Laboratory Resolved Structure of Supercritical Perpendicular Shocks

Endrizzi, Douglass; Egedal, J.; Clark, Michael; Flanagan, K.; Greess, Samuel; Milhone, Jason; Millet-Ayala, Alexander; Olson, Joseph; Peterson, Ethan; Wallace, John; Forest, C. B.

doi:10.1103/physrevlett.126.145001

Cited by 3 publications

(1 citation statement)

References 25 publications

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“…This is a design and technique used in previous BRB studies. 21,22 For average velocity, we divide the change in position by the change in time for the disturbance between the first and last sensors. In this, we find that the average speeds of the CTs lie between 96 and 160 km/s with error for each speed measurement of 615 km/s.…”

Section: Resultsmentioning

confidence: 99%

Creating and studying a scaled interplanetary coronal mass ejection

Bryant,

Young,

LeFevre

et al. 2024

Physics of Plasmas

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The Sun, being an active star, undergoes eruptions of magnetized plasma that reach the Earth and cause the aurorae near the poles. These eruptions, called coronal mass ejections (CMEs), send plasma and magnetic fields out into space. CMEs that reach planetary orbits are called interplanetary coronal mass ejections (ICMEs) and are a source of geomagnetic storms, which can cause major damage to our modern electrical systems with limited warning. To study ICME propagation, we devised a scaled experiment using the Big Red Ball (BRB) plasma containment device at the Wisconsin Plasma Physics Laboratory. These experiments inject a compact torus of plasma as an ICME through an ambient plasma inside the BRB, which acts as the interplanetary medium. Magnetic and temperature probes provide three-dimensional magnetic field information in time and space, as well as temperature and density as a function of time. Using this information, we can identify features in the compact torus that are consistent with those in real ICMEs. We also identify the shock, sheath, and ejecta similar to the structure of an ICME event. This experiment acts as a first step to providing information that can inform predictive models, which can give us time to shield our satellites and large electrical systems in the event that a powerful ICME were to strike.

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Section: Resultsmentioning

confidence: 99%

Creating and studying a scaled interplanetary coronal mass ejection

Bryant,

Young,

LeFevre

et al. 2024

Physics of Plasmas

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Laminar and turbulent plasmoid ejection in a laboratory Parker Spiral current sheet

et al. 2021

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Quasi-periodic plasmoid formation at the tip of magnetic streamer structures is observed to occur in experiments on the Big Red Ball as well as in simulations of these experiments performed with the extended magnetohydrodynamics code, NIMROD. This plasmoid formation is found to occur on a characteristic time scale dependent on pressure gradients and magnetic curvature in both experiment and simulation. Single mode, or laminar, plasmoids exist when the pressure gradient is modest, but give way to turbulent plasmoid ejection when the system drive is higher, which produces plasmoids of many sizes. However, a critical pressure gradient is also observed, below which plasmoids are never formed. A simple heuristic model of this plasmoid formation process is presented and suggested to be a consequence of a dynamic loss of equilibrium in the high- $\beta$ region of the helmet streamer. This model is capable of explaining the periodicity of plasmoids observed in the experiment and simulations, and produces plasmoid periods of 90 minutes when applied to two-dimensional models of solar streamers with a height of $3R_\odot$ . This is consistent with the location and frequency at which periodic plasma blobs have been observed to form by Large Angle and Spectrometric Coronograph and Sun Earth Connection Coronal and Heliospheric Investigation instruments.

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Radiative cooling effects on reverse shocks formed by magnetized supersonic plasma flows

Merlini,

Hare,

Burdiak

et al. 2023

Physics of Plasmas

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We study the structure of reverse shocks formed by the collision of supersonic, magnetized plasma flows driven by an inverse (or exploding) wire array with a planar conducting obstacle. We observe that the structure of these reverse shocks varies dramatically with wire material, despite the similar upstream flow velocities and mass densities. For aluminum wire arrays, the shock is sharp and well-defined, consistent with magneto-hydrodynamic theory. In contrast, we do not observe a well-defined shock using tungsten wires, and instead we see a broad region dominated by density fluctuations on a wide range of spatial scales. We diagnose these two very different interactions using interferometry, Thomson scattering, shadowgraphy, and a newly developed imaging refractometer that is sensitive to small deflections of the probing laser corresponding to small-scale density perturbations. We conclude that the differences in shock structure are most likely due to radiative cooling instabilities, which create small-scale density perturbations elongated along magnetic field lines in the tungsten plasma. These instabilities grow more slowly and are smoothed by thermal conduction in the aluminum plasma.

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Laboratory Resolved Structure of Supercritical Perpendicular Shocks

Cited by 3 publications

References 25 publications

Creating and studying a scaled interplanetary coronal mass ejection

Creating and studying a scaled interplanetary coronal mass ejection

Laminar and turbulent plasmoid ejection in a laboratory Parker Spiral current sheet

Radiative cooling effects on reverse shocks formed by magnetized supersonic plasma flows

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