magnetic field saturates at equipartition field strength near the surface. In the interior, the field is dominated by small-scale structures, but outside the sphere, by the global scale. Azimuthal averages of the field reveal a large-scale field of smaller amplitude also inside the star. The internal angular velocity shows some tendency to be constant along cylinders and is antisolar (fastest at the poles and slowest at the equator).

High resolution mapping of the magnetic field of the solar corona

High resolution KPNO magnetograph measurements of the line-of-sight component of the photospheric magnetic field over the entire dynamic range from 0 to 4000 gauss are used as the basic data for a new analysis of the photospheric and coronal magnetic field distributions. The daily magnetograph measurements collected over a solar rotation are averaged onto a 180 × 360 synoptic grid of equal-area elements. With the assumption that there are no electric currents above the photospheric level of measurement, a unique solution is determined for the global solar magnetic field. Because the solution is in terms of an expansion in spherical harmonics to principal index n = 90, the global photospheric magnetic energy distribution can be analyzed in terms of contributions of different scale-size and geometric pattern. This latter procedure is of value (1) in guiding solar dynamo theories, (2) in monitoring the persistence of the photospheric field pattern and its components, (3) in comparing synoptic magnetic data of different observatories, and (4) in estimating data quality. Different types of maps for the coronal magnetic field are constructed (1) to show the strong field at different resolutions, (2) to trace the field lines which open into interplanetary space and to locate their photospheric origins, and (3) to map in detail coronal regions above (specified) limited photospheric areas.

Magnetoconvection and dynamo coefficients II. Field-direction dependent pumping of magnetic field

We study the pumping of magnetic flux in three-dimensional compressible magnetoconvection in the context of stellar dynamos. The simulation domain represents a rectangular section from the lower part of a stellar convection zone plus the underlying stably stratified layer, with a total depth of up to five pressure scale heights. Once convection has attained a statistically stationary state, a magnetic field is introduced. The magnetic field is subsequently modified by the convective motions, and the resulting pumping eects are isolated by calculating various coecients of the expansion of the electromotive force, u b, in terms of components of the mean magnetic field. The dependence of the pumping eects on rotation, latitude and other parameters is studied. First numerical evidence is found for the existence of pumping eects in the horizontal directions. Evidence is found that the pumping eects act dierently on dierent components of the mean magnetic field. Latitudinal pumping is mainly equatorward for a toroidal field, and can be poleward for a poloidal field. Longitudinal pumping is mainly retrograde for the radial field but prograde for the latitudinal field. The pumping eect in the vertical direction is found to be dominated by the diamagnetic eect, equivalent to a predominating downward advection with a maximum speed in the turbulent case of about 10% of the rms convective velocity. Where possible, an attempt is made to identify the physical origin of the eect. Finally, some consequences of the results for stellar dynamos are discussed.

Epidural catheter and increased prothrombin time after right lobe hepatectomy for living donor transplantation

IMPLICATIONS Donor right hepatic lobectomy for the purpose of living liver transplantation may be associated with postoperative abnormalities in tests of clotting function. This study explores the possible causes and anesthetic implications of this phenomenon.

Magnetoconvection and dynamo coefficients: - Dependence of the

We present numerical simulations of three-dimensional compressible magnetoconvection in a rotating rectangular box that represents a section of the solar convection zone. The box contains a convectively unstable layer, surrounded by stably stratified layers with overshooting convection. The magnetic Reynolds number, Rm, is chosen subcritical, thus excluding spontaneous growth of the magnetic field through dynamo action, and the magnetic energy is maintained by introducing a constant magnetic field into the box, once convection has attained a statistically stationary state. Under the influence of the Coriolis force, the advection of the magnetic field results in a non-vanishing contribution to the mean electric field, given by

\alpha

\langle\vec{u}\times\vec{b}\rangle

effect on rotation and magnetic field

. From this electric field, we calculate the α -effect, separately for the stably and the unstably stratified layers, by averaging over time and over suitably defined volumes. From the variation of α we derive an error estimate, and the dependence of α on rotation and magnetic field strength is studied. Evidence is found for rotational quenching of the vertical α effect, and for a monotonic increase of the horizontal α effect with increasing rotation. For

Observations of subpicosecond dynamics in GaAlAs laser diodes

{\rm Rm}\approx 30

Magnetoconvection and dynamo coefficients - III. α-effect and magnetic pumping in the rapid rotation regime

, our results for both vertical and horizontal α effect are consistent with magnetic quenching by a factor

Maximum minute ventilation test for the ProSeal laryngeal mask airway.

[1+{\rm Rm} (B_0/B_{\rm eq})^2]^{-1}