What are we understanding Coronal Heatings with “Hinode”?

waves vs. nanoflares

R.Kano (NAOJ)

What kinds of corona?

• Different regions– Active Regions, Quiet Sun, and Coronal Holes.

• Different magnetic topologies– closed fields (i.e. coronal loops) and open fields.

• Various time scales– (quasi-)steady structures and

transient events (i.e. flares, microflares).• Various spatial scales

– coronal loops, diffuse extended corona, XBPs, …

Classification of Coronal Features by Physical Parameters

Narukage et al. (Hinode-3)

Classification of StarsHR diagram

Mass & AgeB, L, … ?

Evolution of Coronal Features on T-EM diagram

Narukage et al. (Hinode-3)

Ener

gy in

put

Ener

gy in

put shift toshift to

steady statesteady state

decay t

o QR

decay t

o QR

still

open

fiel

d &

st

ill op

en fi

eld

&

chan

ge to

CH

chan

ge to

CH

field clo

ses &

field clo

ses &

change to

QR

change to

QR

Closed loopClosed loop

Ope

n fie

ldO

pen

field

H burning

He burning

Ejection of envelope

Evolution of Stars

Contents• What topics are we studying by Hinode?

– Heating Functions H(s).• Loop-top, footpoint, or uniform heatings.

– Nanoflares.• Super-hot components• Intensity fluctuations

– (Velocity).– Relation with photospheric magnetic fields.

• What topics should we study by Hinode?

• What I hope for Solar-C.

Heating Function

• In (quasi-)steady coronal loops, T(s) is coupled with H(s).

• However, there are – Multi-temperature structures

(due to fine structures?)– Velocity fields– etc.

H(s)

T(s)

Heating Radiative Cooling Conductive

Cooling

H(s) = n2Λ(T) – κ∥∂T∂s

∂∂s

Heating Function:above polar regions

Kano et al. (2008, PASJ)

Eclipse on 2007 Feb.17

Temperature1.0 1.4MK

gradient(?)

1〜2x104

erg sec-1 cm-2

1.3

1.1

1.2

0 100 200h (Mm)

T (MK) 0.7

(Revised due to a new calibration data)

• XRT filter ratio temperature increased with hight above polar regions.

• The T-grad. might suggest heating not near footpoints but at high altitude.

Heating Function:above polar regionswith multi-T analysis

Kano (Hinode-3)

• However, based on multi-Tanalysis, the EIS & XRT data above polar regions are well explain with hydrostatic changes of isothermal vertical threads with several temperaturesas Aschwanden & Nitta (2000 ApJ) suggested.

Isothermal structure suggestsfootpoint heating.

T (K)105 106

1020

1022

1019

1021

1018

DEM (cm-5 K-1)

For 10”

For 50”

For 100”

Hydrostatic change with height

Aschwanden & Nitta (2000 ApJ)

Heating Function:in Loops with multi-temperature analysis

Tripathi et al. (2009, ApJ)

• Single temperature along LOS.

• dT/ds > 0.• Filling factor around

foot points– 0.02 @ FeXII, SiX– ～1 @ MgVII

T-grad. suggests loop-top heating.

EM Loci plots

Footpoint

Looptop

Heating Function: in Quasi-Steady UpflowImada et al. (2007, PASJ), Imada et al. (2007, ASJ meeting)

FeXIIFeXIII

> 1 hour Quasi-Steady 150km/s -150km/s

Upw

ard

Vel

ocity

km

/sec

Log Te

FeXVFeXIV

FeXIII

FeXII

FeXIFeX

FeVIIIOVHeII

Dashed line：Sound Speed

• T-dependence of upflow triggered with a flare.

• H(s) was derived– by assuming a cross-

section model of vertical fields,

– and using energy-eq. momentum-eq. and mass conservation.

20M

m40

Mm

60M

m0M

m

Hei

ght

√Ａ logT Velocity

FeXVFeXIVFeXIII

FeXII

FeXI

FeX

FeVIIIOV

HeII

H(s)

Heating at high altitude.

1A(eA) + (vA) = H(s) – n2Λ(T) + Aκ∥

pA

mnvA

∂T∂s

∂∂s

∂∂s

∂∂s

Nanoflare studies: Super-Hot Plasma(1)Reale et al. (2009, ApJ)

• From a multi-filter observation by XRT, Realeet al. (2009) reported super-hot (10MK) plasma in non-flaring active region.

• Although it is necessary to check the possibility of an artifact by scattered lights in XRT, it might suggest nanoflare heatings.

Nanoflare studies: Super-Hot Plasma(2)Ishibashi et al. (Hinode2 & Hinode3) .

• In Hinode-2, Ishibashi reported that 15MK component was found in quiet-Sun with the filter-ratio analysis of XRT.

• In Hinode-3, he made assurance double sure with the photon-counting analysis by XRT, and detected Ｘ-ray spectrum from ~10MK plasma in quiet-Sun.

–X-ray spectrum in

Nanoflare studies: Intensity fluctuationsTerzo (TBD)

• He just started this topic.

• From XRT’s high-cadence (~3 sec) observations, auto-correlation of intensity fluctuations may reveal a typical timescale of nanoflare events.

Sakamoto et al. (2008, ApJ)

Upflow & NT-Velocity in AR LoopsHara et al. (2008, ApJ)

• Upflow of hot plasma was observed near the footpoints.

• Large NT-velocity was also observed near the footpoints in on-disk active regions. It is probably a superposition of many upflow components.

The hot plasma upflowssuggest nanoflare heating.

Small NT-velocity (~20km/s) in limb ARs gives a constraint to Alfven-wave heating.

Fe XIV 274AOn-disk AR Limb AR

Hint from simulationsAntolin et al. (2008, ApJ)

x

t x

t

x

t

x

t

x

t

x

t

Alfvén wave heating Nanoflare heating(footpoint)

Nanoflare heating（uniform）

Tem

pera

ture

Vel

ocity

Temporal variation of T(s) or V(s) along loops is important.

Imada pointed out that reconnection sites in major flares (100Mm) do not look hot due to the time lag for ionization.

How about nanoflares? Local enhancement (~1Mm) in T(s) might be hard to be observed.

Relation between Coronal Activities & Photospheric Magnetic Fields

eg. Kano et al. (2010, submitted)

Emerging

Reconnection

Submerging

11:13:51.472

11:15:42-59

11:15:35

SO

T-F

GM

agne

togr

amSO

T-F

GC

a-II

HX

RT

Al/P

oly.

5”5000 km

fluxemergence

• Microflares around a spot were accompanied with magnetic cancellations, some of which were formed with EMF and MMF.

• Although magnetic buoyancy may prevent the submergence of coronal fields under the photosphere, why magnetic cancellations are associated with microflares?

Multiple reconnections may happen not only corona but also in chromosphere or transition region.

Magnetic SubmergencesSubmergence of photospheric B: Chae et al. (2004, ApJ)

Submergence of chromospheric B: Harvey et al. (1999, SP) • The Submergence of

photospheric and chromospheric magnetic fields were observed.

• Non-thermal emission observed with RHESSI above cancellations suggests that reconnection occurred in the corona.

• However, no evidence for the submergence of coronal fields.

Chifor et al. (2008, AA)

Downflow at cancellation site

Chrom.-B disappeared earlier than photo-B.

Chromospheric magnetogram

Photospheric magnetogram

Interaction regions would like to be observed.

• Velocity fields in chromosphere, transition layer, and lower corona.

• Magnetic configuration in chromosphere.

With Hinode/EISand Solar-C/Plan-B.

Emerging

Reconnection

Submerging

?

Studies of Coronal Heating with Hinode(personal view)

• Heating Functions along magnetic fields.– To analyze T(s) in many quasi-steady features for understanding

H(s). But, we have to consider velocity fields. – To find short-lived small increases in T(s) for understanding

localized elemental events in quasi-steady features.• Nanoflare vs. Wave

– To find super-hot plasma in non-flaring features.– Autocorrelation of temporal/spatial variations may reveal some

properties of nanoflares.– To find relations between NT-width and coronal-T for dissipation

of for waves.

• Relations with lower atmospheres– Where do energetic events happen?

• Magnetic configurations.• Wave excitations or reconnections.

What I hope for Solar-C.

1

100

10000

1000” 100” 1” 1”2”10”

1s

1m

1h

10”dx: spatial

resolution

dt: temporalresolution

X: FOV size

R: spectrumresolution

EISraster scan

XRT

Interaction regions would like to be observed.

• Velocity fields in chromosphere, transition layer, and lower corona.

• Magnetic configuration in chromosphere.

With Hinode/EISand Solar-C/Plan-B.

Emerging

Reconnection

Submerging

?