Planetary Migration in Protoplanetary Disks

The known exoplanet population displays a great diversity of orbital architectures, and explaining the origin of this is a major challenge for planet formation theories. The gravitational interaction between young planets and their protoplanetary disks provides one way in which planetary orbits can be shaped during the formation epoch. Disk-planet interactions are strongly influenced by the structure and physical processes that drive the evolution of the protoplanetary disk. In this review we focus on how disk-planet interactions drive the migration of planets when different assumptions are made about the physics of angular momentum transport, and how it drives accretion flows in protoplanetary disk models. In particular, we consider migration in discs where: (i) accretion flows arise because turbulence diffusively transports angular momentum; (ii) laminar accretion flows are confined to thin, ionised layers near disk surfaces and are driven by the launching of magneto-centrifugal winds, with the midplane being completely inert; (iii) laminar accretion flows pervade the full column density of the disc, and are driven by a combination of large scale horizontal and vertical magnetic fields

Indigenous Youth Development through Sport and Physical Activity: Sharing Voices, Stories, and Experiences

Recent research has highlighted the cognitive, physical, emotional, and spiritual benefits of sport and physical activity participation for Indigenous youth (McHugh, Coppola, & Sinclair, 2013; Hanna, 2009; Lavallée, 2007). Despite the importance of Indigenous peoples participating in sport and physical activity (e.g., Forsyth & Giles, 2013), the meaning of youth development in this context is not well understood. The purpose of this research was to understand Indigenous youth development within the context of sport and physical activity through the voices, stories and experiences of Indigenous youth. Participants were 99 Indigenous youth (52 males and 47 females) between the ages of 15 and 25 years who took part in one of 13 sharing circles. Each of the sharing circles was facilitated by a trained Indigenous youth with guidance from an Elder/Traditional person. A Two-Eyed Seeing approach (Bartlett, Marshall, & Marshall, 2012) was used to analyze the sharing circle discussions. This analytical process involved an initial inductive thematic analysis of the transcribed verbatim data followed by an Indigenous symbolic visual analysis of emerging themes using the Medicine Circle. Results revealed that involvement in sport and physical activity impacted Indigenous youth physically, cognitively, and emotionally. The spiritual impact was not as evident. Findings from the research will inform the development of a measure of Indigenous youth development within sport and physical activity settings. &nbsp

ropensci/stats19: stats19 3.0.2

<ul> <li>Fix issue with coordinates as characters (#228)</li> </ul&gt

ropensci/stplanr: stplanr 1.1.2

Export S3 method

Orbital Advection with Magnetohydrodynamics and Vector Potential

Orbital advection is a significant bottleneck in disk simulations, and a particularly tricky one when used in connection with magnetohydrodynamics. We have developed an orbital advection algorithm suitable for the induction equation with magnetic potential. The electromotive force is split into advection and shear term, and we find that we do not need an advective gauge as solving the orbital advection implicitly precludes the shear term from canceling the advection term. We prove and demonstrate the third order in time accuracy of the scheme. The algorithm is also suited for non-magnetic problems. Benchmarked results of (hydrodynamical) planet-disk interaction and the of the magnetorotational instability are reproduced. We include detailed descriptions of the construction and selection of stabilizing dissipations (or high frequency filters) needed to generate practical results. The scheme is self-consistent, accurate, and elegant in its simplicity, making it particularly efficiently in straightforward finite-difference methods. As a result of the work, the algorithm is incorporated in the public version of the Pencil Code, where it can be used by the community.Comment: 11 pages + 4 appendix; 8+1 figures. Accepted by AJ; in pres