Astronomy Lab
Exploring the Structure and Cycles of the Sun
Name ________________________
Introduction: In this session you will examine some real-time and near-time solar data to learn about
some of the characteristics of the Sun and its magnetic cycles. Please place all of your answers on the
answer sheet.
Part 1: The photosphere and sunspots
The photosphere is the zone of the Sun that emits visible light. On this layer sunspots are visible.
Sunspots mark active regions. These are areas where the local solar magnetic field is experiencing
intense disruptive activity – a “storm” of sorts. The outer light grey region of the sunspot is the
penumbra. It is cooler than the surrounding photosphere but warmer than the inner black sunspot
region, the umbra.
To begin, go to http://sdo.gsfc.nasa.gov/gallery/main/item/654 Examine the solar image and read the
caption below. Play the http://sdo.gsfc.nasa.gov/assets/gallery/movies/Sunspotgroup_gray_big.mp4
located below the caption. (This works best on full screen.) Watch as the sunspots move across the solar
disk.
1. List 4 or more changes in the sunspots or sunspot groups as they evolve.
Part 2: Comparing layers of the Sun
Go to: http://sdo.gsfc.nasa.gov/data/ On this page you will see current solar images displayed in a
variety of wavelengths of light. These images are from the Solar Dynamics Observatory- one of the
space observatories that exclusively monitor the Sun. On many of the images, a small “I” symbol
appears at the upper right. Clicking on it will explain that image. Assume North is up and the Equator
crosses the middle of all of the images.
2. Fill in the table on the answer sheet for specifically selected images. For the layer observed, choose
from photosphere, chromosphere (the lower atmosphere, above the photosphere) or corona (the
uppermost atmosphere). You may list more than one.
3. Go back and play the 48 hour recent movie links (48 hr MP4) located under each of these images:
AIA 193, 304, 171, and 131. For each movie, write one observation that could not be seen in the
single (still) image, and one question you have about the activity you observe. The observations and
questions must be different for each layer.
4. What is the value of observing the Sun in multiple wavelengths of light?
5. Magnetograms are images of the solar magnetic field. Which polarity does white indicate? Which
polarity does black indicate?
6. How are the polarities of active areas different on either side of the Sun’s Equator?
7. Sunspots mark the location of active areas of the Sun. In which of the three layers are active areas
visible?
8. Examine the corona images. In the circle on the answer sheet (which represents the Sun), sketch the
location of three coronal holes.
9. Along the edges of the same circle, sketch the location of the visible loop prominences.
Part 3: Solar eruptions and emissions
Go to http://sunearthday.nasa.gov/spaceweather/#
The solar wind is a stream of particles that constantly leave the Sun in all directions. Like the real wind,
it is variable in nature. On the left side menu under Images, Click on the LASCO C2 image, then answer
the following questions:
10. What type of instrument is used to make these images?
11. What controls the shape of coronal streamers in the solar wind?
The particles and energy contained in the solar wind can affect the earth. Click on this link to view
graphs of the current solar wind data: http://www.swpc.noaa.gov/products/ace-real-time-solar-wind
12. What is the purpose of the ACE satellite?
13. Click on the Impacts tab at the bottom. List five space weather impacts of the solar wind on earth.
You must use one complete sentence for each.
14. Return to http://sunearthday.nasa.gov/spaceweather/# and click on the Visualizations tab on the
left side menu. Click and watch the ones on solar flares and coronal mass ejections. Which contains
more energy and is larger? (Hint: vast magnetic blob)
15. Click on the Illustrations tab and open Dynamic and Constant Solar Effects on Earth. Fill in the table
for arrival times of various solar emissions.
Part 4: Solar cycles
Counting sunspots is one of the many ways to gauge solar activity. When sunspot numbers are high, so
is solar activity. The sunspot cycle has been well documented for over 400 years. View this graph of
sunspot numbers in Plot.ly: https://plot.ly/~amacio/441 Then answer these questions:
16. The numbers of sunspots rise and fall in a cycle. What is the average number of years for a cycle?
In synch with every two cycles, the magnetic field of the Sun reverses. Here are some current solar data:
http://www.swpc.noaa.gov/products/solar-cycle-progression
17. Where is the Sun in its cycle now? Is activity declining, increasing, or holding steady?
18. Would you expect solar activity such as CMEs to be high, medium, or low?
The next set of images are archived at this link: http://obs.astro.ucla.edu/torsional.html. Once on the
web page, read the information under the images to interpret then and answer the questions below.
Look first at the Photospheric Magnetic Field graph from 1986-2007 (the years are on the x-axis, last two
digits only).
19. What year did the north pole of the Sun become positive?
20. How many years was it until it reversed its polarity and became negative?
21. What changed its polarity first, the Sun’s north pole or the south pole?
Read on the web page how to identify areas of strong magnetic activity (associated with active areas)
and how to recognize times of solar maximum and minimum.
Refer to the upper Magnetic Supersynoptic Chart for 1974 to 2012 (the years are on the lower x-axis).
22. Was the year 1996 a solar minimum or a solar maximum?
23. How do you know from looking at the graphs? Explain.
24. Does the solar cycle begin during solar maximum or solar minimum?
25. What are the indicators for the beginning of the solar cycle?
26. Find the year 1979. Assume that this is the beginning of a cycle. If this is a sunspot cycle, what year
will it end?
27. If it is a magnetic cycle, what year will it end?
Refer to this page: http://www.nasa.gov/images/content/144051main_ButterflyDiagramLG.jpg
The active areas that produce sunspots migrate over a cycle. Maunder discovered this in the 1800’s and
the pattern has been carefully documented ever since.
28. At the beginning of a sunspot cycle, at what latitudes do sunspots form?
29. What latitude do sunspots move towards as the cycle approaches minimum?
Astronomy Lab answer sheet
Exploring the Structure and Cycles of the Sun
Name ________________________
Part 1: The photosphere and sunspots
1. Four or more changes in sunspots:
Part 2: Comparing layers of the Sun
Image
Layer(s)
Observed
Wavelength
(A)
Temperature
(K)
Good for:
AIA 193
AIA 304
AIA 171
AIA 131
AIA 1700
HMI
Magnetogram
Layer
AIA 193
AIA 304
AIA 171
AIA 131
Observation
Question
4. What is the value of observing the Sun in multiple wavelengths of light?
5. Magnetograms are images of the solar magnetic field. Which polarity does white indicate? Which
polarity does black indicate?
6. How are the polarities of active areas different on either side of the Sun’s Equator?
7. Sunspots mark the location of active areas of the Sun. In which of the three layers are active areas
visible?
8. Examine the corona images. In the circle at the right (which represents
the Sun), sketch the location of three coronal holes.
9. Along the edges of the same circle, sketch the location of the
visible loop prominences.
Part 3: Solar eruptions and emissions
10. What type of instrument is used to make these images?
11. What controls the shape of coronal streamers in the solar wind?
12. What is the purpose of the ACE satellite?
13. List five space weather impacts of the solar wind on earth. You must use one complete sentence for
each.
14. Solar flares or coronal mass ejections: Which contains more energy and is larger? (Hint: vast
magnetic blob)
15.
Dynamic and Constant Solar Effects on Earth
Light
Arrival times
Flare
x-rays
Energetic
particles
Solar wind
Flare
magnetic storm
Part 4: Solar cycles
16. What is the average number of years for a sunspot cycle? ____
17. Where is the Sun in its cycle now? ___________
18. Would you expect solar activity to be high or low? ____________
19. What year did the north pole of the Sun become positive? ________
20. How many years was it until it reversed its polarity and became negative? __________
21. What changed polarity first, the Sun’s north pole or the south pole? ___________
22. Was the year 1996 a solar minimum or a solar maximum? _____________
23. How do you know from looking at the graphs? Explain.
24. Does the solar cycle begin during solar maximum or solar minimum? ____________
25. What are the indicators for the beginning of the solar cycle?
26. If this is a sunspot cycle, what year will it end? ________
27. If it is a magnetic cycle, what year will it end? _________
28. Near the beginning of a sunspot cycle, at what latitudes do sunspots form? ___________
29. What latitude do sunspot move towards as the cycle approaches minimum? __________