coronal loops workshop 6, la roche-en-ardenne, belgium, 25-27 jun 2013 density of active region...

Coronal Loops Workshop 6, La Roche-en-Ardenne, Belgium, 25-27 Jun 2013

Density of active region outflows Density of active region outflows derived from Fe XIV 264/274derived from Fe XIV 264/274

Naomasa KITAGAWA & Takaaki YOKOYAMAThe University of Tokyo, Japan


Discovery of AR outflows

• In dark location• v=50-150 km s-1

• Persistent• Emanated from ‘open’ region

Fe XII intensity Doppler vel. Width(Doschek 2008)


Upflows from footpoints of active region loopsLine profile= EBW + Main component

Intensity

VNT

(Hara et al. 2008)

EBW


R-B asymmetry

• Ubiquitous EBWs in footpoint regions (De Pontieu et al. 2009)• Spatial correspondence with propagating disturbances in fan

loops (Tian et al. 2011)

(Tian et al. 2011)

(De Pontieu et al. 2009)


DEM of AR outflows

• FIP bias of outflows: 3–5– Coronal origin

i.e. not the photospheric

Total emission

EBWAsymmetries of the emission lines peak in the coronal temperature (around Fe XII).

Fe VIII Si X S X

Fe XII Fe XIII Fe XV

(Brooks & Warren 2012)


Motivation• Properties revealed so far

– Persistency– Location: AR edge

• Boundary of close & open field?– Doppler velocity: 50-150 km s-1

– DEM: close to AR• What should we know about AR outflows?

– Driving mechanism– Source (in terms of height)

• Density (ne) of AR outflows ITSELF is one of the key clues to approach the nature of them. cf. ) Density of outflow regions– 7x108 cm-3 (Doschek et al. 2008, Fe XII total emission)– 108.4-8.9 cm-3 (Brooks & Warren 2012, Fe XIII total emission)


Simultaneous fitting for Fe XIV 264/274

• Wavelength calibration– Each component in Fe XIV 264/274 must

have the same Doppler velocity because the emission comes from Fe XIV.

• Double-Gaussian fitting

c

v1264264

c

v1274274 264

274

264

274

EBW

Main

⇒

Histogram for 274/264


Density diagnostics of AR outflows e

274

264 NRI

I

CHIANTI ver.7 (Dere et al. 1997, Landi et al. 2013)

Outflow region

Main component EBW

Density map for each component


Density: EBW vs. Main component• EBW (outflows): ～ 108.7 cm-3

• Main: ～ 109.2 cm-3

EBW (outflows)

Maincomponent

Main component

EBW

EBWs (outflows) are more tenuous than the main component.


Column depth of AR outflows

• EBW: 108.2±0.6 cm• Main: 107.7±0.2 cmAlthough emission of AR outflows is weak, they dominate in terms of the volume.

),( e2e

*

TnGn

Ihfh (h* for two components were calculated separately.)


Density diagnostics without fitting• Derivation of Ne from I264/I274 at e

ach spectral bin.

)(

)()(

274

264e

N

......

spectrum

“-Ne diagram”

Wavelength scale is adjusted. Wavelength scale is adjusted.

△: solution: diagram


-Ne diagram in AR10978

• AR core– log Ne()≃9.5

• Outflow region– Dip around 274.1Å

(v～ 100 km s-1)

AR core Outflow region

It is confirmed that outflows are more tenuous than the dominant, rest component.


Discussion

(1) noutflow < nMain

– The outflows observed here were not likely produced as a result of impulsive heating (e.g., nanoflare).

• However, this is not decisive because we do not know whether the two components in emission lines come from the same magnetic structure or not.

(2) h*outflow > h*

Main

– The volume of the outflows is larger than that of the main component, contrary to their weakness in emission line profiles.

(3) Doppler velocities indicate blueshift for log T≥5.8. – Different from fan loops

Driving mechanism in somewhat steady manner is required.


Summary of results

• EIS observation on AR10978• Density measurement

– Main: ≃109.2 cm-3

– Outflows: ≃ 108.7 cm-3 • Column depth

– Main: 107.7±0.2 cm– Outflows: 108.2±0.6 cm

• Verification by “-Ne diagram”

Histogram for Ne

Outflows

Main


End

coronal loops workshop 6, la roche-en-ardenne, belgium, 25-27 jun 2013 density of active region...

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