Fluxtube model atmospheres and Stokes V zero-crossing wavelengths

First results of the inversion of Stokes I and V profiles from plage regions near disk center are presented. Both low and high spatial resolution spectra of FeI 6301.5 and FeI 6302.5 A obtained with the Advanced Stokes Polarimeter (ASP) have been considered for analysis. The thin flux tube approximation, implemented in an LTE inversion code based on response functions, is used to describe unresolved magnetic elements. The code allows the simultaneous and consistent inference of all atmospheric quantities determining the radiative transfer with the sole assumption of hydrostatic equilibrium. By considering velocity gradients within the tubes we are able to match the full ASP Stokes profiles. The magnetic atmospheres derived from the inversion are characterized by the absence of significant motions in high layers and strong velocity gradients in deeper layers. These are essential to reproduce the asymmetries of the observed profiles. Our scenario predicts a shift of the Stokes V zero-crossing wavelengths which is indeed present in observations made with the Fourier Transform Spectrometer.Comment: To appear in ApJ Letters (1997) (in press

Reconstruction of solar UV irradiance since 1974

Variations of the solar UV irradiance are an important driver of chemical and physical processes in the Earth's upper atmosphere and may also influence global climate. Here we reconstruct solar UV irradiance in the range 115-400 nm over the period 1974-2007 by making use of the recently developed empirical extension of the SATIRE models employing SUSIM data. The evolution of the solar photospheric magnetic flux, which is a central input to the model, is described by the magnetograms and continuum images recorded at the Kitt Peak National Solar Observatory between 1974 and 2003 and by the MDI instrument on SoHO since 1996. The reconstruction extends the available observational record by 1.5 solar cycles. The reconstructed Ly-alpha irradiance agrees well with the composite time series by Woods et al (2000). The amplitude of the irradiance variations grows with decreasing wavelength and in the wavelength regions of special interest for studies of the Earth's climate (Ly-alpha and oxygen absorption continuum and bands between 130 and 350 nm) is one to two orders of magnitude stronger than in the visible or if integrated over all wavelengths (total solar irradiance)

Measuring the Wilson depression of sunspots using the divergence-free condition of the magnetic field vector

Context: The Wilson depression is the difference in geometric height of unit continuum optical depth between the sunspot umbra and the quiet Sun. Measuring the Wilson depression is important for understanding the geometry of sunspots. Current methods suffer from systematic effects or need to make assumptions on the geometry of the magnetic field. This leads to large systematic uncertainties of the derived Wilson depressions. Aims: We aim at developing a robust method for deriving the Wilson depression that only requires the information about the magnetic field that is accessible from spectropolarimetry, and that does not rely on assumptions on the geometry of sunspots or on their magnetic field. Methods: Our method is based on minimizing the divergence of the magnetic field vector derived from spectropolarimetric observations. We focus on large spatial scales only in order to reduce the number of free parameters. Results: We test the performance of our method using synthetic Hinode data derived from two sunspot simulations. We find that the maximum and the umbral averaged Wilson depression for both spots determined with our method typically lies within 100 km of the true value obtained from the simulations. In addition, we apply the method to Hinode observations of a sunspot. The derived Wilson depression (about 600 km) is consistent with results typically obtained from the Wilson effect. We also find that the Wilson depression obtained from using horizontal force balance gives 110 - 180 km smaller Wilson depressions than both, what we find and what we deduce directly from the simulations. This suggests that the magnetic pressure and the magnetic curvature force contribute to the Wilson depression by a similar amount.Comment: 12 pages, 8 figures. Accepted for publication in Astronomy & Astrophysic

On the intensity contrast of solar photospheric faculae and network elements

Sunspots, faculae and the magnetic network contribute to solar irradiance variations. The contribution due to faculae and the network is of basic importance, but suffers from considerable uncertainty. We determine the contrasts of active region faculae and the network, both as a function of heliocentric angle and magnetogram signal. To achieve this, we analyze near-simultaneous full disk images of photospheric continuum intensity and line-of-sight magnetic field provided by the Michelson Doppler Interferometer (MDI) on board the SOHO spacecraft. Starting from the surface distribution of the solar magnetic field we first construct a mask, which is then used to determine the brightness of magnetic features, and the relatively field-free part of the photosphere separately. By sorting the magnetogram signal into different bins we are able to distinguish between the contrasts of different concentrations of magnetic field. We find that the contrasts of active region faculae (large magnetogram signal) and the network (small signal) exhibit a very different CLV, showing that the populations of magnetic flux tubes are different. This implies that these elements need to be treated separately when reconstructing variations of the total solar irradiance with high precision. We have obtained an analytical expression for the contrast of photospheric magnetic features as a function of both position on the disk and magnetic field strength, by performing a 2-dimensional fit to the observations.Comment: 12 pages, 8 figures, uses aa.cl

Electromagnetic Analysis of Solenoid Coil in ANSYS and IES Software : Case Study

The aim of this paper is to get theory technical knowledge of designing a electromagnetic solenoid coil and ogy of verifying induced current in solenoid coil by using ANSYS Software and IES software. For this purpose a 0.3 T coil has been designed with a Poloidal shaped 1500 turn outer coil of 200 cm diameter. To verify such induced current analysis is a challenging task, theoretically which can be equally calculated by a FINITE ELEMENT ANALYSIS package and IES (Integrated Engineering Software) , so a same dimension, assembly and has been modeled and meshed in ANSYS 11.0 FEA package and IES (integrated engineering software) with same load data as given in the software. Theoretical and Simulation results have been compared

Experiment and simulation for Induced current analysis in Outer single turn coil with pulsed electromagnetic Central solenoid air core coil

This paper present idea about the knowledge of designing a pulsed electromagnetic central solenoid air core coil and get methodology of verifying induced current in the modified assembly. 2 T coil has been designed with a toroidal shaped single turn outer coil of 12 cm diameter for this experiment. A 1 KV 640 ?sec pulse has been given to the designed 2 T coil because of which pulsed current was induced in the outer single turn coil. To verify such pulsed induced current analysis is a difficult task, theoretically which can be equally calculated by a FINITE ELEMENT ANALYSIS package, so a same modified assembly has been modeled and meshed in ANSYS 11.0 FEA package with same load data as given in the practical. Theoretical and practical results have been Validated. DOI: 10.17762/ijritcc2321-8169.15083

Design the Pulsed Power Supply for Plasma Reaserch Experiment using Pulse Forming Network

The power supply is very important in the plasma research project. This paper is try to get theory technical knowledge of designing a 1.5 KV Pulsed power supply for plasma research experiment. Different capacitor bank is used for pulsed power supply which is discharged into coils. For designing the pulsed power supply, design of voltage multiplier, Triggering circuit for Thyristor, 15 V power supply circuit are required for experiment of pulsed electromagnetic analysis for future plasma experiments. 15 V Power supply is required for triggering circuit and DC current transducer.[7],[8].using this 1.5 kv pulsed power supply verified the experiment on two coils. Theoretical and Simulation results have been validated