The Physics of Solar Flares
Examining Solar Flares and Radio
Bursts
By
Caylin Mendelowitz and Claire
Rosen
OUTLINE
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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  JB 
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)1/4A1/2 D1/2 = 3sec
• Time scale compares
Flare Prediction
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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