1. STUDY OF A DENSE, CORONAL THICK TARGET SOURCE WITH THE MICROWAVE DATA AND 3D MODELING Gregory Fleishman, Yan Xu, Gelu Nita, & Dale Gary 03/12/2015

2. Introduction A science question: where does the electron acceleration occur in solar flares? Does it happen in dense or tenuous loops? If the acceleration region is dense, it must be detectable in HXR via coronal thick-target emission. Do dense coronal loops exist?

3. Dense Flaring Loops Dense post-flare loops (e.g., Neupert 1971; Marsh & Hurford 1980; Feldman et al. 1982) Dense cold flaring loop in a small flare (White et al. 1992) Dense hot flaring loops (Veronig & Brown 2004) Dense cold flaring loop in a large flare (Bastian, Fleishman, Gary 2007) A subset of dense coronal flares (Xu et al. 2008)

4. Bastian et al. 2007: n 0 ~ 10 11 cm -3 Acceleration region; turbulence-mediated transport of fast electrons

5. Veronig & Brown 2004

6. Implications (Xu et al. 2008)

7. Xu et al. 2008

9. This study OVSA 5.6 GHz

11. Work Flow

12. Compare with 21 May 2004 M2.6 flare

13. 3D Model (our event: 2002-04-12) SoHO/MDIRHESSI 12-25 keV OVSA 5.6 GHz B 0 = 140 G Density; thermal Density; nonthermal

14. Model-to-data Comparison: Images X-ray model on RHESSI 12-25 keV OVSA image at 5.6 GHz on microwave model X-ray model on microwave model on RHESSI 12-25 keV

15. Model-to-data Comparison: Spectra

16. Compare with 21 May 2004 M2.6 flare

17. Summary of the 3D Model

18. Conclusions