Shock Heating Due to Accretion of a Clumpy Cloud onto a Protoplanetary Disk
✍ Scribed by Kyoko K. Tanaka; Hidekazu Tanaka; Kiyoshi Nakazawa; Yoshitsugu Nakagawa
- Publisher
- Elsevier Science
- Year
- 1998
- Tongue
- English
- Weight
- 633 KB
- Volume
- 134
- Category
- Article
- ISSN
- 0019-1035
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✦ Synopsis
I. INTRODUCTION As a candidate of mechanism of chondrule formation we
Chondrules (0.1-to 1-mm-size spherule grains) and have investigated the accretion of a compact clumpy cloud onto course grained CAIs (calcium-aluminum-rich inclusions; the protoplanetary disk near the asteroid orbit by means of numerical simulations in a framework of local one-dimensional centimeter-sized aggregates) are believed to have been gas dynamics. In our simulation, we have taken into account formed through melting and resolidification of condensed precisely the process of radiative transfer which governs the aggregates in the protoplanetary disk (e.g., Hewins 1996). temperature of the disk. On the other hand, we neglected the This means that there existed a high temperature condition detailed structure of the shocks because heating of dust particles followed by an appropriate cooling in the protoplanetary in the shock regions is not effective. The accreting clump is disk. By analytic and experimental studies of chondrules characterized by two parameters, i.e., the size z cl and the surface and CAIs, some constraints which should be satisfied at density ⌺ cl , where we assume that the velocity of the clump is the stage of their formation have been suggested: the high equal to the free fall velocity. For the various clumpy parametemperature circumstances, i.e., 1600-2000 K for chonters, z cl and ⌺ cl , we have made numerical simulations and found drules (Hewins and Radomsky 1990) and 1800-2000 K the qualitative features of the generation and the propagation for CAIs (MacPherson et al. 1988), the short duration of Academic Press 1994), shock heating due to clumpy cloud accretion (Boss Key Words: impact process; meteorites; radiative transfer; and Graham 1993, Hood and Kring 1996), shock heating collisional physics; solar nebula. at the dust rich zone of the protoplanetary disk (Hood and 137