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DTSTAMP:20260718T010736Z
SUMMARY:SPC space/plasma seminar – Vicente Valenzuela-Villaseca (LLNL) 
 – Tues 21st July 11 AM
DESCRIPTION:Collisionless shocks are ubiquitous structures in the universe 
 that can be found in planetary magnetospheres\, supernova remnants\, and w
 hen galaxies merge inside a cluster. In a collisionless shock\, collective
  fields provide complex nonlinear and kinetic interactions that can suppor
 t collisionless/anomalous heating mechanisms in the plasma. Consequently\,
  there is no generally accepted theory of particle energy partitioning and
  heating in collisionless shocks. Electron and ion temperatures are obtain
 ed by spacecraft measurement of planetary bow-shocks and analysis supernov
 a remnant spectra exhibit large statistical variance of the inferred energ
 y partition\, and particle-in-cell simulations often cannot reproduce elec
 tron-ion temperature ratios measured in nature. Laboratory experiments off
 er a complementary approach to satellite measurements and astronomical obs
 ervations.\nIn this talk\, I will present results from magnetized collisio
 nless shock laboratory experiments at conditions relevant to planetary bow
 -shocks (MA~ 8\,  ~ 3). We report the first laboratory observation of f
 ully developed shocks (×3.6 compression ratio and a downstream region dec
 oupled from the piston). The data indicate the presence of a foot ahead of
  the density discontinuity\, where both electrons and ions exhibit signifi
 cant super-adiabatic heating. Surprisingly\, the downstream exhibits signi
 ficant super-adiabatic heating of both species with electrons and ions in 
 thermal equipartition\, with an order-unity electron-ion downstream temper
 ature ratio Te/Ti ~ 0.8. This temperature ratio is inconsistent with a com
 bination of adiabatic compression and electron-ion collisional equilibrati
 on\; thus\, it provides the first laboratory evidence of collisionless ano
 malous heating in a fully developed perpendicular magnetized collisionless
  shock [1].\n\nReferences\n[1] Valenzuela-Villaseca\, et al.\, “Laborato
 ry measurements of energy partitioning and anomalous electron heating in m
 agnetized\, perpendicular collisionless shocks”\, in review at The Astro
 physical Journal. Preprint:\nhttps://doi.org/10.48550/arXiv.2509.12164
URL:https://www.imperial.ac.uk/events/211556/spc-space-plasma-seminar-vicen
 te-valenzuela-villaseca-llnl-tues-21st-july-11-am/
DTSTART;TZID=Europe/London:20260721T110000
DTEND;TZID=Europe/London:20260721T120000
LOCATION:741\, Blackett Building\, South Kensington Campus\, Imperial Colle
 ge London\, London\, SW7 2AZ\, United Kingdom
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