Download Week two: The Sun (pdf, 3.9 MB)

Lecture 2:
The Sun and the Heliophysics
Sun – Earth system
Magnetospheric
Physics
Heliophysics
Ionospheric
Physics
Heliosphere
• Plasma
• Dust
• Cosmic rays
Heliosphere is
the bubble-like
region of space
dominated by
the Sun
Pressure of the
interstellar
medium =
Solar wind
pressure
Heliosphere
on August 25, 2012, Voyager
1 exited the Heliosphere,
when it measured a sudden
increase in plasma density of
about forty times
1 AU= 100 million km
https://www.youtube.com/watch?v=L4hf8HyP0LI
Heliosphere
Spacecraft
Spacecraft
GGS WIND measures
solar wind and energetic
particles from the Sun.
SOHO studies
the sun from
core to outer
corona
RHESSI explores
the particle
physics behind
solar flares.
ACE observes energetic solar,
interplanetary, interstellar,
and galactic particles. Onehour warnings of approaching
geomagnetic storms.
Hinode is the Japanese word
for sunrise. It is a joint
mission between JAXA, NASA
and the ESA to study the
sun's magnetic cycles.
NASA’s twin STEREO
spacecraft provide
stereoscopic views of the
sun to better understand
coronal mass ejections.
SDO records the
Sun's dynamic solar
activity to
understand how it
affects life on Earth.
Very different Sun
Very different Sun
Surface of the Sun
Surface? Not really…
Sharp transition.
T up e- off
Fully Ionized Plasma
Plasma Phase
• Free electrons move among
positively charged ions
Molecules -> atoms
Gas Phase
• Molecules move essentially
unconstrained
Liquid Phase
• Molecules remain together but
move freely
Solid Phase
• Molecules are held tightly in
place
Gas vs Plasma
We don’t
care!
S
Gas
N
Gas vs Plasma
WOW!
S
Plasma
N
Gyration
Gyromotion
•
•
•
•
Differential motion produces current
Currents produce the magnetic field
Plasma and Magnetic field are ‘frozen-in” together
The plasma cannot move unless the magnetic field moves
The Sun’s anatomy
• Found fossils of
primitive creatures
at least 3.5 billion
years old.
• Future: 7 billion
more
• Fueling process?
• Nuclear reaction at
the center of the Sun
• “Nuclear” because it
is an interaction of
atomic nuclei
• Core T=15,600,000 K
• Density=151 g/cm3
• (13 times higher
than lead)
Fusion
Min T=14,000,000 K
Neutrino
Positron
Deuterium
Mass(alpha particle) is 0.7%
lighter than 41H
So what?
Alpha particle
Mass(alpha particle) is 0.7%
lighter than 41H
Every second 700,000,000,000
kg of H fuses into He
H
Used
Left
37, 37%
63, 63%
0.7%=5,000,000,000 kg
E=(5,000,000,000 kg)*c2
C=3*108
m/s
E=4.5*1026
Joules
In 2015 world consumed
5.67 × 1020 Joules
Neutrinos
70 billion solar neutrinos
pass through each square
centimeter of the Earth’s
surface facing the Sun
If we can detect neutrinos
then indeed the Sun is
powered by the H fusion!
In 2002 Ray Davis and
Masatoshi Koshiba won part
of the Nobel Prize in Physics
Neutrino detection
The water Cerenkov neutrino
detector of the SuperKamiokande experiment in
Japan comprises a tank filled
with 50,000 tons of water
and lined with more than
11,000 photomultiplier
tubes.
The interaction of a muon
neutrino inside the SuperKamiokande detector
Radiative Zone
Energy travels through
the radiation zone in the
form of electromagnetic
radiation as photons
Matter in a radiation
zone is so dense that
photons can travel only a
short distance before
they are absorbed or
scattered by another
particle
T drops from 15 million K
to 1.5 million K
it takes an average of
171,000 years for
gamma rays from the
core of the Sun to leave
the radiation zone
Convection Zone
Stellar convection consists of
mass movement of plasma
within the star which usually
forms a circular convection
current with the heated plasma
ascending and the cooled
plasma descending.
10 days -> cools -> sinks
The Solar Atmosphere
Photosphere = the
visible “surface” thin
shell (100 km) from
where the light is
radiated
The chromosphere
emits a reddish glow as
super-heated hydrogen
burns off. But the red
rim can only be seen
during a total solar
eclipse. At other times,
light from the
chromosphere is usually
too weak to be seen
against the brighter
photosphere.
Very nice coincidence
Chromosphere
Luc Viatour
Solar Corona
WHAAAAAAAAAT????
Wave Heating Theory
• Magneto-acoustic waves
• Alfven waves
• turning into shock waves and dissipate their energy as heat.
Differential Rotation
Plasma! “Frozen-in”!!!
Differential Rotation
Plasma! “Frozen-in”!!!
Magnetic Field
Magnetic Field
Magnetic Reconnection
Magnetic Reconnection
Magnetic Field
https://www.youtube.com/watch?v=1jQ0M7K0E3s&ebc=ANyPxKqiBKDz6jocME2LSj0miw81cQQUb_zN_tIQDLF4unByX25uOwgKz3RVSe2kWLhCFo__HUMjafQs17wN
GqJjpc1gsn75Q&nohtml5=False
Solar Flares
Coronagraphs
A coronagraph is a telescope that
can see things very close to the
Sun. It uses a disk to block the
Sun's bright surface, revealing the
faint solar corona, stars, planets
and sungrazing comets. In other
words, a coronagraph produces an
artificial solar eclipse.
Coronagraphs
Coronagraphs
https://www.youtube.com/watch?v=ZnDDIYm55y4
Van Gogh Sun
https://commons.wikimedia.org/w/index.
php?title=File%3AVan_Gogh_Sun.ogv
STEREO
(Solar Terrestrial Relations Observatory)
60-80 thousand C
1 million C
1.5 million C
2.5 million C
Sunspots
• Good indicator of solar activity
• Greek philosopher Anaxagoras observed a
spot in 467 BCE
• Scheiner began his serious study of spots in
October 1611
Sunspots
Sunspots
Solar Cycle
https://www.youtube.com/watch?v=P2hN5M4
g5bY&feature=youtu.be
Coronal Hole
• region on the
Sun where the
magnetic field is
open to
interplanetary
space
• sending coronal
material
speeding out in
what is called a
high-speed solar
wind stream
• wavelengths of
193 Angstroms
Oct. 10, 2015, by NASA's Solar Dynamics Observatory