Magnetic Reconnection in the Solar Wind

Gosling, Phan, et al.

Draping of the Ambient Field about an ICME

The ambient magnetic field ahead of a fast ICME is compressed by its interaction with an ICME and drapes about it.

The most characteristic signature of reconnection is the acceleration of plasma away from the reconnection site in a pair of oppositely directed exhaust regions.

The conversion from magnetic energy to bulk flow energy occurs primarily at the edges of the outflow exhausts and not at the reconnection site.

Magnetic Reconnection

Inflow

Inflow

Outflow Outflow

A Reconnection Exhaust Observed Within an ICME

Accelerated plasma flow at a sharp shear in the magnetic field marks a reconnection exhaust. Note also the dip in B, spikes in Tp and Np.

The exhaust occurred at the interface between open and closed field lines within the ICME.

A large fraction of reconnection exhausts in the solar wind are associated with ICMEs.

Magnetic Field and Flow Velocity Changes Associated With the 10/3/2000 Reconnection Exhaust in the Solar Wind

ExhaustThe event straddled a large (148˚) change in field orientation.

Note the bifurcated nature of the current sheet and the intermediate field orientation in the middle of the exhaust.

V,B changes were anticorrelated at the leading edge and correlated at the trailing edge of the exhaust.

The exhaust was bounded by Alfven waves propagating antisunward along B.

The above is the characteristic signature by which we identify reconnection exhausts in the solar wind.

Reconnection Exhausts in the Solar Wind

We have now identified more than 50 reconnection exhausts of this nature in the ACE solar wind data, including events where the flow acceleration is directed sunward rather than anti-sunward. All have occurred in plasma with low proton beta. Only 3 of these events occurred at the heliospheric current sheet.

Is Reconnection Intrinsically Patchy in Space and Time?

3 S/C Observations of the 2 February 2002 Event

Phan et al.

The signature of the reconnection exhaust was essentially the same as observed at different times at 3 widely separated spacecraft.

Nature 439, 175-178 (12 January 2006) A magnetic reconnection X-line extending more than 390

Earth radii in the solar windT. D. Phan1, J. T. Gosling2, et al.

Is reconnection is fundamentally a process that can occur over an extended region in space or is it patchy and unpredictable in nature?

Solar wind observations of reconnection where the X-line extended at least 390 RE (or 2.5 million km).

Implies that reconnection is fundamentally a large-scale process, and that patchy reconnection observed in the Earth's magnetosphere is likely to be a geophysical effect associated with fluctuating boundary conditions, rather than a fundamental property of reconnection.

SPONTANEOUS RECONNECTION IN A

LABORATORY EXPERIMENT

J Egedal, W Fox, N Katz,

K Reim, & M Porkolab

MIT, PSFC, Cambridge, MA

• Reconnection in the Versatile Toroidal Facility– Experimental setup

– New reconnection drive scenario

– Magnetic signature of spontaneous reconnection

– Alfvenic outflows

– Energy balance

• Conclusions

Outline

The Versatile Toroidal Facility (VTF)

The Versatile Toroidal Facility (VTF)

External Coils

The Versatile Toroidal Facility (VTF)

External Coils

Vacuum Vessel

The Versatile Toroidal Facility (VTF)

External Coils

Vacuum Vessel

TF Coils

The Versatile Toroidal Facility (VTF)

External Coils

Vacuum Vessel

TF Coils

RF-Power

The Versatile Toroidal Facility (VTF)

External Coils

Vacuum Vessel

TF Coils

RF-Power

Diagnostics

Collisionless Reconnection

A new closed cusp by internal coil. Passing electrons &

spontaneous reconnection events.

Two different magnetic configurations

A open cusp magnetic field. Fast reconnection by trapped

electrons. Wind observation

A new reconnection drive scenario

Animations of VTF

• Outside

• Inside

• Merging with Guide Field

Spontaneous reconnection

Rough energy balance

• Magnetic energy released ~ 0.5 × 6 10-6 H × (500A)2 ~ 0.8 J

• Electron heating ~ 400 A × 80V × 10-5s ~ 0.3 J

• Ion flows: ~ 80 eV × 1018m-3 ×0.06m3 ~ 0.8 J

Strong energizations of the ions

Conclusions– A new closed configuration has been implemented

in VTF.

– Spontaneous reconnection events are observed with a strong guide magnetic field.

– A large fraction of the released magnetic energy is converted to kinetic energy in macroscopic ion-flows.

– Fully collisionless plasmas: e 100 m.

– Unique opportunity to address the trigger problem.