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| Titel |
Planetesimal Bow Shocks: Effects of H2 Dissociation and Recombination |
| VerfasserIn |
F. Yamazaki, T. Nakamoto |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250064822
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| Zusammenfassung |
| Chondrules are mm-sized particles included in many meteorites. There are evidences that
they have experienced heating and melting, but the detail of the heating event is still
unknown. One of the ideas for heating mechanism is the shock wave heating model. Based on
this idea, Ciesla et al. (2004) and Nakajima et al. (2012, in preparation) conducted numerical
simulations of planetesimal bow shocks and examined them as a chondrule formation site.
They assumed that the gas consists of hydrogen molecules and the gas changes adiabatically;
the effects of H2 dissociation and recombination were ignored. However, the calculated
temperature behind the shock front was 4000K or more (Nakajima et al. 2012, in
preparation), so H2 dissociation is expected to occur. Once the dissociation of H2 takes
place, the resultant temperature of the gas would be different. Thus, to understand
bow shocks around planetesimals, the gas flow should be investigated with H2
dissociation/recombination.
We conduct numerical hydrodynamics simulation with H2 dissociation and
recombination around planetesimals. We develop an equilibrium calculation code of H2
dissociation/recombination and add it to the ZEUS-2D code.
Our simulation results show that the gas temperature is lower and the density is higher in
front of planetesimals than the results by adiabatic calculations. This can be understood as a
result of the H2 dissociation. Moreover, in the region where the recombination occurs, the
temperature is higher than the one of adiabatic calculation. Also the positions and
the figurations of the shock fronts are slightly different between both calculation
results.
These results suggest that the H2 dissociation and recombination may affect the heating
of chondrule precursors. Precursor dust particles are heated due to the gas drag, which
is susceptible to the gas density. So, the thermal history of dust particles under
the effect of H2 dissociation/recombination should be investigated in the future. |
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