اثرات پخش مغناطیسی و پرتوهای کیهانی بر ناپایداری حرارتی

قلی پور, محمود; اسلامی شفیق, امیرعباس

doi:10.22055/jrmbs.2022.17925

اثرات پخش مغناطیسی و پرتوهای کیهانی بر ناپایداری حرارتی

نوع مقاله : مقاله پژوهشی کامل

نویسندگان

مرکز تحقیقات نجوم و اخترفیزیک مراغه، دانشگاه مراغه، ایران

10.22055/jrmbs.2022.17925

چکیده

در این پژوهش، اثرات پرتوهای کیهانی و پخش مغناطیسی، بر ناپایداری حرارتی در محیط میان‌ستاره‌ای، مورد بررسی قرار می‌گیرد. ما، اثرات دینامیکی و گرمایشی پرتوهای کیهانی بر چگالش حرارتی را، با فرض این که پرتوها در امتداد خطوط میدان مغناطیسی منتشر می‌شوند و پخش مغناطیسی نیز رخ می‌دهد، بررسی می‌کنیم. برای میدان مغناطیسی زمینه، دو حالت در نظر گرفته شده است: میدان ثابت و میدان بی‌نیرو. در دنبالة مطالعات پیشین، ما روش تحلیل اختلال خطی را برای بررسی ناپایداری حرارتی در محیط مورد استفاده قرار داده‌ایم. نتایج به‌دست آمده نشان می‌دهند که پرتوهای کیهانی نرخ رشد مدهای تراکمی مغناطو‌ـ‌حرارتی را کاهش، و نواحی پایداری را افزایش می‌دهند. با این حال، پخش مغناطیسی رفتاری دوگانه بروز می‌دهد که تابعی از شرایط است. منظور از رفتار دوگانه این است که پخش مغناطیسی، نواحی پایداری را به‌ازای موارد کمتر از مقداری مشخص، افزایش، و برای موارد بزرگتر از این مقدار کاهش می‌دهد. علاوه بر این، ما دریافتیم که از بابت اثرات دینامیکی، پخش مغناطیسی بر پرتوهای کیهانی غلبه دارد. در نهایت، نتایج ما دلالت بر وجود ناحیه‌هایی دارند که در آنها تکه‌تکه شدن ابرها به ‌قپه‌ها و هسته‌ها تحت اثر تراکم مغناطو‌ـ‌حرارتی اتفاق می‌افتد.

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

The Effects of Magnetic Diffusion and Cosmic-rays on Thermal Instability

نویسندگان [English]

Amir Abbas Eslami Shafigh
Amir Abbas Eslami Shafigh

Research Institute for Astronomy and Astrophysics of Maragha (RIAAM), University of Maragheh, Maragheh, Iran

چکیده [English]

In this study, we consider the effects of the cosmic rays and the magnetic diffusion on the thermal instability in the interstellar mediums. The dynamical effect as well as the heating effect of the cosmic rays are investigated on the thermal condensation in a medium where the cosmic rays diffuse along the magnetic field lines and the magnetic diffusion is present. Two separate profiles, i.e. constant field and force-free field, are considered for the magnetic field of the medium background. The linear perturbation analysis is used for the study of the thermal instability in a medium with a point of view on the previous works. The results show that the cosmic rays reduce the growth rate of the magnetothermal condensation mode, and increase the domains of stability. However, the magnetic diffusion shows two different behaviors which depend on a number of conditions affecting the magnetic diffusivity. In other words, the magnetic diffusion increases the domains of stability for cases less than a certain value of magnetic diffusivity, and decrease the domains of stability for cases larger than this certain value. Furthermore, we found that the dynamical effect of the magnetic diffusion dominates the dynamical effect of the cosmic rays. Finally, the results address some regions in which the fragmentation of the clouds into clumps and cores can be seen with the magnetothermal condensation effects.

کلیدواژه‌ها [English]

ISM
cosmic rays
instabilities
waves
magnetohydrodynamics

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