150 likes | 263 Views
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).
E N D
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