The Physics of Solar Flares Examining Solar Flares and Radio Bursts By Caylin Mendelowitz and Claire Rosen

OUTLINE Flares Bursts Solar Activity Energy Storage Energy Release Energy Requirements Flare Prediction Summary

Solar Interior Solar interior Gregory, p. 202

Solar Flares What are they? Radiation –optical (H  ) –radio Phases –activation –impulsive –late

Radio Bursts Different Types –type I : thermal –type II & IV: plasma oscillations (shock) & synchrotron –type III & V: plasma oscillations (electrons) & synchrotron Association with flare phases –type III & V coincide with impulsive phase –type II & IV follow impulsive phase –type I in late phase (storm phase)

Solar Activity 22 year cycle Signs of solar activity –flares, CME’s, filaments, sunspots Solar magnetic field –frozen field lines –differential rotation --> twisted magnetic field lines –convection --> kinks –buoyancy -->loops (connect sunspots) Gregory, p.221

Energy Storage Open field lines B|| (above) – B|| (below) =  0 K, where  0 is the permeability of free space and K is surface current density Figure 4 Gregory, p.220

Carroll, p. 424 Field Loop with Current Sheet

Energy Release Accelerated particles –excite plasma oscillations --> type III bursts –synchrotron radiation-- type IV and V bursts –heat plasma --> H  double ribbons X-ray or H  loop prominence loop expands as CME -shock excites plasma oscillations --> type II bursts Tandberg-Hanssen and Emslie, cover

Energy Requirements Typical field strength of active region B = 300 G. Flare energy is ergs Magnetic energy density is = B 2 /8  = 3580 ergs/cm 3 W = P  dV = PV. Solving for V we get V = W/P and –so the minimum volume needed to contain the energy is V = 2.79 * cm 3 Approximate to cube, so L = 3*10 9 cm Length of H  ribbon is cm -- Physical dimensions compare Reconnection time –  R = ½ (R m ) 1/4  A 1/2  D 1/2 = 3sec Time scale compares

Flare Prediction Coronal Mass Ejections (CME’s) Sigmoid regions Zeeman effect Magnetograph Dooling, p. 2

Summary Flares (general) - cause? –Origins --> magnetic energy storage –Mechanism --> reconnection Correlation between radio and optical emission –thermal emission --> H  ribbon (optical) –plasma oscillations and synchrotron --> radio waves Prediction