Name: ___________________________________________________________________The Sun's Magnetism

The sun, like the earth, generates a magnetic field that extends out into space. However, the sun's magnetic field changes both its shape and intensity over the surface, and over time, much more rapidly. Why is that? We'll need to learn some basics about how the solar magnetic field works, to see how these fluctuations can cause sunspots.

Magnetic fields from electrons

Have you ever made a magnet by winding wire around a nail and hooking the ends to a battery? This works because moving electrons, like the electric current in the wire, generates a magnetic field. The magnetic field lines go through loops of wire and the nail, and the nail becomes a

magnet. Something similar happens in the Sun.

X-ray images from the TRACE satellite like this and the one below, right, show loops of solar magnetic field lines. Each loop is a dense bundle of field lines. Sunspots mark the places where the ends emerge and re-enter into the photosphere.

Magnetic fields from convection?

In the Sun, the flows of hot plasma in the convection zone create the solar magnetic field. The plasma is a hot gas "soup" with many free charged particles (electrons and protons). The moving charges are a current, and produce magnetic fields, just like the current in coils of wire around the nail. What's different in the sun? The convection

current is driven by the heat from the Sun's fusion, instead of a battery.

David Dearborn refers to the flows as the "solar dynamo," saying: "So there you have mechanical motion, and that mechanical motion is involved in generating the magnetic fields that cause sunspots." scientists like Dearborn believe that convection creates the varying magnetic field at the sun's surface, but the ultimate reasons for each fluctuation in the flows and fields are not well understood.

Sunspots have magnetic pressure

Sunspots are regions of very strong magnetic field, where the field lines get so crowded together that they push up through the surface, bringing some of the hot plasma with them in a spectacular arc, or loop (prominence). We see the end of the loop as a sunspot on the sun's visible surface, or

Name: ___________________________________________________________________photosphere. This dense bundle of field lines creates huge magnetic pressures that cool the area – hence why they are darker.

Using Sunspots to Learn about our Sun

Scientists can also use sunspots to determine the rate of the sun’s rotation by tracking how long it takes the spots to move.

The Sun undergoes differential rotation meaning, the rotation period of the Sun’s gases varies from 25 days near the equator to 35 days near the solar poles

o WAIT! WHAT? This means the equator spins faster than the poles.

Is this traceable?

Since the numbers of sunspots are influenced by the sun’s magnetic field, there is a traceable pattern of sunspots that we can use to find information about the magnetic field. The cycle is called the sunspot cycle and it takes 11 years to repeat and the magnetic cycle every 22 years.

What effect does this have on the Earth?

Maunder Minimum Little ice age (1645-1715) o A period of almost no sunspots that coincided with the coldest part of the Little Ice

Age Dalton minimum 1800 – 1830

o Year without a summer 1816o The number of sunspots at the peak of the solar cycles was about 1/3 of that

observed during normal solar cycles and they also had unusually long periods of sunspot inactivity.

On the sun, coronal mass ejections occur when solar magnetic field lines snake around each other, forming the letter "S". Usually, they go past each other. But if they connect, it's like a short circuit. The mid-section breaks loose and

Name: ___________________________________________________________________drives out a coronal mass ejection. If this hits the earth it could be a complete destruction of our communication systems and our sky would see beautiful auroras.

Questions1. How do we generate a magnetic field with a nail?

________________________________________________________________________________________________

_______________________________________________________________________________________________

________________________________________________________________________________________________

_______________________________________________________________________________________________

2. How does the sun generate a magnetic field? Explain.

________________________________________________________________________________________________

_______________________________________________________________________________________________

________________________________________________________________________________________________

_______________________________________________________________________________________________

3. How is a sunspot created?

________________________________________________________________________________________________

_______________________________________________________________________________________________

________________________________________________________________________________________________

4. How is a prominence created?

________________________________________________________________________________________________

Name: __________________________________________________________________________________________________________________________________________________________________

________________________________________________________________________________________________

5. How do we track the rotational period of the sun?

________________________________________________________________________________________________

_______________________________________________________________________________________________

________________________________________________________________________________________________

_______________________________________________________________________________________________

6. What does the rotational period of the sun show us about the differing speeds?

________________________________________________________________________________________________

_______________________________________________________________________________________________

________________________________________________________________________________________________

_______________________________________________________________________________________________

7. How are sunspots and the magnetic field created AND tracked? Explain.

________________________________________________________________________________________________

_______________________________________________________________________________________________

________________________________________________________________________________________________

_______________________________________________________________________________________________

________________________________________________________________________________________________

_______________________________________________________________________________________________

8. What effect(s) does this have on the Earth?

________________________________________________________________________________________________

_______________________________________________________________________________________________

________________________________________________________________________________________________

_______________________________________________________________________________________________

________________________________________________________________________________________________

_______________________________________________________________________________________________

________________________________________________________________________________________________

_______________________________________________________________________________________________

Name: ___________________________________________________________________