By- Anamika Nath. B.E. (CSE) - 3rd Semester. NITS Mirza, Assam. Date: 03/12/'11.

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SUBMITTED BY--SUBMITTED BY--
Anamika NathAnamika Nath
B.E. 3rd SemesterB.E. 3rd Semester
G.U. Roll Number: N-10/48G.U. Roll Number: N-10/48
Regn. Number: 67864 / 2010-11Regn. Number: 67864 / 2010-11
Computer Science & EngineeringComputer Science & Engineering
NITSNITS

2. Basic Facts:Basic Facts:
Age = 4.6 billion years
Orbital Speed = 220 km/s
Mass = 2x1030
kg
Radius = 7x108
m = 7x105
km
Distance = 1.5x1011
m = 1.5x108
km = 8.3 light-minutes
Core temperature : 15 million °C
Average surface temperature: 5,500 °C
Luminosity = 3.9x1026
W (Solar Constant = 1350 W/m2
)
Mean Density = Mass/Volume = M/((4/3)πR3
)= 1400 kg/m3
= 1.4 g/cm3
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3. Element Abundance
(percentage of total
number of atoms)
Abundance
(percentage of total
mass)
Hydrogen 91.2 71.0
Helium 8.7 27.1
Oxygen 0.078 0.97
Carbon 0.043 0.40
Nitrogen 0.0088 0.096
Silicon 0.0045 0.099
Magnesium 0.0038 0.076
Neon 0.0035 0.058
Iron 0.0030 0.14
Sulphur 0.0015 0.040
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4. Anatomy of Sun:Anatomy of Sun:
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5. Major Regions:Major Regions:
Interior (“Inner-sphere”)
•Core
•Envelope (Radioactive Zone,
Convective Zone)
•Atmosphere(“Outer-
sphere”)
•Photosphere:Teffctive ~ 5780 K
•Chromosphere
•CoronaNo real “surface” - it is gaseous all the way to the center!
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6. Temperature rises to ~ 500,000 - 1,000,000 K
Highly ionized atoms, such as Fe+13
(also called Fe XIV)
light scattered by ions & electrons (inner) & dust grains (outer)
Heated by complex magnetic/particle activity
CoronaCorona
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7. •Sunspots are the dark
regions that appear on the
surface of Sun.
•The amount of solar
activity on the Sun is not
constant, and is closely
related to the typical
number of sunspots that
are visible.
•The number of
sunspots and the levels
of solar activity vary with
an 11 year period known
as the solar cycle.
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8. Solar Cycle:Solar Cycle:
Number of spots = ~ 11 yrs
Magnetic polarity of spots = 22 years
(to return to starting orientation)
Horace Babcock - Magnetic Dynamo via differential rotation8

9. Solar Flares:Solar Flares:
The most violent events on
the surface of the Sun are
sudden eruptions called solar
flares. Flares typically last a
few minutes and can release
energies equivalent to
millions of hydrogen bombs.
Figure showing multiple solar flaresFigure showing multiple solar flares
It’s the sudden release of
energy equal to 100s of
millions of megatons - radio
through gamma rays
Temperatures exceed 10
million K
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10. Prominences -Prominences - filaments
seen from the side.
•Quiescent Prominences
•Active Prominences
•Eruptive Prominences
Filaments -Filaments - cool streamers
of gas above photosphere
Plages -Plages - heated by rising
magnetic field - compresses gas
Filaments, Plages, Prominences :Filaments, Plages, Prominences :
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11. Limb DarkeningLimb Darkening
The photosphere is hotter as you go deeper
We see deeper when looking at the center of the “disk”
Brightness increases as T4
(Stefan-Boltzmann Law)
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12. Solar WindSolar Wind
Outer atmosphere is flowing away from the
Sun - the solar wind
Speeds up to few million km/hr
Earth is inside the solar wind!
At Earth:
V = 400 - 700 km/s
T = 50,000-500,000 K*
density = 103
- 104
/m3
(Earth at sea level - ~2.5x1025
/m3
)
Solar wind expands outward,
creating the heliosphere
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13. Sunspots:
•Appear in groups
•T~4000-4500 K
•Darker than surrounding photosphere
•Large magnetic fields inhibit convection
umbra
penumbra
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14. Solar Magnetic Field:Solar Magnetic Field:
The heliospheric current sheet extends to the outer reaches
of the Solar System, and results from the influence of the
Sun's rotating magnetic field on the plasma in the
interplanetary medium.
Sun is a Magnetically active Star
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15. Sun’s Effects on Earth:Sun’s Effects on Earth:
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Earth’s greenhouse gasesEarth’s greenhouse gases
The Average TemperatureThe Average Temperature
Profile of Earth's AtmosphereProfile of Earth's Atmosphere

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ConclusionConclusion
• Never see the Sun directly, it can damage eyes

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