مقاله پژوهشی: اثر جریان پلاسما بر امواج طولی ایستاده در لوله‌های شار مغناطیسی با رهیافت اختلالی

نوع مقاله : مقاله پژوهشی

نویسنده

استادیار، گروه فیزیک، دانشکده علوم پایه، دانشگاه رازی، کرمانشاه، ایران

چکیده

در این مقاله، امواج مغناطو (مانیتو) هیدرودینامیکی آرام را در لوله­های شار مغناطیسی تحت شرایط وابسته به تاج خورشید بررسی می‌کنیم. دما و چگالی پلاسمای زمینۀ­ لوله را همگن و ثابت و چسبندگی تراکمی را به عنوان عامل میرایی فرض می‌کنیم. همچنین جریان پلاسما را نیز در لوله در نظر می‌گیریم و با فرض بر این‌که آهنگ میرایی بسیار کوچک‌تر از بسامد نوسان امواج است، روش اختلال را برای حل معادلات حرکت به کار می‌گیریم. بسامد نوسان و ویژه‌توابع نوسان از تقریب مرتبۀ اوّل اختلال و آهنگ میرایی از تقریب مرتبۀ دوّم اختلال به‌دست می‌آید. افزایش تندی جریان در لوله باعث کاهش بسامد نوسان و افزایش آهنگ میرایی می­شود. همچنین افزایش هر یک از موارد تندی جریان و دمای زمینۀ لوله، سبب کاهش نسبت زمان میرایی به دورۀ تناوب امواج می­شود، امّا افزایش طول لوله این نسبت را زیاد می­کند. نتایج به‌دست آمده از این مطالعه با نتایج نظری که از پیش در این زمینه در اختیار است، همخوانی دارد. همچنین نتایج به‌دست آمده در این پژوهش می­تواند شماری از یافته­های مشاهداتی را توجیه کند.

کلیدواژه‌ها


عنوان مقاله [English]

Research Paper:The Effect of Plasma Flow on the Longitudinal Standing Waves in Magnetic Flux Tubes with a Perturbation Approach

نویسنده [English]

  • Karam Bahari
Assistant Professor, Physics department, Razi university, Kermanshah, Iran
چکیده [English]

In this paper, the standing magnetohydrodynamic slow waves in the magnetic flux tubes are investigated under coronal conditions. The temperature and equilibrium plasma density of the tube is assumed to be homogeneous and constant and the compressive viscosity is considered as the damping mechanism. Also, the plasma flow is considered in the flux tube. Assuming that the damping rate to be much smaller than the oscillation frequency of the waves, the perturbation method is used to solve the problem. The oscillation frequency and the eigenfunctions are found from the first-order perturbation while the damping rate is determined from the second-order perturbation. To increase the flow speed makes the oscillation frequency decreases and the damping rate increases. Also, increasing  each of the flow speed and background temperature of the tube, decreases the ratio of the damping time to the oscillation period. But this ratio increases due to the increasing the length of the tube The results found here are consistent with the theoretical results obtained earlier. Also, the obtained results can justify some observational cases.

کلیدواژه‌ها [English]

  • solar corona
  • magnetic fields
  • oscillations
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