P1
Balázs Pintér
Aberystwyth University
Physics Department
An Overview of the Sunand the
Sun-Earth System
Advanced Summer School in Solar System Physics, 4 - 9 September 2016
P3Advanced Summer School in Solar System Physics, 4 - 9 September 2016
Sunset from the Aberystwyth Seafront
by Christina Ong
Advanced Summer School in Solar System Physics, 4 - 9 September 2016
The Sun amongst other Stars
• 4.6 billion years old hot and bright gas ball• G2V type main-sequence (dwarf) star• T(eff) 5780 K• Msun 4.83
P7
EIT 1951,500,000 K
EIT 1711,000,000 K
EIT 30470,000 K
EIT 2842,500,000 K
optical image
magnetic mapvelocity map
http://sohowww.nascom.nasa.gov/data/realtime/realtime-update.html and http://sdo.gsfc.nasa.gov/
outer corona coronal loops
Manifold Faces of the Sun
Main Properties of the Sun
P9P9
• Distance 1 AU = 150,000,000 km = 1.5x1011 m -1.5 cm/y
• Radius 700 Mm ≈ 109 RE [695,970 km]
• Mass Loss Rate 109 kg s-1 0.001% / by
• Mass 2×1030 kg ≈ 330,000mE [1.989×1030 kg]
• Surface Gravity 274 m s-2 30g 2.5s/200km/h
• Central Temperature 15×106 K [1.56×107 K]
• Surface Temperature 6×103 K [5720 K, 6400 K] alloy2015:4,400K
• Equatorial Rot. Period 25 days [sidereal<synodic]
• Polar Rot. Period 35 days [at 70o latitude]
• Fast Solar Wind 800 km s-1
• Slow Solar Wind 300 km s-1
• Spectral Type G2• Luminosity Class V [3.85×1026 W]
• Visibility Photosphere [partially atmosphere]
• Age 4.5x109 years
The Sun is unique in the sky
Much more than a ball of hot and bright gas ( )
- Dynamic Interior
- Structured Atmosphere
- Controlled by Electro-Magnetism
The visible surface of the SunThin (100 km, 0.014%) layer
Photosphere
Faculaebright magnetic spots
Granuleshot fluid rises up
1Mm, 20 min
SunspotsDifferential Rotation
Limb Darkening
Turbulence andLarge Scale Coherent
Photospheric Flows
SupergranulesDopplergram
35Mm, 1-2 days
Mechanism explaining Sunspot Patterns
The Topology of the Sun's Magnetic Fieldand the 22-Year Cycle
ApJ 133 (2), 572–587, 1961Babcock, H. W
North
South
Chromosphere
T: 6,000 K 20,000 K
H and UV CA II K
ChromosphericNetwork
FilamentsPlage
Prominence
Pete Lawrence
Spicules
Corona
The Outer Atmosphere of the SunDensity mg/cm3
Temperature 106 K
Pete Lawrence
Polar Plumes
K108
3.81073
105102107.62
3
2
3
2
1
68
43011
gasSun
molSuncrit
mol
gasrms
Sun
Sun2esc
RR
MGMT
M
TRv
R
mGMmv
Coronal Heating Solar Wind
Solar Wind
Solar Wind blows in everydirection away from theSun with speeds typicallyvarying between 300(over streamers) and 800km/s (over coronal holes).
First Orbit
Rcore
tachocline
corona
chromosphereR014.0
photosphereR0007.0
R27.0
radiationzone
convectivezone
R25.0 R45.0
R029.0
Layers of the Sun
heliosphere
CoreThermonuclear reaction41H4He + 2e+ + 2 + 26.7 MeV
Radiation Zone
Energy transferred outWavelength increases
TachoclineSolid body/differential rotation
Dynamo actionConvection ZoneLarge negative temperature
gradient causes convectiveinstability.
Structure of the Solar Interior
gk101.67
J/eV1060.127
19
CoreThermonuclear reaction41H4He + 2e+ + 2 + 26.7 MeV
Radiation Zone
Energy transferred outIncreasing wavelength
TachoclineDynamo action
Convection ZoneConvective instability due to
large negative temperaturegradient
P30
3.1.5 Adiabatic Approximation
10 hours ofoscillationsshownin 19 seconds
Photospheric Oscillations
Ground-Based and Space-Born Observatories
P31
From GONG observation:
Birmingham Solar-Oscillations Network
Space-Born Instruments – SDO/HMI
Heliospheric and Magnetic Imager (HMI)
Spacecraft: Solar Dynamics Observatory
Ground-Based Observatories – BiSON
Wave Functions in 1 to 3D
Linear Wave Equation:
General Solution:
2
2
22
2 ,1,
t
txu
vx
txu
vtxgvtxftxu ,
xkvtkBvtkAxXtTtxu nnnn sinsincos, L
nkn
mn = 02 mn = 23
nlm = _20 nlm = _32
Standing Wave Modes on a Disk:
Spherical Harmonics:
4n
Cha
plin
et a
l.20
02 M
NR
AS
336
979
Velo
city
(m/s
)Time (hour)
(~ m/s)integrated for the disc
P33
The Helioseismic Observations Cycle
Frequency (μHz)
1.2 x 105
1.0 x 105
8.0 x 104
6.0 x 104
4.0 x 104
2.0 x 104
0Pow
er S
pect
rum
((m
s-1
)2H
z-1 )
GONG11.04.1996-09.06.1998
T = 5 min~ ν ≈ 3.3 mHz
Photospheric Oscillation Spectra
Atmospheric Coupling
P37
Observed Frequency Shifts During a Solar Cycle
(BiSON data)
Chaplin et al. 2004 MNRAS 352 1102
(GONG data)
Tripathy et al. 2006 ESA-SP 6240.50.40.30.20.1
0150
100
50
0
Hz][p γ
sunspot number
1998 2000 2002 2004DATE
Dziembowski & Goode 2005 ApJ 625 548
(MDI data)
HzHowe et al. ApJ, 2002
Contours: Kitt Peak magnetic data
Magnetic Shift and Line Width Variation
P39
f
p1
p3p2
(mH
z)
Frequency shift: ∆ ν~ µHz
High-frequency modes aremore sensitive
Line width: Γ ~ 10 nHz
Low-frequency modes aremore sensitive
fp1p2
p5
p3p4
p8
f
p8
Good agreement with observations
Asteroseismology
P40
51 Pegasi
21 22 23 24 01 02 03hours (UT)
-170
-175
-180
-185
-190
radi
al v
eloc
ity (m
/s)
Haute Provence ObservatoryAugust, 2007
[Vauclair]
rela
tive
inte
nsity
1
0.75
0.5
0.25
frequency (mHz)0 1 2 3
Alpha Centauri A
ampl
itude
0frequency (mHz)0.3 0.35 0.4 0.45 0.5
Delta ScutiTDSA (h):4.654.482.792.28
20.11
Convection, Rotationand Planetary Transits
27th
Dec2006
T ~ 7 min
• We are physicists.
• The Sun is interesting.
• The Sun is the key to understand the stars. (… Because we are physicists …)
• It is our interest to understand how …
• The Sun works
• It changes in short and long time scales
• Our aims are to …
• Copy nuclear fusion – energy production in hot plasmas and
strong magnetic fields;
• Predict space weather;
• Forecast its effects on Earth and on Space.
Why do we study the Sun?
• ‘Sun-Earth Interactions’ ?
• The most fundamental effect:• Gravitational attraction – Orbit
• The obvious effect:• Radiation of EMW - Light and Heat
How does the Sun affect the Earth?
Every second 4 million tonnes ofmass is converted into photons
Solar Radiation
https://glory.gsfc.nasa.gov/overview-tsi.html
Total Solar Irradiance (Reconstructed by a physical model)
Planetary RotationNeutral Atmosphere, Magnetic Field Lines and Plasma: all Co-rotate
Co-Rotation
Robert Fear Univ. of Southampton
• Particle Flow• Continuous Flow
• Solar Wind – It largely determines the size and shape of theEarth’s magnetosphere.
• Variations in the Solar Wind (Magnetic Clouds, InteractingRegions, Composition Variations, Flow Speed) can disturb theEarth’s magnetic structure – causing Magnetic Storms, MagneticSubstorms, Magnetic Pulsation, Aurorae, and Auroral Electrojets
• Short Time-Scale Energetic Events on the Sun:• Solar Flares - produce x-ray and UV radiation,• Erupting Prominences,• Coronal Holes, …
• Long Time Scale Variation of the Solar Constant and Solar Cycle, …
Further Effects of the SunEvery second 1 million tonnes ofmass is blown off as Solar Wind
‘A stream of very fast moving (700 km/s) solar wind has surroundedEarth, sparking geomagnetic storms on Sept. 3rd. Bright auroras arebeing reported around the Arctic Circle, with sightings in somenorthern-tier US states as well. Because this solar wind stream iswide, its influence could continue throughout the weekend.’http://spaceweather.com
Space Weather News 03/092016
‘QUIET WITH A CHANCE OF FLARES: Solar activity is low, however, it might not remainso. Big sunspot AR2585 is developed an unstable 'beta-gamma' magnetic field thatharbors energy for moderately strong solar flares. NOAA forecasters estimate a 20%chance of M-flares …’‘HIGH-SPEED SOLAR WIND SPARKS AURORAS: A stream of very fast moving solar windis buffeting Earth's magnetic field this weekend, and this is causing geomagneticstorms around the poles.‘
Space Weather News 03/09/2016
‘The solar wind is flowing from anunusually large coronal hole on the sun,shown here in an image from SDO:’
• We are physicists.
• The Sun-Earth System is complicated enough to be interesting.
• It is our space. It is our interest to understand how …
• It works;
• It changes in short and long time scales.
• We want to predict space weather
• The Sun-Earth System is the key to understand systems of other stars
and their planets. (… Because we are physicists …)
Why do we Study the Sun-Earth System?