The Magnetic Sun 1

What is the Sun? The Sun is a Star, but seen close-up. The Sun is giant ball of very hot, mostly ionized hydrogen gas that shines under its own power. 2

The Sun IS NOT an average, yellow star. What is the Sun? 3

The Sun produces all the colors of the rainbow in roughly equal amounts, which is white light. If the Sun were yellow, then white T-shirts would look yellow in the mid-day sunshine. When you observe the Sun safely, by projecting its image through a pinhole camera or a telescope, you see that is white. Don’t stare directly at the Sun! The UV radiation can damage your eyes. The Sun is White 4

The Sun is Above Average Most stars in the Universe are small, cool, low-mass dwarfs. The Sun is larger, hotter, and more massive than these. There are stars that are much larger, very hot, and many times more massive than the Sun. But these stars are quite rare compared to the Sun or the low- mass stars. The Sun is also not median, mid-range, or most frequent (mode) in the measures of size, temperature, brightness, or mass. 5

The Sun is 109 times the diameter of Earth Over 1,000,000 Earths could fit inside the Sun. The Sun is 150 million kilometers away from Earth. It takes light 8 minutes to travel to Earth from the Sun. This distance is defined as 1 Astronomical Unit (AU) Earth Moon Size and Distance of the Sun 6

The Spectrum of Light Low Energy Waves High Energy Waves Visible light is a tiny fraction of the Electromagnetic Spectrum Gamma rays--billions of waves per inch Radio waves--up to miles-long wavelengths 7

Looking at the Sun in visible light reveals dark spots on its surface. These magnetic Sunspots are connected to the mysterious events just described. The Sun 8

In this specific color of red light we can see more details of the Sun’s magnetic activity. The Sun 9

From space, we can observe the Sun in ultraviolet light and see hot gas trapped in magnetic fields on the Sun. The Sun 10

In extreme ultraviolet light we see that the hottest places in the Sun’s atmosphere are magnetic. The Sun 11

The Sun 12

The Different Parts of the Sun Core Nuclear Fusion H → He T = 15,000,000 K Radiative Zone Energy transported by light T = 10,000,000 K Convective Zone Energy transported by convection Photosphere Visible surface Far less dense than Earth’s atmosphere T = 5,800 K Sunspots: T = 4,000 K Chromosphere Thin layer above photosphere Produces most of Sun’s UV light T = 10,000 K Corona Tenuous, extends out millions of kilometers Emits X-rays T = 1,000,000 K 13

The Different Parts of the Sun During a total eclipse of the Sun by the Moon, the very bright Photosphere is blocked and the Sun’s outer atmosphere becomes visible. We call it the Corona It extends far out into the Solar System, in fact we live in it! 14

The solar wind is a stream charged particles emanating from the Sun and blowing throughout the Solar System. The Solar Wind 15

The Magnetic Sun Ultraviolet images of the Sun reveal loops of hot ionized gas (plasma) in the corona trapped in magnetic fields above the locations of Sunspots. 16

The number of sunspots and solar flares increase and decrease on an 11-year cycle. The Solar Cycle 17

Solar flares Solar flares are enormous explosions in the atmosphere of the Sun. They release energy that is stored in magnetic fields. Solar Storms 18

Solar Storms Coronal Mass Ejections (CMEs) occur when large- scale magnetic fields “break.” throwing enormous amounts of matter into space. 19

CME’s are sometimes directed at Earth. It takes a few days for the material to arrive. Solar Storms and Earth 20

Moving molten iron in Earth’s outer core causes most of Earth’s magnetic field. Earth: A Huge Bar Magnet 21

Magnetosphere: The magnetic field surrounding Earth Interaction with the Solar Wind compresses Earth’s magnetosphere on the dayside and elongates it on the night-side making a magnetotail. 22

Two small magnetospheric funnels (cusps) are open to solar particles. 3-D rendering Sliced view Most solar wind particles are deflected around Earth’s Magnetosphere. Magnetosphere: The magnetic field surrounding Earth 23

When a CME crashes into Earth’s protective magnetic field it can cause a geomagnetic storm. Solar Storms and Earth 24

A massive blackout leaves millions of people without power 25

Communications are disrupted between the ground and satellites, aircrafts and ships. 26

GPS signals are disrupted and magnetic compasses start pointing to a different location. 27

The aurorae are being spotted as far south as Florida! 28

Energy from Solar Flares and CMEs can damage satellites and change orbits. Disrupt radio communications CME particles traveling near the speed of light threaten Astronauts. CMEs can intensify auroras (Northern and Southern Lights) Electric currents from intense aurora can cause power surges and blackouts. Space Weather 29

Energy Comparisons Food CaloriesJoules Lifting a lemon 1 meter2.388 X Car moving at 60 mph863.6 x 10 5 Burning a liter of oil x 10 6 Human daily diet2 X x 10 6 Lightening bolt Heat a house (1 year) megaton H-bomb1 x x Major geomagnetic storm Earthquake (magnitude 8.0)6 x x Annual U.S. energy usage Impact of dinosaur extinction asteriod Annual sunlight on Earth Large solar flare Earth spinning Earth moving in orbit Annual solar energy output Supernova (exploding star)

NASA’s Heliophysics Missions 31