1. Probing Energy Release of Solar Flares M. Prijatelj Carnegie Mellon University Advisors: B. Chen, P. Jibben (SAO)

2. Overview Motivations Standard Flare Model – Flux rope eruption – Magnetic reconnection – Flare emissions Type III Radio Bursts Instruments – VLA, AIA, HMI, & RHESSI Observed Flare Dynamic Imaging Spectroscopy Results & Conclusions 2

3. Motivations Investigate basic solar flare physics – Energy release, particle acceleration & transportation Understand flares’ cause and impact – Analyzing flare particles Map reconnected coronal magnetic field lines – Dynamic Imaging Spectroscopy 3 Figure 1: AIA image of the sun, wavelength 171Å

4. Standard Flare Model Flux rope eruption Magnetic reconnection Flare emissions 4 Figure 2: Large solar filament eruption http://www.nasa.gov/images/content/683943main_eruption-zoom.jpg

5. Flux Rope Eruption Flux ropes form within solar atmosphere Flux rope loses equilibrium & erupts – Magnetohydrodynamic (MHD) instabilities – Magnetic reconnections Field lines reconnect following eruption 5 Figure 3: Diagram of eruption & magnetic reconnection http://solarmuri.ssl.berkeley.edu/~hhudson/cartoons/thepages/Shibata.html

6. Magnetic Reconnection Inwardly moving antiparallel field lines connect Reconnected lines flow outward Magnetic energy release – Thermal energy – Kinetic energy Particle acceleration Bulk motion Figure 4: Animation of antiparallel magnetic field lines undergoing magnetic reconnection https://upload.wikimedia.org/wikipedia/commons/2/24/Reconnection.gif 6

7. Flare Emissions 7 Figure 5: Radiation emissions generated by magnetic reconnection http://solarmuri.ssl.berkeley.edu/~hhudson/cartoons/thepages/Svestka.html RADIO BURSTS

8. Type III Radio Bursts Created by flare- accelerated electrons – Generate Langmuir waves near plasma frequency f p – Emit radio bursts near f p or 2f p Electron beam direction affects burst drift direction – Upward  Negative – Downward  Positive 8 Frequency Time Upward Downward Negative Drift Positive Drift Figure 6: Trajectories of electron beams (green) from reconnection site (red X) along magnetic field lines (blue) with respect to frequency drifts. Chromosphere

9. Imaging Instruments Karl G. Jansky Very Large Array (VLA): Radio wavelengths Atmospheric Imaging Assembly (AIA): Extreme ultraviolet Helioseismic & Magnetic Imager (HMI): Magnetic field Reuven Ramaty High Energy Solar Spectroscope Imager (RHESSI): Soft & hard X-ray, gamma rays 9

10. VLA Data Broadband dynamic imaging spectroscopy – Large instantaneous bandwidth – High temporal resolution – High spectral resolution – Full Fourier synthesis imaging Dynamic Spectrum & Imaging 10 Figure 7: Spatial imaging of a type III radio burst.

11. AIA, HMI, & RHESSI AIA images solar chromosphere & corona – Seven extreme ultraviolet (EUV) channels HMI photospheric magnetic field measurements – White positive (outward) polarity – Black negative (inward) polarity RHESSI images soft X-rays to gamma rays – X-rays primarily emitted by accelerated electrons 11 Figure 8: Data of C7.2 flare in various wavelengths (clockwise from top left): AIA 171 Å, HMI line-of-sight magnetogram, RHESSI HXR data

12. Observed Solar Flare C7.2 solar flare Observed Nov. 1, 2014 Impulsive phase of the flare – Interested in type III radio bursts 12 Figure 9: GOES X-ray flux data at time of C7.2 flare, 2014-11-01, impulsive phase highlighted http://www.polarlicht-vorhersage.de/goes/2014-11-01_163500_2014-11-01_172600.png

13. Dynamic Imaging Spectroscopy 13 Figure 10: Dynamic spectrum during C7.2 flare, with closer inspection of a negatively-drifting type III burst, indicating an upward-moving electron beam, and a spatial image of the radio burst. Leading Edge

14. AIA Movie of C7.2 Flare 14 Figure 11: AIA 171 Å movie of C7.2 solar flare at 16:37:04 on 2014-11-01

15. AIA & HMI Comparison 15 16:35:00.340 16:42:48.340 17:10:00.340 Post-Flare Loops Flare Ribbons Flux Rope Figure 12: AIA 171 Å images before, during, and after the solar flare. HMI positive (white) & negative (black) polar regions are contoured. Flux Rope Sigmoid

16. Results & Conclusions 16 Figure 13: AIA 171 Å flare image with overlaid VLA radio emission maxima & single flux contour (colored dots & blue contour, respectively), HMI contours (positive regions white, negative regions black), and RHESSI contours (red contours). The magnetic field lines are purple lines, the “X-point” is at the yellow explosion, & the electron beam trajectories are blue arrows. Flux Rope Flare Ribbons HXR Emissions Findings correspond with standard flare model – Reconnection region trails erupting flux rope (AIA) – Electron beams follow reconnected field lines Downward beams create HXR footpoints Type III bursts from upward & downward beams Radio Frequency Maxima

17. Summary VLA indirectly maps reconnected magnetic fields – Radio emissions determine electron beam trajectories – Trajectories follow reconnected field lines AIA, HMI, & RHESSI provide additional context Data juxtaposition demonstrates standard flare model 17

18. Acknowledgements NSF-REU solar physics program at SAO, grant number AGS- 1263241 NASA contract SP02H1701R from Lockheed-Martin to SAO 18

19. Special Thanks To Henry “Trae” Winter & Kathy Reeves Bin Chen & Patricia Jibben Everyone else at Harvard CfA & SAO 19

20. Additional Information AIA images solar chromosphere & corona – Entire solar disk – Seven extreme ultraviolet (EUV) channels – Temperature range from 20 000K to 20 000 000 K – 12 second cadence – 1.5 arcsec resolution Field lines flow positive to negative – “Footpoints” – Plasma flow along field lines RHESSI: – X-rays typically emitted at footpoint Accelerated electrons collide with chromosphere 20