Solar activity forecast with a dynamo model

Although systematic measurements of the solar polar magnetic field exist only from mid 1970s, other proxies can be used to infer the polar field at earlier times. The observational data indicate a strong correlation between the polar field at a sunspot minimum and the strength of the next cycle, although the strength of the cycle is not correlated well with the polar field produced at its end. This suggests that the Babcock Leighton mechanism of poloidal field generation from decaying sunspots involves randomness, whereas the other aspects of the dynamo process must be reasonably ordered and deterministic. Only if the magnetic diffusivity within the convection zone is assumed to be high, we can explain the correlation between the polar field at a minimum and the next cycle. We give several independent arguments that the diffusivity must be of this order. In a dynamo model with diffusivity like this, the poloidal field generated at the mid latitudes is advected toward the poles by the meridional circulation and simultaneously diffuses towards the tachocline, where the toroidal field for the next cycle is produced. To model actual solar cycles with a dynamo model having such high diffusivity, we have to feed the observational data of the poloidal field at the minimum into the theoretical model. We develop a method of doing this in a systematic way. Our model predicts that cycle 24 will be a very weak cycle. Hemispheric asymmetry of solar activity is also calculated with our model and compared with observational data.Comment: 17 pages, 18 figures, submitted to MNRA

Elasticity of DNA and the effect of Dendrimer Binding

Negatively charged DNA can be compacted by positively charged dendrimers and the degree of compaction is a delicate balance between the strength of the electrostatic interaction and the elasticity of DNA. We report various elastic properties of short double stranded DNA (dsDNA) and the effect of dendrimer binding using fully atomistic molecular dynamics and numerical simulations. In equilibrium at room temperature, the contour length distribution P(L) and end-to-end distance distribution P(R) are nearly Gaussian, the former gives an estimate of the stretch modulus {\gamma}_1 of dsDNA in quantitative agreement with the literature value. The bend angle distribution P({\theta}) of the dsDNA also has a Gaussian form and allows to extract a persistence length, L_p of 43 nm. When the dsDNA is compacted by positively charged dendrimer, the stretch modulus stays invariant but the effective bending rigidity estimated from the end-to-end distance distribution decreases dramatically due to backbone charge neutralization of dsDNA by dendrimer. We support our observations with numerical solutions of the worm-like-chain (WLC) model as well as using non-equilibrium dsDNA stretching simulations. These results are helpful in understanding the dsDNA elasticity at short length scales as well as how the elasticity is modulated when dsDNA binds to a charged object such as a dendrimer or protein.Comment: 21 pages, 5 figure

The Waldmeier Effect in Sunspot Cycles

We discuss two aspects of the Waldmeier Effect, namely (1) the rise times of sunspot cycles are anti-correlated to their strengths (WE1) and (2) the rates of rise of the cycles are correlated to their strengths (WE2). From analysis of four different data sets we conclude that both WE1 and WE2 exist in all the data sets. We study these effects theoretically by introducing suitable stochastic fluctuations in our regular solar dynamo model.Comment: Magnetic Coupling between the Interior and Atmosphere of the Sun; Astrophysics and Space Science Proceeding

Reply to comments of Dikpati et al

We present here our response to Dikpati et al.'s criticism of our recent solar dynamo model.Comment: 8 pages, 2 figure

Tungsten Heavy Alloys with Two phase Matrix

WNiCo alloys subjected to a two-stage or cyclic heat treatment develop a unique microstructure wherein apart from tungsten grains and matrix phase, fine tungsten precipitates are distributed in the matrix. This is unlike conventional heavy alloys such as WNiFe and WNiFeCo where the matrix is single phase without any secondary microstructural features. The purpose of developing a two-phase matrix is to realise superior mechanical properties compared to conventional alloys, especially strength with comparable or superior elongation and impact toughness. This advantage has rendered WNiCo alloys (with two-phase matrix) suitable candidates for advanced kinetic energy penetrators. The present study focusses on processing 92W-5Ni-3Co alloy using cyclic heat treatment and optimisation of parameters involved in cyclic heat treatment as well as subsequent vacuum heat treatment. Any refinement in processing parameters will help in improving the mechanical properties given the fact that processing parameters, microstructural features and mechanical properties are strongly interdependent in the case of tungsten heavy alloys

Survey of incidence of various surface defects in goat and sheep skin in Madras

23,429 goat skins and 37,026 sheep skins were examined to find out the incidence of various surface defects in them. 33.44 percent of goat skins and 14.6 per cent of sheep skins were found to be affected in quality. Major defects common to both goat and sheep skins were abscess, fire-mark and psoroptosis. In addition to the above common defects demodecosis and sheep pox appreciably deteriorated the quality of goat and sheep skins respectively. Seasonal variation in the incidence of the major defects were also studied