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SUMMARY:Cosmic-rays: a possible explanation for the difference of mean dis
 k sizes in star-forming regions
DTSTART;VALUE=DATE-TIME:20200511T143500Z
DTEND;VALUE=DATE-TIME:20200511T145500Z
DTSTAMP;VALUE=DATE-TIME:20241101T160705Z
UID:indico-contribution-9-37@meetings.aip.de
DESCRIPTION:Speakers: Michael Küffmeier (Zentrum für Astronomie Heidelbe
 rg (ZAH))\nSurveys of protoplanetary disks in star-forming regions of simi
 lar age revealed \nsignificant variations in average disk mass between som
 e regions. Disks in the Orion Nebular Cluster (ONC) and Corona Australis (
 CrA) are on average a factor of a few smaller than disks observed in Lupus
 \, Taurus\, Chamaeleon I or Ophiuchus. We aim for an understanding of the 
 physical mechanism behind this spread by testing the influence of cosmic-r
 ay ionization rates on the formation process of protoplanetary disks. We r
 un non-ideal magnetohydrodynamical protostellar collapse simulations assum
 ing different cosmic-ray ionization rates. We compute the resitivities for
  ambipolar diffusion and Ohmic dissipation with a chemical network. Consis
 tent with previous results\, our models demonstrate that a higher cosmic-r
 ay ionization rate leads to stronger magnetic braking\, and hence to the f
 ormation of smaller disks. Considering recent findings that protostars act
  as forges of comsic rays\, we show that a high average cosmic-ray ionizat
 ion rate in \nstar-forming regions like the ONC or CrA can explain the det
 ection of smaller disks in these regions. Our results show that on average
  a higher cosmic-ray ionization rate leads to the formation of smaller dis
 ks. Therefore\, smaller disks in regions of similar age can be the consequ
 ence of different levels of ionization\, and may not exclusively be caused
  by disk truncation via external photoevaporation. We strongly encourage o
 bservations that allow measuring the cosmic-ray ionization degrees in diff
 erent star-forming regions to test our hypothesis.\n\nhttps://iaus379.aip.
 de/event/1/contributions/37/
LOCATION:Leibniz Institute for Astrophysics Potsdam (AIP) Lecture Hall
URL:https://iaus379.aip.de/event/1/contributions/37/
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BEGIN:VEVENT
SUMMARY:Observational Constraints on Envelope Ionization in Class I Protos
 tars
DTSTART;VALUE=DATE-TIME:20200511T141000Z
DTEND;VALUE=DATE-TIME:20200511T143000Z
DTSTAMP;VALUE=DATE-TIME:20241101T160705Z
UID:indico-contribution-9-32@meetings.aip.de
DESCRIPTION:Speakers: Kamber Schwarz (University of Arizona)\nIonization r
 ate is one of the most important parameters controlling both the chemical 
 and dynamical processes in protoplanetary disks. What few observational co
 nstrains on ionization currently exists suggest overall low ionization\, l
 imiting the processes able to take place. I will present new NOEMA observa
 tions which\, when combined with chemical modeling\, are indicative of enh
 anced ionization rates in the envelopes of three Class I protostars.  I wi
 ll then discuss the potential impact of this early enhancement on the evol
 ution of protoplanetary disks.\n\nhttps://iaus379.aip.de/event/1/contribut
 ions/32/
LOCATION:Leibniz Institute for Astrophysics Potsdam (AIP) Lecture Hall
URL:https://iaus379.aip.de/event/1/contributions/32/
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SUMMARY:The regulation of angular momentum by non-ideal MHD
DTSTART;VALUE=DATE-TIME:20200511T134500Z
DTEND;VALUE=DATE-TIME:20200511T140500Z
DTSTAMP;VALUE=DATE-TIME:20241101T160705Z
UID:indico-contribution-9-56@meetings.aip.de
DESCRIPTION:Speakers: Pierre Marchand (American Museum of Natural History)
 \nMagnetic fields play a major role in the regulation of angular momentum 
 during the protostellar collapse\, hence for the formation of the protopla
 netary disk. The magnetic braking is able to slow the rotation and extract
  the angular momentum from the disk. However\, this process is tampered by
  a decoupling between neutral and charged particles\, especially the ions 
 through the ambipolar diffusion. The decoupling is heavily impacted by the
  chemistry at stake\, and particularly by the grain size distribution. I w
 ill show how a modification of the grain size distribution enhances the de
 coupling between the magnetic field and the gas\, and how it modifies the 
 distribution and transport of angular momentum.\n\nhttps://iaus379.aip.de/
 event/1/contributions/56/
LOCATION:Leibniz Institute for Astrophysics Potsdam (AIP) Lecture Hall
URL:https://iaus379.aip.de/event/1/contributions/56/
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