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VERSION:2.0
CALSCALE:GREGORIAN
PRODID:UW-Madison-Physics-Events
BEGIN:VEVENT
SEQUENCE:2
UID:UW-Physics-Event-8621
DTSTART:20240314T180000Z
DTEND:20240314T190000Z
DTSTAMP:20260413T223601Z
LAST-MODIFIED:20240313T145042Z
LOCATION:B343 Sterling Hall
SUMMARY:Understanding the plasma universe through laboratory experimen
 ts and related models\, Plasma Seminar\, Yang Zhang\, Caltech
DESCRIPTION:Laboratory experiments and the models they inspire are pow
 erful tools for studying the plasma universe. In this talk\, I will pr
 esent possible solutions to two big problems in the plasma universe\, 
 namely how solar flares are generated and how accretion disks transpor
 t angular momentum and generate astrophysical jets. Addressing the fir
 st problem\, I will present observations from a laboratory experiment 
 that simulates solar coronal loop physics. Transient\, localized 7.6-k
 eV X-ray bursts and a several-kilovolt voltage spike are observed to b
 e associated with the breaking of braided magnetic flux ropes containi
 ng 2 eV plasma. These spikes occur when the braid strand radius is cho
 ked down to be at the kinetic scale by either MHD kink or magnetic Ray
 leigh–Taylor instabilities. The observed sequence reveals an MHD to 
 non-MHD cross-scale coupling that is likely responsible for generating
  solar energetic particles and X-ray bursts. Addressing the second pro
 blem\, I will present a first-principles angular momentum transport me
 chanism based only on collisions between neutrals and charged particle
 s in the presence of gravitational and magnetic fields. I find that io
 ns and electrons drift in opposite radial directions as a result of co
 lliding with Kepler-motion neutrals. This reduces the ordinary angular
  momentum of neutrals and increases the canonical angular momentum of 
 charged particles in a manner such that the net global canonical angul
 ar momentum is conserved. This process provides a gravitational dynamo
  converting gravitational energy into the electric energy that powers 
 an astrophysical jet. The model predicts an accretion rate of 3 × 10â
 ˆ’8 solar mass per year in good agreement with observed accretion rate
 s. Finally\, I will discuss my future research plans for using laborat
 ory experiments and related models to study the plasma cosmos. 
URL:https://www.physics.wisc.edu/events/?id=8621
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