Solar activity and sunspots

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Solar activity and sunspots
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Our Sun Composed of 91.2 H, 8.7 He 840,000
miles in diameter, weighs 4.41030 lbs More than
1 million Earth's could fit inside and is 330,000
times the weight of Earth Only body in our solar
system large enough to have internal temperatures
and pressures that allow nuclear fusion
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Appears to be on fire because the H atoms
collide, undergoing nuclear fusion, and fuse to
become He This process creates enormous amounts
of energy
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On the surface can be seen darker spots called
sunspots caused by huge magnetic storms Can be
up to 12 times the size of Earth
Figure 2.2
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Sunspots occur in cycles, with minimum and
maximum, averaging every 11 years Sunspots
increase the amount of material ejected from the
sun May have some effect on Earth's climate
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Solar Energy From Sun to Earth  

• Solar Activity and Solar Wind  
• Electromagnetic Spectrum of Radiant Energy
• Intercepted Energy at the Top of the Atmosphere 

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In addition to light, sun emits electrically
charged particles that spread outward in all
directions Called solar wind
Particles move slower than light and extend
beyond the edge of our solar system
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Solar wind is deflected by Earth's magnetic field
toward the poles Very little enters the
atmosphere Interaction of solar wind with Earth's
upper atmosphere create the auroras seen in
regions near the poles During sunspot maxima,
auroras can be seen in areas much further south
such as Texas and California
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Apparent link between solar maxima and minima and
Earths climate Wetter periods in midlatitudes
solar maxima Droughts solar minima But weather
patterns lag 2-3 years Is it just coincidence or
not?
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Electromagnetic spectrum Energy travels from the
sun to Earth in waves Visible light is only part
of the spectrum of solar radiation Wavelength
determines the type of energy (ex visible light,
infrared, radio waves)
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The Electromagnetic Spectrum

• Sun radiates shortwave energy
• Shorter wavelengths have higher energy
• Earth radiates longwave energy

Figure 2.5
Figure 2.6
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An object radiates energy in wavelengths related
to its temperature Hotter objects emit shorter
wavelengthsThe suns energy 47 visible, 45
infrared, and 8 shorter wavelengths Earth, much
cooler, emits energy only in the infrared
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Earths Energy Budget
Figure 2.8
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Solar and Terrestrial Energy
Figure 2.7
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• Tropics receive more concentrated insolation
  (2.5x more) than the poles due to the Earths
  curvature

Figure 2.9
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What is insolation? The total amount of
radiation (the full energy spectrum from the sun
visible light and heat energy) That reaches the
surface of Earth
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What affects insolation?

• Latitude further from the equator means less
  insolation.
• Clouds more clouds less insolation

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Note that areas of highest insolation occur over
low latitude deserts (because of frequent
cloudless skies)
Figure 4.4
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Energy Pathways through the atmosphere

• Transmission
• Passage of energy through atmosphere or water
• Scattering
• Changing direction of lights movement, without
  altering its wavelengths

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Transmission
Some wavelengths of solar radiation are absorbed
by the atmosphere.
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Scattering why is the sky blue?
Gas molecules, dust, water vapor in the
atmosphere scatter incoming solar radiation. The
smaller molecules scatter shorter wavelengths
(blue light) better.
Moonrise
Earthrise
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Rayleigh scattering
Red light has longer wavelength, blue light has
shorter wavelength and is scattered more
efficiently This is why our sky is blue during
the day in full sun At sunset and sunrise,
sunlight passes through atmosphere at shallow
angle and all the blue light is scattered away
and only red and orange light is visible
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The color of the sky - how clean is the
air? Clean air is made of small molecules
scatter shorter wavelengths (blue) better blue
sky On a hazy day there are larger molecules in
the air all the wavelengths are scattered sky
looks white
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Diffuse radiation the downward component of
scattered light
Caused by scattering in the clouds Creates
multi-directional light that casts shadowless
light on the ground
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Note the sky is not blue on all planets The sky
on the moon looks black there is no atmosphere
to scatter the light Venus has a much thicker
atmosphere the sky always looks red or orange
The sky on Mars looks pink because of all the
dust particles blown into the atmosphere during
huge wind storms