The solar gravitational figure: J2 and J4

The theory of the solar gravitational figure is derived including the effects of differential rotation. It is shown that J sub 4 is smaller than J sub 2 by a factor of about 10 rather than being of order J sub 2 squared as would be expected for rigid rotation. The dependence of both J sub 2 and J sub 4 on envelope mass is given. High order p-mode oscillation frequencies provide a constraint on solar structure which limits the range in envelope mass to the range 0.01 M sub E/solar mass 0.04. For an assumed rotation law in which the surface pattern of differential rotation extends uniformly throughout the convective envelope, this structural constraint limits the ranges of J sub 2 and J sub 4 in units of 10 to the -8th power to 10 J sub 2 15 and 0.6 -J sub 4 1.5. Deviations from these ranges would imply that the rotation law is not constant with depth and would provide a measure of this rotation law

Scaling laws in spherical shell dynamos with free-slip boundaries

Numerical simulations of convection driven rotating spherical shell dynamos have often been performed with rigid boundary conditions, as is appropriate for the metallic cores of terrestrial planets. Free-slip boundaries are more appropriate for dynamos in other astrophysical objects, such as gas-giants or stars. Using a set of 57 direct numerical simulations, we investigate the effect of free-slip boundary conditions on the scaling properties of heat flow, flow velocity and magnetic field strength and compare it with earlier results for rigid boundaries. We find that the nature of the mechanical boundary condition has only a minor influence on the scaling laws. We also find that although dipolar and multipolar dynamos exhibit approximately the same scaling exponents, there is an offset in the scaling pre-factors for velocity and magnetic field strength. We argue that the offset can be attributed to the differences in the zonal flow contribution between dipolar and multipolar dynamos.Comment: 10 pages, 9 figures, 1 table. To appear in ICARU

Interpretation of Solar Magnetic Field Strength Observations

This study based on longitudinal Zeeman effect magnetograms and spectral line scans investigates the dependence of solar surface magnetic fields on the spectral line used and the way the line is sampled in order to estimate the magnetic flux emerging above the solar atmosphere and penetrating to the corona from magnetograms of the Mt. Wilson 150-foot tower synoptic program (MWO). We have compared the synoptic program \lambda5250\AA line of Fe I to the line of Fe I at \lambda5233\AA since this latter line has a broad shape with a profile that is nearly linear over a large portion of its wings. The present study uses five pairs of sampling points on the $\lambda5233$\AA line. We recommend adoption of the field determined with a line bisector method with a sampling point as close as possible to the line core as the best estimate of the emergent photospheric flux. The combination of the line profile measurements and the cross-correlation of fields measured simultaneously with \lambda5250\AA and \lambda5233\AA yields a formula for the scale factor 1/\delta that multiplies the MWO synoptic magnetic fields. The new calibration shows that magnetic fields measured by the MDI system on the SOHO spacecraft are equal to 0.619+/-0.018 times the true value at a center-to-limb position 30 deg. Berger and Lites (2003) found this factor to be 0.64+/-0.013 based on a comparison the the Advanced Stokes Polarimeter.Comment: Accepted by Solar Physic

Formation of starspots in self-consistent global dynamo models: Polar spots on cool stars

Observations of cool stars reveal dark spot-like features on their surfaces. Compared to sunspots, starspots can be bigger or cover a larger fraction of the stellar surface. While sunspots appear only at low latitudes, starspots are also found in polar regions, in particular on rapidly rotating stars. Sunspots are believed to result from the eruption of magnetic flux-tubes rising from the deep interior of the Sun. The strong magnetic field locally reduces convective heat transport to the solar surface. Such flux-tube models have also been invoked to explain starspot properties. However, these models use several simplifications and so far the generation of either sunspots or starspots has not been demonstrated in a self-consistent simulation of stellar magnetic convection. Here we show that direct numerical simulations of a distributed dynamo operating in a density-stratified rotating spherical shell can spontaneously generate cool spots. Convection in the interior of the model produces a large scale magnetic field which interacts with near surface granular convection leading to strong concentrations of magnetic flux and formation of starspots. Prerequisites for the formation of sizeable high-latitude spots in the model are sufficiently strong density stratification and rapid rotation. Our model presents an alternate mechanism for starspot formation by distributed dynamo action.Comment: 14 pages; Important additions in version 2; To appear in A&

Predominant utilization of V beta 8+ T cell receptor genes in the H-2Ld- restricted cytotoxic T cell response against the immediate-early protein pp89 of the murine cytomegalovirus

Cytotoxic T cell responses to the murine Cytomegalovirus (MCMV) were elicited in BALB/c mice (H-2d) by infectious virus. Eight days after infection, MCMV-primed local lymph node T cells were either depleted for T cells expressing a V beta 8+ TCR or separated into V beta 8+ and V beta 8- subpopulations by a cell sorter using the mAb F23.1. T cells were then expanded in vitro under limiting dilution conditions in the presence of IL-2 and in the absence of viral Ag to avoid selection by Ag in vitro. Frequencies of CTL precursors specific for the Immediate- Early-Ag 1 of MCMV and restricted to H-2Ld were determined. L cells of the endogenous haplotype H-2k cotransfected with the genes for MCMV-IE 1 and H-2Ld were used as target cells. Detection of a CTL response required previous priming of the animals by infection in vivo (less than 1/10(6) for nonimmunized animals). In primed animals CTL precursors of this specificity and restriction were three to fivefold more frequent in the V beta 8+ population (1/9.900 to 1/22.300) than in the V beta 8- population (1/57.000 to 1/87.200). Control experiments showed that frequencies were not influenced by the treatment with the anti-V beta 8-antibody and the fluorescein-labeled anti-Ig itself. V beta 8+ and V beta 8- T cells did not reveal any frequency differences when several other responses were determined (TNP-specific self- restricted CTL precursor; Th cells specific for keyhole limpet hemocyanin or Listeria monocytogenes)

Kinematic analysis of handwriting movements in patients with Alzheimer's disease, mild cognitive impairment, depression and healthy subjects

A variety of studies have demonstrated that motor disorders, parkinsonism and extrapyramidal motor symptoms (EPMS) are common in patients with Alzheimer's disease (AD). Several studies have reported an association of EPMS with severity, progression and poor prognosis of AD. The majority of these studies used clinical assessments for the rating of EPMS. In this study, kinematic handwriting analysis was used to quantify differences in fine hand motor function in patients with probable AD and mild cognitive impairment (MCl, as an assumed initial stage of AD) compared to depressed patients and healthy controls. Both patients with MCl and patients with probable AD exhibited loss of fine motor performance. Movements of AD patients were significantly less regular than those of healthy controls. Copyright (C) 2003 S. Karger AG, Basel

Characteristics of Magnetohydrodynamic Oscillations Observed with Michelson Doppler Imager

We report on the spatial distribution of magnetogram oscillatory power and phase angles between velocity and magnetogram signals as observed with the Michelson Doppler Imager. The dataset is 151.25 arcsec times 151.25 arcsec containing sunspot from Dec 2, 1997 with a temporal sampling interval of 60 seconds and spatial sampling of 0.605 arcsec. Simultaneously observed continuum intensity and surface velocity accompany the magnetic information. We focus on three frequency regimes: 0.5-1.0, 3.0-3.5 and 5.5-6.0 mHz corresponding roughly to timescales of magnetic evolution, p-modes and the 3 minute resonant sunspot oscillation. Significant low frequency magnetogram power is found in lower flux pixels, 100-300 Gauss, in a striking ring with filamentary structure surrounding sunspot. Five minute magnetogram power peaks in extended regions of flux 600-800 Gauss. The 3 minute oscillation is observed in sunspot umbra in pixels whose flux measures 1300-1500 Gauss. Phase angles of approximately -90 degrees between velocity and magnetic flux in the 3.0-3.5 and 5.5-6.0 mHz regimes are found in regions of significant cross amplitude.Comment: 4 Pages, 4 Figures -- For better Figure files see: http://www.astro.ucla.edu/~norton/pub_list.htm

Solar Seismology from Space. a Conference at Snowmass, Colorado

The quality of the ground based observing environment suffers from several degrading factors: diurnal interruptions and thermal variations, atmospheric seeing and transparency fluctuations and adverse weather interruptions are among the chief difficulties. The limited fraction of the solar surface observable from only one vantage point is also a potential limitation to the quality of the data available without going to space. Primary conference goals were to discuss in depth the scientific return from current observations and analyses of solar oscillations, to discuss the instrumental and site requirements for realizing the full potential of the seismic analysis method, and to help bring new workers into the field by collecting and summarizing the key background theory. At the conclusion of the conference there was a clear consensus that ground based observation would not be able to provide data of the quality required to permit a substantial analysis of the solar convection zone dynamics or to permit a full deduction of the solar interior structure