Microphysical Plasma Processes in Astrophysics

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Microphysical Plasma Processes in Astrophysics

• Uppsala 2004

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Matter

• More than 99 of all visible matter in the
  Universe is in the plasma state
• Invisible matter is unknown but weakly (i.e.
  mainly gravitationally) interacting, thus of
  importance for structure formation but not of
  primary importance for life and men
• Locally almost all matter is in a collisionless
  (if understood as non-anomalous) state

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Main Thesis

• If astrophysicist or astronomers could perform
  only one single measurement in situ this would
  have desastrous consequences for most
  astrophysical theories and models
• Astrophysical theories and models would turn out
  to be basically wrong and would have to be
  overthrown and replaced by new local theories
  which should include basic aspects of
  microphysics
• The relevant microphysics is kinetic plasma
  physics

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Justification

• The paradigm is Space Physics
• Almost all physical predictions which in space
  physics have been based on purely theoretical
  reasoning have turned out to be wrong (or at
  least only marginally correct) after the advent
  of rocket and spacecraft measurements in situ
• In situ measurements have generated an entirely
  new and before unknown and unimaginable world of
  problems in space physics
• This fact demonstrates the lack of imagination in
  human thinking and reasoning

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Problems

• Reconnection
• Jet stability
• Interacting plasma shells
• Particle acceleration
• Radiation

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Reconnection

• Reconnection in almost all astrophysical systems
  is collisionless
• Resistive reconnection is a myth unless the
  matter is dominated by neutrals
• If this is correct then MHD does not apply to
  reconnection independent of scales

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Estimates

• Presence of Neutrals
• ?mfp 1/ nn?c
• For resistive reconnection
• ?mfp lt c/?pi
• ?pi ion plasma frequency
• n/nn lt nc/?pi
• Weakly ionized plasma only!

• Fully Ionized Plasma
• ?mfp 64??D(ND/lnND)
• ND 1

64??D(ND/lnND) lt c/?pi
ND lt c/v Only satisfied for very low temperatures
T0 Reconnection in fully ionized plasma is
always collisionless! W/nT gt (m_e/m_i)1/2ve/c anom
alous or Bohm diffusion
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Example Reconnection on the Sun

• N 1016 m-3
• T50-100 eV
• ve 10000 km/s
• ?e-i 700 Hz
• c/?pe 10 cm
• c/?pi 5 m
• ?mfp 1-10 km
• Solar atmosphere is absolutely collisionless what
  concerns any reconnection taking place there!

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Broadband Noise Spectra in Turbulence behind
Shocks
Pickett et al. Ann. Geophys. 10, 2003
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Solitons in Post-Shock-Turbulence and their
Spectrum
Pickett et al. Ann. Geophys. 10, 2003
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Parallel Electric Fields/Potential Drops and
Particle Acceleration
Ergun et al. PoP. 9, 2002
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Solitons in low-ß Regions
McFadden et al. JGR. 108, 2003
Ergun et al. PoP. 9, 2002
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Electron Modulation in Solitons
McFadden et al. JGR. 108, 2003
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Magnetospheric Field Line Structure (Empirical
Tsyganenko Model)
Solar Wind
Magnetosheath
Z (RE)
Bow Shock
Lobes
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X-point
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1
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Magnetopause
B
X (RE)
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The Meaning of Reconnection
Axford 1984
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Generalized Ohms Law(Fluid Approach)
Assumptions two-fluid (protons/electrons) idea
l conditions collisionless me/mi ltlt1, ? ? 0
E v ? B - ?j (?0?pe2)-1??t j ?? (jv vj
(en)-1j j) (en)-1 j ? B - ?? Pe Fepmf ?
Hall term
Inertial term
Wave pmf
In quasi-equilibrium the electron pressure
gradient term is the ion pressure term, for
then j ? B - ?? Pe ? ? Pi
Wave ponderomotive force usually neglected
without justification (?) May be important in a
turbulent plasmasheet
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Reconstruction of Hall Current System in the
Magnetotail (Nagai et al., 1998, 2001)
Unmagnetised Electrons
?e
Unmagnetised Ions
Electron Hall Current System
?i
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Hall-Effect in Magnetotail 2
Oieroset et al., Nature 412, 416, 2001 Received
1. May 2001
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Electron Acceleration in Magnetotail Reconnection
Reconnection Region Acceleration of Electrons
FACs connected to Hall Current
Wrong ! No Hall current !
Oieroset et al. (2002)
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Lower-hybrid Waves at Magnetopause
Bale et al., GRL 24, 2180, 2002
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Guide Field Simulation
Drake et al. Science 299, 2003
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Solitons in Reconnection Connected Boundary
Cattell et al. GRL 26, 1999
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M87 Radiolobes around a central Black Hole
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Cygnus A und B0218357 Radiolobes
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Radiogalaxien
Seyfert2G ESO428-g14
NGC6946 (6 cm)
Halpha Bild
M84 (4.9 GHz)
Mk34
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Synchrotron Radiation in Reconnection
Fe(?)
Synch-spectrum
EII
P(?)
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Particle Acceleration by Electric Fields
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Particle Acceleration by Electric Fields
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Electric Wave Forms and Spectra
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Sol itons
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Radiation Fine Structure
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Phase Space Distribution
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Distributions and Holes
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Hole Dynamics in Radiation Source
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The Inefficiency of the Loss-cone Maser
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Small Growth of Loss-cone Maser
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