The Magnetic Sun

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Students build a simple version of a magnetometer, an instrument capable of detecting areas that have strong magnetic fields. Students use their magnetometer and models of the Sun to investigate areas that have strong magnetic fields. Students examine images of the Sun to describe the features associated with the Sun's strongest magnetic fields and learn more about the features they have identified either through student research or teacher presentation.

Learning Objectives

  • Students will build an instrument (magnetometer) that can detect the direction of a magnetic field.
  • Students will observe magnetic fields using their magnetometer.
  • Students will identify the positions of strong magnetic fields on models of the Sun.
  • Students will describe the features associated with strong magnetic fields on the Sun.


To make the Sun models, you will need:

  • Approximately 18 ceramic donut magnets (or rare-Earth magnets)
  • 7 file folders (can also use padded mailing envelopes or pizza boxes)
  • Masking tape
  • Scissors
    •     Print color copies of each of the seven Sun Model Images

Note: For large classes, you may want to make two sets of the Sun models. If so, double the materials listed above.

To make the magnetometers, you will need:

  • Approximately 10 donut or bar magnets for magnetizing the pins
  • Sewing thread (7 inches for each magnetometer)
  • Masking tape
  • Steel straight pins (2 per magnetometer)
  • Drinking straws (4-inch-long piece per magnetometer)
  • OPTIONAL:  The Magnetic Sun Slide Deck (use in place of printed Magnetometer Directions)

Other activity materials:


Construct the Sun image models:

  • These models can be used for multiple class periods and will last for many years. Consider laminating them to increase longevity.
  • Print the Sun Model Images (pages 17) in color and cut the key off along the dotted line. (For large classes, print two copies of each.) If you do not have a color copier, many of the images can be printed effectively from a high-quality black and white printer (omit images that appear gray).
  • Glue or tape each image to the outside cover of a file folder (or mailing envelope/pizza box).
  • Arrange magnets within the folder as indicated in the associated key. The magnets represent the locations of features on the Sun that have intense magnetic fields, so take care to locate them with the appropriate features.
  • Secure the magnets in place with tape and then tape the folder closed. In certain cases, the polar orientation of the magnets matters. Make sure that students do not disturb the locations of the magnets during the activity.
  • Arrange the Sun image models at numbered stations around the classroom.

Prepare student supplies for constructing magnetometers:

  • Cut drinking straws and thread into pieces beforehand for younger students or to save time.
  • Prepare enough supplies for each pair of students to construct a magnetometer.
  • Make copies of Student Pages (1-3) for each student.

Note about magnets: Ceramic donut magnets can be found online and at most hardware stores. One face of these magnets is positive polarity while the opposite face is negative. The orientation of the magnets is specified in some models. Rare-Earth magnets can also be used and are advised for some of the models. They are somewhat more expensive but are small and strong.


  • Introduce the lesson by telling students that there are features on the Sun that have very strong magnetic fields and that the objective of this lesson is to identify what those features are like.
  • To do this, students will make a tool to detect the presence of magnetic fields.s.

Making the Magnetometer tool:

  1. Project the magnetometer directions in the Magnetic Sun Slide Deck (slides 2–4) or provide copies of the Magnetometer Directions Handout and guide students through the directions to construct their magnetometers. Once students have constructed their magnetometers, have them stroke the pins lengthwise from left to right several times with one pole of a donut or rare Earth magnet. This will magnetize the pins.
  2. Have students test their magnetometers with a magnet to make sure the pins are properly magnetized to indicate the presence of a strong magnetic field. (The pins should orient themselves with the field.) If students are unfamiliar with magnets, consider allowing them to explore the fields of various magnets using their magnetometer.

Using the magnetometer to detect strong magnetic fields on the Sun:

  1. Hand out the Student Pages (1–3) and review the directions to orient students to the activity. The students should use their magnetometers to test each of the Sun images for strong magnetic fields. Once they have tested all the images, they should draw conclusions about what sorts of features on the Sun are associated with strong magnetic fields.
  2. Allow students to circulate around the room, visit each station, and test each image. They should sketch the location of strong magnetic fields for each image and describe the appearance of the magnetic features on their Student Pages (1–2).

Summarizing and Reflecting:

  1. Ask students to come to the blackboard/whiteboard and draw the features that had strong magnetic fields.
  2. If time permits, have students research the types of features for themselves using the Sun & Space Weather section of the website and report their findings to the class.
  3. If time is limited, show images of sunspots, prominences, and coronal mass ejections, and explain each using slides 5-12 of the Magnetic Sun Slide Deck. Ask students to identify what types of features were present on each Sun image.
  4. Have students answer the summary questions on Student Page 3 to assess understanding.


The Force of Magnetism

The force of magnetism causes magnetized material to align itself with a magnetic force. Magnetic fields are invisible; we can only see their effects. Magnetometers are devices used to detect and measure the strength of magnetic fields. (Compasses are basically magnetometers with directions marked on them.) A magnetometer will dip or point toward a source of magnetism. The magnetometers used in this activity can also be used for other activities. For example, have students use their magnetometer to find things in your room or at home that are magnetic, or try the activities listed under the Related Resources section below.


Sunspots are caused by extremely strong, localized magnetic fields on the Sun. Loops of magnetism, or magnetic "ropes," are generated within the Sun by flowing ionized gas called plasma. The plasma can flow freely along magnetic field lines. These loops thread through the visible surface (photosphere) of the Sun, and they produce sunspots. Sunspots generally appear in pairs with opposite magnetic polarities: one where the bundle of "ropes" emerges from the solar surface, and the other where the bundle plunges back down through the photosphere. Magnetic field strengths within sunspots are thousands of times more intense than the Sun's global average magnetic field (which is approximately 1 gauss). Larger sunspots may have higher magnetic field strengths.

This is an image of the Sun's corona, showing the Umbra in the middle surrounded by the Penumbra. Arrows point out the location of convection cells within the Penumbra.

Anatomy of a Sunspot

Sunspots come in a variety of sizes and are often as large as planets. Sunspots are darker than the rest of the sun because of their very strong magnetic fields inhibit convection and are thus cooler than the surrounding areas. The penumbra is the lighter outer region of a sunspot. It has radiating lines called spines which indicate the magnetic field. The dark central portion is called the umbra. Small sunspots may not have a well-defined umbra.

Solar Flares and Coronal Mass Ejections (CMEs)

Solar flares are a sudden brightening of light in a region of the Sun. All wavelengths of light brighten during a solar flare, but especially those at the x-ray end of the electromagnetic spectrum. Solar flares are formed in areas of intense magnetic fields in the vicinity of active regions on the Sun. Coronal mass ejections (CMEs) are explosions in the Sun's corona which add a great number of charged particles to the solar wind. Sudden changes in the Sun’s magnetic field generate energetic solar flares and vast CMEs. Visit UCAR's Sun and Space Weather website for more information.

About Models

This activity uses models of the Sun and its magnetic fields to help students understand the connections between visual features on the Sun and magnetic fields. To accomplish this educational goal, these models somewhat simplify the complex nature of the Sun's magnetic fields. When using this type of activity with more advanced students, it is useful to engage the class in a discussion about the benefits and limitations of models.


Exploring Magnetic Fields:Have students sprinkle iron filings on a sheet of paper and place a button or donut magnet beneath. Ask students to describe the pattern the filings make when they are affected by a magnetic field. The filings will radiate from the magnet, with one of their poles pointing towards the opposite pole of the magnet. This will look somewhat like the spines within a sunspot's penumbra. The spines are similar in that they reflect the shape of a sunspot's magnetic field. If a variety of magnet types are available, ask students to experiment with the shape of the iron filings around different magnets or combinations of magnets.

Related Resources