Observations and NLFFF Observations and NLFFF Modeling of AR 10953Modeling of AR 10953

Yingna SuYingna Su1,21,2

Collaborators:Collaborators: A. A. Van BallegooijenA. A. Van Ballegooijen11, E. E. Deluca, E. E. Deluca11, Leon Golub, Leon Golub11 P. GrigisP. Grigis11, B. Lites, B. Lites3, 3, G. L. HuangG. L. Huang22

1.1. Harvard-Smithsonian Center for Astrophysics, USAHarvard-Smithsonian Center for Astrophysics, USA 2. Purple Mountain Observatory, China2. Purple Mountain Observatory, China 3. High Altitude Observatory, USA3. High Altitude Observatory, USA

AGU/SPD, Fort Lauderdale, 05/29/2008AGU/SPD, Fort Lauderdale, 05/29/2008

OutlineOutline Background

NLFFF Modeling of (pre-flare) AR 10953

• Flux Rope Insertion Method

• Data: SOHO/MDI, Hinode/SOT, KSO/H-alpha, Hinode/XRT

Observations of a C8.5 Flare in AR 10953

• Data: Hinode/XRT, TRACE, RHESSI, MLSO/H-alpha

Interpretations and Conclusions

BackgroundBackground

Existing methods for constructing NLFFFs (non-linear force free fields)

• Most methods: extrapolating photospheric vector fields to the corona

(Schijver et al. 2006). • The method we adopted: “flux rope insertion method” (van Ballegooijen 2004;

Bobra etal. 2008) which requires line of sight magnetograms. This method was tested byBobra et al. (2008), and the model was constrained by TRACE observations.

What is the 3D pre-flare magnetic configuration? Where and how is the flare initiated?

In this work, we construct NLFFF models for the pre-flare stateof AR 10953, and the model is constrained by multiple non-potential X-ray loops observed by XRT.

Flux Rope Insertion MethodFlux Rope Insertion Method

PF model Insert Flux Rope NLFFF Model

MDI+SOT/SP

2007-May-02 17:30 UT

KSO/H-alpha

2007-May-02 11:31 UT 2007-May-02 14:59 UT

XRT MDI+SOT/SP

Magneto

Friction

Van Ballegooijen 2004; Bobra et al. 2008

Model Constraint: X-ray LoopsModel Constraint: X-ray Loops

• Best fit model field lines for four non-potential X-ray loops• Model Free Parameters: Axial flux and Poloidal flux of the flux rope

Model

Axial

Flux (Mx)

Loop 1

14:49:09 UT

Loop 2

15:17:04 UT

Loop 3

22:58:20 UT

Loop 4

18:17:27 UT

NLFFF

5e20 0.0017 0.0035 0.0039 0.0067 Y

7e20 0.0020 0.0022 0.0018 0.0047 Y

9e20 0.0025 0.0024 0.0013 0.0034 Y

12e20 0.0031 0.0026 0.0018 0.0020 Y

15e20 0.0056 0.0031 0.0024 0.0012 ?

Table 1 The Average Distance (in solar radii) of the projected best-fit model field lines from the observed X-ray loops for various models with fixed Poloidal Flux (1e10 Mx/cm).

Calculation Solution SetCalculation Solution Set

Best Fit Model: Axial Flux=7e20±2e20 Mx , Poloidal Flux ~ 1e9 to 1e11 Mx/cm (larger range); Eruption for Axial Flux~ 15e20 Mx

Loop 4 may be in a non-stable state.

Comparison with SOT/SP Vector Comparison with SOT/SP Vector MagnetogramMagnetogram

Best Fit Model: Axial Flux=7e20 and 9e20 Mx

Blue Vector: Observation Black Vector: Model

Vector Magnetogram: Obs. Versus ModVector Magnetogram: Obs. Versus Mod..

Best Fit Model: Axial Flux=7e20 and 9e20 Mx

Blue Vector: Observation Black Vector: Model

worst fit good fit worse fit

Observations of C8.5 Flare

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MLSO/H-alpha TRACE/171 XRT/Ti_poly

Filament activation (23:30 UT) associated with the flare Filament activation (23:30 UT) associated with the flare was seen in H-alpha and EUV, not Xwas seen in H-alpha and EUV, not X-ray.-ray.

Two-ribbon flare: unsheared-sheared-unsheared.Two-ribbon flare: unsheared-sheared-unsheared.

Not associated with filament eruption and CME.Not associated with filament eruption and CME.

Light Curves of C8.5 Flare

EUV flare starts about 20 minutes later than theEUV flare starts about 20 minutes later than theX-ray (XRT and RHESSI) flare, Why?X-ray (XRT and RHESSI) flare, Why?

Pre-EUV flare X-ray brightenings

XRT

XRT

RHESSI

XRT

TRACE

RHESSI Spectral fitting suggests that the pre-EUV flare X-ray sources are mainly caused by thermal bremsstrahlung emission.

Where Does the Flare Start?

At flare onset, the flare loop is unsheared. This suggests the flare starts near the outer edge of the flux rope.

XRT 2007-May-02 23:09:24 UT

Z=14

flare loop

flare loop

Current layer

* Reconnection site?

Conclusions (I)Conclusions (I)

Comparison of modeled and observed X-ray loops for pre-flare (C8.5) state of AR 10953

Axial Flux: 7e20±2e20 Mx (good constraints from X-ray loops)Poloidal Flux: 1e9-1e11 Mx/cm (wide range)Upper limit: Axial Flux~15e20 MxFree Energy: ~0.85e32 erg, Potential Energy: 9.62e32 erg

Similar result obtained by comparisons of observed and modeled photospheric vector magnetograms.

The axial flux (7e20±2e20 Mx) in the flux rope is far away from the upper limit (15e20 Mx) for eruption, which is consistent with the fact that no successful filament eruption occurred in this active region.

Conclusions (II)Conclusions (II)

The X-ray brightenings appear about 20 minutes earlier than the EUV flare associated with a filament activation, which may be caused by the localized coronal heating.

Open question: Why does the heating not propagate to the

chromosphere where EUV flare occurs?

This flare starts from unsheared brightenings, unlike most two-ribbon flares (Su et al. 2007).

Interpretation: the flare starts near the outer edge of the flux rope, Not at the inner side or at the bottom as suggested in the standard flare model (e.g., Moore et al. 2001).

Thank you Thank you for for

your attention !your attention !