# Astroplasmas Seminar

Fridays at 12:30pm, Dome Room, Peyton Hall

**Next seminar**** **

**Monday, April 11th 2022, 2.00pm**

*Characterization of quasi-Keplerian, Differentially Rotating, Free-Boundary Laboratory Plasmas*

*Characterization of quasi-Keplerian, Differentially Rotating, Free-Boundary Laboratory Plasmas*

**Vicente Valenzuela-Villaseca (Imperial College London)**

Abstract: In this talk I will present results from the Rotating Plasma Experiment (RPX), a novel laboratory platform developed on the MAGPIE pulsed-power generator (1.4 MA, 240 ns rise-time). RPX drives differentially rotating high-energy-density plasma flows using the slightly off-radial inward-convergence of 8 magnetized plasma jets. The goal is to interpret and model the rotation profile and pressure balance of differentially rotating plasmas, and study their stability and overall evolution, which are relevant to laboratory modeling of astrophysical accretion disks and protostellar jets.

The data shows that rotating plasmas have a hollow density structure and are radially confined by the ram pressure of the ablation flows. A combination of axial thermal and magnetic pressure launches an axial, highly collimated, supersonic jet with a velocity ~ 100 km/s (M > 5). The axial jet also rotates, transporting angular momentum, as it remains collimated by a hot (Ti ~ 250 eV) surrounding plasma halo. It is inferred that the plasma halo is magnetized by a ~ 3 T magnetic field. I will discuss the thermal and possible magnetic structure of the halo and its impact on jet collimation. Finally, the rotation velocity radial distribution such that angular frequency decreases with radius, as the opposite happens to specific angular momentum. The calculated squared epicyclic frequency (Rayleigh determinant) of the flow is estimated to be κ2 ~ r-2.8 > 0. This implies that the flows at RPX are quasi-Keplerian and share stability properties of gravitationally driven accretion disks.

**Scheduled seminars (****Fall 2021 / Spring 2022****)**

**24 Sept:** Jens Mahlmann (Princeton University)

**01 Oct:** Bart Ripperda (Center for Computational Astrophysics and Princeton University)

**08 Oct:** David Hosking (Oxford University)

**15**** Oct:** Ben Prather (University of Illinois)

**22**** Oct:** Tamar Faran (The Hebrew University of Jerusalem) and Luciano Combi (Instituto Argentino de Radioastronomía)

**29**** Oct:** Aaron Tran (Columbia University) and Itai Linial (The Hebrew University of Jerusalem)

**05 Nov:** Lorenzo Perrone (Cambridge University)

**19**** Nov:** Fabio Bacchini (University of Colorado)

**03**** Dec:** Elizabeth Tolman (Institute of Advanced Studies)

**10**** Dec:** Elias Most (Institute of Advanced Studies and Princeton University)

**1****4**** ****Jan****:** Emily Lichko (University of Arizona)

**28 Jan:** Wenbin Lu (Princeton University)

**25 Feb:** Kun Hu (Rice University)

**18**** ****Mar****:** Christopher Thompson (CITA)

**30 Mar:** Artem Bohdan (DESY)

**11**** ****Apr****:** Vicente Valenzuela-Villaseca (Imperial College)