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Why the chemical composition of the Sun varies

Solar corona during a total solar eclipse

The solar corona seen in white light during a total solar eclipse on August 21, 2017 from Mitchell, Oregon. The moon blocks the central part of the sun, allowing detailed outer areas to be seen in full detail. The image was courtesy of Benjamin Boe and was first published in “CME-induced thermodynamic changes in the corona derived from observations of Fe XI and Fe XIV emissions during the Total Solar Eclipse on August 21, 2017,” Boe, Habbal, Druckmüller, Ding, Hodérova, & Štarha, Astrophysical Journal, 888, 100, (January 10, 2020). Credit: American Astronomical Society (AAS)

About 17 years ago, J. Martin Laming, an astrophysicist at the US Naval Research Laboratory, theorizes why the chemical composition of the Sun’s thinnest outermost layer differs from that below. His theory is recent validated by combined observations of the Sun’s magnetic waves from Earth and space.

Its most recent article in a scientific journal describes how these magnetic waves modify the chemical composition in a process completely new to solar physics or astrophysics, but already known in the optical sciences after being awarded the Nobel Prizes to Stephen Chu in 1997 and Arthur Ashkin in 2018.

Laming began studying these phenomena in the mid-1990s and first published the theory in 2004.

“It’s a pleasure to learn that the new observations demonstrate what’s going on under the hood in theory, and that it’s actually happening on the sun,” he said.

The sun is made up of many layers. Astronomers call its outermost layer the solar corona, which is only visible from the earth during a total solar eclipse. All solar activity in the corona is controlled by the solar magnetic field. This activity consists of solar flares, coronal mass ejections, high-speed solar wind and solar energy particles. All these different manifestations of solar activity propagate or are triggered by oscillations or waves along the lines of the magnetic field.

“The same waves when they hit the lower solar regions cause a change in the chemical composition we see in the corona as this material moves upward,” Laming said. “In this way, the coronary chemical composition offers a new way of understanding the waves in the solar atmosphere and new insights into the origin of solar activity.”

Christoph Englert, head of the Space Department at the US Naval Laboratory, points out the benefits of predicting the time of the Sun and how Laming theory can help predict changes in our ability to communicate on Earth.

“We believe that the sun is 91 percent hydrogen, but the small fraction, measured by insignificant ions such as iron, silicon or magnesium, dominates the emission of ultraviolet and X-rays from the corona,” he said. “If the abundance of these ions changes, the emitting output changes.”

“What is happening on the Sun has a significant impact on the Earth’s upper layers, which is important for communication and radar technologies that rely on the propagation of radio frequencies beyond the horizon or from Earth to space,” Englert said.

It also has an impact on objects in orbit. Radiation is absorbed in the upper layers of the Earth’s atmosphere, which leads to the formation of the upper layers of the atmosphere plasma, the ionosphere and expand and contract, affecting atmospheric resistance on satellites and orbital debris.

“The sun also releases high-energy particles,” Laming said. “They can cause damage to satellites and other space objects. The high-energy particles themselves are microscopic, but it is their speed that makes them dangerous to electronics, solar panels and space navigation equipment. “

Englert said that reliable prediction of solar activity is a long-term goal that requires us to understand the inner workings of our star. This latest achievement is a step in that direction.

“It has a long history of advances in astronomy, sowing technological progress all the way to Galileo,” Englert said. “We are excited to continue this tradition in support of the US Navy.”

The Department of Space Sciences performs research, development, tests and evaluations in solar physics, astrophysics, upper / middle atmosphere science and astronomy. These include satellite flight tools, sounding rockets and balloons, as well as ground equipment and mathematical models.

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