1. Modeling the Neupert Effect in Flares: Connecting Theory and Observation Andrea Egan Advisors: Dr. Trae Winter and Dr. Kathy Reeves

2. What is a Solar Flare? Sudden brightening in the solar corona typically observed in EUV or X-ray Video courtesy of Andrew Sterner

3. What is a Solar Flare? Occur in active regions Timescale of minutes Material is heated to temperatures of >10 7 K Energies on the order of 10 30 ergs 6,000-7,000 years of US electricity usage 10 12 Nuclear fission bombs Source: Google Public Data Explorer Image: NOAA

4. Where Does the Energy Come from? We’re not entirely sure Magnetic field lines are stressed, then snap and reconnect Changing magnetic fields release stored energy Image: Cargill and Priest, 1983

5. The Observed Neupert Effect Hard X-rays – 12-120 KeV – 0.1-1 Angstroms Soft X-rays – 0.12-12 KeV – 1-10 Angstroms

6. The Observed Neupert Effect Image: Dennis and Zarro, 1993 Hard X-Rays GOES Derivative GOES Flux Solar Flare March 27, 1980 Universal Time (hh:mm:ss)

7. Theory behind the Neupert Effect Non-thermal particles and thermal plasma

8. Theory behind the Neupert Effect Magnetic reconnection accelerates particles Non-thermal Bremsstrahlung radiation Thermal plasma is gradually heated Image: Rhessi Science Nugget, 1998

9. Theory behind the Neupert Effect We can’t see the microphysics How do we test it out? Image: Rhessi Science Nugget, 1998

10. Numerical Modeling Allows us to test hypotheses Still an approximation Make assumptions Limited by computing power

11. Trae’s Model: Hyloop Single monolithic loop 1D Hydrodynamic Code Interfaces with NT particle tracking software Multiple runs ensure reasonable results Movie: Trae Winter

12. Trying out different Initial Parameters Pitch Angle – Method of Acceleration Energy Budget (NT particles) – 100% – 75% – 50% Test the different conditions against the model itself Random Scattering Beamed along Magnetic Field Betatron Acceleration

13. Quantifying The Neupert Effect Temptation to “eyeball” results Veronig et al 2002 Time difference between GOES peak and the end of the HXR emission Limited temporal resolution Image: Veronig et al 2002

14. Temperature and Density

15. Differing Heating Mechanisms

16. Quantifying The Neupert Effect How do we quantify the Neupert effect? We simulate what our instruments would see GOES Satellite 1-8 Å HXR Observations 12-25 KeV (0.5-1 Å) GOES Derivative Time (s)

17. Normalized Emissions

18. Do Our Flares Pass the Test? NT=100%NT=75%NT=50% Beamed Particles14 seconds-33 seconds-39 seconds Random Scattering2 seconds-33 seconds-38 seconds Betatron Acceleration-3 seconds-34 seconds-39 seconds Time of peak of GOES -- point where HXR reaches 1% of max Normalized Emissions Time (s) NT=100%NT=75% NT=50%

19. Conclusions Cases with 100% NT particles exhibited some of the properties of the Neupert Effect Acceleration mechanism does not greatly affect the time delay Further research – Multiple Loops – Amount of energy input

20. Thank You! Trae Kathy CFA SSXG Jonathan and Alisdair NSF (grant number ATM-0851866) Fellow summer interns