Density of active region outflows derived from fe xiv 264 274
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Density of active region outflows derived from Fe XIV 264/274. Naomasa KITAGAWA & Takaaki YOKOYAMA The 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).

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

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

Naomasa KITAGAWA & Takaaki YOKOYAMA

The 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 loops

Line profile

= EBW + Main component

Intensity

EBW

VNT

(Hara et al. 2008)


R-B asymmetry

(Tian et al. 2011)

  • Ubiquitous EBWs in footpoint regions (De Pontieu et al. 2009)

  • Spatial correspondence with propagating disturbances in fan loops (Tian et al. 2011)

(De Pontieu et al. 2009)


DEM of AR outflows

Total emission

(Brooks & Warren 2012)

  • FIP bias of outflows: 3–5

    • Coronal origin

      i.e. not the photospheric

Fe VIII

S X

Si X

Fe XII

Fe XIII

Fe XV

EBW

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


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

Histogram for l274/l264

Main

EBW


Density diagnostics of AR outflows

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

Density map for each component

Outflow region

Main component

EBW


Density: EBW vs. Main component

  • EBW (outflows): ~108.7 cm-3

  • Main: ~109.2 cm-3

Main

component

Main component

EBW (outflows)

EBW

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


Column depth of AR outflows

(h* for two components were calculated separately.)

  • EBW: 108.2±0.6 cm

  • Main: 107.7±0.2 cm

    Although emission of AR outflows is weak, they dominate in terms of the volume.


Density diagnostics without fitting

  • Derivation of Ne from I264/I274 at each spectral bin.

“l-Ne diagram”

spectrum

Wavelength scale is adjusted.

......

△: solution

: diagram


l-Ne diagram in AR10978

  • AR core

    • log Ne(l)≃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

    “l-Ne diagram”

Histogram for Ne

Main

Outflows


End


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