Interesting Facts about Our Sun

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Magnetic field lines

Mass ejection from the sun often follow magnetic field loops.

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Slide 13

The Solar Cycle

11-year cycle

Reversal of magnetic polarity

After 11 years, North/South order of leading/trailing sun spots is reversed

=> Total solar cycle = 22 years

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Slide 14

The Sun’s Magnetic Cycle

After 11 years, the magnetic field pattern becomes so complex that the field structure is re-arranged.

→ New magnetic field structure is similar to the original one, but reversed!

→ New 11-year cycle starts with reversed magnetic-field orientation

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Slide 15

The Solar Cycle (II)

Maunder Butterfly Diagram

Sun spot cycle starts out with spots at higher latitudes on the sun

Evolve to lower latitudes (towards the equator) throughout the cycle.

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Slide 16

The Maunder Minimum

The sun spot number also fluctuates on much longer time scales:

Historical data indicate a very quiet phase of the sun, ~ 1650 – 1700: The Maunder Minimum

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Slide 17

Prominences

Looped Prominences: gas ejected from the sun’s photosphere, flowing along magnetic loops

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Slide 18

Eruptive Prominences

(Ultraviolet images)

Extreme events, called coronal mass ejections (CMEs) and solar flares, can significantly influence Earth’s magnetic field structure and cause northern lights (aurora borealis).

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Slide 19

Eruptive Prominences

(Ultraviolet images)

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Slide 20

Solar Aurora

Sound waves produced by a solar flare

~ 5 minutes

Coronal mass ejections

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Slide 21

The Chromosphere

Chromospheric structures visible in Ha emission

Region of sun’s atmosphere just above the photosphere.

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T: 4400 K → 25,000 K

n: 1011 cm-3 → 107 cm-3

Absorption and emission lines from singly ionized metals (He II, Fe II, Si II, Cr II, Ca II)

Slide 22

The Chromosphere (II)

Spicules = filaments of hot gas, visible in Ha emission.

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Streams extend up to ~ 10,000 km above photosphere