Victor V. Grechnev, Alexandr Altyntsev, Sergey Konovalov, Sergey Lesovoi (Institute of Solar-Terrestrial Physics SD RAS, Irkutsk, Russia)
Processes of the solar activity induced by exit of abyssal magnetic fields move in the solar corona. Radio observations allow to study the solar corona on the background of the solar disk and add essentially the measurements which are carried out in soft and hard X-rays. Radio observations are sensitive to both thermal and non-thermal components of plasma in quiet and perturbed conditions in corona up to coronal mass ejections. They provide the only method of measuring of coronal magnetic fields as their calculations after photospheric data are not reliable in the perturbed conditions. They also make possible a diagnostics of parameters of high-energy electrons. Radio observations give the only way to study processes of particle acceleration and energy release in the outer corona.
However, a variety of emission mechanisms and their dependence on parameters of the emitting electrons makes extremely difficult the study of the solar processes without knowledge of information which can be provided by other spectral ranges. Namely, the magnetic configuration given by magnetograms, temperature and density distribution given by X-ray observations contribute essentially to the correct interpretation of radio data. This is the reason why the study of the solar activity based on radio observations is connected with use of multi-spectral data.
Thanks to development of the Internet, astronomers can use now, in fact, data of all ground-based and orbital observatories. On the other hand, involvement of heterogeneous material requires various methods of data processing, coordination (overlay) of solar images in different formats, etc.
Experience shows that data processing is performed, as a rule, in a few stages. At the first stage, routine procedures are performed (rejection of records, bringing them to the standard form, building of maps, etc.). Subsequent stages include previewing, selection of foremost records, their correlation with data obtained in other ranges of the emission, measuring of parameters of radio sources and, finally, estimates of physical conditions and model calculations.
The first level of data reduction, as a rule, is executed by routine instrument-specific software. Subsequent data processing is often carried out under conditions when not only techniques, but also an approach to the solution of a particular physical task are not clear. These conditions suggest interactive work when various techniques of data processing can be tested.
An effective tool to solve such tasks is Interactive Data Language (IDL) which is used by many observatories and institutions for some years. Taking into account its advantages, we have chosen it as the base in solving of our tasks. We would like to present a set of IDL programs which process data obtained by the Siberian Solar Radio Telescope (SSRT) together with data of other spectral ranges: Nobeyama Radioheliograph (NRH), Yohkoh, BATSE, Kitt Peak, etc. Besides well-known methods, these programs realize some specific techniques developed by us.
Astronomical instruments provide a lot of images during an event which contain a great amount of information. Integral characteristics help to reveal essential features. Along with the well-known total flux, we use also the effective height which can be measured either as a weighted center, or as coordinates where the second derivative has its minima. However, structural variations are masked in this case. Some additional features can be detected by means of another integral characteristic, the effective area of an emitting region computed as its flux divided by maximum of the brightness temperature over the image. Changes of the maximum of the brightness temperature describe that growth which is in fact, and the changes of flux reflect also proceeded transformations of the structure.
The developed set of programs and routines provides, among the others, the following means:
Some programs have widget-based graphical interface which allows to perform standard measurements efficiently.
The programs and routines have been checked under MS Windows 95 and UNIX with IDL versions since 3.0.1 to 5.0.2. They are extensively used in our data processing of the SSRT and the NRH. By means of this software a range of solar events since 1992 was comprehensively investigated.
We plan to put our IDL programs onto our home page (http://www.iszf.irk.ru).