Searching for Solar Shocks

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Searching for Solar Shocks

• Including a brief history of
• X-ray astronomy
• H. Hudson, SPRC/UCSD/ISAS

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Beautiful Chandra shock
(E0102-72)
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How X-ray astronomy began

• September 21, 1859 (Carrington)
• Kew Gardens - magnetic effects
• The proper conservatism of L. Kelvin of Largs

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Latent discoveries

• X-rays (Roentgen, 1895)
• The ionosphere (Heaviside, 1902)
• Collisionless shock waves - ?
• Space weather - ??

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Oliver Heaviside

• Maxwells equations
• Laplace transforms
• The Heaviside function
• Telegraph equation - Pupin Laboratory
• Heavy opposition to quaternions
• T.S. Eliot, Cats, Journey to the Heaviside
  Layer
• Not the father of X-ray astronomy (due credit to
  B. Rossi, of course)
• Why should I refuse a good dinner simply because
  I don't understand the digestive processes
  involved.

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Were in a golden era of coronal observation
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The dynamic corona
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The boundary between Photosphere and corona

• Density plummets precipitously
• Collisionality diminishes
• Radiation decouples
• Plasma beta drops drastically

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T.R.
T
B
0
Height in corona
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Solar shock Type II burst
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A Type II burst is the same thing as a slow
drift burst - perhaps discovered by early
military radars explained by J. P. Wild and Y.
Uchida
(recall l-2 ne)
III
Wavelength
II
Time
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Meter-waves and soft X-rays

• Megahertz vs Exahertz
• Radiative transfer vs direct view
• Magnetic effects vs Bremsstrahlung
• Inherent fuzziness vs sharp resolution
• But - by 1998, wed seen Types I, III, IV and
  others

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But not the simplest and most obvious Type II!
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X-ray observation of a global wave

• Wave propagation tells us about coronal structure
• The innermost (earliest) motions tell us about
  the flare process itself

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Moreton-Ramsey wave and EIT wave
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Why didnt SXT discover SXT waves?

• SXT views the whole corona
• Fast-mode MHD waves must involve compressional
  heating
• SXT response increases monotonically with
  temperature
• So why did it take 8 years and the competitive
  example of EIT?

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Factors abetting wave detectionin soft X-rays

• The wave neednt be shocked
• The SXT response strongly favors detection of a
  temperature increase (adiabatic law)

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Sensitivity estimation
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SXT and TRACE responses
Courtesy N. V. Nitta
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Factors reducing sensitivity

• Poor CCD dynamic range (AEC)
• Limited SXT telemetry(Velocity filter)
• Photon counting statistics
• Scattering from grazing-incidence mirror
• Flare mode

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May 6, 1998
FOV 10 arc min
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FOV 5 arc min
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Gas pressure in flare loops
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SOHO/ EIT
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Uchidas 1968 model
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A.R.
Uchida
S.W.
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OK, so what caused the wave?

• In principle we can see it all in soft X-rays
• The earliest manifestation of the wave is within
  20,000 km of the flare core
• But it is significantly displaced from the soft
  X-ray core of the flare

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Mysteries of low b plasma

• Everything seems to expand (cf. Aly)
• The Virial Theorem looks goofy too

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Implosion conjecture

• At low b, the coronal energy is purely B2/8p
• During a flare, theres no time for energy
  transport through the photosphere
• Therefore, some field lines must shorten

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Open field lines
Closed field lines
Isomagnetobars
How low-b implosions must work
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MHD Virial Theorem
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The end, thanks
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The end, thanks
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