Anomalous Ion Heating Status and Research Plan

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Anomalous Ion HeatingStatus and Research Plan
Gennady Fiksel Robert Rosner UW Madison Center
for Magnetic Self-Organization in Laboratory and
Astrophysical Plasma August 4-6, Madison, WI
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Preamble

• Anomalous ion heating and/or acceleration is
  present in many laboratory and space plasmas.
• There are no reliable and experimentally proved
  explanations of that.
• There is definite correlation with magnetic
  reconnections and/or magnetic turbulence.
• The goal is to understand the nature of ion
  heating and unravel the relation to magnetic
  turbulence and reconnection.

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Outline

• Overview of results. Similarities and differences
  in different experiments/observations.
• Ion heating and magnetic turbulence
• Plans and progress.

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MST - anomalously high ion temperature observed
It is expected that Ti /Te 0.1 based on the
balance between collisional e/i heating and
losses.
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MST - fast ion heating in during reconnection
events
Heating phase Required heating power
1MW/m3 What can provide it?
Cooling phase Why so fast?
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MST - Ion heating is isotropic
No fast Alfvenic flows were detected.
Distribution function remains Maxwellian
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MRX - Enhanced ion heating inside reconnection
region
(Hsu et al. 00)
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Solar corona - strong heating of protons and
heavy ions
Heating is M and Z dependent
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Solar corona - strong flow, ion heating is
anisotropic
From Cranmer et al., ApJ, 511, 481 (1998)
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SSX - Alfvenic flows and ion heating
Ion energy distribution measured with
electrostatic analyzers
C. Cothran M. Brown
Fit to a thermal distribution with
drift T3311eV and V8620eV
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Comparison table
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We do not know if the ion heating mechanism is
the same or different in these cases
Magnetic fluctuations and/or magnetic
reconnection present in all cases and thought to
be the main candidate for ion heating.
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MST - correlation of ion heating with active
control of magnetic activity
In improved confinement regimes with low magnetic
fluctuations the anomalous contribution to ion
heating decreases.
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MST - correlation of ion heating with active
control of magnetic activity
In improved confinement regimes with low magnetic
fluctuations the anomalous contribution to ion
heating decreases.
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MRX - Broad spectra of magnetic turbulence
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Solar magnetic turbulence
Wave frequencies vary extremely widely in the
outflowing solar wind
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Questions

• What is the free energy source?
• What is relation between ion heating and
  reconnections?
• Viscous damping of reconnection flows or
  fluctuation induced heating?
• What fluctuations are responsible for ion
  accelerating and heating and what is the
  absorption mechanism?
• Energy flow from the energy source into
  fluctuations - direct excitation or non-linear
  cascade?
• Ion heating in different lab/space plasma -
  manifestation of the same mechanism?

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MST diagnostic set

• Coming online very soon
• New Diagnostic Neutral Beam for CHERS - longer
  pulse, higher energy
• New insertable probes for local ion Doppler
  spectroscopy
• New probe for local measurements of ion energy
  deposition ltJiEgt
• New Mach probe for local ion flow measurements

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MST experimental plans

• Detailed accounting of ion energy balance -
  spatial profile of Ti, Te, ne, radiation, and CX
  losses. Models of ion thermal transport.
• Isotropy of ion heating, Z and M dependence.
• Cross-correlation of Ti with magnetic
  fluctuations in time and frequency domains,
  contribution from different modes.
• Local (edge) measurements of ion energy
  deposition ltJiEgt
• Local measurements of ion flows and evaluation of
  ion viscous heating - cross with the flow and
  momentum group.
• Active control of magnetic activity.
• Active ion heating from externally driven E.

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MRX
Newly upgraded MRX has expanded operation regimes
to study ion heating, such as more collisionless
or larger S plasmas.
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SSX

• Study ion heating and flow generation in FRC-like
  equilibrium
• ion Doppler spectroscopy (with contribution from
  MST)
• single shot measurement of Ti, vi (1 ?s
  resolution)

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Theory plans

• Ion acceleration by E field - effect of
  impurities, mirror trapping, stochastic magnetic
  field, and magnetic islands.
• Dielectric tensor for ion heating from tearing
  modes.
• Viscous heating by compression tearing modes.
• Ion heating in self consistent streaming electron
  emission theory
• Cascade processes to generate small-scale/high-fre
  quencies. Assessment of Alfven cascades.
• Ion and electron heating via Alfven cascades.
• 2-fluid Nimrod study of ion heating from
  reconnection.
• PIC simulation of ion heating from reconnection.

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Solar corona and astrophysics
Bob Rosner - next