Accretion flows are ubiquitous in astrophysics: they occur around protostars, accreting compact objects in binary systems, and supermassive black holes at the cores of galaxies. Much of professor James M. Stone's work has concerned studies of the local hydrodynamic and magnetohydrodynamics (MHD) processes that can lead to outward angular momentum transport in accretion disks. As computers become more powerful, previous studies of local patches of an accretion flow are being expanded into global studies that encompass the entire disk.
Accretion flows that cannot cool via emission of radiation become vertically thick and nearly spherical. Thus, they are intrinsically multidimensional. To study the structure and evolution of non-radiative accretion flows, 2D (axisymmetric) hydrodynamical simulations were performed using a non-uniform grid that spanned more than two decades in radius.
The most striking property of the flow is the large fluctuations produced by strong convection. Convective eddies transport a lot of mass both inwards and outwards, but the net mass accretion rate is very small and set by the properties of the flow near the inner boundary. A vanishingly small accretion rate may help to explain the deficit of high energy emission observed from accreting compact sources.
While understanding the properties of hydrodynamical accretion flows is important, it is generally agreed that angular momentum transport is in fact mediated by magnetic stresses. Thus, repeating the global simulations of non-radiative accretion flows with MHD calculations is vital.
Credit: James M. Stone
rendu: Youtube links to a playlist about Sophie Calle
if you are in the Boston area, like zines, comics, Rookie mag, or want to see more alternative media/music/art with a POC perspective, I highly recommend attending this reading/lecture!
"Suzy X frontwoman of Brooklyn-based punk rock witchcore band Shady Hawkins, contributor at Rookie and Bitch Media , illustrator, zine maker, blogger, team member at POC Zine Project and Girls Rock Camp Volunteer will be speaking about her self-archiving in her blog/project ‘Memoirs of a Mallgoth’ and zine ‘Malcriada’".
Saturday, February 1 @ 5 pm
@ the Van Alan Clark Jr. Library at the School of the Museum of Fine Arts, Boston!
In this series of pieces I hope to develop a new grammar to talk about asexuality outside of the ways in which it has been co-opted by neoliberal identity politics. I am interested in reclaiming and developing an analysis of (a)sexuality in our collective efforts toward racial justice and…
It’s hard to hide your feelings, when they’re rolling down your face.