X-ray Candles: Solar Flares on Your Birthday
Student Activity

Solar Flare Introduction    

Activity Instructions    

RHESSI Education Page    


Students will "discover" the solar cycle through an investigation of solar x-ray flares. Using GOES x-ray data, they will record the total number of flares in their birth month over 11 years and will compute the percentage of high class flares which occur for each year. Students will graph their findings to help them identify the long term pattern of flare activity on the Sun. If you have not already done so, please visit the previous page for an introduction to solar flares.

This activity has been featured as part of NASA Connect's Having a Solar Blast program for educators.
The associated activity guide will be helpful in completing the lesson.


Follow Up:

What do you notice from your graph? You should see that the percentage of high-energy flares from the Sun is not constant in time. This is also true of the total number of flares, and the total number of M class flares. You should see a minimum percentage of M class flares in 1996 and a higher percentage near the year 2000. If you were to extend the graph for a much longer period of time, you would discover that the rise and fall occurs in a very regular cycle that repeats itself every eleven years.

Scientists also see this eleven-year activity pattern in the number of sunspots on the Sun, and solar flares are known to originate in regions where there are sunspots. The image below shows a simulated RHESSI flare (white circles) superimposed on an image of the Sun. You can see the expected correlation, that solar flares occur in regions over sunspots. In general, the Sun goes through a regular activity cycle with eleven years from one maximum (or minimum) to the next. The last solar maximum occurred in the year 2000, and the last solar minimum was in 1996. This pattern should be visible in your graph. Can you predict when the next solar maximum, or solar minimum, will be?


To learn more about the Sun's 11 year cycle, visit the links below.

Sunspots and the Solar Cycle

The Sunspot Cycle

Sunspot Cycle Predictions

Here is an interactive web activity about the correlation between sunspots and flares.

The complete GOES X-ray flare data files are available on-line (at the data page click on the link labeled xray1975, for example, to see the data from 1975). The page that explains the format of these particular data files is available here.

Lesson designed and developed by Michelle B. Larson
Please send questions or comments to michelle@krl.caltech.edu