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New clue to solving the mystery of the Sun's hot atmosphere
August 3, 2017
New clue to solving the mystery of the sun's hot atmosphere
Sun's 1 million degree corona at a time of low activity on May 14, 2010. Credit: NASA
The elemental composition of the Sun's hot atmosphere known as the 'corona' is strongly linked to the 11-year solar magnetic activity cycle, a team of scientists from UCL, George Mason University and Naval Research Laboratory has revealed for the first time.
The study, published in Nature Communications and funded by the NASA Hinode program, shows that an increase in magnetic activity goes hand in hand with an increase of certain elements, such as Iron, in the solar corona. It is thought that the results could have significant implications for understanding the process leading to the heating of the Sun's corona.
"Elemental composition is an important component of the flow of mass and energy into the atmospheres of the Sun and other stars. How that composition changes, if it does indeed change, as material flows from the surface of the Sun to its corona influences ideas we have about the heating and activity in atmospheres of other stars," said Dr Deborah Baker (UCL Space & Climate Physics).
Through its 11-year cycle, the Sun moves from relatively quiet periods at solar minimum, to intense magnetic activity at solar maximum, when large numbers of sunspots appear and there is an increase in radiation.
"Previously, many astronomers thought that elemental composition in a star's atmosphere depended on the properties of the star that don't change, such as the rotation rate or surface gravity. Our results suggest that it may also be linked with the magnetic activity and heating processes in the atmosphere itself, and they change with time, at least in the Sun," said the study's lead author, Dr David H. Brooks (George Mason University).
New clue to solving the mystery of the sun's hot atmosphere
The largest active region of the solar cycle on October 23, 2014. Credit: NASA
The Sun's surface, the photosphere, has a temperature of around 6000 degrees, but the outer atmosphere, the corona - best seen from Earth during total solar eclipses - is several hundred times hotter. How the corona is heated to millions of degrees is one of the most significant unsolved problems in astrophysics. The solution will help scientists better understand the heating of other stars.
"Why the Sun's corona is so hot is a long-standing puzzle. It's as if a flame were coming out of an ice cube. It doesn't make any sense! Solar astronomers think that the key lies in the magnetic field, but there are still arguments about the details," added Dr Brooks.
The team of scientists analysed observations from the Solar Dynamics Observatory at a time of low activity (solar minimum) starting in 2010, and through till 2014 when huge magnetic active regions crossing the solar disk were common.
An unknown mechanism preferentially transports certain elements, such as Iron, into the corona instead of others, giving the corona its own distinctive elemental signature. The team think that the mechanism that separates the elements and supplies material to the corona may also be closely related to the transport of energy, and that understanding it may provide clues to explain the whole coronal heating process.
"Our observations started in 2010, near the last solar minimum, and so observations of the global coronal spectrum for a complete solar cycle have not been possible. The fact that we detected this variation of the Sun in a relatively small period of time really highlights the importance of observing stars over complete stellar cycles, which we hope to do in the future. Currently we tend to just have snapshots of stars, but these are potentially missing some important clues," said Dr Baker.
Whilst it would require long-term planning, the scientists expect that observing full stellar cycles would provide new insight into the nature of the atmospheres of stars and how they are heated to million degree temperatures.
Explore further: National Solar Observatory predicts shape of solar corona for august eclipse
More information: David H. Brooks et al, A Solar cycle correlation of coronal element abundances in Sun-as-a-star observations, Nature Communications (2017). DOI: 10.1038/s41467-017-00328-7
Journal reference: Nature Communications
Provided by: University College London
Read more at: https://phys.org/news/2017-08-clue-mystery-sun-hot-atmosphere.html#jCp
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Baru petunjuk untuk memecahkan misteri matahari panas suasana
3 Agustus 2017
Komposisi unsur suasana panas matahari yang dikenal sebagai 'corona' sangat terkait dengan aktivitas magnetik matahari 11-tahun siklus, sebuah tim ilmuwan dari UCL, George Mason University, dan angkatan laut laboratorium penelitian telah mengungkapkan untuk pertama kalinya. Studi, yang diterbitkan di Nature komunikasi dan didanai oleh program NASA Hinode, menunjukkan bahwa peningkatan aktivitas magnetik berjalan bergandengan tangan dengan peningkatan dari elemen tertentu, seperti besi, di corona surya. Diperkirakan bahwa hasilnya bisa memiliki implikasi penting untuk memahami proses menuju pemanasan matahari corona. "Komposisi unsur merupakan komponen penting dari aliran massa dan energi ke atmosfer matahari dan bintang lainnya. Bagaimana bahwa komposisi perubahan, jika memang mengubah, seperti bahan mengalir dari permukaan matahari untuk corona yang ide-ide yang kita miliki tentang pemanas dan aktivitas di atmosfer bintang lainnya,"kata Dr Deborah Baker (UCL ruang & iklim Phy...
Petunjuk baru untuk memecahkan misteri matahari panas suasana wilayah aktif terbesar dari siklus matahari pada 23 Oktober 2014. Kredit: NASA
Permukaan matahari, photosphere, memiliki suhu sekitar 6000 derajat, tetapi bagian luar atmosfer, corona - terbaik dilihat dari bumi selama gerhana matahari total - adalah beberapa ratus kali. Bagaimana corona dipanaskan sampai jutaan derajat adalah salah satu masalah yang belum terpecahkan paling signifikan dalam astrofisika. Solusi yang akan membantu para ilmuwan lebih memahami pemanasan bintang lainnya. "Mengapa matahari corona begitu panas adalah lama. Ianya seolah-olah satu nyala api yang keluar dari es batu. Itu tidak membuat rasa! Para astronom Solar berpikir bahwa kunci terletak di Medan magnet, tetapi masih ada argumen mengenai rincian,"tambah Dr Brooks. Tim ilmuwan dianalisis pengamatan dari Observatorium dinamika surya pada saat aktivitas rendah (surya minimal) mulai tahun 2010, dan melalui sampai 2014 ketika besar daerah aktif magnetik menyeberangi disk surya yang umum.
Mekanisme yang tidak diketahui preferentially mengangkut elemen tertentu, seperti besi, ke corona bukan lain, memberikan corona khasnya elemen khas sendiri. Tim berpikir bahwa mekanisme yang memisahkan unsur-unsur dan persediaan bahan untuk corona mungkin juga erat terkait dengan transportasi energi, dan bahwa pemahaman ini dapat memberikan petunjuk untuk menjelaskan coronal seluruh proses pemanasan. "Pengamatan kami mulai pada tahun 2010, dekat minimum matahari terakhir, dan jadi pengamatan spektrum koronal global untuk siklus matahari lengkap belum mungkin. Fakta bahwa kami mendeteksi variasi ini matahari dalam jangka waktu yang relatif kecil ini benar-benar menyoroti pentingnya mengamati bintang-bintang selama siklus stellar yang lengkap, yang kami harap lakukan di masa depan. Saat ini kita cenderung hanya memiliki gambaran dari bintang-bintang, tapi ini berpotensi hilang beberapa petunjuk penting,"kata Dr Baker.
Sementara itu akan memerlukan perencanaan jangka panjang, para ilmuwan mengharapkan bahwa mengamati siklus penuh bintang akan memberikan wawasan baru ke dalam sifat atmosfer bintang dan bagaimana mereka yang dipanaskan untuk juta derajat suhu. Jelajahi lebih lanjut: National Solar Observatory memprediksi bentuk surya corona untuk eclipse Agustus selengkapnya: David H. Brooks et al, Solar siklus korelasi koronal elemen kesuksesan matahari-sebagai-a-bintang pengamatan, Nature komunikasi (2017). DOI: 10.1038/s41467-017-00328-7 jurnal referensi: alam komunikasi yang disediakan oleh: University College London
Baca lebih lanjut di: https://phys.org/news/2017-08-clue-mystery-sun-hot-atmosphere.html#jCp