An International Research Journal

AJP

SSN : 0971 - 3093

Vol  16, No. 1, January-March, 2007


Asian Journal of Physics                                                                                                          Vol. 16, No 1 (2007) 1-9


Variation in area and intensity of the solar chromospheric network elements

and their contribution to UV irradiance variability


R Kariyappa, B A Varghese and L Dame*

Indian Institute ofAstrophysics, Bangalore 560 034, India

*Service d'Aeronomie du CNRS, BP # 3, 91371 Verrieres-le-Buisson Cedex, France

rkari@iiap.res.in

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The Sun is the primary source of energy responsible for governing both the weather and climate of Earth. For that reason alone one would expect that changes in the amount and type of energy Earth received from the Sun could alter weather and climate on the Earth. The variations in the UV irradiance are produced by surface manifestation of solar magnetic activity. Considering the variations in the solar UV flux may cause significant changes in the Earth's climate, understanding the physical origin of UV irradiance changes is an extremely important issue in Solar and Space Physics.

We have segregated the (i) plages, (ii) magnetic network, and (iii) intranetwork + the background regions from the CaII  K spectroheliograms of 1980 and 1992, observed at the National Solar Observatory at Sacramento Peak, using their histograms taken for the full-disk. The different parameters like the intensity and area of the chromospheric features, the full-disk intensity (spatial K index), and the full width at half maximum (FWHM) of the histograms [1], have been derived from the images. The spatial K index, FWHM, and the intensity of various features have been compared to the UV irradiance measured in the MgII h and k lines by the Nimbus7 and NOAA9 satellites and it has been found that they are correlated with the MgII h and k c/w ratio. We established, for the first time, from the results of 1992 images [1] and of 1980 that the FWHM can be used as a good index for measuring and describing the chromospheric activity in the K-line. The results of both 1980 and 1992 images show an anticorrelation between the intensity and area of the network elements, which confirm the earlier findings derived entirely from different data set from Kodaikanal CaII K spectroheliograms analyzed for the center of the solar disc in a quiet regions for a longer time interval of 1957 to 1983 [2]. During solar minimum the network is fainter but covers a larger area than during solar maximum. These results suggest that the variations in both the intensity and area of the various chromospheric features have to be taken into account in irradiance models.

Keywords: Chromospheric features, Spatial K index, full width at half maximum (FWHM)

© Anita Publications. All rights reserved.

Total Refs: 24

References

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Asian Journal of Physics                                                                                                                   Vol 16, No 1 (2007) 11-16


The study of Raman, FT-IR reflection and transmission spectroscopy of acidic
α-LiIO3 crystal and its birefringence properties


R Malekfar and M Rezvani Jalal

Physics Department

Faculty of Basic Sciences, Tarbiat Modarres University, P.O. Box 14115-175, Tehran, I. R. Iran

Malekfar@Modares.ac.ir; Rasoul_Malekfar@yahoo.com.au

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α-LiIO3 crystal has found wide spread applications in second harmonic generation, nonlinear optics, one dimensional ionic conductors and acousto-optic modulators especially in the visible and near infrared region. This crystal was grown from acidic saturated solution of α-LiIO3 salt by the method of slow evaporation of isothermal solution with about 1 × 1 2 cm3 dimensions. In the visible region this crystal is transparent and is a negative uniaxial crystal. The Raman, FT-IR reflection and transmission spectra of this crystal from both surfaces parallel and perpendicular to the crystal optical axis  were obtained. With the help of Kramers - Kronig relations of reflection the ordinary and extra- ordinary refractive indices in the 400 - 4000 cm-1 region were calculated and it was shown that in this range, and particularly in the 700 -900 cm-1 region, this crystal converts to a positive uniaxial crystal. The imaginary part of the refractive index and the electrical susceptibilities of the crystal in the mentioned directions and in the 400 - 1000 cm-1  region were also calculated.

Keywords: LiIO3 crystal, Raman and  FT-IR reflection, Kramers - Kronig relations

©Anita Publications. All rights reserved.

Total Refs: 10

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