Dynamics of Cosmic Rays in Thunderstorm Atmosphere and Generation of Elementary Particles by Thunderclouds

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Dynamics of Cosmic Rays in Thunderstorm
Atmosphere and Generation of Elementary Particles
by Thunderclouds

• N.S. Khaerdinov A. S. Lidvansky
•  Institute for Nuclear Research, Russian Academy
  of Sciences, Moscow, Russia

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Plan

• Experimental data obtained at Baksan on variation
  of the CR soft component (10-30 MeV) and muons
  during thunderstorms
• Calculated transformation of energy spectra of
  the soft component in weak near-earth electric
  field. Can describe regular behavior of CR
  intensity at moderate fields
• Calculated transformation of energy spectra in
  strong (critical) field of clouds. Cannot
  describe the bright enhancements of intensity
  with sections of exponential growth
• The model of particle production in thunderclouds
  is suggested based on a feedback cycling process

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Experimental data soft component

• Regular variations intensity versus field
  averaged over many thunderstorm events.
• Strong enhancements of intensity (often before
  lightning) that sometimes demonstrate exponential
  increase
• Published in
• N.S. Khaerdinov, A.S. Lidvansky, and V.B.
  Petkov, Electric Field of Thunderclouds and
  Cosmic Rays Evidence for Acceleration of
  Particles (Runaway Electrons), Atmospheric
  Research, vol. 76, issues 1-4, July-August 2005,
  pp. 346-354.

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Relative deviation of the soft component
intensity from the mean value versus local field
(52 thunderstorm events)
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Thunderstorm on Sept 26, 2001, Baksan Valley
(North Caucasus)

• Electric field
• Soft component
• (10-30 MeV)
• Hard component
• (gt 90 MeV)
• Intensity of muons
• (gt 1 GeV)

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Experimental data muons

• Regular variations intensity versus field
  averaged over many thunderstorm events. Negative
  linear and negative quadratic effect
• Strong dependence on the muon threshold energy
  (both linear and quadratic coefficients increase
  with decreasing threshold)
• N.S. Khaerdinov, A.S. Lidvansky, and V.B.
  Petkov, Variations of the Intensity of Cosmic Ray
  Muons due to Thunderstorm Electric Fields, 29th
  Intern. Conf. on Cosmic Rays, Pune, August 3-10,
  2005, vol. 2, pp. 389-392.

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Thunderstorm on August 6, 2003, averaging over
15 s,one of the longest and most profound muon
effect

• Electric field strength
• Soft component
• Muons gt1 GeV
• Hard component
• (muons gt 90 MeV)
• Stopping muons (20-80 MeV)

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Muons with E? gt 90 MeV Stopping muons (20 lt
E? lt 80 MeV) Muons with E? gt 1 GeV
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Weighted mean coefficients of approximations by
second-degree polynomials of the intensity
field regression curves for different components
Component Energy Linear coefficient, per kV/m Quadratic coefficient, per (kV/m)2
Muons gt 1 GeV ? 0.00277 ? 0.00034 ? 0.00045 ? 0.00005
Hard component (muons) gt 90 MeV ? 0.00794 ? 0.0013 ? 0.00235 ? 0.00002
Stopping muons 20 80 MeV ? 0.04124 ? 0.01260 ? 0.00845 ? 0.00201
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A great increase of the soft component

• The event of September 7, 2000
• A view on a large time scale
• Averaging over 4-s intervals

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Thunderstorm on Sept 7, 2000, fine structure of
the largest increase in the soft component

• Electric field
• Soft component
• (10-30 ???)
• Hard component
• (gt 70 ???)
• Precipitation
• electric current

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Sept 7, 2000 event The largest increase is
exponential with high precision and has an abrupt
stop at the instant of lightning
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Outstanding event during thunderstorm on Oct 11,
2003

• The largest enhancement ever detected
• Lightning strokes interrupt the fast exponential
  rise in one case and slow exponential decay in
  the other

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Correlation of the intensity of soft CR component
with near-earth electric field as measured and
calculated (on the left panel). The difference
(effect not explained by the spectrum
transformation in the weak field near the ground
surface is shown on the right panel.
Accelerated near the ground
Accelerated in the clouds
Electrons
Positrons
Electrons
Positrons
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• Examples of vertical profiles of thunderstorm
  electric field measured in a balloon experiment
  (Marshall et al., 1996)

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The layered structure of electric field in the
atmosphere during thunderstorms (measured and
used in calculations). S.S. Davydenko et al., 12
Int. Conf. on Atmospheric Electricity,
Versailles, 2003)

• Due to this
• structure,
• there is
• always a field
• with an
• opposite sign
• overhead

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Admissible regions for runaway and feedback
particles
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Under stable conditions and at sufficient
strength (D) and extension (from x0 to x1) of the
field the intensity of particles increases
exponentially (K is the probability of one cycle,
and ? is its duration)
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Different effect of lightning in the Oct 11,
2003 event

• The estimates of
• minimum distances
• are 4.4 and 3.1 km
• for the two
• lightning having
• strong effect.
• No effect is
• produced by the third
• nearby lightning.

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Field strength versus field extension for
particle generation process with different rise
time. Red line is the boundary of stability,
thick blue line corresponds to 10 s, as e-folding
time in our 11 Oct 2003 event.
Fundamental limit on electrostatic field in air
calculated by J.R. Dwyer. Monte Carlo simulation
(Geophys. Res. Lett., 30, 2055 (2003)) at a
pressure of 1 atm.
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The upper limits to which intensity can be
increased due to transformation of equilibrium
background electron-positron spectrum of cosmic
rays by strong (critical) electric field versus
the lower boundary of this field (analysis of Oct
11, 2003 event)
Analytical estimates (solid lines) made under
extreme assumptions and the results of Monte
Carlo simulations (points) for gamma-rays
starting from three altitudes (1, 2, and 3 km)
with an ultimately steep energy spectrum.
Vertical line corresponds to the altitude of near
mountains ( 4000 m a.s.l.).
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Arguments in favor of the suggested mechanism

• Intervals with exponential growth of intensity
  are explained in a natural way
• Distances to lightning discharges having an
  effect on the development of the process agree
  with sufficiently distant location of
  acceleration region (intensity argument)
• The spectrum of the observed effect is far
  steeper than extreme estimation for spectrum
  transformation effect (spectral argument)

But more direct proof is needed!
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Conclusions

• At moderate field strengths the transformation of
  the spectrum of cosmic rays is measured.
• There are enhancements of the soft component of
  cosmic rays that do not correlate with measured
  near-earth field. We interpret them as Wilsons
  runaway electrons (or ?-rays from them).
• Events with fast exponential increase of
  intensity are interpreted as a feedback effect
  for runaway particles.
• It is shown that the critical field and particle
  energy for this process are 300 kV/m and 10 MeV,
  respectively.

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The view on the feedback process applications
(more conclusions)
From the point of view of Generation of particles by thunderclouds is
Environment science New type of natural radioactivity
Climatology Amplification factor for CR effects
Physics of atmosphere Mechanism of regulation of electric field strength and ion production
Physics of gas discharge New type of discharge stimulated by relativistic particles
Physics of particle acceleration Effect of bulk acceleration of diffused particle flux in dense medium
Astrophysics Ready model of gamma-ray sources (including cosmic gamma-ray bursts)