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Tuesday, 26 November 2019

First direct observation of the transfer of energy between the surface and the crown of the Sun

Although it has been studied for decades, the Sun still has some mysteries. This is particularly the case of the temperature difference observed between the crown and the solar surface, the first being much hotter than the second. Several theoretical models have been proposed to explain this phenomenon, in particular the model of plasma spicules. And for the first time, astrophysicists were able to directly observe this process.

Astrophysicists have already suggested that solar plasma jets called spicules, from within, were responsible for the warming effect, and for the first time, they were able to directly observe this process. New observations show that when the magnetic fields on the Sun's surface reverse and realign, spicules are formed. The study was published in the journal Science.

Direct and detailed observation of solar spicules

The energy of the magnetic field is converted into kinetic and thermal energy, which is then transferred to the spicules pushing through the chromosphere to the outermost layer of the Sun's atmosphere, the corona.

The idea of ​​the spicules responsible for the magnetic tension of the Sun has already been evoked using detailed computer simulations. Now, using high resolution images of Big Bear Solar Observatory (BBSO) telescopes, astronomers have seen this in situ .

" The unprecedented high-resolution observations of BBSO's Goode solar telescope clearly show that when magnetic fields of opposite polarities reconnect in the lower atmosphere of the Sun, these plasma jets are powerfully ejected, " explains solar physicist Wenda Cao, from New Jersey Institute of Technology.

BBSO telescopes allowed astrophysicists to obtain detailed images of the formation and evolution of solar spicules. Credits: Tanmoy Samanta et al. 2019

These jets are 200 to 500 kilometers wide and reach thousands of kilometers before dissipating. They also move about 100 km / s. The researchers also used images captured by NASA's Solar Dynamics Observatory satellite in the Extreme Ultraviolet Spectrum (EUV) to measure energy transfer in the upper layers of the Sun's atmosphere.

Better understand the dynamics of spicules and their role in the enigma of the temperature of the solar corona

These images confirmed that spicules could reach temperatures of about 1 million degrees Celsius. This high energy explosion may well be enough to heat the crown at the high temperatures recorded by the instruments. High resolution images with BBSO are essential for data collection. They offer unprecedented levels of detail.

Multilayer view of solar spicules: (left to right) NASA Solar Dynamics observatory crown observations, followed by images of NJIT's Big Bear Solar Observatory on the chromosphere, photosphere, and magnetic fields associates. Credits: NJIT

This is the first time we have seen direct evidence of how spicules are generated. We followed these dynamic characteristics of the H-alpha spectral line, measured magnetic fields at their starting point, captured the migration of emerging magnetic elements, and verified their interaction with existing magnetic fields of opposite polarity, "says Cao.

Although the new study is not enough to prove exhaustively that spicules heat the crown, the dynamics of spicules are much better understood now. " Our observations on spike formation, subsequent warming, and return fluxes reveal a complete mass cycle process between the chromosphere and the crown, " the researchers conclude.

In this video, NASA explores the solar structure and its different components using different instruments:


 Generation of solar spicules and subsequent atmospheric heating

Tanmoy Samanta1, Hui Tian1,*, Vasyl Yurchyshyn2, Hardi Peter3, Wenda Cao2, Alphonse Sterling4, Robertus Erdélyi5,6, Kwangsu Ahn2, Song Feng7, Dominik Utz8, Dipankar Banerjee9, Yajie Chen1

Science  15 Nov 2019:
Vol. 366, Issue 6467, pp. 890-894
DOI: 10.1126/science.aaw2796

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