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Chapter 11: The Sun
Week 8
The Solar Interior
Bahcall, Pinnsonneault, Basu 2001 (linked from class syllabus) will
expand upon Chapter 11 in our book.
http://www.physics.sfsu.edu/~fischer/courses/Astr420/hmwk/Bahcall_Pinsonneault_Basu.pdf
Additional reading:
http://www.physics.sfsu.edu/~fischer/courses/Astr420/hmwk/missing_neutrinos.pdf
Solar atmosphere
Solar Cycle
Chapter 11: The Sun
SOHO http://sohowww.nascom.nasa.gov/
Chapter 11: The Sun
SOHO http://sohowww.nascom.nasa.gov/
Chapter 11: The Sun
SOHO http://sohowww.nascom.nasa.gov/
SOHO’s orbit around
the L1 point.
Chapter 11: The Sun Chapter 11: The Sun
The solar interior
Is the Sun getting brighter or dimmer?
Every second, the Sun turns 700 billion
tons of protons into helium...
At an age of about 4.5 Gyr, about half of
the hydrogen in the core of the Sun has
been fused into He.
Current surface composition: X = 0.74,
Y = 0.24, Z = 0.02.
Current Central Conditions:
Temperature 1.57 x 107 K
Pressure 2.34 x 1016 N m-2
Density 1.527 x 105 kg m-3
X 0.34
Y 0.64
Chapter 11: The Sun
The solar interior
Over the past 40 years, solar models have been refined, tested by
observations of helioseismology (measuring pressure-mode oscillations and velocity fields as a function of radius and depth of the convective
zone) and neutrino flux.
The standard solar model (revised continuously) is a model constructed
with the best physics and input data. Fits the observed luminosity and radiu of the sun at the present epoch, as well as the heavy-element-to-
hydrogen ratio.
Constructed with OPAL EOS.
Chapter 11: The Sun
The solar interior
In 1982, the solar model consisted of 27 radial shells, with ten
variables for each shell: mass, radius, temperature, density, hydrogen fraction, helium fraction, luminosity, and source density
of p-p, 7Be, and 8B neutrinos.
Current models have 875 shells, with additonal variables:
pressure, electron number density, mass fractions of 3He, 7Be, 12C, 14N, 16O, and source densities for all eight of the most important solar neutrino fluxes.
Chapter 11: The Sun
The solar interior
Time-dependent evolution
of the Sun.
As a result of changes to
internal composition, the
Sun is becoming larger
and more luminous.
Chapter 11: The Sun
The solar interior
Energy generation by different nuclear
fusion rxns as a function of solar age.
At 1Gyr, red-circled p-p chain dominates.
The situation changes as the Sun heats
up - by 8Gyr, the CNO cycle becomes
important.
Chapter 11: The Sun
Convective Zone
The depth of the CZ is increasing with time
(black curve) but is roughly proportional to the
stellar radius at all times (red curve).
Time is limited to 6.5Gyr because of the onset of semiconvection (triggered by element
diffusion). As metals accumulate under the
CZ, the opacity increases and the former
radiative zone becomes convective. Metals
mix into the CZ, and the boundary recedes as
the opacity decreases.
The mass of the CZ is decreasing with time
(black curve) but is roughly proportional to the
square of the stellar radius at all times (red
curve). After 6.8Gyr, the CZ mass begins to
increase.
Chapter 11: The Sun
Convective Zone Boundary
The base of the CZ is
defined by the
Schwarzchild criterion;
the density of an
adiabatic cell decreases
as it rises relative to the
surrounding gas:
!PL
MT4~ const
Temperature and opacity
change slowly, the increase of
luminosity is compensated by
a decrease in pressure at the
boundary between radiative
and convective equilibrium
Chapter 11: The Sun
Central values
Tct( )
Rsun
t( )= const
Solar luminosity is derived from
H-fusion, and Xc decreases by
a factor of 2 from ZAMS to
present time.
Chapter 11: The Sun
The solar interior
Radial composition of the Sun
today. 3He is normally destroyed
rapidly, but it has a longer lifetime
at the top of the H-burning region
where the temperatures are
cooler than in the core.
Convective zone
Chapter 11: The Sun
The solar interior
The luminosity increases
rapidly to a maximum value.
The luminosity gradient
peaks at the edge of the H-
burning core.
Temperature and Pressure
drop rapidly.
Chapter 11: The Sun
Energy transport
Schwarzchild condition for
convection plotted vs radius. At the center of the Sun, the
pressure gradient approaches that for
convective instability.
For stars where the CNO cycle takes place (more
massive stars) the cores are
unstable to convection.
Stellar Pulsations
Saskia Hekker
(See Ch 14 in the textbook)
Paper 1: Line Profine Analysis of the Pulsating Red Giant Star Eps Ophiuchi
Paper 2: Pulsations detected in the line profile variations of red giants
Questions
•! Name some groups of pulsating stars?
•! Possible uses of pulsating stars?
•! Types of pulsations?
Discoveries
•! 1595 David Fabricius observed o Ceti
–!star vanished from the sky and re-appears
month later ! Mira
–!11 month period variation of 7 magnitudes
Discoveries
•! 1784 John Goodricke observed !
Cephei
–!variation less than 1 magnitude
–!period 5 minutes, 8 hours, 48 minutes
Cepheids
•! late 1800s and start 1900s
Henrietta Swan Leavitt
discovered 2400 classical Cepheids
in the SMC ! same distance
•! More luminous Cepheids take longer to
go through their pulsation cycle!
m !M = 5log10d
10pc
"
# $
%
& '
Period-luminosity relation
Stellar oscillations occur in almost all
phases of stellar evolution. However
there exist a particular region in the HR
diagram in which the density of pulsating
stars is more outspoken than elsewhere:
the classical instability strip
Pulsation modes
•! p-modes: acoustic waves, restoring force is pressure –!driven by ! mechanism
–!driven by turbulent convection
•! g-modes: restoring force is gravity –!driven by density fluctuations close to the
core
! mechanism
•! suggested by Eddington: if a layer of a
star becomes more opaque upon
compression it could hold the energy
flowing towards to the surface and push
the surface layers upward. The
expanded layer would become more
transparent, the trapped heat could
escape and the layer would fall back.
! mechanism
How could the opacity increase with compression?
Kramers law:
compression: !, T increase, opacity
decrease
special circumstances:
partial ionization zones
! "#
T3.5
! mechanism
•! Hydrogen partial ionization zone:
H I !H II, He I!He II @ 1.5 x 104 K
•! He II partial ionization zone:
He II!He III @ 4 X 104 K
•! also partially ionized iron can cause the
pulsation
! mechanism
•! hot star Teff = 7500 K: ionization zone close
to the surface ! density to low to drive
pulsations ! blue edge instability strip
•! cool star Teff = 5500 K: ionization zone deep
enough to drive pulsations, BUT pulsations
damped in outer layers due to convection
! red edge instability strip
Internal gravity waves
slight density changes close to the core of
the star ! net force pushes it back to
equilibrium position ! harmonic
oscillation incre
asin
g p
ressu
re
!in>!out
!in=!out
Internal gravity waves
•! rapid fluctuations close to the core
•! damp towards the outer parts of the star
•! not known to reach the surface of stars
with a convective outer layer
Solar-like oscillations
•! driven by turbulent convection in stellar
atmosphere
•! timescales shorter than fundamental
radial period
•! expected to be present in all stars with
convective outer layers
•! parameters:
–! frequency
–!number and orientation nodal lines
Solar-like oscillations
•! n = number of nodal lines in radial
direction
•! l = number of nodal lines on surface
•! m = orientation of nodal lines
l=3,m=3 l=3,m=0 l=3,m=1 l=3,m=2
orie
nta
tion
rota
tion
axis
Solar-like oscillations
160 day observations with VIRGO on SOHO
Solar-like Oscillations
!!: large separation ! average density
D0: small separation ! sound speed near the core
!: constant sensitive to surface layers
!n,l
= "!(n +1
2l + #) $ l(l +1)D
0
Solar-like oscillations
•! amplitudes ! Luminosity / Mass
! m/s amplitudes in red giants
•! frequency peak ! Mass / (Radius2 *
!Teff)
decreases from dwarfs to giants
! periods of a few hours in red giants
Target Selection (spectroscopy)
•! bright ! high signal to noise ratio
observing time short enough not to
average over a large fraction of the
oscillation period.
•! slow rotating ! narrow spectral lines
•! no companions or spots
•! low declination ! multi site campaign
•! Red giants:
-! ! Ophiuchi (G9.5III)
-! ! Serpentis (K0III)
-! ! Hydrae (G7III)
-! ! Eridani (K0IV)
(confirmed solar-like
oscillators)
! Ophiuchi
•! G 9.5 giant (De Ridder et al. 2006)
•! mv = 3.24 ± 0.02 mag
•! Mv = 0.65 ± 0.06 mag
•! B - V = 0.96 ± 0.01 mag
•! d = 33.0 ± 0.9 pc
•! Teff = 4900 ± 100 K
•! vsini = 3.4 ± 0.5 km/s
•! dec = -04 41 33.0
•! ~ 900 observations over 3 month with CORALIE and ELODIE
! Ophiuchi
o Coralie data
x Elodie data
De Ridder et al. 2006
! Ophiuchi Period Analysis
Fourier analysis: one tries to define a
function of test frequencies in such a
way that it reaches an extreme for the
test frequency that is close to the true
frequency present in the data.
Observations show 1 day aliasing!
! Ophiuchi ! Ophiuchi
2 possible large separations:
-! !! = 4.8 !Hz
-! mass = 1.9 Msun
-! !! = 6.9 !Hz
-! mass = 2.8 Msun
! Ophiuchi
MOST (Canadian microsatelite) observations, 28
consecutive days, !! ~ 5 !Hz
Barban et al. 2006 How to get the modes?
•! Line shape analysis
Moments
<v>: the centroid of a spectral line
<v2>: the width of the spectral line
<v3>: skewness of the spectral line
variations over time in these moments
provides information on oscillations
other diagnostic: line bisector
< vn
>=
vnp(v)dv
!"
+"
#p(v)dv
!"
+"
#
v: total velocity in line of site
p(v): line profile
! Ophiuchi
line bisector
first moment
De Ridder et
al. 2006
Line shape fits Line shape fits
l=0,m=0 l=1,m=0 l=1,m=1
Line shape fits
l=2,m=0 l=2,m=1 l=2,m=2
Line shape fits ! Ophiuchi
!=58.2!Hz !=63.2!Hz
!=67.5!Hz
! Ophiuchi
Evidence for non-radial modes in red giants:
•! Not predicted so far by theory: only non-radial
modes should be observable
•! Important to derive the internal structure of
the stars. Why?
Internal structure
Derive in a quasi
direct way the
internal structure
of a star!
Chapter 11: The Sun
What is the solar neutrino mystery?
How was it resolved?
In a spectral line, is the core of the line formed
deeper or higher up in the photosphere than the
continuum?
What is the typical size and lifetime of
granulation cells?
Chapter 11: The Sun
Solar Neutrino Mystery
Two neutrinos produced in the p-p chain.
If 700 billion tons of H are fused every second, where are the neutrinos?
Should be 100 billion neutrinos passing
through your thumbnail every second.
However they are practically massless and weakly interacting.
Only 1 out of every 100 billion neutrinos
that pass through the Earth is expected to
interact with material in the Earth.
Neutrinos escape easily from the solar interior.
4 p!4He + 2e
++ 2" e
Chapter 11: The Sun
Three types of neutrinos
!e
! µ
!"
Electron neutrinos - expected as by products
of the pp chain.
muon neutrinos
Tau neutrinos
No charge, each neutrino has its own anti-neutrino.
Once thought to be massless.
Chapter 11: The Sun
Homestake Neutrino Detector
Raymond Davis built a neutrino detector in the
Homestake Gold Mine in South Dakota.
The detector consisted of a tank filled with 100,000 gal of
C2Cl4. Electron neutrinos interact with the isotope 37Cl,
which undergoes radioactive decay to form 37Ar.
The goal: to confirm hydrogen fusion as the energy source
for the Sun. The threshold energy for this rxn is 0.814 eV,
less than the neutrino energies produced in every step of
the p-p chain except the first one. So, the detector was only
sensitive to neutrinos coming from the decay of Boron:
17
37Cl + !
e"
18
37Ar + e
#
5
8B!
4
8Be + "
e+ e
+
Chapter 11: The Sun
Homestake Neutrino Detector
Every few months, the accumulated argon was purged from
the detector. The capture rate was measured as:
1 SNU = 10-36 rxns per target atom per second.
Only 1/3 of the expected neutrinos were detected => the
“Solar Neutrino Problem.”
•!Wrong rate of production?
•!Incorrect estimate of interaction in Chlorine detector
to form 37Ar? Experimental design error?
•!New neutrino physics?
Chapter 11: The Sun
The solar neutrino problem
Kamiokande
GALLEX
SAGE
Gallium detectors have a different energy threshold;
measure low energy p-p chain neutrinos (theoretical
predictions better for these neutrinos)
Super-Kamiokande: Inner volume of 32,000 tons
of water surrounded by 11,000 PMT’s surrounded by 18,000 tons of water. The PMT’s detect pale
blue Cherenkov light emitted when neutrinos scatter electrons, causing them to move faster
than the speed of light in water.
Confirmed the deficit of neutrinos: only 1/2 the
expected number were detected.
!e
+31
71Ga"
32
71Ga+ e
#
Chapter 11: The Sun
The solar neutrino problem
Meanwhile, the standard solar model was re-examined. Helioseismology
measurements fit theoretical interior velocities to 0.1% accuracy, suggesting that the theoretical reaction rates were correct.
Solar neutrino observatory (SNO): contained 1000 tons of D2O, surrounded
by a steel structure containing 10000 PMTs.
Observation mode that was sensitive to
electron neutrinos only detected 1/3 the
number predicted by the standard model.
Chapter 11: The Sun
The solar neutrino problem
Combining the total number of neutrinos from all experiments
(electron, muon, tau) gives the number of neutrinos expected from the standard model, but electron neutrinos only constituted about 1/3
of all these neutrinos.
Mikheyev-Smirnov-Wolfstein (MSW) effect proposed: neutrinos
change form.
The standard model from particle physics only predicted electron
neutrinos - the standard model was wrong.
Chapter 11: The Sun
The solar neutrino problem
The SNO data showed that solar neutrinos are not missing. Most of the neutrinos that form in the core of the Sun undergo
oscillations and change into muon and tau neutrinos by the time they reach Earth. In order for neutrinos to undergo oscillations, they must
have mass (standard model assumed that they were massless). The simplest model now suggest neutrino masses that are 108 times
smaller than the mass of an electron.
Standard solar model vindicated!
Standard model of particle physics had to be revised!
Chapter 11: The Sun
The solar neutrino problem
Flavor Mass Electric Charge
(GeV/c2) (e)
!e electron neutrino <7 x 10-9 0
e- electron 0.000511 -1
!! muon neutrino <0.0003 0
!! muon (mu-minus) 0.106 -1
!! tau neutrino <0.03 0
!! tau (tau-minus) 1.7771 -1
Chapter 11: The Sun
The solar atmosphere
Sun appears to have an edge, but the
atmosphere changes fromopticaly thin ot optically thick over about 600 km
(0.1% RSUN).
Temperature in the photosphere varies
from ~9400K at -100km (! ~ 23.6) to ~4400K at the top of the photosphere.
Temperature reversal occurs going
higher into the chromosphere.
T = 5777K at !!= 2/3
Continuum opacity: H- even though only
1 in 107 H atoms forms H-, neutral H is transparent.
Chapter 11: The Sun
The solar atmosphere
Recall: Spectral lines
formed at different depths
in the photosphere.
Spectral lines start
forming at the same
depth as the continuum,
however the line cores
are formed higher in the
atmosphere where the
gas is cooler and opacity
is therefore greater.
Chapter 11: The Sun
The solar atmosphere
Chapter 11: The Sun
The solar atmosphere
Typical cell size is 700 km
Characteristic lifetime is 5 - 10
minutes
Typical radial velocities of the
cells: ~500 m/s
Rotational speed varies with
latitude and depth
Chapter 11: The Sun
Solar rotation
From helioseismology, know that rotation changes with depth.
The tachocline is the boundary between the core and
convective zone (CZ). Strong shear in this region results in
electric currents that likely generate the Sun’s magnetic field.
Chapter 11: The Sun
Differential rotation
Rotation rate at the solar equator is about 25 days.
At the poles it is about 36 days.
Chapter 11: The Sun
Chromosphere
Lower densities, higher temperatures than the
photosphere. Boltzmann-Saha equation shows that lines
not formed in the photosphere can form in the
chromosphere. HeII, FeII, SiII, CrII, CaII (H & K lines)
Chapter 11: The Sun
Solar activity
Chapter 11: The Sun Chapter 11: The Sun
Chapter 11: The Sun
Corona
Temperature rises through the
transition zone. Since the density is
low (10-10 times the density of air at
sea level), the gas is not in LTE and
there is not a well defined
temerpature. Thermal motion,
ionization levels and radio emissions
give consistent results. The
presence of FeXIV indicates
temperatures greater than 1 x 106 K
Chapter 11: The Sun
Coronal Holes and the Solar Wind
X-ray image of the sun shows bright
regions that appear/disappear on
timescales of hours. Closed magnetic
field lines trap charged particles - the
higher density of charged accelerating
particles create bright spots at X-ray
wavelengths.
Dark coronal holes are tied to the global
magetic field of the Sun. These holes are
associated with regions where the
magnetic field lines are open. Charged
particles can flow out along the open
field lines, creating a solar wind.
Chapter 11: The Sun
Solar Wind
Fast solar wind (longer solid red
lines): continuous stream of charged particles moving at
speeds of about 750 km/s.
Gusty, slow, dense, solar wind
(short, dashed red arrows): produced by streamers in the
corona associated with magnetic
fields. Travels at about half the speed of the fast solar wind.
Chapter 11: The Sun
Corona If the velocity of solar wind particles above the Earth’s
atmosphere (r = 1.5 x 108 km) is 500 km/s, and the density of the particles is 7 x 106 protons m-3, what is the mass loss
rate from the Sun? (MSUN = 1.99 x 1030 kg)
dM = !dV = ! 4"r2vdt( )dM
dt= ! 4"r2v = 3#10$14Msun yr
$1
Chapter 11: The Sun
For the past few days, the
Earth has been passing
through a stream of solar
wind that is flowing out of this
coronal hole (seen here on
March 12-14, 2007). Since
coronal holes are 'open'
magnetically, strong solar
wind gusts can escape from
them and carry solar
particles out to our
magnetosphere and beyond.
Solar wind streams take
several days to travel from
the Sun to Earth.
The magnetic field lines in a
coronal hole open out into
the solar wind rather than
connecting to a nearby part
of the Sun's surface. Coronal
Chapter 11: The Sun
d
dr2nkT( ) = !
GMSUNnmp
r2
dn
n= !
GMSunmp
2kT
"
# $
%
& ' dr
r2
ln(n)r0
r= C
1
r!1
r0
(
) *
+
, - = !Cr0 1!
r
r0
(
) *
+
, -
n(r) = n0e!. 1!r0 / r( )
P(r) = P0e!. 1!r0 / r( )
Assume isothermal gas,
collect terms and integrate
Let: !! = Cr0
P0
= 2n0kTSince:
The Parker Wind Model
Chapter 11: The Sun
But the pressure does not go
to zero as r approaches infinity. So, why does this
derivation fail?
One of our assumptions must be wrong. The isothermal
assumption is not too bad - measuring the temperature of particles near the Earth ( r ~ 215 RSUN ), the wind has a
temperature of about 105 K, similar to the corona.
It is the assumption of hydrostatic equilibrium that is incorrect.
Since P(infinity) exceeds the pressure in the ISM, material
must be expanding outward from the Sun, implying the
existence of a solar wind.
P(r) = P0e!" 1!r0 / r( )
The Parker Wind Model
Chapter 11: The Sun
The Parker Wind Model: how does the solar corona
produce a solar wind?
dP
dr= !
GMSUN"
r2
" = nmH
µ =1
2
Pg ="kT
µmH
= 2nkT
d
dr2nkT( ) = !
GMSUNnmp
r2
The eqn of ….
Assume gas of
ionized hydrogen
Chapter 11: The Sun
Replace hydrostatic equations with
hydrodynamic equations
d2r
dt2
=dv
dt=dv
dr
dr
dt= v
dv
dr
!d2r
dt2
= !vdv
dr= "
dP
dr"GM
r!
r2
4#r2!v = const
d !vr2( )dr
= 0
Hydrodynamic equations
Conservation of mass flow across a boundary:
at the top of the CZ, the motion of hot rising gas and the return flow of cool gas sets up
longitudinal waves (pressure waves) that propagate outward through the photosphere
and into the chromosphere.
Chapter 11: The Sun
The outward flux of energy
FE
=1
2!v
w
2vsound
vsound
= "P /!
vsound
="kT
µmH
# T
Hydrodynamic equations
Sound speed: proportional to the
square root of the temperature.
Chapter 11: The Sun
The velocity amplitude of particles in the solar
wind, vw, starts out less than the sound speed. But, the density of gas decreases by 4 orders
of magnitude over 1000km through the transition zone. The sound speed changes by
sqrt(2) because the temperature change is
only a factor of 2.
FE
=1
2!v
w
2vsound
vsound
" T
Supersonic flow
As a result, the wave speed quickly becomes supersonic (Vw > Vs).
The pressure wave develops into a shock wave. As a shock moves through gas, it produces heating through collisional, turbulent motion
and the gas behind the shock is highly ionized. The shock quickly dissipates. Thus, gas in the chromosphere and above is effectively
heated by mass motions in the CZ.
8:05
11:23
Calculate the speed of the
particle wave (solar wind).
Each white tick is one solar
radius.
Chapter 11: The Sun
The temperature gradient through the corona is also tied to
the presence of a magnetic field, coupled with dynamo motion in the CZ. MHD is the study of the interactions
between magnetic fields and plasmas.
Magnetohydrodynamics and Alfven waves
Energy is needed to create a magnetic field - that
energy is stored in the field as the magnetic energy density.
If you were to compress the field, the work done:
would be stored in the magnetic field. Therefore,
the magnetic pressure is equal to the magnetic energy density.
µm
=B2
2µ0
Pm
= µm
=B2
2µ0
W = PdV!
Chapter 11: The Sun
When the magnetic field line is displaced, a magnetic
pressure gradient is established that tends to push back in the opposite direction to restore the original field line position.
Magnetohydrodynamics and Alfven waves
Adiabatic sound speed
vsound =!Pg
"
vAlfven =Pm
"=
B
µ0"
By analogy, the Alfven wave
velocity increases with the
strength of the magnetic field
Chapter 11: The Sun
The gas pressure at the top of the photosphere is about 140 N m-2,
with a density of 4.9 x 10-6 kg m-3. The surface magnetic field strength is about 2 x 10-4 T. Assuming an ideal monatomic gas, calculate the
sound speed and Alfven speeds
Speed of Sound and Alfven waves in the Sun
Sqrt[(5/3)*140./4.9e-6] = 7000 ms-1
vsound =!Pg
"
vAlfven =B
µ0" (0.0002 / sqrt((1.2e-6 * 4.9e-6) ) = 85 ms-1
(negligible)
Chapter 11: The Sun
The rotation of the Sun
drags the magnetic field lines, transferring angular
momentum away from the Sun. The Parker Spiral is the
shape of the Sun’s extended
magnetic field. Results in a change in the shape of the
Suns magnetic field beyond 10 - 20 AU from poloidal to
toroidal. The Parker Spiral
may be responsible for the differential rotation observed
in the Sun.
Parker Spiral
Chapter 11: The Sun
Solar constant?
Chapter 11: The Sun
Solar constant?
Solar minimum now -
what is the impact on
global climate change?
Chapter 11: The Sun
Butterfly diagram
Chapter 11: The Sun
Maunder Minimum One of the most well-
documented connection between solar activity and
climate change is the Maunder Minimum. This
was a 40-year period
when extreme cold weather prevailed in
Europe. It also coincided with astronomers watching
the sun and not seeing
many sunspots! Eddy pointed this out in the
1970's, and since then many other sun-climate
connections have been
looked for and in some cases uncovered.
Chapter 11: The Sun
At optical wavelengths,
the darkness of spots is
caused by cooler
temperatures. The
temperature in the central
spots may be as low as
3900K compared to
5770K for the effective
temperature of the Sun
Chapter 11: The Sun
Bright H-alpha emission
in the chromosphere,
around sunspots. Plages
are particularly visible
when photographed
through filters passing the
spectral light of hydrogen
or calcium. The adjacent
image shows plages near
a sunspot (the white
cloud-like feature) as
imaged by the Big Bear
Solar Observatory
Solar Plages
Chapter 11: The Sun
Release 1017- 1025 J of
energy in time intervals of
minutes to hours.
Magnetic field lines are
associated with creation
of a sheet of current in
the highly conducting
plasma, heats
temperatures to 107K.
Surface nuclear
reactions, spallation,
break down heavier
elements into lighter
ones. This is the one way
for lithium to be created.
Solar Flares
Chapter 11: The Sun
Solar prominences are cooler
clouds of gas that float above the
solar surface.
Prominences are not very stable
and quite often they do break away
from the Sun when the magnetic
forces that hold it in place become
disrupted. Neither the previous
image taken just six hours before
this or the one taken six hours later
show any sign of a filament.
At about the time prominence this
appeared, another instrument on
SOHO observed a solar outburst
called a "streamer" eruption near
the same general area of this
prominence.
Solar Prominences
Chapter 11: The Sun
More spectacular, CME’s average
to about 1 per day. When sunspot
activity is stronger, there may be
3-4 per day. During sunspot
minima, there will only be one CME
every few days.
Generally associated with solar
prominences. Up to 1013 kg
material may be ejected at speeds
exceeding 1000 km/s.
Coronal Mass Ejections