STOCHASTIC COUPLING OF SOLAR PHOTOSPHERE AND CORONA ( Astrophysical J., 2012, 2013)
The Sun - Cornell University is believed the magnetic field of the sun carries energy from the...
40
10/17/2012 1 The Sun Structure Atmosphere Variability and Activity Interactions with Earth
Transcript of The Sun - Cornell University is believed the magnetic field of the sun carries energy from the...
10/17/2012
1
The Sun
Structure
Atmosphere
Variability and Activity
Interactions with Earth
10/17/2012
2
10/17/2012
3
10/17/2012
4
10/17/2012
5
AKHENATON (1353-1335 BC)
THE HERETIC PHARAOH
“LE DIEU SOLEIL’’
ATON The Supreme SUN God
Monotheistic religion with a good natured
God, the disc of life giving Sun
10/17/2012
6
AMONG THE WORSHIPERS OF THE SUN:
Pharaoh Akhenaton (1353-1335 BC) “Dieu Soleil”
Roman Emperor Constantin (274-337) “Sol Invictus”
King Louis XIV (1643-1715) “Roi Soleil”
10/17/2012
7
10/17/2012
8
10/17/2012
9
10/17/2012
10
10/17/2012
11
10/17/2012
12
10/17/2012
13
Solar flare affects communications, disruptions possible
Thursday, September 8, 2005; Posted: 7:36 a.m. EDT (11:36 GMT)
The solar flare is fourth largest in the last 15 years, a solar forecaster said.
• NOAA Space Environment Center
WASHINGTON (AP) -- A large solar flare was reported Wednesday and forecasters
warned of potential electrical and communications disruptions.
The flare was reported by the National Oceanic and Atmospheric Administration's
Space Environment Center in Boulder, Colorado.
Significant solar eruptions are possible in the coming days and there could be
disruptions in spacecraft operations, electric power systems, high frequency
communications and low-frequency navigation systems, the agency said.
"This flare, the fourth largest in the last 15 years, erupted just as the ... sunspot cluster
was rotating onto the visible disk of the sun," said Larry Combs, solar forecaster at the
center.
The flare has affected some high-frequency communications on the sunlit side of
Earth, NOAA reported.
Copyright 2005 The Associated Press
10/17/2012
14
10/17/2012
15
The Sun
The sun is a huge ball of fire.
A million Earths can fit inside the sun.
10/17/2012
16
The sun is a normal star.
There are two hundred billion stars in the
Milky Way galaxy.
We observe BILLIONS of galaxies in the
universe.
Basic Solar Information The sun is a gaseous fire ball with:
Mass: 1.991033 gm
Radius: 6.961010 cm
Mean Density: 1.41 gm/cm3
Surface Temperature: 5780 K
Rotational Period: 25 days (at equator)
Luminosity: 3.851033 erg/sec
Distance from Earth: 1.496108 km
The sun is a Main Sequence star.
10/17/2012
17
Birth of the Sun and Solar System
The sun was formed 5 billion years ago by the gravitational collapse of an interstellar cloud.
Debris left behind formed the planets, satellites, and asteroids.
The Solar System
10/17/2012
18
Solar-Earth Interaction
The sun is continuously active with storms and flares.
These greatly affect the Earth and its atmosphere.
Evolution of the Sun
10/17/2012
19
The Core
The core of the sun is the place where nuclear
fusion reactions power the sun.
It is approximately 15106 K.
The sun has been burning for 5 billion years
and theoretically should continue burning for
another 4 to 5 billion.
Should the core stop burning the star’s
luminous life would be at an end.
The Proton-Proton Chain Reaction
Three steps complete this fusion reaction:
1H + 1H 2H + e+ +
2H + 1H 3He + energy
3He + 3He 4He + 1H + 1H + energy
Net effect reaction:
4(1H) 4He + energy
10/17/2012
20
The CNO Cycle
Six steps complete this fusion reaction:
12C + 1H 13N +
13N 13C + e+ +
13C + 1H 14N +
14N + 1H 15O +
15O 15N + e+ +
15N + 1H 12C + 4He
Solar Interior
Radiative zone:
Energy is transported by electromagnetic radiation
Convection zone:
Energy carried by convection
10/17/2012
21
Photosphere
This is the visible layer of the sun.
It has a density low enough to allow light to escape.
The photosphere is gaseous and very thin ~ 500 km, and is covered by granules and supergranules (boiling bubbles).
Granulation
10/17/2012
22
Granulation
Granules cover the surface of the photosphere,
and are surrounded by darker boundary regions.
The granules are rising gas that is hotter than the
sinking gas of the boundaries.
They are about 1000 km (the size of Texas) and
each lasts several minutes.
Supergranules measure about 30000 km across
and are believed to be caused by large, deep
convective cells under the photosphere.
Chromosphere Very faint layer above the photosphere, which is
about 10000 km thick.
Only visible during a total solar eclipse.
Spicules fire up through the chromosphere, these
originate along the edges of supergranules.
10/17/2012
23
Heliosiesmology
This is the study of the vibrations of the sun using the Doppler Effect.
We are able to estimate the interior of the sun this way.
Analogous to measuring seismic waves in an Earthquake.
Corona Solar Outermost Thin Atmosphere
10/17/2012
24
10/17/2012
25
10/17/2012
26
Corona Solar Outermost Thin Atmosphere
The corona is much hotter (2 million Kelvin) than
the surface of the sun and has a density much
lower than the photosphere. It is normally seen
during a total solar eclipse.
It is believed the magnetic field of the sun carries
energy from the photosphere to the corona, thus
heating it.
10/17/2012
27
Corona Solar Outermost Thin Atmosphere
It changes size and shape according to the stage
of the solar cycle.
Occasionally releases magnetic energy into the
solar wind, which interacts with the Earth’s upper
atmosphere, causing auroras, and the possibility
of triggering a magnetic storm causing strong
electrical currents to run through the earth.
Earth Is Shown For
Size Comparison Earth
Magnetic Cloud
Coronal
Mass
Ejection
SUN
Coronal Mass Ejections
10/17/2012
28
10/17/2012
29
10/17/2012
30
10/17/2012
31
Solar Wind
Hot gases and EM radiation escape from the
corona constantly and are unleashed into the
solar system.
The matter in the corona is constantly
replaced by matter from the underlying layers.
This wind interacts with Earth’s own magnetic
field.
Sunspots These are dark “spots” on the sun’s photosphere
which are about a few times the size of Earth.
They often occur in groups and they vary in
duration lasting anywhere from a few days to a
few months.
At any one time dozens of sunspots to none at all
can be seen on the sun.
10/17/2012
32
Sunspots
The darker appearance is because sunspots are
cooler (4500 K) than the surrounding photosphere.
The center of the sunspot is known as the umbra,
and the outer region is the penumbra.
10/17/2012
33
The Sunspot Cycle
Sunspots are associated with strong
magnetic fields and are probably
magnetically interconnected below the
photosphere.
Every 11 years the number of sunspots
hits a maximum then declines, this cycle
has been known for 100’s of years.
The Sunspot Cycle
1850 1860 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000
10/17/2012
34
The Maunder Minimum
Magnetic Field and Sunspots
The magnetic field in sunspots has been
measured to be 1000 times stronger than the
surrounding photosphere.
Sunspots are caused by localized magnetic
enhancements through the photosphere.
Sunspots are polarized with respect to which
hemisphere they occupy. The northern
hemisphere sunspots are oppositely polarized
from those in the southern hemisphere.
10/17/2012
35
The Solar Cycle
A full solar cycle is 22 years in duration.
Every 11 years the magnetic polarity of the
sun reverses.
Thus for a full cycle to complete two
polarity reverses must occur.
Prominences
These arch-shaped explosions of hot
ionized gas stem from groups of sunspots.
They are thought to be caused by
magnetic instabilities around the sunspots.
Eruptive prominences may shoot up to
500,000 km in a few hours.
10/17/2012
36
Prominences
10/17/2012
37
Solar Flares
Flares are eruptions on
the surface of the sun
which seem similar to
prominences.
Solar flares may only last
minutes or hours, and
releases enormous
amounts of energy.
Solar Flares
The energy equivalent of that released by solar
flares is comparable to millions of 100 megaton
hydrogen bombs exploding at the same time.
Flares almost always occur near sunspots, thus
linking them to magnetic field activity.
A large fraction of radiation from flares escapes
the sun and some interacts with Earth.
10/17/2012
38
The Sun-Earth Relationship The sun affects many facets of life on Earth.
Even small permanent changes in solar weather would destroy much of life on Earth.
Space weather can disrupt communications, the power grid, and cause variations of the Earth’s atmosphere.
Surface temperatures, cloud cover, drought,
rainfall, tropical cyclones, and forest fires all
mutually compare to the sunspot cycle.
Coronal ejections into the solar wind are the
cause of auroras often seen in the Northern
latitudes.
Climate and Weather
10/17/2012
39
Technology Coronal mass ejections increase the ionization in Earth’s
ionosphere which interferes with shortwave radio signals.
Coronal ejections also are the cause of electrical ground
currents running through the earth, historically burning
telegram wires and starting fires. These currents can
greatly disrupt power grids causing blackouts to millions at
great cost.
Recent strong solar flares have caused complete failure of
electronic systems on several artificial satellites.
Radiation
Normally, the radiation received from the sun
is thought as inconsequential, this is ignoring
abnormally prolonged exposures.
However, astronauts and airline crews, with
their higher altitude careers are exposed to
more radiation than the average person on the
ground, and this amount of radiation is
increased when solar flares erupt.
Enhanced solar radiation reaching the Earth is
harmful to life and could be fatal.
10/17/2012
40
The Sun Arguably the sun is the
most important energy
source for life.
Understanding the activities
of the sun better will allow
for predictions of potentially
damaging flares and bursts
that may even threaten life
on Earth.
