%0 Journal Article
%T Preliminary Results on Irradiance Measurements from Lyra and Swap
%A S. T. Kumara
%A R. Kariyappa
%A M. Dominique
%A D. Berghmans
%A L. Dam¨¦
%A J. F. Hochedez
%A V. H. Doddamani
%A Lakshmi Pradeep Chitta
%J Advances in Astronomy
%D 2012
%I Hindawi Publishing Corporation
%R 10.1155/2012/623709
%X The first and preliminary results of the photometry of Large Yield Radiometer (LYRA) and Sun Watcher using Active Pixel system detector and Image Processing (SWAP) onboard PROBA2 are presented in this paper. To study the day-to-day variations of LYRA irradiance, we have compared the LYRA irradiance values (observed Sun as a star) measured in Aluminum filter channel (171£¿£¿¨C500£¿£¿) with spatially resolved full-disk integrated intensity values measured with SWAP (174£¿£¿) and Ca II K 1 £¿ index values (ground-based observations from NSO/Sac Peak) for the period from 01 April 2010 to 15 Mar 2011. We found that there is a good correlation between these parameters. This indicates that the spatial resolution of SWAP complements the high temporal resolution of LYRA. Hence SWAP can be considered as an additional radiometric channel. Also the K emission index is the integrated intensity (or flux) over a 1 £¿ band centered on the K line and is proportional to the total emission from the chromosphere; this comparison clearly explains that the LYRA irradiance variations are due to the various magnetic features, which are contributing significantly. In addition to this we have made an attempt to segregate coronal features from full-disk SWAP images. This will help to understand and determine the actual contribution of the individual coronal feature to LYRA irradiance variations. 1. Introduction 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. Hence the knowledge of the solar spectral irradiance is of large interest to solar physics, aeronomy, and to other fields of heliospheric or planetary research. The solar ultraviolet (UV) irradiance below 3000£¿£¿ is the main source of the energy converted in the Earth¡¯s atmosphere, controlling its thermal structure, dynamics, and chemistry through photodissociation and photoionization [1]. Because of these, changes in UV irradiance influence the concentration of the ozone in the Earth¡¯s atmosphere [2, 3] and may play a significant role in the process of the global warming. The balance of the ozone formed by radiation below 2400£¿£¿ in the stratosphere and mesosphere is of special interest for life and mankind. However, the photons above 2000£¿£¿ get dissociated in the stratosphere and disturb the balance of the ozone (e.g., [4, 5]). This is because the ozone gas is produced naturally in the stratosphere where it strongly
%U http://www.hindawi.com/journals/aa/2012/623709/