Transcript solarflares
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 ( v B) B – frozen field lines – differential rotation --> twisted magnetic field lines – convection --> kinks – buoyancy -->loops (connect sunspots) F JB Gregory, p.221 Energy Storage • Open field lines Figure 3 Figure 4 Gregory, p.220 • B|| (above) – B|| (below) = 0K, where 0 is the permeability of free space and K is surface current density Field Loop with Current Sheet Carroll, p. 424 Energy Release • Accelerated particles Tandberg-Hanssen and Emslie, cover – 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 http://sohowww.nascom.nasa.gov/ Energy Requirements • Typical field strength of active region B = 300 G. Flare energy is 1032 ergs • Magnetic energy density is = B2/8 = 3580 ergs/cm3 • 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 * 1028 cm3 • Approximate to cube, so L = 3*109 cm • Length of H ribbon is 1010 cm -- Physical dimensions compare • Reconnection time – R = ½ (R m)1/4A1/2 D1/2 = 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