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

BBv

BJF

)(

Energy Storage• Open field lines

• B|| (above) – B|| (below) = 0K, where 0 is the permeability of free space and K is surface current density

Figure 4

Figure 3

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

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)1/4A

1/2 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