Sains Malaysiana 50(1)(2021): 253-260

http://dx.doi.org/10.17576/jsm-2021-5001-24

Case Studies of Photospheric Magnetic Field Properties of Active Regions Associated with X-class Solar Flares

(Kajian Kes Sifat Medan Magnet Fotosfera Rantau Aktif dikaitkan dengan Suar Matahari Kelas X)

WAI-LEONG TEH¹* & FARAHANA KAMARUDIN²

¹Space Science Centre, Institute of Climate Change, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor Darul Ehsan, Malaysia

²Langkawi National Observatory, Malaysian Space Agency, Empangan Bukit Malut, 07000 Langkawi, Kedah Darul Aman, Malaysia

Diserahkan: 17 Mac 2020/Diterima: 12 Jun 2020

ABSTRACT

Solar flares are a transient phenomenon occurred in the active region (AR) on the Sun’s surface, producing intense emissions in EUV and soft X-ray that can wreak havoc in the near-Earth space mission and satellite as well as radio-based communication and navigation. The ARs are accompanied with strong magnetic fields and manifested as dark spots on the photosphere. To understand the photospheric magnetic field properties of the ARs that produce intense flares, two ARs associated with X-class flares, namely AR 12192 and AR 12297, occurred respectively on 25 October 2014 and 11 March 2015, are studied in terms of magnetic classification and various physical magnetic parameters. Solar images from the Langkawi National Observatory (LNO) and physical magnetic parameters from the Space-weather HMI Active Region Patches (SHARP) are used in this study. A total of seven SHARP magnetic parameters are examined which are calculated as sums of various magnetic quantities and have been identified as useful predictors for flare forecast. These two ARs are classified as  sunspots whereas their formation and size are quite different from each other. Our results showed that the intensity of a flare has little relationship with the area of an AR and the magnetic free energy; and the temporal variation of individual magnetic parameter has no obvious and consistent pre-flare feature. It is concluded that the temporal variation of individual magnetic parameter may not be useful for predicting the onset time of a flare.

Keywords: Active region; photospheric magnetic field; solar flare

ABSTRAK

Suar suria ialah satu fenomena yang berlaku di rantau aktif permukaan Matahari dengan menghasilkan pancaran peramatan dalam EUV dan sinar-X lembut yang boleh memberikan kesan kepada misi angkasa lepas-bumi dan satelit serta komunikasi berasaskan radio dan navigasi. Rantau aktif ini mempunyai medan magnet yang kuat dan dimanifestasikan sebagai tompok gelap pada permukaan fotosfera Matahari. Bagi memahami ciri medan magnet di lapisan fotosfera, dua kawasan rantau aktif iaitu daripada AR 12192 dan AR 12297 yang telah menghasilkan suar suria kelas X pada 25 Oktober 2014 dan 11 Mac 2015 telah dikaji dalam penyelidikan ini bagi meneliti pengelasan magnet dan pelbagai parameter fizikal magnet. Imej Matahari dari Observatori Negara Langkawi dan parameter fizikal magnet dari Space-weather HMI Active Region Patches (SHARP) telah digunakan dalam kajian ini. Sebanyak tujuh parameter magnet dari SHARP dianalisis dan parameter ini telah dikenal pasti dapat membantu dalam peramalan suar suria. Kedua-dua rantau aktif ini dikelaskan dalam tompok matahari berkelas  sedangkan pembentukan dan saiz kedua-dua rantau ini agak berbeza antara satu sama lain. Hasil penyelidikan menunjukkan keamatan suar suria mempunyai sedikit hubungan dengan kawasan rantau aktif dan tenaga bebas magnet serta perubahan parameter magnet bagi setiap rantau aktif tidak mempunyai ciri awalan pancaran yang jelas dan tekal. Dengan itu, dapat disimpulkan bahawa perubahan parameter magnet individu mungkin tidak boleh digunakan sebagai salah satu ciri dalam peramalan permulaan suar.

Kata kunci: Medan magnet fotosfera; rantau aktif; suar suria

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*Pengarang untuk surat-menyurat; email: wteh@ukm.edu.my