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The Sun’s enduring mysteriesThe Sun’s enduring mysteries
To prepare for the coming yearsTo prepare for the coming years
What we knowWhat we know
What we don’t understandWhat we don’t understand
What is importantWhat is important
Axel Brandenburg (Nordita, Stockholm)Axel Brandenburg (Nordita, Stockholm)
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Coming years?
• New satellites (Solar Orbiter, …)– Out of ecliptic (like Ulysses)
• Ground based (ATST)– Science goals: solar magnetism, variability
• Helioseismology: global & local– Precursors to erruptions
• More global simulations– Coupled to exterior (corona, wind, …)
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Monitoring & observing
• Solar orbiter: 2017 (ESA/NASA)– (45 R = 0.2 AU, heliosynch, + solar probe)
• SDO: 2010 (NASA, geosynch)
• Stereo: 2006 (NASA), 2 space crafts
• SOHO: 1995 (ESA/NASA)
• Ulysses: 1990 (NASA/ESA)
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Further reading
• M. Stix “Solar Physics” Springer
• Wikipedia: …
• A. Kosovichev et al. “Triennial report of IAU commission 12”
• ADS– search on titles/abstracts
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What we know about the SunWhat we know about the Sun
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What we understand• Source of energy: nuclear (not thermal)• Internal structure: 15 M Kelvin core temp.• Depth of convection zone• Solar granulation • Solar wind (Parker 1958)• Differential rotation (except details)• Dynamo theory in general• Coronal heating (Parker’s nano flare idea)• …
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15 M Kelvin? solar neutrino problem
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1968: accurate measurements
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Input from helioseismology
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5 min oscillations helioseismologyD
isco
vere
d in
196
0 (L
eigh
ton
et a
l. 19
62)
Was thought to be response of upper atmosphere to convection
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5 min osc are global
Roger Ulrich (1970)
Franz-Ludwig Deubner (1974)
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Degree Degree ll, order , order mm
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GONGGONGglobal global
oscillation oscillation network network groupgroup
Since late 1980ties
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Current Current state of state of the artthe art
SOHOSpace craft1993 – 2014(lost in 1998)
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Only p-modes observedOnly p-modes observed
0..;24
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RefractionRefractionReflectionReflection
Top: reflectionwhen wavenlength~ density scale height
Deeper down:Sound speed large
RT
cs 2
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Inversion: input/outputInversion: input/output
Duval law: collapsed k-diagram Sound speed
uuFu
G
GuuFu
0
0
d )(' 1
)(
d )(' )(
2
rknR
r
r d 0
0
22
2 )1(
r
ll
ck
sr
2
2
2
)1(
llu
c
r
s
22
2 )1(
ll
c
r
rk
sr Abel integral eqn
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What else from helioseismology?
spoke-like at equ.d/dr>0 at bottomd/dr<0 at topRigid below CZ
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Active region subsurface flowsActive region subsurface flows
Hindman et al. (2009, ApJ)
Ring diagramanalysis
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Surface flows: granulationHorizontal size L=1 Mm,
sound speed 6 km/s
Correlation time 5 min = sound travel time
Nor
dlun
d, S
tein
, Sch
arm
er, a
nd o
ther
s
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What is notnot well understood
• Unexpected abundence revisions
• Mixing beneath convection zone
• Spoke-like differential rotation
• Location of solar dynamo
• What releases coronal mass ejections
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Revised solar abundances
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In conflict with helioseismology
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Overshoot below convection zone
Charbonnel et al. (1999) Tschaepe & Rudiger (1999)
• Lithium is primordial• Burns at T > 2.6 M Kelvin• Some distance below CZ:• But why is depletion 1/140• And not all?
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SunspotsSunspots
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Large scale coherenceLarge scale coherence
Active regions, bi-polaritysystematic east-west orientationopposite in the south
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Buoyant rise of flux tubesBuoyant rise of flux tubes
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Solar 11 year sunspot cycle
• Sunspots between +/- 30 degrees around equator: why?• New cycle begins at high latitude• Ends at low latitudes
– equatorward migration: why?
butterfly diagram
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-effect dynamos (large scale)-effect dynamos (large scale)
Differential rotation(faster inside) Cyclonic convection;
Buoyant flux tubesEquatorward
migration
New loop
-effect
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How deeply seated? How deeply seated? Clues from Clues from
helioseismology: helioseismology: (r,(r,))
No cyclic modulation at great depth
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Sunspot predictions (of 2008)Sunspot predictions (of 2008)
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Sunspot predictions (current)Sunspot predictions (current)
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Predicting Solar Activity
Sunspots
Polar Fields
Solar Prediction Panel, 2006
Observations and theory suggest that the magnetic field at the poles of the Sun at solar minimum is a good predictor
of the next solar cycle.
Theory:Deep circu-lation? The low polar fields at the
recent solar minimum predicted a small cycle 24
-400
-300
-200
-100
0
100
200
300
400
1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015
MSO* WSO
North - South Solar Polar fields [microTesla]
Sunspots 2423
2221
MWO* WSO
?
WSO
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Asymmetric Solar Activity Spots & Groups
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Cycic Maunder mininum: Cycic Maunder mininum: 1010Be recordBe record
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Brun, Brown, Browning, Miesch, ToomreBrun, Brown, Browning, Miesch, Toomre
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• Cycle now common!
• Activity from bottom of CZ
• but at high latitudes
Ghizaru, Ghizaru, Charbonneau, Charbonneau,
Racine, …Racine, …
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PencilPencilcodecode
Käpylä, Mantere,Brandenburg (2012)
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Dynamo wave from simulations Kapyla et al (2012)
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Importance of solar activityImportance of solar activity
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Historic space weather events
• 21 Dec 1806 Humbold: erratic compass var.
• 1 Sep 1859 Carrington flare: telegraphs disr.
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More recent weather events
• 2 Aug 1972: life-threatening particle expos.– Apollo 16: 16 Apr 1972– Apollo 17: 7 Dec 1972
• 13 Mar 1989: Quebec blackout
• Aug 1989: halt of all trading in Toronto– Story in New Scientist of 9 Sept
• Now routinely rerouting transpolar routes
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Need a holistic approachNeed a holistic approachW
arnecke, B
randen
burg, Mitra (2011, A
&A
, 534, A11)
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