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

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

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 ergs 6,000-7,000 years of US electricity usage Nuclear fission bombs Source: Google Public Data Explorer Image: NOAA

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

The Observed Neupert Effect Hard X-rays – KeV – Angstroms Soft X-rays – KeV – 1-10 Angstroms

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)

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

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

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

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

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

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

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

Temperature and Density

Differing Heating Mechanisms

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 KeV (0.5-1 Å) GOES Derivative Time (s)

Normalized Emissions

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%

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

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