Magnetic Flux Transport at the Solar Surface

After emerging to the solar surface, the Sun's magnetic field displays a complex and intricate evolution. The evolution of the surface field is important for several reasons. One is that the surface field, and its dynamics, sets the boundary condition for the coronal and heliospheric magnetic fields. Another is that the surface evolution gives us insight into the dynamo process. In particular, it plays an essential role in the Babcock-Leighton model of the solar dynamo. Describing this evolution is the aim of the surface flux transport model. The model starts from the emergence of magnetic bipoles. Thereafter, the model is based on the induction equation and the fact that after emergence the magnetic field is observed to evolve as if it were purely radial. The induction equation then describes how the surface flows -- differential rotation, meridional circulation, granular, supergranular flows, and active region inflows -- determine the evolution of the field (now taken to be purely radial). In this paper, we review the modeling of the various processes that determine the evolution of the surface field. We restrict our attention to their role in the surface flux transport model. We also discuss the success of the model and some of the results that have been obtained using this model.Comment: 39 pages, 15 figures, accepted for publication in Space Sci. Re

Geomagnetic Activity Indicates Large Amplitude for Sunspot Cycle 24

The level of geomagnetic activity near the time of solar activity minimum has been shown to be a reliable indicator for the amplitude of the following solar activity maximum. The geomagnetic activity index aa can be split into two components: one associated with solar flares, prominence eruptions, and coronal mass ejections which follows the solar activity cycle and a second component associated with recurrent high speed solar wind streams which is out of phase with the solar activity cycle. This second component often peaks before solar activity minimum and has been one of the most reliable indicators for the amplitude of the following maximum. The size of the recent maximum in this second component indicates that solar activity cycle 24 will be much higher than average - similar in size to cycles 21 and 22

A Standard Law for the Equatorward Drift of the Sunspot Zones

The latitudinal location of the sunspot zones in each hemisphere is determined by calculating the centroid position of sunspot areas for each solar rotation from May 1874 to June 2011. When these centroid positions are plotted and analyzed as functions of time from each sunspot cycle maximum there appears to be systematic differences in the positions and equatorward drift rates as a function of sunspot cycle amplitude. If, instead, these centroid positions are plotted and analyzed as functions of time from each sunspot cycle minimum then most of the differences in the positions and equatorward drift rates disappear. The differences that remain disappear entirely if curve fitting is used to determine the starting times (which vary by as much as 8 months from the times of minima). The sunspot zone latitudes and equatorward drift measured relative to this starting time follow a standard path for all cycles with no dependence upon cycle strength or hemispheric dominance. Although Cycle 23 was peculiar in its length and the strength of the polar fields it produced, it too shows no significant variation from this standard. This standard law, and the lack of variation with sunspot cycle characteristics, is consistent with Dynamo Wave mechanisms but not consistent with current Flux Transport Dynamo models for the equatorward drift of the sunspot zones.Comment: 12 pages, 7 color figure

Codling moth (Lepid.: Tortricidae): Disruption of sexual communication with an antipheromone [(E,E)-8,1O-dodecadien-1-O1 acetate]

When broadcast applications of [E, E]-8,10-dodecadien-1l-ol acetate an antipheromone of the codling moth, <i>Cydia pomonella</i> (L.), were made to apple or pear orchards, the catch of male codling moths was reduced in traps baited with either synthetic sex pheromone or virgin females. When the antipheromone, at a rate of 11.25g AI/0.4 ha was applied broadcast to pear trees using a ground dispenser, male response to pheromone- or female-baited traps was completely inhibited for 9 days with no significant reduction thereafter. Based on these and earlier results, it is concluded that (E,E)-8,10-dodecadien-1l-o1 acetate inhibits male codling moth response, whether the sources are placed in close proximity to the attractive agent or distributed in a broadcast application. These results contradict previous arguments that antipheromones as a group may not be effective in the field when used to permeate large volumes of air

Measurements of the unsteady flow field within the stator row of a transonic axial-flow fan. 1: Measurement and analysis technique

This two-part paper presents laser anemometer measurements of the unsteady velocity field within the stator row of a transonic axial-flow fan. The objective is to provide additional insight into unsteady blade-row interactions within high speed compressors which affect stage efficiency, energy transfer, and other design considerations. Part 1 describes the measurement and analysis techniques used for resolving the unsteady flow field features. The ensemble-average and variance of the measured velocities are used to identify the rotor wake generated and unresolved unsteadiness, respectively. (Rotor wake generated unsteadiness refers to the unsteadiness generated by the rotor wake velocity deficit and the term unresolved unsteadiness refers to all remaining contributions to unsteadiness such as vortex shedding, turbulence, mass flow fluctuations, etc.). A procedure for calculating auto and cross correlations of the rotor wake generated and unresolved unsteady velocity fluctuations is described. These unsteady-velocity correlations have significance since they also result from a decomposition of the Navier-Stokes equations. This decomposition of the Navier-Stokes equations resulting in the velocity correlations used to describe the unsteady velocity field will also be outlined in this paper

Carotene Content of Native Nebraska Grasses

The carotene content of twenty-four grasses native to Nebraska were determined at approximately monthly intervals from June to November. While the carotene concentration of most of the grasses was moderately high during the growing season, it declined to a rather low point by late November. With the exception of Switchgrass, Hairy Grama, Little Bluestem and Prairie Dropseed, all of the grasses contained enough carotene to supply the needs of range cattle until late November. However, only eighteen of the grasses still contained enough carotene by the latter part of September to furnish the carotene required by dairy cows. Even as early as July the Northern reedgrass, Buffalo grass, Bluejoint and Lovegrass were unsatisfactory as a source of carotene for dairy cows. While the carotene values observed during the periods of greatest concentration varied from 511.6 ppm (Sandhill bluestem) to 122.6 ppm (Northern reedgrass), these values ranged from 60.7 ppm (June grass) to 1.6 ppm (Little bluestem) during the periods of lowest concentration

Requirements Study for System Implementation of an Atmospheric Laser Propagation Experiment Program, Volume II

Program planning, ground support and airborne equipment for laser space communication syste

Solar Multi-Scale Convection and Rotation Gradients Studied in Shallow Spherical Shells

The differential rotation of the sun, as deduced from helioseismology, exhibits a prominent radial shear layer near the top of the convection zone wherein negative radial gradients of angular velocity are evident in the low- and mid-latitude regions spanning the outer 5% of the solar radius. Supergranulation and related scales of turbulent convection are likely to play a significant role in the maintenance of such radial gradients, and may influence dynamics on a global scale in ways that are not yet understood. To investigate such dynamics, we have constructed a series of three-dimensional numerical simulations of turbulent compressible convection within spherical shells, dealing with shallow domains to make such modeling computationally tractable. These simulations are the first models of solar convection in a spherical geometry that can explicitly resolve both the largest dynamical scales of the system (of order the solar radius) as well as smaller-scale convective overturning motions comparable in size to solar supergranulation (20--40 Mm). We find that convection within these simulations spans a large range of horizontal scales, and that the radial angular velocity gradient in these models is typically negative, especially in low- and mid-latitude regions. Analyses of the angular momentum transport indicates that such gradients are maintained by Reynolds stresses associated with the convection, transporting angular momentum inward to balance the outward transport achieved by viscous diffusion and large-scale flows in the meridional plane. We suggest that similar mechanisms associated with smaller-scale convection in the sun may contribute to the maintenance of the observed radial shear layer located immediately below the solar photosphere.Comment: 45 pages, 17 figures, ApJ in press. A preprint of paper with hi-res figures can be found at http://www-lcd.colorado.edu/~derosa/modelling/modelling.htm

Codling moth (Lepid.: Tortricidae): Disruption of sexual communication with an antipheromone [(E,E)-8,1O-dodecadien-1-O1 acetate]

When broadcast applications of [E, E]-8,10-dodecadien-1l-ol acetate an antipheromone of the codling moth, Cydia pomonella (L.), were made to apple or pear orchards, the catch of male codling moths was reduced in traps baited with either synthetic sex pheromone or virgin females. When the antipheromone, at a rate of 11.25g AI/0.4 ha was applied broadcast to pear trees using a ground dispenser, male response to pheromone- or female-baited traps was completely inhibited for 9 days with no significant reduction thereafter. Based on these and earlier results, it is concluded that (E,E)-8,10-dodecadien-1l-o1 acetate inhibits male codling moth response, whether the sources are placed in close proximity to the attractive agent or distributed in a broadcast application. These results contradict previous arguments that antipheromones as a group may not be effective in the field when used to permeate large volumes of air