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

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

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

Standard Flare Model Flux rope eruption Magnetic reconnection Flare emissions 4 Figure 2: Large solar filament eruption

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

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 6

Flare Emissions 7 Figure 5: Radiation emissions generated by magnetic reconnection RADIO BURSTS

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

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

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.

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

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, , impulsive phase highlighted

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

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

AIA & HMI Comparison 15 16:35: :42: :10: 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

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

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

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

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

Additional Information AIA images solar chromosphere & corona – Entire solar disk – Seven extreme ultraviolet (EUV) channels – Temperature range from K to 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