The Active Sun

Sunspots

Umbra Penumbra

Granulation

Features of Sunspots

Darker than surrounding photosphereCooler

Granulation inhibited (movie)Occur in pairsSunspot Cycle

Sunspot Cycle

0

40

80

120

160

200

1700 1750 1800 1850 1900 1950 2000

Year

Su

nsp

ot

Nu

mb

er

Maunder Butterfly Diagram

Magnetic Polarities

Opposite polarities within

a pair

Pairs in opposite hemispheres have opposite

polarity

Entire structure reverses

every cycle

S

N

S

N

S

N

Beginning of cycle Later in the same cycle

N

N

S

S

SN

N

S

The next cycle

N

N

S

S

Babcock Model

Two features combine to produce sunspotsGeneral Magnetic FieldDifferential Rotation

Wrapping Field Lines

Link

Model Check ListSpots first appear 30° from equator

opposite polarities within pairswitched polarities in other hemisphere

Become more numerous and closer to the equator as the wrapping continuesMaximum is reached midway

Magnetic field lines untanglefewer spots, closer to equatorwhen totally untangled, the field is flipped

Should Other Stars Have Spot Cycles?

RequirementsMagnetic FieldDifferential RotationInstability below photosphere

• Convective Zone

Plages

Prominences

Movie

Flares

October 29, 2003

Coronal Mass Ejection

Solar-Terrestrial Relationships

Light - HeatParticles - Solar Wind, Flares

Radio Communication DisruptionAurorae (The Movie)

Aurora Borealis

Earth’s Magnetic Field

Tree Rings

Width follows a 22-year cycleIn phase with sunspots

Maunder Minimum

Global Climate