Post on 06-Jan-2016
description
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Imaging The Active Region TR Imaging The Active Region TR With The CDS Wide SlitWith The CDS Wide Slit
Mike Marsh
Centre for Astrophysics, University of Central Lancashire, Preston, UK
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The Wide Slit
Mg IX368 Å
He I584 Å
O V629 Å
•90˝× 240˝ FOV•26s cadence•Produces intensity images (not rastered) in He I, O V & Mg IX•But no spectral data
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Wide Slit Calibration
Mg IX uncalibrated Mg IX calibrated
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AR 10570
TRACE 171 Å
TRACE 1600 Å
TRACE WLEIT 171 Å
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AR 10570
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TRACE 1600 Å
TRACE 1600 +171 Å
TRACE 1600 +O V
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Composite MovieTRACE 1600 Å O V TRACE 171 Å
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Composite MovieO V TRACE 171 Å
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Rastered data
Rastered data gains line profile data, but loses time variability information
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MDI WL + O V + 171TRACE 171 + O
VTRACE 171
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Fourier power maps
Power significant to 95%
3 min band (4.7 – 6.6 mHz) (150 – 210 s)
3-min umbral oscillationsBeckers & Tallant (1969), Gurman (1982), Fludra (2001), Brynildsen (2002)
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3 min He I time series
• He I oscillation amplitude ~2%
• FFT has 2 dominant periods ~(6.1 & 7.1) mHz(140 & 160) Seconds
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3 min O V time series
• O V oscillation amplitude ~4%
• FFT has 2 dominant periods ~(5.9 & 7.3) mHz(140 & 170) Seconds
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AR 10570 with TRACE
~80 kms-1 projected velocity cf. De Moortel et al. (2002) Robbrecht et al. (2001)
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3 min TRACE 171 time series
• TRACE oscillation amplitude ~3%
• FFT has 3 dominant periods ~(3, 5.9 & 7.3) mHz(330, 140 & 170) Seconds
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Conclusions
• Chromospheric/TR Acoustic Waves (Brynildsen, 2004)
• Waves propagate through chromosphere, TR and into the corona
• 3 min oscillations above sunspot umbra in the Chromosphere & TR where the umbral magnetic field is vertical
• Oscillations observed as 3 min propagations at TRACE temperatures where the field is more inclined.
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Acoustic Energy Flux
22
1332
64
I
I
m
TkN
kxtiVeV '
VV 2
2
1
• Assuming acoustic waves with velocity and pressure perturbations V' and P'
• The energy flux of the wave ε is given by:
kxtiPeP '
Assuming:• Optically thin emission →• Ideal gas• Complete ionisation of the plasma & Relative
abundances X=0.9 Y=0.1→
The energy flux of the wave is given by:
2I
eNN 91.0 pmm 29.1
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Acoustic Energy Flux
Log T (K) Log N (cm-3) ΔI/I ε (erg cm-2 s-1)
He I 4.5 10.959 0.02 28.3
O V 5.4 9.859 0.04 201.0
TRACE 171Å 6.0 9.259 0.03 225.6
O VDoyle (2003) derive Ne in sunspot plumes using O V diagnostic
TRACE 171Del Zanna (2003) derive Ne in the footpoints of quiescent coronal loops
He IEstimated Log Ne=11cm-3 for active regions
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Conclusion
• Acoustic waves propagate through chromosphere, TR and into the corona
• Acoustic waves are insufficient to heat active regions
• Technique may be used as a seismological tool to determine plasma properties ρ, T,…
• If ε constant through the atmosphere; may allow derivation of Ne at He I temperatures
• Need active region Ne measurement at He I temperatures