Lecture 2 - University of Colorado Boulderlcd-axbr9098/teach/ASTR_3760/lectures/ASTR_… · 1...
Transcript of Lecture 2 - University of Colorado Boulderlcd-axbr9098/teach/ASTR_3760/lectures/ASTR_… · 1...
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Lecture 2
• Long-term solar variability
– Grant minima/maxima
– Total solar irradiance
• Spectral irradiance
– Black body, gray body
• Internal structure of the Sun
– Y-dependence
– Intensity & radiation transport
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Summary of previous lecture
• Previous space weather events
– Halloween storm, Carrington flare, etc
• Effect on aviation, GPS, radiation, GICs, etc
– GPS stories: climbers on Mt Everest, Heathrow…
– Biol. impact measured in
(A) Grey, (B) Curie, © Sieverts, (D) rem?
• Kp index
• Sun’s position in HR diagram (L=3.8x1026W)
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Long-term variability
J. Eddy E. Maunder S. Schwaber
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Past sunspot predictions
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Low, but not as low as 1913
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Little Ice Age
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Cycle progression as of now
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Total solar
irrradiance
FrL 24
Integrated flux
Over all l
AU1r
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Pyrheliometer
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Conversion of spectral
distribution function
dTITF ),()(
ll
c)(
or
lll dTITF ),()(
Hint: compute l
d
d
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Dimensional analysis
Hzm
W),(
2TI
dcba kcTvTI B),(
K
J1038.1 23
B
k
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Planck
spectrum
1
12),(
B/2
3
Tkhec
hTI
Tkhe
c
hB/
2
32
Tkch
Tk
c
hB2
2
B
2
3 22
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Rayleigh-Jeans law
Tkc
TI B2
22),(
Tkc
c
cTITI B22
2
2
2),(),(
l
ll l
Tkc
B4
2
l
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Visible spectrum: most of energy
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Infrared: l-4 law
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Radio:
interesting
break
• Clue about hot corona
• Brightness temperature
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“Gray body” at short wavelengths
Page 78 of
Knipp (2011)
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Internal structure of the Sun
• Seeing deeper – Different wavelengths
– Ca, Fe lines (slightly higher up)
– infrared (slightly deeper)
• Helioseismology
• Neutrinos
• Theory (depends on Y and mixing length) – X+Y+Z=1
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Dependence on Y
• Solve time-dependent stellar structure eqns
• Produce more Y
R and L grow (faint sun paradox)
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More on intensity
),ˆ,( tI nx
SI
ds
dI
SI
d
dI dsd
SII n̂
depends also
on direction
for each ray path…
or
with
optical depth
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Related to homework