Halo benzeri güneş koronası. Kredi bilgileri: NASA
Şaşırtıcı nedeni belirlemede atılım.
Araştırmacılar, Güneş’i çevreleyen atmosfer olan “güneş koronasının” onu yayan güneş yüzeyinden neden çok daha sıcak olduğunu açıklayan, daha önce bilinmeyen bir ısıtma mekanizması keşfettiler.
ABD Enerji Bakanlığı’na (DOE) bağlı Princeton Plazma Fiziği Laboratuvarı’ndaki (PPPL) bulgu, yıldız oluşumu, evrendeki büyük ölçekli manyetik alanların kaynağı ve yıldızların tahmini de dahil olmak üzere birçok astrofiziksel gizemi çözmeye yardımcı olma potansiyeline sahip. Dünya’da cep telefonu kesintilerine ve elektrik şebekesi arızalarına neden olabilecek uzay hava olayları. Isıtma sürecini anlamak, füzyon enerjisi araştırmaları için de önemli etkilere sahiptir.
İlk net 3D açıklama
Fizikçi Chuanfei Dong, “Doğrudan sayısal simülasyonumuz, bu ısıtma mekanizmasının 3B uzayda net bir şekilde tanımlanmasını sağlayan ilk simülasyondur” dedi.[{” attribute=””>PPPL and Princeton University who unmasked the process by conducting 200 million hours of computer time for the world’s largest simulation of its kind. “Current telescope and spacecraft instruments may not have high enough resolution to identify the process occurring at small scales,” said Dong, who details the breakthrough in the journal Science Advances.
The hidden ingredient is a process called magnetic reconnection that separates and violently reconnects magnetic fields in plasma, the soup of electrons and atomic nuclei that forms the solar atmosphere. Dong’s simulation revealed how rapid reconnection of the magnetic field lines turns the large-scale turbulent energy into small-sale internal energy. As a consequence the turbulent energy is efficiently converted to thermal energy at small scales, thus superheating the corona.
“Think of putting cream in coffee,” Dong said. “The drops of cream soon become whorls and slender curls. Similarly, magnetic fields form thin sheets of electric current that break up due to magnetic reconnection. This process facilitates the energy cascade from large-scale to small-scale, making the process more efficient in the turbulent solar corona than previously thought.”
When the reconnection process is slow while the turbulent cascade is fast, reconnection cannot affect the transfer of energy across scales, he said. But when the reconnection rate becomes fast enough to exceed the traditional cascade rate, reconnection can move the cascade toward small scales more efficiently.
It does this by breaking and rejoining the magnetic field lines to generate chains of small twisted lines called plasmoids. This changes the understanding of the turbulent energy cascade that has been widely accepted for more than half a century, the paper says. The new finding ties the energy transfer rate to how fast the plasmoids grow, enhancing the transfer of energy from large to small scales and strongly heating the corona at these scales.
The new discovery demonstrates a regime with an unprecedentedly large magnetic Reynolds number as in the solar corona. The large number characterizes the new high energy transfer rate of the turbulent cascade. “The higher the magnetic Reynolds number is, the more efficient the reconnection-driven energy transfer is,” said Dong, who is moving to Boston University to take up a faculty position.
200 million hours
“Chuanfei has carried out the world’s largest turbulence simulation of its kind that has taken over 200 million computer CPUs [central processing units] de[{” attribute=””>NASA Advanced Supercomputing (NAS) facility,” said PPPL physicist Amitava Bhattacharjee, a Princeton professor of astrophysical sciences who supervised the research. “This numerical experiment has produced undisputed evidence for the first time of a theoretically predicted mechanism for a previously undiscovered range of turbulent energy cascade controlled by the growth of the plasmoids.
“His paper in the high-impact journal Science Advances completes the computational program he began with his earlier 2D results published in Physical Review Letters. These papers form a coda to the impressive work that Chuanfei has done as a member of the Princeton Center for Heliophysics,” a joint Princeton and PPPL facility. “We are grateful for a PPPL LDRD [Laboratory Directed Research & Development] bu çalışmayı kolaylaştıran hibe ve bilgisayar zamanını cömertçe tahsis ettiği için NASA High-End Computing (HEC) programına.”
Bu bulgunun astrofiziksel sistemlerdeki çeşitli ölçeklerdeki etkisi, mevcut ve gelecekteki uzay araçları ve teleskoplarla keşfedilebilir. Gazeteye göre, enerji aktarım sürecini ölçekler arasında açmak, kilit kozmik gizemleri çözmek için çok önemli olacak.
Referans: Chuanfei Dong, Liang Wang, Yi-Min Huang, Luca Comisso, Timothy A. Sandstrom ve Amitava Bhattacharjee tarafından yazılan “Manyetohidrodinamik türbülansta yeniden bağlanma güdümlü enerji kaskadı”, 7 Aralık 2022, Bilim Gelişmeleri.
DOI: 10.1126/sciadv.abn7627
Çalışma, DOE Office of Science (FES) ve NASA tarafından, NASA HEC tarafından Ulusal Enerji Araştırması Bilimsel Hesaplama Merkezi, bir DOE Office of Science kullanıcı tesisi ve NSF sponsorluğunda Hesaplama ve Bilgi ile birlikte sağlanan bilgisayar kaynakları ile finanse edildi. Sistem Laboratuvarı.
