On the transit of Venus 2012: Method of computation for prediction of contact timings

Transit of Venus over the solar disc is an extremely rare event. The phenomenon occurred last time on June 8, 2004 when the entire event was visible from all parts of India. Another Transit of Venus is going to occur on June 6, 2012, though the entire event will not be visible from India. The Positional Astronomy Centre publishes data on Transit of Mercury and Venus in its annual publication ‘The Indian Astronomical Ephemeris’. In this paper an attempt has been made to provide documentation on the methodology for computation of contact timings of the event. Using the methodology, the geocentric contact timings and local contact timings for important places of India for the event of Transit of Venus of June 6, 2012 have been predicted. The result thus obtained for different geocentric phases of the event has been compared with the predicted timings published by The Nautical Almanac Office, United States Naval Observatory and NASA.

Analyses of Early Sunspot Records by Jean Tarde (1615 – 1617) and Jan Smogulecki (1621 – 1625)

Jean Tarde and Jan Smogulecki carried out sunspot observations in the 1610s and 1620s at the dawn of the telescopic era. We analysed their original observational records to revise their sunspot-group numbers in the existing database. In this study, we provide a new counting as a basis for future scientific discussions. Furthermore, we compared Smogulecki’s sunspot observations with those of Scheiner and Schönberger on the same observation days. We also detected a big sunspot group on 2 – 3 February 1622 in Smogulecki’s sunspot drawings and estimated its area to be approximately 1600 millionths of the solar disc. In addition, we measured the sunspot positions in Tarde’s and Smogulecki’s sunspot drawings to construct a butterfly diagram for this early period.

Psychophysical study of the moon illusion in paintings and landscape photos

The moon illusion is a visual deception when people perceive the angular diameter of the Moon/Sun near the horizon larger than that of the one higher in the sky. Some theories have been proposed to explain this illusion, but not any is generally accepted. Although several psychophysical experiments have been performed to study different aspects of the moon illusion, their results have sometimes contradicted each other. Artists frequently display(ed) the Moon/Sun in their paintings. If the Moon/Sun appears near the horizon, its painted disc is often exaggeratedly large. How great is the magnitude of moon illusion of painters? How different are the size enlargements of depicted lunar/solar discs? To answer these questions, we measured these magnitudes on 100 paintings collected from the period of 1534–2017. In psychophysical experiments, we also investigated the moon illusion of 10 test persons who had to estimate the size of the lunar/solar disc on 100 paintings and 100 landscape photographs from which the Moon/Sun was retouched. Compared to the lunar/solar disc calculated from reference distances estimated by test persons in paintings, painters overestimated the Moon's size on average Q = 2.1 ± 1.6 times, while the Sun was painted Q = 1.8 ± 1.2 times larger than the real one, where Q = r painted / r real is the ratio of the radii of painted ( r painted ) and real ( r real ) Moons/Suns. In landscape photos, test persons overestimated the Moon's size Q = 1.6 ± 0.4 times and the Sun was assumed Q = 1.7 ± 0.5 times larger than in reality, where Q = r test / r real is the ratio of the radius r test estimated by the test persons and the real radius r real of Moons/Suns. The majority of the magnitude of moon illusion Q = 1.6, 1.7, 1.8, 2.1, 2.8, 2.9 measured by us are larger than the Q -values 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.8 obtained in previous psychophysical experiments due to methodological differences.

Filling Factors of Sunspots in SODISM Images

The calculated filling factors (FFs) for a feature reflect the fraction of the solar disc covered by that feature, and the assignment of reference synthetic spectra. In this paper, the FFs, specified as a function of radial position on the solar disc, are computed for each image in a tabular form. The filling factor (FF) is an important parameter and is defined as the fraction of area in a pixel covered with the magnetic field, whereas the rest of the area in the pixel is field-free. However, this does not provide extensive information about the experiments conducted on tens or hundreds of such images. This is the first time that filling factors for SODISM images have been catalogued in tabular formation. This paper presents a new method that provides the means to detect sunspots on full-disk solar images recorded by the Solar Diameter Imager and Surface Mapper (SODISM) on the PICARD satellite. The method is a totally automated detection process that achieves a sunspot recognition rate of 97.6%. The number of sunspots detected by this method strongly agrees with the NOAA catalogue. The sunspot areas calculated by this method have a 99% correlation with SOHO over the same period, and thus help to calculate the filling factor for wavelength (W.L.) 607nm.

A new automated solar disc for water disinfection by pasteurization

A new automated Solar Water Pasteurization Disc of double reflection of 3.8 and 1.3 m in diameter for the first and second reflectors has been erected and tested for performing microbiological disinfection of water in a simple, efficient, and continuous treatment in Brazil.

Comparison of theoretical and observed Ca II 8542 Stokes profiles in quiet regions at the centre of the solar disc

Context. Interpreting the Stokes profiles observed in quiet regions of the solar chromosphere is a challenging task. The Stokes Q and U profiles are dominated by the scattering polarisation and the Hanle effect, and these processes can only be correctly quantified if 3D radiative transfer effects are taken into account. Forward-modelling of the intensity and polarisation of spectral lines using a 3D model atmosphere is a suitable approach in order to statistically compare the theoretical and observed line profiles. Aims. Our aim is to present novel observations of the Ca II 8542 Å line profiles in a quiet region at the centre of the solar disc and to quantitatively compare them with the theoretical Stokes profiles obtained by solving the problem of the generation and transfer of polarised radiation in a 3D model atmosphere. We aim at estimating the reliability of the 3D model atmosphere, excluding its known lack of dynamics and/or insufficient density, using not only the line intensity but the full vector of Stokes parameters. Methods. We used data obtained with the ZIMPOL instrument at the Istituto Ricerche Solari Locarno (IRSOL) and compared the observations with the theoretical profiles computed with the PORTA radiative transfer code, using as solar model atmosphere a 3D snapshot taken from a radiation-magnetohydrodynamics simulation. The synthetic profiles were degraded to match the instrument and observing conditions. Results. The degraded theoretical profiles of the Ca II 8542 line are qualitatively similar to the observed ones. We confirm that there is a fundamental difference in the widths of all Stokes profiles: the observed lines are wider than the theoretical lines. We find that the amplitudes of the observed profiles are larger than those of the theoretical ones, which suggests that the symmetry breaking effects in the solar chromosphere are stronger than in the model atmosphere. This means that the isosurfaces of temperature, velocity, and magnetic field strength and orientation are more corrugated in the solar chromosphere than in the currently available 3D radiation-magnetohydrodynamics simulation.

Relationship between plasma flow Doppler velocities and magnetic field parameters during the appearance of active regions at the solar photospheric level

Using data obtained with the Michelson Doppler Imager (MDI) onboard the Solar and Heliospheric Observatory (SOHO), we have conducted a statistical study of the relationship between plasma flow Doppler velocities and magnetic field parameters during the appearance of active regions at the solar photospheric level. We have examined 224 emerging active regions having different spatial scales and positions on the solar disc. The following relationships have been analysed: 1) those between the negative Doppler velocities and the position of active regions emerging on the solar disc; 2) those between the negative and positive Doppler velocities and the magnetic field parameters in the ac-tive regions emerging near the solar disc centre (the vertical component); 3) those between the negative and positive Doppler velocities and the magnetic field pa-rameters in the active regions emerging near the limb (the horizontal component); 4) those between the mag-netic flux growth rate and the strength of emerging magnetic fields; 5) those between the Doppler velocities and the magnetic field parameters during the first hours after the appearance of active regions with the total unsigned magnetic flux at the peak of their development.

Response of High Latitude Ionospheric TEC to Enhanced Radiation Fluxes during the Major Solar Flare Events

We have investigated the response of ionosphere to major solar flare events that occurred during 1998 to 2011. The effect of enhanced radiation fluxes in the X-ray and EUV band on the GPS derived Total Electron Content (TEC) is examined. The data of X-ray flux from Geostationary Operational Environment Satellite (GOES) and EUV flux from Solar EUV Monitor (SEM) onboard SOHO spacecraft were correlated with the Total Electron Content (TEC) data of a high latitude station, Davis (68.570S, 77.960E). We found that peak intensities of X-ray and EUV flux correlate very well with the peak values of TEC. We also studied the correlation of peak enhancement of these fluxes with the peak enhancement of TEC and found that peak enhancement of these fluxes correlate highly with the peak enhancement of TEC than with the peak values themselves. It is also found that correlation is extraordinarily improved when these fluxes are multiplied by Cos(CMD) where CMD is Central Meridian Distance on the solar disc, thereby showing that the location of flares on the solar disc plays an important role while investigating the ionospheric influences of solar flares. Keywords: Ionosphere; TEC; CMD; Solar Flare. © 2014 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved. doi: http://dx.doi.org/10.3329/jsr.v6i1.14100 J. Sci. Res. 6 (1), 43-49 (2014)