understanding the origin of solar flares
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Understanding the Origin of Solar Flares. Joseph M. Davila (GSFC). Can We Confirm Observationally Some Basic Flare Assumptions?. Flares originate from energy stored in the corona Reconnection in the corona releases this stored energy - PowerPoint PPT PresentationTRANSCRIPT
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Understanding the Origin of Solar Flares
Joseph M. Davila (GSFC)
Moore, eta al Antiochos
ForbesGibson
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Can We Confirm Observationally Some Basic Flare Assumptions?
• Flares originate from energy stored in the corona
• Reconnection in the corona releases this stored energy
• Accelerated electron beams which travel to denser regions where energetic emission is observed.
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Two New Enabling Discoveries• High Resolution white light corona imaging
– Contrary to previous conventional wisdom, recent eclipse images show that fine-scale (1 arcsec) structures are present and visible
– These structures are tracers of magnetic field lines • New diagnostic capability developed
– Davila and Reginald have developed and demonstrated at a series of recent eclipses a new temperature and velocity diagnostic capability applicable to ONSET-type white light coronagraphs
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2010
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2008
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Eclipse 7-22-2009 COR1 7-22-2009
Coronagraph-Eclipse Comparison
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Diagnostic Capability• Currently white light
coronagraph images provide electron density
Density
Temperature
Velocity
• The next generation of coronagraphs will use spectral information, to also determine
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How Does it Work?
• High temperature coronal electron distribution “smooths” photospheric spectrum
• The degree of smoothing is proportional to the electron temperature
• Doppler shift of the entire spectrum is proportional to the flow speed
Coronal Model Spectrum
Photospheric Spectrum
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Temperature Measurement
• The ratio of intensity two 50 A wide bands is temperature sensitive
• Velocity sensitive ratio is available also
Coronal Model Spectrum
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Thomson Scattering Physics• Wavelength conserved in the frame
of the moving electron• Doppler shift of source is observed in
scattered radiation Even if motion is transverse
• Integration over Maxwellian velocity distribution, and line of sight sums all red and blue shift contributions
• Spectral shift of approximately 4 A per 100 km/s
• Technique demonstrated by observations during total solar eclipse
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Temperature Results from China Eclipse (2008)
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Radial Cut
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Results
Mg X 1.1 MK
N V 180 000 K
S II 25 000 K
H I Ly a 20 000 K)
C I < 10 000 K)
1.2 1.4
1
2
3
Tem
p (M
K)
1.0
r/Rsun
SUMER Limb ScansFilter Ratio Temperature
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West Limb Temperature (2006 Eclipse)
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March 28, 2006 SPSE MeetingWaw au Namous, Libya
Reconnection Jets
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March 28, 2006 SPSE MeetingWaw au Namous, Libya
Observing Reconnection
Line of Sight 1
Line of Sight 2
Sun
Wavelength
Flux
Rat
ioFew percent difference
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Reconnection Jets