A100 The Sun
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Transcript of A100 The Sun
Today’s APOD
Homework and Quiz 9 TodayReading for next week on
Oncourse
The Sun Today
A100 The Sun
Reading for next week available from the Resource Tool on Oncourse
Quiz 9 – Question 1: The diameter of the Sun is about how large compared to the diameter of the Earth?
A. Twice as bigB. One half as bigC. 10 times as bigD. 100 times as bigE. 10,000 times as big
Question 2: The Sun is supported against the crushing force of its own gravity by
A. Magnetic forcesB. Its rapid rotationC. The force exerted by escaping
neutrinosD. Gas pressureE. A solid, crystalline ball of metallic
hydrogen that fills the interior of the Sun
What we covered on Wednesday:
Internal structure of the SunComposition of the SunSource of the Sun’s energyThe Sun’s lifetimeBalancing pressure, gravity, and
temperatureHelioseismologyWhat neutrinos tell us about the Sun
Today: The Sun’s Atmosphere
Recall the structure of the Sun…
Corona
The Sun’s Atmosphere: Photosphere, Chromosphere, Corona, Solar Wind
Photosphere
Umbra
Penumbra
Sunspots
Active regions
TheSun Corona
Chromosphere
three layers of the Sun’s atmospherephotospherechromospherecorona
Photosphere
Limb
Convection
Supergranules
Granulation
Limbdarkening
Umbra
Penumbra
Sunspots
Active regions
Prominence
Limb darkening: …when we look near the Sun’s limb we do not see as deeply into the photosphere
Photosphere
The photosphere is opaque to visible light
The density is only 1% the density of air
Temperature decreases from inside the Sun to a minimum of 4400K just above the photosphere
convection cells ~ 1000 km (600 mi)
The difference in Tfrom center to edge is about 300 K
> hot gas from lower levels rises upward, cools off, and falls back into the Sun
Cells form and disappear in few minutes.
The Solar Photosphere – the layer we see
GRANULATION
The convection moves at 1400 km/h =900 mi/hSupergranules last about a day
Supergranules35,000 km in diameter
Question 3: The Sun produces its energy from
A. Fusion of neutrinos into heliumB. Fusion of positrons into heliumC. Disintegration (fission) of helium
into hydrogenD. Fusion of hydrogen into heliumE. Electric currents generated in the
core
Solar Atmosphere Absorption lines
from the photosphere and chromosphere
67 different elements in various stages of excitation and ionization
The spectrum gives us a picture of the physical conditions in the solar atmosphere
Umbra
Penumbra
Blotchy sunspots
appear on the Sun’s
“surface”
Note also the “granulation” resulting fromconvection under the surface
Sunspot grouping
Sunspots are low-temperature regions inthe Sun’s photosphere
Sometimes they are isolated but frequently in sunspost groups
~ diameter of Earth (lasting between hours or months)
T (umbra) = 4300 KT (penumbra) = 5000 KT (photosphere = 5800 K
The brightness depends on the 4th power of the temperature (energy flux T4 )
Photosphere
The number of sunspots varies in an 11 year cycle
Question 4: Why are sunspots darker than their surroundings?
A. They are cool relative to the gas around them
B. They contain 10 times as much iron as surrounding regions
C. Nuclear reactions occur in them more slowly than in the surrounding gas
D. Clouds in the corona block our view of the hot photosphere
E. The gas within them is too hot to emit any light
Magnetic Carpet
Chromosphere
Spicules
Prominence
Above the photosphere, the
temperature increases again from 4400 K to
25,000 K at the top of the
chromosphere
The chromosphere is characterized by spikes of rising gas
Above the photosphere, the gas density is much lower (10-4 less than the photosphere) but gas is much warmer (25,000 K)
Red color from the emission line of hot hydrogen
(Using Hydrogen filter)
• Spicules last about 15 minutes• they rise at speeds of 20km/s• 300,000 spicules cover the Sun at any one time
Spicules: jets of rising gasSpicules extend upward from the photosphere into the chromosphere along the boundaries of supergranules
dense jets of gas that shoot up from the
chromosphere
Solar Wind
Coronal MassEjection
Corona
AuroraCoronal Holes
The corona, the outermost layer of the solar atmosphere, is made of very high-temperature gases at extremely low density
The solar corona blends into the solar wind at great distances from the Sun
CORONA
The corona extends for millionsof kilometers out from the Sun
a million times fainter
than the photosphere...
In the narrow region between the chromosphere and the corona, the temperature rises abruptly to more than a million degrees!
(BUT NOT MUCH HEAT!)
Activity in the corona
includes coronal mass ejections and coronal holes
The Sun also produces huge
flares that burst into space A solar flare is a brief
eruption of hot, ionized gases from a sunspot group
A coronal mass ejection is a much larger eruption that involves immense amounts of gas from the corona
The Solar Wind
The Sun is “evaporating” constantly (ONLY 0.1% of its mass since its formation)
Interact with objects in the solar system Earth: cause aurorae Comets: produces tails Interacts with edge of solar system: heliopause
Radiation reach Earth in 8 min, particles take a few days (v= 500 km/s)
Coronal particles (mostly electrons and protons)
are thrown with such velocity that they cannot
be held by the Sun’s gravity
Photosphere
Limb
Convection
Supergranules
Granulation
Limbdarkening
Umbra
Penumbra
Sunspots
Active regions
TheSun
Magnetic Carpet
Solar Wind
Coronal MassEjection
Corona
AuroraCoronal Holes
Chromosphere
Spicules
Prominence
The X-raySun
coronal
hole
What causes all this violent activity on the Sun?????
Rotation and Magnetic Fields!
massejectio
n
Sunspots show
the Sun is
rotating(Galileo!
)
The Sun does not rotate rigidly: the equatorial regions rotate faster (25 days) than the poles (36 days) --- Differential Rotation
The Sunrotates atdifferentrates at
different solar
latitudes
Pequator=25 days
Ppole=36 days
The Sun’s differential rotation winds up the Sun’s magnetic field, storing energyWhen the magnetic field suddenly unwinds, that energy is released
The Solar MagneticField
The differential rotation “wraps up” the magneticfield of the Sun
Sunspots and othersolar activity are causedby the twisted magnetic field of the Sun
Solar Activity Varies in an Eleven Year Cycle
The Sun’s magnetic field takes 11 years to twist up and then reestablish itself
The number of sunspots, as well as the number of violent events depends on the state of the magnetic field
Variations in Sunspot Activity
n
MaunderMinimum
Question 5: How many years elapse between times of maximum solar activity?
A. 3B. 5C. 11D. 33E. 105
Space Weather:
What is it?Space Weather refers to conditions in space that can influence the performance and reliability of space-borne and ground-based technological systems and can endanger human life or health.
Earth
Sun: •Energy released in the form of photons, particles, and magnetic fields
•Sources of major disturbances:•Coronal Holes•Solar Flares•Coronal Mass Ejections•Solar Particle Events
SPACE WEATHER
Hurricanes and Tornados
Weather Space Weather
Solar Corornal Mass Ejection
Space Weather
Geomagnetic Storm Effects Telegraph
Operations - September 3, 1859Boston (to Portland operator).--"Please cut off your battery entirely from the line for fifteen minutes."
Portland.--"Will do so. It is now disconnected."
Boston.--"Mine is also disconnected and we are working with the auroral current. How do you receive my writing?"
Portland.--"Better than with our batteries on. Current comes and goes gradually."
Boston.--"My current is very strong at times, and we can work better without batteries, as the aurora seems to neutralize and augment our batteries alternately, making the current too strong at times for our relay magnets. Suppose we work without batteries while we are affected by this trouble?"
Portland.--"Very well. Shall I go ahead with business?"
Boston.--"Yes. Go ahead."(Annual of Scientific Discovery, ed. by D.A. Wells, Boston, Gould and Lincoln, p414, 1860; Singer, H.J., Magnetospheric Pulsations, Model and Observations of Standing Alfven Wave Resonances, Thesis, UCLA, 1980.)
1958 Geomagnetic StormOn February 9, 1958 an explosive brightening was observed on the solar disk at the Sacramento Peak Observatory
A notice was radioed to the IGY Data Center on Solar Activity at the Univ. Colorado’s High Altitude Observatory in Boulder
28 hours later one of the greatest magnetic storms on record began
It was the 13th most disturbed day from 1932 to the present
Effects:
Toronto area plunged into temporary darknessWestern Union experienced serious interruptions on its nine North Atlantic telegraph cablesOverseas airlines communications problems
Brooks, J., The Subtle Storm, New Yorker Magazine, 39-77, Feb. 7, 1959.
NOAANational Weather Service
Weather
Accuweather
Space WeatherNOAA Space Environment Center
MONITORING SPACE WEATHER
www.uhaul.com/supergraphic
Unveiling of U-Haul Truck Supergraphic Representing Colorado at Space Weather Week 2001
Graphic on the side of several thousand U-Haul Trucks
Solar “butterfly” diagram
At the beginning of the solar cycle, sunspots appear at high latitude on the Sun
As the cycle progresses, sunspots appear closer and closer to the solar equator
Reading, homework, quiz next week
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Dates to Remember