The Sun

Chapter 29Section 29.2 and Spaceweather

SUNSPOTS

• cooler areas within photosphere

• caused by magnetic fields

• occur on an 11 year cycle

• larger than earth...

• Can last hours or several months

Play: Spinning.mov

Zooming in for a closer look From a far away sunspots

appear like dark blobs on the Sun, but up close, they reveal incredible complexity. In the most close-up video view, each little cell-like gray area you see is about the size of Texas.

Credit: Swedish Solar Telescope

Play: zoom_Aug_4.mov

The average sunspot is about the size of Earth, though the largest can be 20 times the size of Earth.

Butterfly Diagram

Butterfly Diagram

• Plot of sunspot latitude v. time

• Most sunspots fall between 30°N and 30°S

• A new cycle starts every 11 years.

• Sunspots first form at mid-latitudes, widen, and then move toward the equator as each cycle progresses.

Current Solar Cycle

Many cycles are double peaked but this is the first in which the second peak in sunspot number was larger than the first. We are currently over five years into Cycle 24. The current predicted and observed size makes this the smallest sunspot cycle since Cycle 14 which had a maximum of 64.2 in February of 1906.

• First observed by watching sunspots.

• Does not rotate at the same rate everywhere because it is a gas

• Equator is faster than poles

• Causes the magnetic fields to be stretched and solar storms develop

• Average is 27 days

Sun’s Rotation

-

Solar Prominences• Clouds of

glowing gas• Arch from one

sunspot to another

• Follow magnetic field lines

Solar Flare• Sudden, rapid, and

intense variation in brightness.

• Occurs when magnetic energy that has built up is suddenly released.

• Most violent eruption of plasma

Solar flaresThey appear as bright flashes

sometimes followed by a burst of high energy particles that can travel at half the speed of light. Large flares can occur several times a year when the Sun is near its peak activity.

• The “snow” in the clip is radiation from the storm hitting the spacecraft

(Green tint has been added)

Play: Flare.mov

Coronal Mass Ejection• Parts of the

corona are thrown off the sun.

• Can be larger than the sun.

• Can cause a disturbance in the earth’s magnetic field

CME in a CoronagraphIn this stop-motion clip with the Sun blocked (red disk) to reveal the faint corona, we see a coronal mass ejection (CME) bursting into space over a few hours. This instrument that produced this kind of image is a coronagraph. The white circle represents the covered Sun.

Play: Slo_mo.mov

Auroras

Auroras• Aurora Borealis (the

Northern Lights)

• Aurora Australis (the Southern Lights)

• Solar wind ions enter Earth’s atmosphere by following magnetic field lines.

• Ions interact with gasses in the Earth’s atmosphere causing different colors

• Strongest near the polar regions Green - oxygen, up to 150 miles in altitude

Red - oxygen, above 150 miles in altitude Blue - nitrogen, up to 60 miles in altitude Purple/violet - nitrogen, above 60 miles in altitude

Play: Aurora.mov

Aurora from space

Aurora develop around 40 miles (70 Km) above Earth -- you can see their depth here.

The changing conditions on the Sun and in space that influence the performance and reliability of spaceborne and groundbased technology as well as endanger life or health.

Space Weather

Space weather upsets

There are less pleasant space weather effects. Energy pumped into our atmosphere upsets modern technology. Radio signals and communications become disrupted. Satellites orbiting around Earth can suffer damage. On the ground, magnetic field changes can damage electrical equipment on

Earth.

Play: Impacts.mov

Power system damage

Communication disruptions

Spacecraft malfunctions

Navigational problems

Astronaut safety

Astronauts can get high doses of radiation from solar storms and cosmic radiation when out in space. For humans to travel to the Moon and

Mars, better storm forecasting and shielding will be needed.

Studying the Sun• National Solar

Observatory

SOHO• a joint mission of NASA

and the European Space Agency (ESA) studying the Sun since 1996

• 12 instruments to study the Sun’s interior, atmosphere, and solar wind all day, every day

• a major tool for monitoring space weather

• weighs 2 tons; its solar panels span 25 feet

• SOHO is 1 million miles (1.6 million km) towards the Sun

(Solar and Heliospheric Observatory)

Play: SOHO_fly.mov

TRACE• Studies the Sun and

solar events at a much smaller scale than SOHO

• Launched in 1999• Works closely with

SOHO

Some TRACE Results

• Close-ups of flares and loops

Video credit: SolarMax IMAX film

Play: Trace.mov

The newest solar mission, STEREO, launched in Oct. 2006, is unique. A pair of nearly identical NASA spacecraft are studying the Sun from positions ahead of and trailing Earth. They are identifying particle data and providing 3-D views of solar storms for the first time ever.

Play: STEREO_Station.mov

First STEREO images

• New coronagraph and ultraviolet images with sharper details than ever before(December 2006)

Fine solar details from STEREO

Because STEREO has large imagers, it can capture more full disk details than previous solar missions. These loops show particles racing along magnetic field lines .

Play: arcs.mov