# Presentation: 153682

## RHESSI X-ray Images Challenge Standard Flare Model

- Linhui Sui (CUA/NASA GSFC)
- Gordon D. Holman, Brian R. Dennis (NASA GSFC)

## Outline

- Review of standard flare model
- New RHESSI observations
- flare loops
- coronal sources above flare loops
- Summary

## The Standard Flare Model

- (Adapted from Shibata et al. 1995)

## Flare Loops  

- 	Model predictions:
- chromospheric evaporation(Wuelser et al. 1994)
- apparent loop expansion(Svestka et al. 1995)
- cusp  (Tsuneta 1992)
- outer loops hotter (Tsuneta 1992)

- Rising loop

**Svestka et al. 1995**

- Loop Altitude (km)

- Yohkoh/SXT

- 2.35 km/s

## New Evidence for Chromospheric Evaporation

**New Evidence for Chromospheric Evaporation**

- 3-6 keV

- 3-6 keV

- C4.3 flare on 2002/08/03

- Early impulsive flare
- (minimal preheating) Poster SH13A-0291

**3-6 keV**

**6-12 keV**

**12-25 keV**

**25-50 keV**

- 06:12-06:12:20 UT

- 06:12:40-06:13 UT

- TRACE 171

- TRACE 171

- 06:37 UT

- TRACE 171

## Source motion along flare loops

**Source motion along flare loops**

- C1.0 flare on 2002/11/28

**3-6 keV**

**GOES**

**25-50 keV**

**3-6 keV**

**6-12 keV**

**25-50 keV**

**12-25 keV**

- 1

- 2

- 3

- 4

- 5

- 6

- 7

- 8

- 9

**Downward motion followed by  upward motion of coronal sources in loops**
-         (Liu et al. 2005 reported the
-        upward motion in another event)

## Evidence for Nonthermal Emission at 3-6 keV

- (Sui et al., 2005 in preparation)

**3-6 keV**

**6-12 keV**

**25-50 keV**

**12-25 keV**

**lower-energy sources higher than ****higher-energy sources**      nonthermal thick-target emission at 3-6 keV!
**Interpretation of downward motion**
- 1. density decrease in loop
- 2. low-energy cutoff correlates with HXR flux
- (see poster SH13A-0291)

**Evidence for Nonthermal Emission at 3-6 keV**

## Looptop Downward Motion

- 2002/04/15

**Observations **(Sui & Holman 2003, Veronig et al. 2005)
-  in early impulsive phase, before expansion
-  tens of km/s
-  height decreases by 10-30%
-  also seen in radio (Li & Gan 2005)

**10-25 keV**

**Statistical Results**
- (Poster SH13A-0288 by Holman et al.)
-  84% of flares with upward expansion show early downward motion.

## Interpretation of Loop Contraction

**10-25 keV**

- Source moving horizontally along arcade (**no**)
- Current sheet formation (Sui & Holman 2003,  Sui et al. 2004)
- Magnetic shrinkage
-     (Acton & Forbes1996, Lin 2004)
- 4. Collapsing magnetic trap (Veronig et al. 2005)
- 5. Magnetic Implosion
-     (Hudson 2000)

- reduced

## Upward Motion Correlates with HXR flux

**Upward Motion Correlates ****with HXR flux**

- 12-25 keV

-  equivalent to correlations between V**footpoint**  (Krucker et al. 2003) or V**footpoint ** B**photosphere** (Qiu et al 2004) and HXR flux
-  loop growth delayed by 20~40 s, consistent with chromospheric evaporation (Sui et al. 2004)

**V****loop**

-   Sui et al. 2004

**V****foot**

- 2002/04/14 M3.7

- 2003/07/23 X4.8 flare Krucker et al. 2003

## Above-the-Loop Coronal Source

- Model predictions:
- Plasma outflow from reconnection at Alfven speed ~ 1000 km/s (Shibata et al. 1995,  Kim et al. 2005)
- Expanding twisted loop(Ohyama & Shibata 1996)

**Ohyama & Shibata 1996**

- Yohkoh/SXT

## 10 – 25 keV

**10 – 25 keV**

**Impulsive rise**

**HXR Peak**

**300 km/s**

## Motion of Coronal Sources

**Motion of Coronal Sources**

**Three Steps**
**Step 1:**  Separating from the loop
**Step 2:**  Staying stationary
**Step 3:**  Moving outward rapidly

- Sui et al. 2005

- CME Association

**LASCO/C2**

**LASCO/C3**

**RHESSI**

**300 km/s**

## Evidence for Large-Scale Current Sheet

**14-16 keV**

**12-14 keV**

**10-12 keV**

**8-10 keV**

**12-14 keV**

**16-20 keV**

**footpoints**

**Evidence for Large-Scale Current Sheet**

**current sheet**

- 2002/04/15 M1.2 flare

## Evidence for Continued Existence of Reconnection Current Sheet

**Evidence for Continued Existence ****of Reconnection Current Sheet**

- 23:13:40 UT

- 23:16:40 UT

- Sui et al. 2005

- 2002/04/15 M1.2 flare

- Counts s-1

- Counts s-1

**25-50 keV**

**25-50 keV**

## Summary

** ****Observations supporting standard model:**
- Chromospheric evaporation
- Correlation between loop growth speed with HXR flux
- Temperature distribution of flare loop and coronal source
- Multiple above-loop coronal sources along a line below CME
** ****Observations not predicted by standard model:**
- Nonthermal source moving down along flare loops
- Early looptop downward motion
- Coronal source staying stationary before moving outward

**Conclusion:  **
-  Many RHESSI observations support standard flare model.
-  Model must be revised to accommodate unpredicted results.

## Energy Distribution of Coronal Sources

**Energy Distribution of Coronal Sources**

**10-12 keV**

**12-14 keV**

**14-16 keV**

- Sui & Holman 2003

- 2002/04/15 M1.2 flare (23:11 UT)

## Energy Distribution of Coronal Sources

**Energy Distribution of Coronal Sources**

- 2002/04/16 M2.5 flare (13:04:20 UT)

- Sui 2005, Dissertation

## Krucker et al. 2004

**Krucker et al. 2004**