Dynamics and Erosion of Solids in Protoplanetary Disks

Noemi Schaffer

    Forskningsoutput: AvhandlingDoktorsavhandling (sammanläggning)

    Sammanfattning

    Protoplanetary disks are the natural by-product of star formation and the sites of planet formation. Initially, they are composed of the gas and small solids they inherit from the molecular cloud they form in. The interactions between this material is complex and understanding their details is key for a complete picture of planet formation. The planet formation process begins with growth form about micrometer-sized solids to about centimeter sized pebbles. These pebbles can then concentrate into clumps through mechanisms such as the streaming instability, where we take into account that there is mutual drag between the gas and the solids. Due to the backreaction of the gas, given an initial small solid clump, its drift velocity is decreased. This leads to further growth as the inward drifting solids from the
    outer disk are incorporated in the initial clump. Once the critical density is reached, the clumps gravitationally collapse into planetesimals. Then, through the accretion of pebbles, other planetesimals and gas, planets form.

    In this thesis I cover the early stages of the planet formation process. Based on results of protoplanetary disk observations and laboratory experiments, I investigate the efficiency of the streaming instability given multiple solid sizes and their interaction with the gas. In Paper I and Paper III, we found that the multi-species streaming instability changes the dynamics of the system. We found that particles with different sizes interact with each other through the gas. The large species, which are located close to the midplane, trigger the streaming instability and drive the vertical and radial diffusion of all species. In both Papers I and III we found that there is no clear trend in how the steepness of the particle size distribution in combination with the minimum and maximum particle size affects the outcome of the instability. In Paper III we furthermore conclude that the multi-species instability is successful in forming particle clumps and that numerical effects such as particle number do not lead to significant change in the efficiency of clump formation.

    In this thesis I also investigate the how gas erosion affects disk solids. In Paper II, we found that solids in the inner disk
    on eccentric orbits erode fast, due to the headwind from the gas. We also found that along the surface of the solid,
    erosion is fastest near the top and bottom and slowest near the stagnation points of the flow.
    Originalspråkengelska
    KvalifikationDoktor
    Handledare
    • Johansen, Anders, handledare
    • Lambrechts, Michiel, handledare
    • Yang, Chao-Chin, handledare
    Tilldelningsdatum2021 apr. 29
    UtgivningsortLund, Sweden
    Förlag
    ISBN (tryckt)978-91-7895-789-7
    ISBN (elektroniskt)978-91-7895-790-3
    StatusPublished - 2021 mars 15

    Bibliografisk information

    Defence details
    Date: [2021-04-29]
    Time: [15:00]
    Place: [Lundmarksalen Astronomihuset Sölvegatan 27 ] Join via zoom: https://lu-se.zoom.us/j/61604689514?pwd=UFFPMWVxTnVHMDdxTm5DRzMvYjVQdz09 passcode 2020
    External reviewer(s)
    Name: [Simon, Jacob]
    Title: [Assistant professor]
    Affiliation: [Iowa State University]

    Ämnesklassifikation (UKÄ)

    • Astronomi, astrofysik och kosmologi

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