磁化等溫非旋轉環狀結構重力塌縮的磁耗散性磁流體力學數值模擬研究

Abstract

分子雲中的緻密核透過重力塌縮形成恆星。這些雲的磁化性質藉磁力影響塌縮。磁場具有擴散性。在本研究中，我們使用非理想磁流體研究Ohmic阻抗的擴散效應。我們探討了基於Li & Shu (1996)論文的初始密度分布塌縮時，磁場與Ohmic擴散的影響。我們使用ZeusTW進行非理想磁流體力學模擬，我們測試了由n表徵的環狀密度結構，以及三種不同的Ohmic磁阻率η。我們使用Python來進行模擬資料的視覺化與分析，以檢視數種物理量在演化過程中的行為。在我們所有的模擬中，都有pseudodisk的生成。並且結果皆展現了良好的自相似性傾向。我們亦討論了pseudodisk性質與n和η的關聯。較大的n值會形成較扁平的pseudodisk，以及較大的mass infall rate。大的η將會提高mass infall rate，且減緩pseudodisk尺寸的成長。

Stars form by the gravitational collapse of dense cores in molecular clouds. These clouds are magnetized, which influences the collapse through magnetic forces. The magnetic fields have diffusivity. In this work, we study the diffusive effect of Ohmic resistivity using non-ideal magnetohydrodynamics. We explore the effects of the magnetic fields and Ohmic diffusion, during the collapse of an initial density distribution based on the paper Li & Shu (1996). Using ZeusTW code to conduct non-ideal magnetohydrodynamic simulations, we tested the collapse of the toroids characterized by n, with three Ohmic diffusivity η. We then utilized Python for data visualization and analysis to examine the behavior of several physical quantities during the evolution. Formation of pseudodisk is observed in all our simulations. The results show a great tendency to have self-similarity. We also discuss the dependence of pseudodisk properties on n and η. Larger n leads to flatter pseudodisks and larger mass infall rates. Larger η increases the mass infall rate and decreases the pseudodisk size.