Magnetism and the Sun

NEIU 19 ~ NASA Endeavour 5 March 2008

What do you know about Magnetism???

Seeing Magnetism

Please observe and respond to the following questions

1) What is happening that is impacting the speed and direction of the iron filings?

2) What did you observe about iron filings near the bar magnet?

3) Why do you think that this happened?

Magnetism

• Force of Nature

• All atoms are magnetic meaning that they have charges moving within them– For an object to act as a MAGNET, the

magnetic fields within it (charged particles) must align with one another

– In order to line up, the charged particles must be able to move freely

Charged Particles

External Magnetic Field

Is it Magnetized or Not?

What Do Magnets What Do Magnets Do?Do?

MAGNET WARS!!!

What Do Magnets What Do Magnets Do?Do?Attract or repel other magnets

(exert a force)

Attract other magnetic metals

Have at least 2 distinct ends (poles) eachLike poles repel, opposite poles attract!

Notes:Do not need to touch to exert force (can exert force through empty space)Can turn other magnetic metal objects into temporary magnets

What is a Force?What is a Force?Force is a push or pull that causes a change in motion.

A Force Field is the pattern in space of how that force is felt by other objects.

Fundamental Forces arise from fundamental properties of matter:

Gravity arise from Mass: mass attracts mass

Electric force arises from Charge: two kinds of charge (positive and negative), like charges repel and opposite charges attract

Gravitational field of a point of mass Electric field of 2 opposite charges

Electric field of 2 like charges

Describing the Earth’s Magnetic Field

Introducing Magnetic Field Lines !!!

Magnetic FieldMagnetic FieldMagnetic field of a Bar Magnet: 2 poles, called North and South

Dipole field

Field has direction: lines point away from N and toward S

Definition of a Pole: Where lines meet (converge)

e.g.: lines of longitude on a globe meet at poles

Moving molten iron in Earth’s outer core causes most of Earth’s magnetic field.

Magnetic field poles are NOT aligned with geographic poles. They also wander and flip (500,000 yrs between flips, 10,000 yrs to complete flip).

Earth: A Huge Bar Earth: A Huge Bar MagnetMagnet

Earth’s Magnetic Field

The Sun’s Differential Rotation

The Sun does not rotate as a solid body: its equator rotates once every 25 days, while regions near the poles rotate every 30 days.

Your Hypothesis: What happens to the Sun’s Magnetic Field?

Follow the North/South Field Lines

What begins to happen?

The Sun’s Magnetic Field

Imagine the Sun as a bar magnet, with magnetic field lines cutting through it. The field lines are attached to the Sun.

After a while, differential rotation stretches and stresses the field lines. Kinks develop.

Solar Magnetic Field Line Twisting!

Solar rotation causes magnetic field lines to become twisted and stretched to the breaking point. These eventually break and reconnect, creating heat, intense active regions, and solar blasts of charged particles.

Stretching the Magnetic FieldThe magnetic field kinks appear on the surface as pairs of sunspots.

The spots appear dark because they are cooler than their surroundings – their energy is stored in the magnetic field.

Images from NASA SOHO’s EIT

Prominences and Flares

Eventually, something has to give. Just like a rubber band, the field lines will break and release their energy.

Solar Prominence

Solar Flare

Solar Flare from TRACE

The Sun and EarthWhen the Sun has a lot of sunspots, solar flares, and prominences

The earth is warmed by all the additional energy The earth is bombarded with cosmic rays (i.e., high energy

hydrogen and helium nuclei that are ejected from the Sun. (In other words, a stronger solar wind Stream of charged particles emitted from the sun.) The earth’s magnetic field and atmosphere protects us from these particles; those that get through are funneled into the atmosphere at the poles.

Impact!

• Solar Flares can accelerate solar wind particles to nearly the speed of light

• Can harm astronauts• Can harm NASA

Satellites

Solar Wind

Questions????