[Physics-grads-open] PASS talk on Stellar Accretion Disks

[Pooyan Goodarzi]

Happening in ~3 hours from now in the *Conference* room.

On 2/27/26 3:03 PM, Pooyan Goodarzi wrote:
>
> Hi all,
>
>
> We will have a PASS talk by Morgan on *Monday, March 2nd*. Please join 
> us at noon (*from 12:00 to 1:00 pm*) in the *Conference Room* (PHYS 3051).
>
>
> *Morgan Ohana, PhD Student*
>  Monday, 12:00 pm, Conference Room (PHYS 3051)
>
> *Simulations of Eccentricity Growth in Compact Binary Accretion Disks 
> with Magnetohydrodynamic Turbulence*
>
> We present the results of four magnetohydrodynamic simulations and one 
> alpha-disk simulation of accretion disks in a compact binary system, 
> neglecting vertical stratification and assuming a locally isothermal 
> equation of state. We demonstrate that in the presence of a net 
> vertical field, disks that extend out to the 3:1 mean-motion resonance 
> grow eccentricity in full MHD in much the same way as in 
> hydrodynamical disks. Hence, turbulence due to the magnetorotational 
> instability (MRI) does not impede the tidally driven growth of 
> eccentricity in any meaningful way. However, we find two important 
> differences with alpha-disk theory. First, in MHD, eccentricity builds 
> up in the inner disk with a series of episodes of radial disk-breaking 
> into two misaligned eccentric disks, separated by a region of circular 
> orbits. Standing eccentric waves are often present in the inner 
> eccentric disk. Second, the successful spreading of an accretion disk 
> with MRI turbulence out to the resonant radius is nontrivial—and much 
> harder than spreading an alpha disk. This is due to the tendency to 
> develop overdense rings in which tidal torques overwhelm MRI transport 
> and truncate the disk too early. We believe that the inability to 
> spread the disk sufficiently was the reason why our previous attempt 
> to excite eccentricity via the 3:1 mean-motion resonance with MHD 
> failed. Exactly how MHD disks successfully spread outward in compact 
> binary systems is an important problem that has not yet been understood.
>
>
>
> *If you’re interested in sharing your work as a speaker, please feel 
> free to add your name to this spreadsheet [Google Sheet 
> <https://docs.google.com/spreadsheets/d/1N3ncf43jdB6aHYHhyWmyHMycxDg4_phHZXLkQvviO0o/edit?usp=sharing>]. 
> Recordings of all the previous talks are available on our website: 
> https://ucrpass.arxiv.social*
> *
> *
>
> Best,
> Pooyan
> Physics and Astronomy Student Seminar (PASS)
> https://ucrpass.arxiv.social
>
>
>
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