مشاهده‌ی نوسان‌های بسیار طولانیِ پیش‌شراره‌ای ، برای دوازده شراره خورشیدی، به عنوان یک نشانه ‌وقوع شراره

نوع مقاله : پژوهشی

نویسندگان

1 استادیار فیزیک، استادیار فیزیک، ایران، تهران، دانشگاه پیام نور، دانشکده فیزیک، صندوق پستی۳۶۹۷- 19395.

2 دانشجوی کارشناسی ارشد، دانشگاه پیام نور، دانشکده فیزیک.

چکیده

شراره‌های خورشیدی طغیان‌های ناگهانی در آتمسفر خورشید هستند که تابش‌هایی در طول موج‌های رادیویی تا اشعه گاما دارند و با توجه به انرژی‌شان در کلاس‌های مختلف (به ترتیب A, B, C, M, X) طبقه‌بندی می‌شوند. پیش‌بینی زمان وقوع یک شراره و مشخص کردن نوع کلاس آن می‌تواند به کم کردن اثرات مخرب آن بر روی زمین کمک کند. یکی از فرآیندهای پیش از وقوع شراره که می تواند به پیش‌بینی وقوع آن کمک کند نوسانات با دوره تناوب طولانی (VLP) در فاز پیش‌شراره است که نخستین بار توسط تان و همکاران (2016) گزارش شد.

ما در این مقاله با استفاده از داده‌های ماهواره GOES، نوزده شراره را به لحاظ وقوع های پیش شراره انتخاب و بررسی کردیم که ۷ شراره در کلاس Cو ۱۲ شراره در کلاس M هستند. از این میان در دوازده مورد از آن‌ها VLPهای منظم را پیش از وقوع شراره مشاهده کردیم که به جز یکی بقیه در کلاس M بودند. دوره تناوبی که برای VLPهای این شراره ها با کمک تبدیل فوریه ی سریع، محاسبه کردیم ۱۴ تا ۳۴.۶ دقیقه است که با نتایجِ تان و همکاران (۲۰۱۶) در توافق است و در ضمن نشان می دهد دوره تناوب VLPها می تواند بیشتر از ۳۰ دقیقه نیز باشد. تعداد پالس های مشاهده شده در هر پیش شراره بین ۳ تا ۷ عدد است. برای هفت شراره ی دیگرِ باقی مانده از مجموعه ی منتخب ما، نیز VLP منظمی مشاهده نشد، که آن ها به جز یک مورد همه در کلاس C بودند.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Observing of Pre-flare Very Long-period Pulsations, for 12 Solar Flares, as a Sign of Flare’s Onset

نویسندگان [English]

  • Narges Fathalian 1
  • Arezoo JalaliRad 2
1 Assistant Professor, Department of Physics, Payame Noor University (PNU), P.O.Box 19395-3697, Tehran, Iran.
2 MSc. Student, Department of Physics, PayameNoor University. Narges Fathalian
چکیده [English]

Solar flares are sudden bursts in the solar atmosphere, which have emissions, from radio wavelengths up to gamma rays, and according to their energy are classified into different classes (A, B, C, M, and X, respectively). The process of releasing magnetic energy in flares is done by magnetic reconnection, which is often created by a complex magnetic field. Flares accelerate many electrons and ions, raising their energy to the limit of relative energy. These accelerating particles play a very important role in the release of large solar flare energies. Considering the fact that flares emit radiation when they explode, most of them create light spectrum and sometimes X-rays and ultraviolet rays, which are emitted mainly by the photosphere and chromosphere into concentrated sources called footpoints and ribbons. These radiations and emissions occur when the lower layers of the sun's atmosphere heat up during a flare, and this heating due to the collision of particles probably plays an important role in the occurrence of the flare; In addition, they emit high-energy radiation such as hard X-rays (HXR) from electrons and gamma rays from ions. The main part of these emissions is in the form of electromagnetic emission (soft X-rays) and energetic particles. Emissions radiated from a large flare or a solar mass eruption (with an energy more than 〖10〗^25 J ), when reaching the earth, can have destructive effects on the Earth's atmosphere, as well as the orbits of satellites or magnetic and electrical facilities of devices like ships and airplanes. Therefore, predicting the time of the flare occurrence and determining its class type can help reduce these destructive effects.

One of the observable structures that can be seen before a flare occurs, are oscillations with very long period pulsations (VLPs) of the order of 8-30 minutes, which occur about one to two hours before the flare onset, and were first reported by Tan et al. (2016) in the pre-flare phase. MHD oscillations and longitudinal electric current in flare loops can be appropriate candidates to explain the formation of VLPs. Investigating pre-flare VLPs can also help us in understanding the origin of flares. With the help of observational data of X-ray radiation (SXR), onboard the GOES satellite, during the pre-flare phase, these pulses can be observed at similar time scales during flare processes.

In this paper, using the abovementioned data, we selected nineteen flares for the study, of which 7 flares are in class C and 12 flares are in class M. Of these, twelve had typical VLPs before flare-onset, which were all in the M class, with the exception of one. The periodicity that we calculated for the VLPs of these flares, with the help of the Fast Fourier Transform is 14 to 34.6 minutes, which is in agreement with the results of Tan et al. (2016) and also shows that the periodicity of VLPs can exceed 30 minutes. The number of pulses observed in each pre-flare is between 3 and 7. For the other seven remaining flares of our selection, no typical pre-flare VLP was observed, which all but one of them, were in Class C.

کلیدواژه‌ها [English]

  • Flare
  • Pre-flare Phase
  • Flare Forecast
  • Pre-flare Very Long-period Pulsations
  • GOES data