The SunThe SunOur Nearest StarOur Nearest Star

The Source of the Sun’s EnergyThe Source of the Sun’s Energy                  

• Fusion of light elements into heavier elements.• Hydrogen converts to helium

– Four hydrogen nuclei (each with a mass of about 4.030 mass units) join to form a helium nucleus with a mass of only about 4.003 energy units.

 

Isotopes of hydrogen

• The mass that seems to have been lost is converted into energy which is radiated into space.

• Estimates indicate that about 4 million metric tons of matter are converted into energy every second but because the Sun is so massive, this process can continue for another five billion years!

The Sun’s Structure• Photosphere

– Visible Surface– Currents at top form

granules• Chromosphere

– Inner layer of atmosphere

Corona – Thin outer atmosphere

Prominences

• Huge, red, flame-like arches of material that occur in the corona.

• Appear like flames but the light is caused by changes in the cooler, denser parts of the corona.

• Prominences may last for hours and can extend millions of kilometers about the photosphere

Huge curtains of gas >100,000 km long - Relatively cool

Sunspots

• Dark spots on photosphere

• Strong magnetic field– 1000 x stronger than

surrounding region• Cooler than

surrounding photosphere

Sunspots

SunspotsSunspotsUmbra

Penumbra

Solar FlaresSolar Flares• Occur near sunspots• Particles ejected from

the sun

Solar FlaresSolar Flares

Space WeatherSpace Weather• Space weather happens with a

solar storm from the Sun travels through space and impacts the Earth’s magnetosphere.

• Solar storms can affect the advanced technology we have become so dependent upon in our everyday lives.

Energy and radiation from solar flares and coronal mass ejections can:• Harm astronauts in space

• Damage sensitive electronics on orbiting spacecraft• Cause colorful auroras, often seen in the higher latitudes• Create blackouts on Earth when they cause surges in power grids.

Protection from Earth’s Magnetic FieldProtection from Earth’s Magnetic Field

Solar WindSolar Wind

• Stream of charged particles emitted from the Sun’s outer atmosphere.– Mostly protons and

electrons• Hydrogen atom

• Escape due to high kinetic energy and high temperature of the corona

Solar StormSolar Storm• High levels of radiation occur due to:

– Solar Flares:  Sudden, powerful bursts of magnetic energy that has built up in the Sun's atmosphere.

• They are associated with sunspots • Energy released is equivalent to 10’s of millions of

hydrogen bombs.– Coronal Mass Ejections: Explosions in which

billions of charged particles are blasted into space at high speed.

Geomagnetic StormGeomagnetic Storm

•  A temporary disturbance of the Earth's magnetosphere

• Associated with solar coronal mass ejections, coronal holes, or solar flare– Caused by a solar wind shock wave which

typically strikes the Earth's magnetic field 24 to 36 hours after the event.

Radio BlackoutsRadio Blackouts

• Solar events– High energy electromagnetic radiation (e.g., x-

rays– Ions

• Affects the ionosphere– Impacts radio communications– Satellites