low-energy coronal sources observed with rhessi
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Low-Energy Coronal Sources Low-Energy Coronal Sources Observed with RHESSIObserved with RHESSI
Linhui Sui (CUA / NASA GSFC)Linhui Sui (CUA / NASA GSFC)
OutlineOutline
Above-the-loop coronal sourcesAbove-the-loop coronal sources
Loop-top coronal sourcesLoop-top coronal sources
Inside-loop coronal sourcesInside-loop coronal sources
SummarySummary
Above-the-Loop Coronal SourceAbove-the-Loop Coronal Source
Ohyama & Shibata 1996
• Yohkoh/SXT observations:Yohkoh/SXT observations: out-flowing speed of 50-400 km/sout-flowing speed of 50-400 km/s jet or twisted loopjet or twisted loop
Interpretations:Interpretations: flux ropeflux rope
Shibata et al. 1995, Ohyama & Shibata 1996, Kim et al. 2005
Three RHESSI FlaresThree RHESSI FlaresM3.7
M1.2
M2.5
6-12 keV
25-50 keV
April 14-15, 2002
April 15
April 16Sui & Holman 2003Sui et al. 2004Sui 2005
Three RHESSI Flares (I)Three RHESSI Flares (I)
M1.2
April 15
10 – 25 keV Impulsive rise
HXR Peak
300 km/s
10 – 25 keV Impulsive rise
25-50 keV
HXR Peak
300 km/s
Revisit the Yohkoh eventRevisit the Yohkoh event Ohyama & Shibata 1996
10-12 keV 12-14 keV 14-16 keV
Energy DistributionEnergy Distribution (2002/04/15 23:11 – 23:11:20 UT)(2002/04/15 23:11 – 23:11:20 UT)
Sui & Holman 2003
Energy DistributionsEnergy Distributions
Sui & Holman 2003
8-10 keV
12-14 keV 16-20 keV
footpoints
Temperature DistributionTemperature Distribution
Temperature DistributionTemperature Distribution
14-16 keV 12-14 keV10-12 keV
8-10 keV
12-14 keV 16-20 keV
footpoints
Associated CMEAssociated CME
C2 04/16 02:26 C3 04/16 06:18
(V~ 300 km/s)
Sui et al. 2005
Coronal Source and CMECoronal Source and CME
coronal source
CME front
Sui et al. 2005
High Coronal X-ray SourcesHigh Coronal X-ray SourcesTearing Mode Instability?
23:13:40 UT 23:16:40 UT
Sui et al. 2005
Three RHESSI Flares (II)Three RHESSI Flares (II)
April 16
April 16, 2002
12-25 keV
6-12 keV
25-50 keV
RHESSI ImagesRHESSI Images
(6-12 keV)(6-12 keV)
Step 1 (rise phase): Coronal source connected to the loop.
RHESSI ImagesRHESSI Images
(6-12 keV)(6-12 keV)
Step 2 (impulsive phase): The coronal source separates from the loopand move outward (it maystay stationary for a while)
Implication:Current sheet formation
140 km/s
Sui 2005
6-8 keV 8-10 keV 10-12 keV
Energy DistributionEnergy Distribution (2002/04/16 13:04:20 – 13:05:20 UT)(2002/04/16 13:04:20 – 13:05:20 UT)
Sui 2005
Rising Flux RopeRising Flux Rope& CME & CME
Goff et al. 2005
RHESSI + TRACE
13:50 UT
Impulsive rise 25-50 keV
Three RHESSI Flares (III)Three RHESSI Flares (III)
Flare of April 14-15Flare of April 14-15(12-25 keV)
Sui et al. 2004
More EventsMore Events
2003/11/03 X3.9
Veronig et al. 2005
A New Type of Coronal Source?A New Type of Coronal Source?C9.4 flare on 2002/06/02
TRACE 195
3-6 keV
6-12 keV
12-25 keV
25-50 keV50-100 keV
The coronal source was located at the cusp region.
Is this Low-energy Masuda source?
Particle acceleration is more efficient before cusp was formed!!
Sui et al. 2006
Rising Flare LoopsRising Flare Loops
Yohkoh/SXT
Loop height increase with time is the foundation of the current flare standard model.
Svestka et al. 1995
2.4 km/s
Loops Seen with RHESSILoops Seen with RHESSI
2002/04/15
Looptop Downward Motion (04/15)Looptop Downward Motion (04/15)
25-50 keV
6-12 keV
Sui & Holman 2003
Altitude decrease: 24% (6-12 keV) 33% (12-25 keV)
• Falling speed: 15 km/s 23 km/s
• Rising speed: 15 km/s 21 km/s
Looptop Downward Motion (04/15)Looptop Downward Motion (04/15)
25-50 keV
6-12 keV
Sui & Holman 2003
Looptop Downward Motion (04/14)Looptop Downward Motion (04/14)
Altitude Decrease: 13% (6-12 keV) 20% (12-25 keV)
Falling Speed: 10 km/s 11 km/s
Sui et al. 2004
Loop growth speed correlates with the hard X-ray flux
Loop growth delayed by 20~40 s
Hloop / vevaporation
= 2 X104 / 300~800= 20~60 s
Upward Speed Correlates with HXRUpward Speed Correlates with HXR
Sui et al. 2004
Analogy of Footpoint MotionAnalogy of Footpoint Motion
• Equivalent to correlations between Vfootpoint (Krucker et al. 2003) or Vfootpoint × Bphotosphere (Qiu et al. 2004) and HXR flux.
2003/07/23 X4.8 flare Krucker et al. 2003
Looptop Downward Motion (04/16)Looptop Downward Motion (04/16)
More eventsMore events
Veronig et al.2005
2003/11/03 X3.9 flare
2002/09/20 M1.2
25-50 keV
Downward Motion in Other WavelengthDownward Motion in Other Wavelength10-25 keV
Radio Observation (NoRH) EUV Observation (TRACE)
Li & Gan (2005) Li & Gan (2006)
Converging HConverging Hαα Kernels and Kernels and downward motion downward motion
(Ji et al. 2006)
Converging Hα kernels
Converging footpoints
Downward moving looptops
Statistical ResultsStatistical Results10-25 keV
Of the 88 limb flares that had an identifiable loop structure: 79% of the sample showed upward expansion. 66% showed downward contraction followed by upward expansion. Therefore, 84% of the loops showing upward expansion were preceded by downward contraction.
(Holman et al. 2005)
Interpretation of Loop ContractionInterpretation of Loop Contraction10-25 keV
1. Source moving horizontally along arcade (no)
2. Current sheet formation (Sui & Holman 2003, Sui et al. 2004)
3. Magnetic shrinkage (Svestka et al.1987)
4. Collapsing magnetic trap (Veronig et al. 2005)
5. Magnetic Implosion (Hudson 2000)
V dVB )8/( 2 reduced
Coronal Sources Inside LoopsCoronal Sources Inside Loops
Some background information…Some background information…
Typical Flares in X-raysTypical Flares in X-rays
2002/04/15 M1.2
Preheating
Troubles: hiding evidence for low-energy cutoffs
losing low-energy electrons (Emslie 2003, Galloway et al. 2005)
hiding weak coronal sources
Plasma Pre-heatingPlasma Pre-heating
2002/04/15 M1.2
Thermal
Nonthermal
C9.6 Flare
Early Impulsive FlaresEarly Impulsive Flares
Hard X-ray flux (> 25 keV) increases before the soft X-ray flux rises significantly. 160 early impulsive flares in 2002 (~25% flares with 25-50 keV)
C9.4 flareSui et al. 2006
One Early Impulsive FlareOne Early Impulsive Flare
GOES
3-6 keV
6-12 keV
12-25 keV25-50 keV
Sui et al. 2006
3-6 keV
3-6 keV
6-12 keV
25-50 keV
12-25 keV
1 2 3
4 5 6
7 8 9
Moving Down
Moving Up
Source MotionSource Motion
Sui et al. 2006
3-6 keV
3-6 keV
6-12 keV
25-50 keV
12-25 keV
1 2 3
4 5 6
7 8 9
Moving Down
Moving Up
1 2 3
4 5 6
7 8 9
6-7 keV
Source MotionSource Motion
Source AltitueSource Altitue
700 km/s
500 km/s
340 km/s
45 km/s
3-6 keV
6-12 keV
25-50 keV
12-25 keV
Downward moving source is nonthermal thick-target emission
Energy DistributionEnergy Distribution
3-6 keV
6-12 keV
25-50 keV
12-25 keV
Power-law at Low EnergiesPower-law at Low Energies
Nonthermal iron line excitation?
3-6 keV
C1.2 flare
More EventsMore Events
More EventsMore Events
10-16 keV
For downward motion: plasma density decrease inside loops (X) spectral hardening low-energy cutoff increasing
For upward motion: chromospheric evaporation spectral softening
low-energy cutoff decreasing
Interpretations for the MotionsInterpretations for the Motions
1. The appearance of the above X-loop coronal source and its evolution may suggest existence of a large-scale of current sheet. (why not more?)
2. The looptop downward motion earlier in the flare could be the result of formation of the current sheet. (need simulations)
3. The correlation of the 3. The correlation of the loop growth speed and HXR flux support the standard flare model. (more events)
4. Multiple plasma blobs appeared along a line above the loop may suggest elongation of the current sheet. (need more events!)
5. Downward and upward motions of coronal sources inside of loops are direct evidence for electron transport along the loop. Electron spectral evolution may explain both motions. (simulation is ongoing)
SummarySummary
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