What could Hinode results tell us about cosmic

magnetic fields?

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Saku Tsuneta Institute of Space and Astronautical Science, JAXA

ISAS Astrophysics Colloquia 2015 February 26 11-12am

EUV Imaging Spectrometer（EIS）

Solar Optical Telescope（SOT）

X-ray Telescope （XRT）

Japan-US-UK-ESA project Orbit: Polar Sun Synchronous Launched 2006 Autumn

Satellite Hinode (JAXA SOLAR-B)

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EUV Imaging Spectrometer（EIS）

Solar Optical Telescope（SOT）

X-ray Telescope （XRT）

Hinode mission objective: Systems approach to understand generation, transport and ultimate dissipation of solar magnetic fields with 3 well-coordinated advanced telescopes.

Japan-US-UK-ESA project Orbit: Polar Sun Synchronous Launched 2006 Autumn

Satellite Hinode (JAXA SOLAR-B)

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Too-strong Magnetic field in the Universe How does Universe create such strong fields?

• Early universe: 10-21G? • Galaxies and Clusters of Galaxy: 10-6 G • Late type stars 103G • Bottom of convection zone 105 G • Pulser 1012G • Magnetor 1015 G

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Fossil or Compressive process? Dynamo? global dynamo? Local (turbulent) dynamo?

Too-strong Magnetic field in the Universe How does Universe create such strong fields?

• Early universe: 10-21G? • Galaxies and Clusters of Galaxy: 10-6 G • Late type stars 103G • Bottom of convection zone 105 G • Pulser 1012G • Magnetor 1015 G

Fossil or Compressive process? Dynamo? global dynamo? Local (turbulent) dynamo?

Dynamo+? Dynamo+compression

Dynamo+?

Dynamo Compression and fossil?

needs dynamo

needs dynamo Compression and fossil

Any dynamo mechanism can amplify the magnetic fields upto equi-partition fields Be But not beyond! We sometimes need a mechanism to go beyond the equi-partition fields.

Kinetic Energy

Magnetic Energy

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21

8ru

p»eB

5

l 1.4 GHz

lVLA Galactic center Solar corona

Does nature prefer flux tubes? i.e. Does nature prefer higher magnetic energy state? 6

Courtesy of Sofue

NASA TRACE

7

l 300 MHz

lStrong magnetic field of mG lMuch smaller than equi-partition field corresponding to the local gas lEquivalent to equi-partition field corresponding to galactic rotation (100-200 km/s)

Courtesy of Sofue

Galactic center：flux tubes? vertical to the G-plane

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9 Emer

genc

e of

mag

netic

fiel

ds

in a

form

of s

lend

er fl

ux tu

bes

With

B a

roun

d eq

ui-p

artit

ion

Magnetic fields have a form of flux tube

Strong kG magnetic field in between convection cells exceeding equi- partition B

10

11

1000km

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Hinode highest resolution Stokes-V map

(vertical component of B) Does nature prefer isolated flux tubes?

1000km

Ishikawa+09

Distribution function of magnetic field strength

Peaks at 1.5kG Super-equipartition

majority:below500G Sub-equipartition

Two components

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Hinode result

Equi-partition field strength

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Sub-equipartition B 500G

Super-equipartition B 2000G 200 sec

Formation of super equipartition from sub-equipartition magnetic fields

Parker prediction：supersonic down flow associated with thermal instability results in compression of magnetic fields

Nagata+08

Convection plus weak magnetic fields result in strong magnetic fields

Parker (1978); Hasan (1985), Hasan et al. (2003), Bunte, Hasan,Kalkofen, (1983)

G400421

82

2

»»

»

upr

rup

B

Be

kG218

2

-»

=+

B

PBP ei p

Magnetic Flux tube

Solar surface

Convection flow

Downflow Inside flux tube

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15

Sub-equipartition B Super-equipartition B

Inhibit thermal energy due to B

Cooling and downflow

Stronger B due to lateral P balance

Ishikawa+08

Convective collapse creates1.5kG flux tubes (This is not dynamo)

Convective collapse!! 500G 1.5kG Smaller total B energy

Larger total B energy

Peak at 1.5kG due to convective collapse

90% is below 500G Just born?

Higher T.

Lower T.

Reduce heat Input from below

Lateral heat input from side

Slender flux tube

You are looking at deeper layer due to magnetic pressure

Dark sunspot and bright faculae

Emission From hot wall Solar surface is a

rias coastline due to thin flux tubes. It serves as heat sink.

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Same temperature

Sun as seen in UV Bright faculae Dark sunpsot

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0.1-0.2％

Non-constant solar constant

Faculae (slender flux tubes win)!

Sola

r con

stan

t

year

amplitude of 0.1-0.2%

Vertical magnetic flux Horizontal magnetic flux

Quiet Sun magnetic fields

Ubiquitous linear polarization patches Lites+08, Orozco+07,08, Centeno+08 Ishikawa+08, 09, 10,11ab, Jin+09, Martınez Gonzalez+09 etc, Danilovic+10

Wherever convection, horizontal fields exist!?

250000km

120000km

Lites+08

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Local dynamo process discovered with Hinode

Ishikawa & Tsuneta (2008)

Total flux = 10-100 x sunspot Field strength < equi-partition Life time < granulation lifetime Size <granulation size

Horizontal B below equi-partition

Equi-partition field strength

Discovery of New Dynamo Mechanism with Hinode

• Differential rotation of Sun amplifies magnetic

field 北極

南極

Magnetic field

Convection Energy

Magnetic Energy

北極

南極

北極

南極

Rotation Energy

Magnetic Energy

Convection cell 1000km Magnetic field

• Convection motion of plasma amplifies magnetic field

Sunspot Horizontal fields

Known mechanism Newly discovered

2006 Dec 17 20:00-21:00 UT CaII H broad band filter images taken with Hinode/SOT

Chromosphere more dynamic than expected! Chromospheric jets and fountain

driven by magnetic force

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KM late type star： Fully convective Active corona Not consistent with Solar paradigm

Early type star： No convection zone No corona

Hayashi track: Proto star Convection dominant Active corona

Differential rotation driven global scale Dynamo and convection-driven dynamo

T tauri star： Convection Fast rotation Sunspot, wind Strong X-rays

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KM late type star： Fully convective Active corona Not consistent with Solar paradigm

Early type star： No convection zone No corona

Hayashi track: Proto star Convection dominant Active corona

Differential rotation driven global scale Dynamo and convection-driven dynamo

T tauri star： Convection Fast rotation Sunspot, wind Strong X-rays Convection

convection-driven local dynamo rotation⇒Reynolds stress ⇒differential rotation ⇒global dynamo

Takeda & Takada-Hidai, PASJ (2011) • Subaru observations on 24

moderately to extremely metal-poor late type MS stars – Probably slowly or non-rotating

stars with global dynamo not operative

• HeI 1083nm detected for all stars – High excitation line (19.7 eV) – Excellent indicator for coronal

&chromospheric activities – He abundance independent of

metallicity • Nearly constant EW for all stars

– Corona exists regardless of metallicity (i.e. age, rotation period)

• Not driven by global dynamo

Sun

Extremely metal-poor

Neutral universe with zero magnetic field due to zero electric current

First stars and re-ionization

B=1-30μG

B=0G

28 From website

Conservation of magnetic flux

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0)(0)0(

0

=FÞ==F

=F

ttDtD

How could we make such a strong magnetic fields currently observed?

Early universe present time

)()(,0;0

)(

)(

;)0(

2

2

ttBBt

Be

Mce

pcvt

ven

pncBvtB

jenp

cBvE

e

e

ww

w

rrww

w

µ===

=

Ñ´Ñ-´´Ñ=

¶¶

´Ñ=

Ñ´Ñ-´´Ñ=

¶¶

=Ñ

-=´

+

じ；式が同じなら解も同

；渦度の誘導方程式

；渦度の定義

；誘導方程式

運動方程式

Sim

ilarit

y of

Indu

ctio

n eq

. an

d vo

rtex

eq.

30 R. Kulsrud, 2005, Plasma physics for astrophysics Princeton University Press

Initial magnetic field strength after re-ionization epoch

• If baroclinic, vorticity exists and Biermann battery mechanism works, resulting in magnetic fields from zero value.

• How large is the magnetic fields? – r=100kpc, M=1011Mo – v=3x105 m/s(virial theorem） – ω～v/r=10-16 /s – B～10-20G!

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• Equi-partition field due to local dynamo OK! – n=10-3 cm-3

– v=3x105 m/s – T=100eV (106K)

• Maximum turnover time OK! – r/v=3x1023cm/3x107cm/s=1016s<<4x1017s （cosmic

life time） – Since actual Eddy size is smaller than the largest

scale size r taken here, this is a conservative estimate.

• A potential problem: not organized field

Turbulent dynamo then works to amplify the small magnetic fields to the current values

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G108

5

22

-»

=

eq

eq

B

vB

rp

宇宙は電離しておらず 電流なしのため磁場 ゼロ

第1世代銀河の形成 と宇宙の再電離

B=1μG

B=0G

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Vortex in proto-galaxy produces magnetic fields as large as B=10-20G（Biermann Battery） ↓ Hinode: convection-driven dynamo amplifies B upto B=Beq=10-6G ↓ Global galactic dynamo B>10-6G

From website

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Galactic magnetic fields along spiral arms

• Highly organized • Observed magnetic

fields comparable to equi-partition field strength for local velocity dispersion

• Umag=B2/8π=U(ISM) • B=10μG

Courtesy of Sofue

Discovery of transverse waves along magnetic field with Hinode (Okamoto et al 2008)

Spicules, coronal rains, and prominece over an active region 35

Transverse Wave along magnetic field line carrying

substantial amount of energy

Alfven wave

Magnetic fields

gas

Figures Courtesy Joten Okamoto

Polarimetric data provides phase relationship among magnetic, velocity and intensity fluctuation, confirming transverse MHD waves (Fujimura, Tsuneta, 2009).

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In-Situ-like observations of MHD waves in solar photosphere

Field strength

Stokes-I Photometirc Intensity

Stokes-V • mode of waves • direction of wave • propagating or • standing waves • properties of flux • tubes

Observables: • δInteisnty(t) • δB / / (t), δB┴(t) • δVLOS(t) • center-to-limb var.

Doppler vel.

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Half of flux tubes show such clean common peak

Velocity Intensity Magnetic flux Ti

me

Prof

ile

Pow

er s

pect

ra

Fujimura&Tsuneta 09

Fujimura&Tsuneta 09

Phase difference (deg) Phase difference (deg)

Phase difference (deg) Phase difference (deg)

φB-φV φV-φI(core)

φI(core)-φB φI(cont)-φI(core)

Fujimura&Tsuneta 09

--90deg --90deg

180deg -0 deg

-3-9min

Solid: pores+flux tubes

Dashed: pores

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Velocity leads magnetic fields by quarter of waves.

Importance of phase relation to identify wave mode and direction of

propagation

Discovery of Alfven waves from phase relation between δB and δ v, but almost

stationary waves!

δB- δ v:0 or 180 deg

δB- δ v:90 deg

Significant reflection of upward waves at photosphere-corona transition layer

Kink mode

Sausage mode

Fujimura&Tsuneta 09

Residual Poyning Flux of kink wave Differential (upward – downward) Poynting flux is

proportional to cos(φB – φv)

An example with low intensity fluctuation (dI/I=0.3%)

f=0.73, B0=1.7x103 (G), δB＝21(G), δv=0.059(km/ s), φB－φv=－96˚ giving ΔF=2.7x106 (erg/ s/ cm2)

f : average filling factor B0 : vertical magnetic field δB/ δv: root-mean-square transverse magnetic field/ velocity fluctuation

)cos(4 vBvBfBF ffddp

--=D

Fujimura&Tsuneta 09

Sunspot number is a good proxy for magnetic activity of the Sun

11 year cycle of sunspot number from the era of Galileo

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Year

Suns

pot n

umbe

r

Maunder minimum Dalton minimum

Gradual decrease of solar activity Mean Sunspot number

1.0

0.0

-1.0 North

South

High latitude average magnetic flux Wilcox

Royal Belgium observatory

西暦

西暦 Reversal of high latitude field At around solar maximum 43

Importance of polar fields to predict future solar activity (Choudhuri)

N

S

N

S

N

S

Cause Weak polar field

Result Less number of sunspots

130 rotations in 11 year

▽Ω-dynamo

45 ひので

西暦 西暦

Magnetic Flux (G)

Minus Plus

Minus Plus

Asymmetric north and south poles Still significant as of now

• Northern flux decreases rapidly • Southern flux has much slower decrease.

North South

Quadruple poloidal fields (sketch）

Quadruple Bipolar 47

N

S

N

N Bipolar mode Quadruple mode

Bipolar + Quadruple

Strong diffusion Weak diffusion

Sokoloff and Nesme-Ribes1994

Anti-Joy’s law due to quadruple poloidal field

N N

N S

N S

Bipolar Sun Quadruple Sun

Anti-Joy’s law AR#11429 signature of quadruple poloidal field?

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N

N

S

S

N S

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1950-1990 (Recent normal cycle)

1670-1710 (Maunder minimum)

Smaller number of sunspots are located only in

Southern hemisphere

North

North

South

South

1680 1690 1700 1710 1720 1680

1950 1960 1970 1980 1990

Latit

ude

Latit

ude

+50

-50

Sokoloff and Nesme-Ribes1994

Location of sunspot emergence

The dynamo equation

2015/2/26 52

[ ]

operation)in (dynamo )(1

)( Eq.induction ofcomponent

1

)( Eq.induction ofcomponent

22

22

ff

f

ffff

f

f

f

ah

h

BcEAr

rAr

vprt

ABBpoloidal

Brr

vrB

rB

vprt

B

BBtoroidalvvvBBB

ppp

p

p

p

p

p

=+úûù

êëé -Ñ=úû

ùêëé Ñ×+

¶

¶

Þ

úûù

êëé -Ñ+ú

û

ùêë

éÑ×=Ñ×+

¶¶

Þ

+=

+=

S

Bp

Ap On meridional plane: poloidal Perpen. to M.P.: toroidal

One interpretation If cyclic phase differs between hemispheres,

Vector potential

Near-surface higher turbulent diffusivity

Hotta, Yokoyama, 2010 Fast meridional flow

Cycle length: 12.6 year！

黒点数

西暦年

黒点数

Longer cycle period is also seen just before Dalton minimum

Dalton minimum

Year

Suns

pot n

umbe

r

Past 6 cycles (overlaid) Current cycle Northern hemispehre Southern hemisphere

Suns

pot n

umbe

r

NAOJ solar observatory

More anomaly of the Sun

period～14yr

period～13yr period～12.6yr

Are we entering Maunder minimum?

55

NS-asymmetry

N-S asymmetry?

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present

11400yr

4000yr

Sunspot number in the past 11400 years 56

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“Sports on a Frozen River” by Aert van der Neer Courtesy: The Metropolitan Museum of Art

The Maunder minimum

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Rotation

Turbulence

⇒ Differential rotation

Solitary star like the sun has strong magnetic fields!

⇒Local dynamo

⇒ Global dynamo

Role of Magnetic fields in Stars and Cosmos and Hinode

• Carry energy through waves • Store energy • Dissipate stored energy with magnetic

reconnection • Induce MHD instability and eruptions • Suppress cross-field transport for mass

and heat • Suppress convection i.e. energy transport

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