Experiments on the interaction of current channels in a laboratory plasma: relaxation to the force-free state

Gekelman, Walter; Maggs, J. E.; Pfister, Hans

doi:10.1109/27.199501

Cited by 20 publications

(19 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…One key attribute of RSX is the ability to continuously adjust the axial guide field ( B 0 z = 0–2 kGauss) and ion gyro radius independently of the plasma and current density, providing scans of plasma β . RSX is one of a few devices [ Hansen et al , 2004; Gekelman et al , 1992] that have ever been used to study flux 3‐D rope dynamics.…”

Section: Description Of the System Under Considerationmentioning

confidence: 99%

“…[13] The Reconnection Scaling Experiment (RSX) at Los Alamos National Laboratory is described by Furno et al [2003Furno et al [ , 2005 and takes advantage of recently developed plasma gun technology [Fiksel et al, 1996] to create a flux rope that is initially linear but supports fully three-dimensional (3-D) evolution. One key attribute of RSX is the ability to continuously adjust the axial guide field (B 0z = 0 -2 kGauss) and ion gyro radius independently of the plasma and current density, providing scans of plasma b. RSX is one of a few devices [Hansen et al, 2004;Gekelman et al, 1992] that have ever been used to study flux 3-D rope dynamics.…”

Section: Description Of the System Under Considerationmentioning

confidence: 99%

See 1 more Smart Citation

Kink instability of flux ropes anchored at one end and free at the other

et al. 2006

View full text Add to dashboard Cite

[1] The kink instability of a magnetized plasma column (flux rope) is a fundamental process observed in laboratory and in natural plasmas. Previous theoretical, experimental, and observational work has focused either on the case of periodic (infinite) ropes (relevant to toroidal systems) or on finite ropes with both ends tied to a specified boundary (relevant to coronal ropes tied at the photosphere). However, in the Sun's corona and in astrophysical systems there is an abundant presence of finite flux ropes tied at one end but free at the other. Motivated by recent experiments conducted on the RSX device and by recent theoretical work , the present paper investigates by simulation the linear and nonlinear evolution of free-ended flux ropes. The approach is based on comparing the classic case of a periodic flux rope with the case of a rope tied at one end and free at the other. In the linear phase, periodic and free ropes behave radically differently. A simulation analysis of the linear phase confirms the experimental and phenomenological findings relative to an increased instability of a free rope: the new stability limit is shown to be just half of the classic limit for periodic ropes. In the nonlinear phase, reconnection is observed to be a fundamental enabler to reach the eventual steady state. The mechanism for saturation of a flux rope is investigated and compared with the classic theory (the so-called bubble state model) by Rosenbluth et al. (1976). A remarkable agreement is found for the classic periodic case. The case of a free rope is again very different. The saturated state is observed to present a outwardly spiraling configuration with the displacement of the plasma column increasing progressively and monotonically from the tied end to the free end. The maximum displacement is observed at the free end where it is consistent with the displacement observed in a periodic rope. The key distinction is that in a periodic rope the same displacement is observed throughout the whole rope to form a helix with constant radius.

show abstract

Section: Description Of the System Under Considerationmentioning

confidence: 99%

Section: Description Of the System Under Considerationmentioning

confidence: 99%

Kink instability of flux ropes anchored at one end and free at the other

et al. 2006

View full text Add to dashboard Cite

show abstract

“…5,6 In magnetically confined laboratory plasmas for fusion research, flux rope interactions can determine the dynamics of relaxation processes, such as sawtooth oscillations in tokamaks, 7 and spheromak formation. 8 Recently, laboratory experiments in both toroidal [9][10][11][12][13] and linear geometry 14 together with numerical simulations [15][16][17] have highlighted the importance of three-dimensional ͑3D͒ effects in the dynamics of flux rope evolution. In the reconnection scaling experiment 18 ͑RSX͒ at Los Alamos National Laboratory, we take advantage of recently developed plasma gun technology 19 to create parallel flux ropes and to study their interaction in a linear geometry that supports fully 3D evolution.…”

Section: Introductionmentioning

confidence: 99%

Coalescence of two magnetic flux ropes via collisional magnetic reconnection

et al. 2005

View full text Add to dashboard Cite

Spectroscopic observation of simultaneous bi-directional reconnection outflows in a laboratory plasma Phys. Plasmas 19, 080704 (2012) The role of compressibility in energy release by magnetic reconnection Phys. Plasmas 19, 082109 (2012) Design of a dual sensor probe array for internal field measurement in Versatile Experiment Spherical Torus Rev. Sci. Instrum. 83, 10D721 (2012) Additional information on Phys. Plasmas Quasi-two-dimensional coalescence of two parallel cylindrical flux ropes and the development of three-dimensional merged structures are observed and studied in the reconnection scaling experiment ͓Furno et al., Rev. Sci. Instrum. 74, 2324 ͑2003͔͒. These experiments were conducted in a collisional regime with very strong guide magnetic field ͑B guide ӷ B reconnection ͒, which can be adjusted independently of plasma density, current density, and temperature. During initial coalescence, a reconnection current sheet forms between the two flux ropes, and the direction of the current is opposite to the flux rope currents. The measured current sheet thickness is larger than the electron skin depth but smaller than the ion skin depth. Furthermore, the thickness does not vary for three different values of the strong external guide field. It is shown that the geometry of the observed current sheet is consistent with the Sweet-Parker model using a parallel Spitzer resistivity. The flux ropes eventually become kink unstable due to increasing current and fast-gated camera images show the development of three-dimensional merged structures.

show abstract

“…7,8 The first laboratory experiment on magnetic reconnection provided detailed measurements of the relaxation to force-free fields produced by coalescing current filaments. [9][10][11] Later, a number of experiments investigated magnetic reconnection in spheromak plasmas. [12][13][14][15][16] These experiments are characterized by a magnetohydrodynamic ͑MHD͒ relevant plasma, with i ӶL, L being the linear dimension of the system, and i the ion Larmor radius, but relative high collisionality ͑ mfp Ӷ device size͒.…”

Section: Introductionmentioning

confidence: 99%

Plasma generation and confinement in a toroidal magnetic cusp

Egedal

Fasoli

Porkoláb

et al. 2000

Review of Scientific Instruments

View full text Add to dashboard Cite

The first measurements of plasma parameters in a discharge created by electron cyclotron resonance heating in a toroidal cusp configuration are discussed along with the predictions of particle orbits and confinement from a guiding center model. The configuration appears to be suitable for basic investigations of the physics of plasma flows and instabilities around a magnetic null, hence of magnetic reconnection.

show abstract

Experiments on the interaction of current channels in a laboratory plasma: relaxation to the force-free state

Cited by 20 publications

References 15 publications

Kink instability of flux ropes anchored at one end and free at the other

Kink instability of flux ropes anchored at one end and free at the other

Coalescence of two magnetic flux ropes via collisional magnetic reconnection

Plasma generation and confinement in a toroidal magnetic cusp

Contact Info

Product

Resources

About