Gennady Fiksel

Robert Rosner

UW Madison

Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasma

August 4-6, Madison, WI

Anomalous Ion Heating

Status and Research Plan

CMSO

CMSO Meeting • August 4-6 2004 • Madison WI

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.

CMSO

CMSO Meeting • August 4-6 2004 • Madison WI

Outline

• Overview of results. Similarities and differences in different experiments/observations.

• Ion heating and magnetic turbulence• Plans and progress.

CMSO

CMSO Meeting • August 4-6 2004 • Madison WI

MST - anomalously high ion temperature observed

200

250

300

350

400

0.8 1 1.2 1.4 1.6 1.8

Ip = 400ka, D, 17 oct 2000 Te (TS)Ti (RS)

ne (1013 cm-3 )

Temperature (eV)

It is expected that Ti /Te ≈ 0.1 based on the balancebetween collisional e/i heating and losses.

CMSO

CMSO Meeting • August 4-6 2004 • Madison WI

MST - fast ion heating in during reconnection events

Both impurities and majority components are rapidly heated.Stronger heating of heavy ions.

TD TC4+ Te

electrons

Deuterium

C4+

Heating phase:Required heating power ~ 1MW/m3

What can provide it?

Cooling phase:Why so fast?

CMSO

CMSO Meeting • August 4-6 2004 • Madison WI

MST - Ion heating is isotropic

T|| ≈ T

No fast Alfvenic flows were detected. Distribution function remains Maxwellian

CMSO

CMSO Meeting • August 4-6 2004 • Madison WI

MRX - Enhanced ion heating inside reconnection region

(Hsu et al. ‘00)

CMSO

CMSO Meeting • August 4-6 2004 • Madison WI

Solar corona - strong heating of protons and heavy ions

Heating is M and Z dependent

CMSO

CMSO Meeting • August 4-6 2004 • Madison WI

Solar corona - strong flow, ion heating is anisotropic

From: Cranmer et al.,

ApJ, 511, 481 (1998) Note the large anisotropy: TO/TO 10

CMSO

CMSO Meeting • August 4-6 2004 • Madison WI

SSX - Alfvenic flows and ion heating

Fit to a thermal distribution with drift:T=33±11eV and V=86±20eV

Ion energy distribution measured with electrostatic analyzersC. Cothran

M. Brown

CMSO

CMSO Meeting • August 4-6 2004 • Madison WI

Comparison table

MST MRX SSX Solar corona

T|| / T ≈1 ? ? < 1

<<1 in wind

Vflow/VA small small ≈ 1 from <<1

to >> 1

TZ/Tp ≥1 ? ? >> 1

Localization global.

better resolution

soon

reconnection layer

reconnection

layer

narrow regions in

corona

CMSO

CMSO Meeting • August 4-6 2004 • Madison WI

Magnetic fluctuations and/or magnetic reconnection present in all cases and thought to be the maincandidate for ion heating.

We do not know if the ion heating mechanism is the same or different in these cases

CMSO

CMSO Meeting • August 4-6 2004 • Madison WI

MST - correlation of ion heating with active control of magnetic activity

In improved confinement regimes with low magnetic fluctuationsthe “anomalous” contribution to ion heating decreases.Ion heating drastically decreases when reversal surface q=0 and edge resonant m=0 fluctuations are removed from plasma

Reversal surfaceinside plasma qwall < 0

Reversal surfaceremoved qwall > 0

Time (ms)0-1-212-101Time (ms)Ti (eV)040801200200400600051015bt(a)/B(a) (%)m=1m=0051015

CMSO

CMSO Meeting • August 4-6 2004 • Madison WI

MST - correlation of ion heating with active control of magnetic activity

In improved confinement regimes with low magnetic fluctuationsthe “anomalous” contribution to ion heating decreases.Ion heating drastically decreases when reversal surface q=0 and edge resonant m=0 fluctuations are removed from plasma

Reversal surfaceinside plasma qwall < 0

Reversal surfaceremoved qwall > 0

Time (ms)0-1-212-101Time (ms)Ti (eV)040801200200400600051015bt(a)/B(a) (%)m=1m=0051015

CMSO

CMSO Meeting • August 4-6 2004 • Madison WI

MRX - Broad spectra of magnetic turbulence

CMSO

CMSO Meeting • August 4-6 2004 • Madison WI

Solar magnetic turbulenceFr

equency

(H

z)

Solar distance (units of RS)

Wave frequencies vary extremely widely in the outflowing solar wind

CMSO

CMSO Meeting • August 4-6 2004 • Madison WI

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?

CMSO

CMSO Meeting • August 4-6 2004 • Madison WI

MST diagnostic set

• RS - Rutherford scattering diagnostic - local measurements of majority ion temperature.

• IDS - passive Ion Doppler Spectroscopy - chord averaged ion impurities temperature and flow.

• Thomson scattering - Te

Existing diagnostics

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 <JiE>• New Mach probe for local ion flow measurements

• Upgraded CHERS - active Doppler spectroscopy. Ion impurities temperature and flow. Good spatial (few cm) and temporal (10 usec) resolution.

• New high resolution, high frequency magnetic fluctuation probes

Commissioned and upgraded since the last CSMO meeting

CMSO

CMSO Meeting • August 4-6 2004 • Madison WI

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 <JiE>

• 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.

CMSO

CMSO Meeting • August 4-6 2004 • Madison WI

MRX

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

CMSO

CMSO Meeting • August 4-6 2004 • Madison WI

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)

CMSO

CMSO Meeting • August 4-6 2004 • Madison WI

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-frequencies.

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.

CMSO

CMSO Meeting • August 4-6 2004 • Madison WI

Solar corona and astrophysics

Bob Rosner - next