Title：UV Observations of Solar Corona: from plasma emission processes to raw and calibrated UV spectroscopic data 

　　Speaker：Silvio Giordano, Senior Scientist（UVCS软件的主要编写者）（INAF-Turin Astrophysical Observatory, Turin, Italy） 

　　Time & place：March 27 09:30-10:30 am & 3-302 

　　Abstract：The presentation is intended to serve as a general overview of the physical processes that underlie the formation of the ultraviolet spectral lines observed in the solar corona by UVCS aboard SOHO and as a guide for those interested in analyzing the data acquired over more than a full solar cycle from 1996 to 2012. Here we provide an overview of the ionization processes and of the main collisional and radiative emission mechanisms relevant in the solar coronal plasma, this description is at the base of the diagnostics which allow determining the physical parameters and modeling the corona. A brief description of the UVCS instrument and a summary of the observed spectral lines is provided, with some details about the calibration and data reduction issues. We describe also how to instrument has been characterized on laboratory before the launch and how the performances have been updated on flight during the mission. Then, we present the UVCS Data Analysis Software (UVCS-DAS) developed by UVCS team in Interactive Data Language (IDL) and released within the SolarSoft package, this code with his Graphical User Interface allows to read, display and calibrate the observational data. We describe the pipeline to select the data of interest and to obtain the fundamental physical parameters from the observed spectral lines, such as the emitted intensity, the kinetic temperature and the velocity along the line of sight. We pay attention to the uncertainties in determining these parameters due to the statistics and the instrument performance. 

　　We also introduce the different features of the code for creating and visualizing data not only in terms of spectra but also as 2D reconstructed images of the solar corona and as images of the evolution of the corona itself, moreover, we present the possibility to compare the ultraviolet  bservations with the visible light corona detected simultaneously by the LASCO coronagraphs onboard SOHO. Finally, we give information on how to use the SOHO data catalogs, UVCS observations and events catalog embedded into UVCS-DAS or online available. As an appendix to the seminar, for those interested, we can plan an interactive session for playing with UVCS observations, starting from searching data on catalogs to obtain physical parameters and images through data reduction, calibration, and analysis. 

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