Ellerman Bombs in a Solar Active Region:

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Ellerman Bombs in a Solar Active
Region Statistical Properties and
Implications Manolis K. Georgoulis, David M.
Rust Pietro N. Bernasconi Johns Hopkins
University Applied Physics Laboratory 11100 Johns
Hopkins Rd Laurel MD, 20723 USA
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• What are Ellerman Bombs (EB) and where do
  they occur ?

EB are frequent short-lived, localized
enhancements in Ha emission in the
low chromosphere, close to the Tmin region.

• Characteristics of EB

• Very frequent (approx. 1.4 / min)
• Spatial scale of the order of a few arcsec
• Duration of the order of a few min
• They occur on the blue and red wing of the Ha
  line, instead of its center

• Where do EB occur ?

• EB appear related to magnetic activity.
• The majority of events occur above neutral lines
  of Bz.

NOAA 8844 - 01/25/00
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• EB appear related to magnetic activity and
  steep gradients of the magnetic energy density,
  possibly built from plasma motions.

• A statistical study revealed that

• 70 of the EB detected are associated with
  neutral lines in Bz
• 60 of the EB detected are associated with
  overlying UV 1600 A activity

• Conclusions

• EB are probably triggered by some small-scale
  reconnection processes.
• In several cases, they appear associated with
  the footpoints of small loops, bright in UV 1600
  A emission.

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• The triggering mechanism of EB appears
  self-similar

• Area statistics We identify the background
  emission in several ways and plot the
  distribution functions of the areas of EB. We
  note the following

• In all cases, the distribution functions are
  described by power laws.
• The power-law index is insensitive to the
  definition of the background.

• Fractal features The structures are fractal.
  The fractal dimension remains roughly constant,
  varying in the range 0.68, 0.78 with a mean
  value of

• Remark Small-scale flickering events
  triggered by a rather unique physical mechanism.

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• Several EB parameters obey power-law
  distribution functions.
• Typical parameters of EB are correlated to
  each other.

• Total Integrated Intensity

• Definitions

• Integrated Intensity

• Max Integrated Intensity

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Conclusions

• EB are related to magnetic activity (possibly
  forced magnetic reconnection triggered by plasma
  motions).
• EB share several features in common with EUV
  bright points and transient brightenings.
• EB are correlated with overlying UV bright
  points indicating a common triggering mechanism
  for both types of emission.
• This triggering mechanism appears inherently
  self-similar.

• Future Prospects

• We are working towards an estimation of
  typical energies of EB.
• We underline the opportunity for the
  development of a unified modeling philosophy for
  the small-scale activity in the solar atmosphere.
• Possible candidate concepts could be
  Self-Organized Criticality and the probabilistic
  Percolation theory.

• Further information on the Flare Genesis
  Experiment

http//sd-www.jhuapl.edu/FlareGenesis