Frequently Asked Questions

Q1. Why the Solar Feature Catalogues?

A1. SFCs offer you locations of the features (sunspots, active regions and filaments/prominences) on a solar disk, their shape, intensity and many other parameters that can be useful for your research in solar activity (see some samples in the Use Case document).

Q2. How do I access the Solar Feature Catalogues?

A2. There are two ways of accessing SFCs. The first way is directly from the this site where you need first to register your details and then login into the SFCs. The second way is to access it via the EGSO web site http://mssl.ucl.ac.uk/egso directly from any IDL code using the web services provided by us.

Q3. What can get from the Solar Feature Catalogues?

A3. After logging in into the web site you can use pre-designed searches and retrieve any feature by their time of appearance, location, size or area, elongation (filaments) and location in particular part of the disk (polar crown filaments). On the other hand, by using the EGSO entry you can retrieve the data directly into your IDL environment.

Q4. In what format can I get the data from the catalogue?

A4. You can get them as ASCII files or VOTable (XML products)

Q5. Is the SFC freely available to use?

A5. Yes, SFC is a free to use database, but you need to register and obtain a username and password to access the SFC. The registration information you provide will help us to provide statistics of web page traffic

Q6. Is the SFC data copyrighted?

A6. The SFC data are copyright to the authors. All rights reserved. If you use the data please reference the following paper and cite it in any publications. “Zharkova, V V., Aboudarham, J., Zharkov, S., Ipson, S.S., Benkhalil A.K., Fuller, N. Searchable Solar Feature Catalogues: Solar Physics, Topical Issue, 16p, in press, 2005.”

Q7. Where I could find more information and publications?

A7. Please check the wp5 web page and the publication list.

Q8. Whom to contact if I have more questions or inquiries?

A8. For further information please send an email to the EGSO FR team.

Q9. What feature parameters are provided for active regions?

A9. For each automatically extracted AR a number of physical parameters are extracted and populated into the AR feature table of the SFC database. These parameters include: the center-of-gravity in pixel and heliographic coordinates; minimum, maximum and mean intensities within the AR; area in square degrees and dimensions in pixels; contrast ratios; a chain-code representation of the AR boundary; and a bounding rectangle

Q10. What is the chain code?

A10. The boundary of an active region is represented by a chain code which starting from any boundary pixel lists the directions required to move from one pixel to the next anti-clockwise round the boundary until the starting pixel is reached. The direction to the next boundary pixel is represented by an ASCII codes for the 0 to 7. The coordinates of the pixel at the start of a chain code are stored in the SFC as units of pixels and arcsecs.

Q11. What is the bounding rectangle?

A11. The bounding rectangle associated with an active region is the smallest rectangle which encloses the active region and is represented by four integers representing the x, y coordinates, in pixel or arcsec, of the lower left corner followed by the upper right corner of the rectangle.

Q12.How is the area of a sunspot and active region calculated?

A12. The area of an active region calculated by mapping (back projection) the detected region onto the heliographic surface (in units of 0.1 degree by default).