Sustained spheromaks with ideal <i>n</i> = 1 kink stability and pressure confinement

Victor, B.S.; Jarboe, T. R.; Hansen, Chris; Akçay, C.; Morgan, Kyle; Hossack, Aaron; Nelson, B.A.

doi:10.1063/1.4892261

Cited by 19 publications

(21 citation statements)

References 25 publications

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“…The helicity injection circuit maintains the higher λ inj . This leads to a two-step-like λ-profile of the sort observed in the HIT-SI experiment (Jarboe et al 2012;Victor et al 2014).…”

Section: Sustaining Stable Plasma Currents By Helicity Injection Curr...mentioning

confidence: 77%

Evidence for a shallow thin magnetic structure and solar dynamo: the driver of torsional oscillations

Jarboe,

Benedett,

Everson

et al. 2017

Preprint

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The solar dynamo and the solar Global internal Magnetic Structure (GMS) appear to be a thin (∼2 Mm thick) structure near (∼1 Mm below) the solar surface. Evidence for these properties are found from the amplitude of the torsional oscillations and in their velocity contours relationship to solar magnetogram; the power to the chromosphere; power to the corona and the solar wind; the current in the helio-current-sheet measured at the radius of the orbit of Earth; the calculated size (∼1 Mm) of the expanding polar flux when it enters the photosphere; the dynamo forces the rigid rotation of the heliosphere with the Sun surface out to at least 1.4 au, giving the solar wind; and from the observation that solar magnetic activity is generated near the surface. A thin stable minimum energy state seems to be covering most of the solar surface just below the photosphere. The magnetic field lines should be parallel to the solar surface and rotate with distance from the surface for 2π radians in ∼2 Mm. Resistive diffusion helps to push the magnetic fields to the surface and the GMS seems to lose π radians every 11 years, causing the observed 180 • flipping of the solar magnetic fields including the flipping of the polar flux. Further evidence for this GMS and its loss is that solar prominences are made of thin sheets of magnetized plasma, which are, likely, remnants of the lost thin sheet of the GMS. The loss process is consistent with the butterfly pattern of the sunspots and with the differences observed between solar maximum and solar minimum in the corona. The solar dynamo drives current parallel to the polar flux, which, in turn, sustains the GMS using cross-field current drive. For completeness, the formation of sunspots, CMEs and flares is discussed.

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“…The helicity injection circuit maintains the higher λ inj . This leads to a two-step-like λ-profile of the sort observed in the HIT-SI experiment (Jarboe et al 2012;Victor et al 2014).…”

Section: Sustaining Stable Plasma Currents By Helicity Injection Curr...mentioning

confidence: 77%

Evidence for a shallow thin magnetic structure and solar dynamo: the driver of torsional oscillations

Jarboe,

Benedett,

Everson

et al. 2017

Preprint

Self Cite

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“…6 This is thought to be due to the absence of pressure-driven effects in the current model, which are observed to be important in this regime. 20 Although experimentally plasma density is flat in HIT-SI, local fluctuations, whose amplitude decreases with increasing frequency, are present, with a frequency that matches the injector's, indicating plasma pressure may play a role in field reversal and other small scale dynamics. Temperature profiles on the other hand are expected to be fairly broad due to Ohmic heating and a flat current profile, 20 with variation to produce the observed b resulting in a resistivity profile-modifying helicity dissipation and the required current drive.…”

Section: Discussionmentioning

confidence: 94%

“…For HIT-SI, the majority of the magnetic energy is contained in the spheromak equilibrium so the first chrono reproduces the shape of the toroidal current as evaluated using the Amperian method. 20 Due to the differences in formation behavior discussed in Sec. III A only data after 1.22 ms (indicated by the green dashed line) will be used for the metric comparisons to follow.…”

Section: B Validation Metrics Using Biorthogonal Decompositionmentioning

confidence: 98%

Numerical studies and metric development for validation of magnetohydrodynamic models on the HIT-SI experimenta)

et al. 2015

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We present application of three scalar metrics derived from the Biorthogonal Decomposition (BD) technique to evaluate the level of agreement between macroscopic plasma dynamics in different data sets. BD decomposes large data sets, as produced by distributed diagnostic arrays, into principal mode structures without assumptions on spatial or temporal structure. These metrics have been applied to validation of the Hall-MHD model using experimental data from the Helicity Injected Torus with Steady Inductive helicity injection experiment. Each metric provides a measure of correlation between mode structures extracted from experimental data and simulations for an array of 192 surface-mounted magnetic probes. Numerical validation studies have been performed using the NIMROD code, where the injectors are modeled as boundary conditions on the flux conserver, and the PSI-TET code, where the entire plasma volume is treated. Initial results from a comprehensive validation study of high performance operation with different injector frequencies are presented, illustrating application of the BD method. Using a simplified (constant, uniform density and temperature) Hall-MHD model, simulation results agree with experimental observation for two of the three defined metrics when the injectors are driven with a frequency of 14.5 kHz. V C 2015 AIP Publishing LLC. [http://dx.

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“…Active control of the magnetic reconnection process in the MST RFP has been effective in making energy confinement in the RFP comparable to that in a tokamak when compared at low magnetic field [ 9 ]. Helicity injection current drive has been used to form and sustain the spheromak configuration fully inductively at low current [ 10 ]. This may provide a new pathway towards higher-performance sustained spheromaks.…”

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confidence: 99%