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

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