Post on 15-Dec-2015
transcript
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