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)

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, …)

2

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)

3

Further reading

• M. Stix “Solar Physics” Springer

• Wikipedia: …

• A. Kosovichev et al. “Triennial report of IAU commission 12”

• ADS– search on titles/abstracts

4

5

What we know about the SunWhat we know about the Sun

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)• …

6

15 M Kelvin? solar neutrino problem

7

1968: accurate measurements

Input from helioseismology

8

9

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

10

5 min osc are global

Roger Ulrich (1970)

Franz-Ludwig Deubner (1974)

11

Degree Degree ll, order , order mm

12

GONGGONGglobal global

oscillation oscillation network network groupgroup

Since late 1980ties

13

Current Current state of state of the artthe art

SOHOSpace craft1993 – 2014(lost in 1998)

14

Only p-modes observedOnly p-modes observed

0..;24

15

RefractionRefractionReflectionReflection

Top: reflectionwhen wavenlength~ density scale height

Deeper down:Sound speed large

RT

cs 2

16

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

17

What else from helioseismology?

spoke-like at equ.d/dr>0 at bottomd/dr<0 at topRigid below CZ

18

Active region subsurface flowsActive region subsurface flows

Hindman et al. (2009, ApJ)

Ring diagramanalysis

19

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

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

20

21

Revised solar abundances

22

In conflict with helioseismology

23

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?

24

SunspotsSunspots

25

Large scale coherenceLarge scale coherence

Active regions, bi-polaritysystematic east-west orientationopposite in the south

26

Buoyant rise of flux tubesBuoyant rise of flux tubes

27

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

28

-effect dynamos (large scale)-effect dynamos (large scale)

Differential rotation(faster inside) Cyclonic convection;

Buoyant flux tubesEquatorward

migration

New loop

-effect

29

How deeply seated? How deeply seated? Clues from Clues from

helioseismology: helioseismology: (r,(r,))

No cyclic modulation at great depth

30

Sunspot predictions (of 2008)Sunspot predictions (of 2008)

31

Sunspot predictions (current)Sunspot predictions (current)

32

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

33

Asymmetric Solar Activity Spots & Groups

18

34

Cycic Maunder mininum: Cycic Maunder mininum: 1010Be recordBe record

Brun, Brown, Browning, Miesch, ToomreBrun, Brown, Browning, Miesch, Toomre

35

36

• Cycle now common!

• Activity from bottom of CZ

• but at high latitudes

Ghizaru, Ghizaru, Charbonneau, Charbonneau,

Racine, …Racine, …

PencilPencilcodecode

Käpylä, Mantere,Brandenburg (2012)

38

Dynamo wave from simulations Kapyla et al (2012)

39

Importance of solar activityImportance of solar activity

Historic space weather events

• 21 Dec 1806 Humbold: erratic compass var.

• 1 Sep 1859 Carrington flare: telegraphs disr.

40

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

41

42

Need a holistic approachNeed a holistic approachW

arnecke, B

randen

burg, Mitra (2011, A

&A

, 534, A11)

43