Astronomy 23/223 Homework:

Fun with the Sun

 Scientists use lots of different instruments and techniques to observe the Sun. Starting in early 1996, the SOHO satellite has compiled a web based collection of images of the Sun both from SOHO (the SOHO Summary database) and from other spacecraft and telescopes all over the world (the Synoptic Database) These images can be used to study various features on the Sun, watch the Sun rotate, and observe how the Sun changes as we move from the minimum of the Sun's 11 year cycle in 1996 to its maximum around 2000. The Sun emits light from radio wavelengths through gamma rays. Its appearance differs wildly over this range. Some features that are dark at visible wavelengths, glow when observed in ultraviolet and x-rays. Others which are dark in X-rays seem to glow in radio waves, still other features which are easy to see in some wavelengths are invisible in images made with other kinds of light or with different techniques. We need to be able to account for all these things to say we really understand what is going on. That's why we collect all this different data. Several government web sites keep track of solar data from satellites and Earth-Based observations. In this exercise,we will use the collection of observations on the SOHO web site. For this week’s homework: 1. Look around at the images of solar prominences on the SOHO database. At which ultraviolet wavelengths are the Sun's erupting prominences most visible, and cite your evidence for this result? What type of synoptic data can also be used to study prominences? 2. Given a seven day sequence of EIT images from the SOHO database, plot two active areas on a solar grid. For this purpose, you will need a solar grid. Note that the grid has 36 divisions. (Remember the sun is spherical: 18 in front and 18 in back. Some are closer together than others, due to perspective, but all are equal.) Once you have plotted all the positions, compare the rotation speeds at different latitudes, and comment on your results. 3. Using this link, http://sohowww.nascom.nasa.gov/explore/lessons/cme_activity.html calculate the velocity and acceleration of the coronal mass ejection at two different positions: the outermost edge of the bright structure AND the inner edge of the dark loop shape. Compare your results from the two features, and discuss why they are different or the same.

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