1. Today’s Papers 1. Flare-Related Magnetic Anomaly with a Sign Reversal Jiong Qiu and Dale E. Gary, 2003, ApJ, 599, 615 2. Impulsive and Gradual Nonthermal Emissions in an X-Class Flare Jiong Qiu, Jeongwoo Lee, and Dale E. Gary, 2004, ApJ, 603, 335 3. Others… Solar Seminar on 2004 April 19 by Ayumi Asai

2. Flare-Related Magnetic Anomaly with a Sign Reversal Qiu J. and Gary D., 2003, ApJ, 599, 615 Magnetic anomaly : transient change of magnetic field during a flare (apparent sign reversal of magnetic polarity)  produced by distortion of line as a result of nonthermal beam impact on the atmosphere of the flare region

3. 1. Introduction What is “magnetic anomaly?” polarity reversal @HXR sources  associated with nonthermal beams strong B (umbrae) transient phenomena ~a few minutes  distortion of measurements due to unusual conditions Fig. 1b MDI HXT H

4. Contents simulation of the MDI measurements to understand the role of a modified Ni I line profile in producing the magnetic anomaly analysis of the HXR observation to deduce the energy flux deposited at the location of the anomaly discussion about the probable mechanisms for the flare-related magnetic anomaly effects of saturation and velocity field on MDI measurements

5. 2. Observation of Magnetic Anomaly polarity reversal occurs temporally, and resume there is no significant change except for flare kernels different from saturation (persistent throughout the flare)  failure of the onboard algorithm Fig. 2d saturation > 1000G

6. Velocity Field downflow < 2km/s Fig. 4 velocity contour upflow downflow not exactly overlap with the areas of the magnetic anomaly

7. Temporal Correlation with HXR close temporal association between magnetic anomaly and the footpoint HXR emissions both the timing and the locations of the downflow are not particularly well correlated with magnetic anomaly Fig. 5

8. 3. MDI Measurements on Changing Line Profiles flare-induced line profile changes no comprehensive treatment of line formation and radiative transfer simulated MDI output, by adjusting line intensity, width, and asymmetry  how significantly the change in the line profile would affect the measurements?  Do the sign reversal of magnetic polarity (magnetic anomaly) really occur?

9. 3.1. Absorption Profiles line profiles with B=0 velocity ~2km/s simulated B measured B simulated B measured v red asymmetry Fig. 6aFig. 6b

10. 3.2. Emission in strong-field region (>1500 G), a sign reversal is generated with background velocity field, a sign reversal is produced even in weak-field regions measured velocity field is also sign-reversed Fig. 6c

11. 3.3. Centrally Reversed Profiles centrally reversed profile  lower atmosphere is predominantly heated a sign reversal of measurement depends on the line width and the intensity of central reversal with background velocity field, a sign reversal occurs in weak-field regions Fig. 6e

12. 3.4. Summary variety of combinations of line profiles and velocity fields result in the apparent sign reversal  convert absorption to emission gap of the sign reversal of velocity field is also explained  significantly broadened line profiles with a strong central reversal moderate velocity field would lead to the sign reversal in weak magnetic field region, and not in strong magnetic field region  information of real velocity field is needed  result of nonthermal beam impact

13. 4. Nonthermal Beam Effect on the Atmosphere HXT /M1-M2-H electron which can reach TMR energy deposit by nonthermal beam to turn absorption to emission / centrally reversed line TMR is not directly heated by >350keV electrons nonthermal excitation and ionization generate a enhance source function to turn the absorption to emission (Ding et al. 2002)

14. 6. Conclusions magnetic anomaly in MDI correlate with HXR sources, appear at flare maximum, in umbral regions of strong magnetic field  sign reversal is associated with precipitating nonthermal electrons sign reversal is generated when absorption is centrally reversed or comes into emission sign reversal may not be produced by direct penetration, but by a comprehensive radiative transfer effect

15. Impulsive and Gradual Nonthermal Emissions in an X-Class Flare Qiu J., Lee J., and Gary D., 2004, ApJ, 603, 335 Comprehensive case study of an X- class (X5.6) flare observed on 2001 April 6 Spatially resolved features of a gradual hardening flare with HXR and microwave data

16. Impulsive / Gradual Burst Fig. 1 impulsivegradual

17. Evolution of the Flare HXR sources in gradual phase are also generated by thick-target emissions due to precipitation of nonthermal particles Fig. 2

18. Footpoint Motion support successive magnetic reconnection Fig. 4

19. Spatially Resolved Index FP A and FP C shows the same spectral evolution These are “conjugate footpoints”

20. Gradual Hard Flare difference of spectral and light curve evolutions  different acceleration mechanism in impulsive/gradual phases gradual hardening

21. Spectral Evolution microwave data : Owens Valley Solar Array spectral evolution in microwave optically thick in impulsive phase optically thin in gradual phase optically thick optically thin Fig. 5a

22. 7. Conclusions gradual burst is produced by a physical mechanism different from that for the impulsive components both impulsive and gradual HXR sources are thick-target ones  support magnetic reconnection model

23. Downflow at Flare Ribbons 2001 April 10 Flare DST multi-wavelength observation H  : -5.0, -1.5, -0.8, -0.4, center, +0.4, +0.8, +1.5 spatially resolved red asymmetry

24. Red Asymmetry chromospheric condensation due to rapid pressure enhancement  precipitation of nonthermal particle and thermal conduction front

25. Dopplergram I

26. 2001 April 10 Flare +1.5 A-1.5 A

27. Dopplergram II

28. Scatter Plot bright in red bright in blue bright dark