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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

Aberystwyth

Sheffield

Aberystwyth Seafront Old College

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

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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

Sun (Mercury) (Venus) Earth

1 AU

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

Structure of the Solar Atmosphere

Corona

Transition Region

Chromosphere

Photosphere

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

One Hour of a Sunspot

Ellipses that Best Fits the Boundaries

t Flares?

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

Sunspot Area Variation

Chromosphere

T: 6,000 K 20,000 K

H and UV CA II K

ChromosphericNetwork

FilamentsPlage

Prominence

Pete Lawrence

Spicules

Transition Region

T: 20,000 K 1,000,000 K

UV: C IV, O IV, Si IV

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

Solar Wind Profiles

…

Solar Wind Profile

magneticenergy

dominates

plasmaenergy

dominates

+ solar rotation:

Heliosphere

Rcore

tachocline

corona

chromosphereR014.0

photosphereR0007.0

R27.0

radiationzone

convectivezone

R25.0 R45.0

R029.0

Layers of the Sun

heliosphere

Structure of the Solar Interior

Core

Radiation Zone

Tachocline

Convection Zone

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

Density Profile of the Solar Interior

Temperature Profile of the Solar Interior

?

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

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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

Sound Waves in the Sun

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Three Types of Oscillation Mode

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g modes, f modes, and p modes

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fast and slow rotation rates

Discoveries from Helioseismology

Atmospheric Coupling

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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

Atmospheric Coupling of Oscillation Modes

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evanescent

2005 ESA SP-600 162

Magnetic Shift and Line Width Variation

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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

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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 (Mercury) (Venus) Earth

1 AU

• ‘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)

Sunlight without atmospheric absorption

Spectrum of Solar Radiation

Sunlight at sealevel

The dynamo in the Earth’s core produces a dipole:

The Earth’s Magnetic Field

Dungey Cycle

Robert Fear Univ. of Southampton

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?

• We are physicists / scientists.

Proxima Centauri b

Proxima Centauri

Alpha Centauri AB

http://www.spaceweather.gc.ca/

http://solarscience.msfc.nasa.gov/

Rob Fear @ Southampton Unversity