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SUMMARY:The First Ionization Potential Effect in Solar/Stellar Coronae and
  Winds - Martin Laming (Naval Research Laboratory\, Washington DC)
DTSTART:20240304T140000Z
DTEND:20240304T150000Z
UID:TALK209047@talks.cam.ac.uk
CONTACT:Roger Dufresne
DESCRIPTION:Since 1963\, we have known\, or at least suspected\, that elem
 ent abundances in the solar corona and wind are different to those in the 
 photosphere. Elements that are predominantly ionized in the photosphere an
 d chromosphere\, e.g. Fe\, Si\, Mg\, are observed to be enhanced in abunda
 nce once transported to the corona and wind by a factor of typically 3-4\,
  while elements that are mainly neutral are relatively unaffected. Due to 
 the dependence on the ionization potential\, this phenomenon has been dubb
 ed the First Ionization Potential (FIP) Effect. A model capturing the FIP 
 and effect and the various modifications to it seen in different coronal r
 egions and the solar wind invokes ion-neutral separation by the ponderomot
 ive force due to Alfven and magnetosonic waves propagating through the chr
 omosphere. This acts on ions\, but not neutrals\, and depends on the inter
 action of the waves with the magnetic geometry of the solar atmosphere.\n\
 nThe launch of the Extreme Ultraviolet Explorer (EUVE) in 1992 afforded us
  the first observations of abundances in stellar coronae. This\, and succe
 eding missions like Chandra\, XMM-Newton and Suzaku\, have shown that sola
 r-like stars show a similar FIP effect\, which transitions to Inverse FIP 
 (IFIP)\, i.e. a coronal depletion of Fe\, Si\, Mg\, etc.\, as the activity
  level increases.\n\nIn this presentation\, I will review the theoretical 
 basis of FIP and IFIP fractionation by the ponderomotive force. Fractionat
 ion by such means is new to solar physics and astrophysics\, but is not ne
 w to science. Manipulation of atoms\, molecules\, biological samples\, etc
 . by the forces due to refraction of photons from lasers\, known as “opt
 ical tweezers”\, has a rather long history in optical sciences\, and won
  Nobel Prizes for Steven Chu (in 1997) and Arthur Ashkin (in 2018). Our mo
 del is a precise analog of this work\, but with magnetohydrodynamic waves 
 instead of optical photons. This connection leads to a better physical und
 erstanding of the mechanisms at work in FIP fractionated plasma.\n\nWork s
 upported by NASA Heliophysics Supporting Research Program (80HQTR20T0076)\
 , and by Basic Research Funds of the Office of Naval Research.
LOCATION:MR14 DAMTP and online
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