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Measure Image Areas



Where am I now?

This is your solar science "laboratory." This section includes the Java applet program you will use to measure areas on the solar images, instructions for using the program, and information you may need about the images. You can always return to another part of the site for review by using the navigation bar at the top.

How to use the Java applet  program link and solar image

About these images link and rocket launch image


What's an active region? link and solar image

Prepare: Get general information about your image data using the icon labeled, ABOUT THE IMAGES. Click on the icon labeled USING THE PROGRAM for detailed instructions. This will prepare you for the discussion of how to define the active x-ray regions in ACTIVE REGIONS, which is very important to your work.

Measure areas of sunspots in the white light images, and active regions in the x-ray images using the program below. You will do this by "launching" the program in a new window, loading each image into a viewer, and "painting in" the areas you want to measure with the mouse. The program will keep track of how much area you paint in each image. You may be instructed to measure a certain subset of the 28 image pairs.

Painting = measuring
Your goal is to test the hypothesis that there is a relationship between areas of sunspot activity and areas of x-ray activity. To look for a relationship, you must measure the areas. This is what you are doing by paining the images. The program produces a number for each area you paint: the area in pixels. Each pixel, by the way, is about the size of the earth!

To launch the Java program please click the button below. (You'll need a java-compatible browser, we recommend Netscape 4.0 or higher)

Tip: You should also write down the areas you measure. If you happen to reload an image you measured before, the previous data will be lost and you'll have to redo the painting!


Sample graph from the Java program with plot points

Sample graph from Java program

Plot the values on a graph
You will compare the sunspot and x-ray areas on a graph with sunspot areas on the horizontal axis, and x-ray areas on the vertical axis. The program will plot the points for you, or you may want to plot them for yourself. Use the button marked "plot" to see a display like the one at right.

The program puts a point on the graph for each day's pair of images, where a line up from the horizontal axis at the value for the sunspot area meets a line over from the vertical axis at the height of the x-ray area. The points will not be positioned in time order because time is not one of the axes on the graph. Compare some point locations on your own graph to the "values" list to check this out.

Why a graph?
The heart of your science is in how you interpret the resulting graph. Scientists make graphs because they show relationships immediately and visually. By looking at the graphs of these areas, you might be able to make some guesses about whether the sunspots and x-ray areas are related. Try to determine whether the graph shows a simple relationship, sometimes called a
correlation, between the two quantities. Will the points look like they fall near a line or a smooth curve?

This is how scientists find a correlation: plot the two quantities and hope that something simple and obvious shows up! (Science involves a certain amount of hoping and praying.) You could try to compare the two columns of numbers, but we think you'll find that looking for a line or simple curve on a plot of sunspot area vs. x-ray area is an easier way to see a relationship exists between the two quantities.

To scientists, one graph can be worth a thousand numbers. Will you agree? What will you discover? Write down your analysis of the data, and compare your conclusions with others.


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