According to foreign media reports, aurora is the dancing light emitted by luminous ionized particles in the upper atmosphere of the Earth. This phenomenon exists in the atmospheres of other planets in the solar system except Mercury, even Jupiter’s moon Europa San and Europa also have aurora.
However, scientists have never detected comet aurora before, but the recent analysis of the latest observation data from the “Rosetta” probe shows that far ultraviolet auroral radiation is emitted around comet 67P.
Jim Burch, a physicist at the Southwest Research Institute in the United States, said: “I have been studying the aurora on Earth for 50 years. It is surprising and fascinating to find aurora near Comet 67P, which has no magnetic field.”
Aurora is generated by the stimulation of charged particles in the atmosphere. On the earth, the solar wind blows into the magnetosphere and interacts with the charged particles in the magnetosphere. These charged particles drop down to the upper atmosphere like raindrops and reach the poles along the magnetic field lines, forming a rippling light curtain here.
But the role of aurora in different celestial bodies is different. The aurora of Europa and Europa are produced by the interaction of Jupiter’s magnetic field. So far, scientists have not discovered that Venus itself cannot form a magnetic field, but it generates a magnetic field strong enough to form an aurora during its interaction with the solar wind.
The atmosphere of Mars is very thin, but its weak magnetic field can produce aurora. Jupiter’s permanent aurora is not caused by solar wind, but from a mysterious mechanism that needs to be discovered.
Although Saturn’s auroral rings seem to be produced by the solar wind, the formation of part of the aurora is unpredictable, which is still an unsolved mystery. Comet 67P doesn’t even have a “borrowed” magnetic field, but this comet has an atmosphere, which is a gas shell called coma. When an active comet gets close enough to the sun, it sublimates and releases its ice.
The far-ultraviolet spectrometer of the “Rosetta” detector and the “Alice” instrument detected the far-ultraviolet glow in the 67P coma, and the ion and electronic sensor (IES) of the “Alice” instrument detected a bigger surprise discovery— -Electrons from the solar wind.
According to Joel Parker, an astronomer at the Southwest Research Institute, we initially thought that the ultraviolet radiation emitted by comet 67P was a phenomenon called “daylight”, which was the result of the interaction between solar photons and comet gas. We were surprised to find that ultraviolet radiation is aurora, not driven by photons, but driven by electrons in the solar wind. The solar wind breaks down the water and other molecules in the coma and accelerates in the environment near the comet.
The research team simulated a comet faintly escaping gas and found that the interplanetary magnetic field covering the comet was sufficient to provide a path for accelerating solar wind electrons to enter the potential well created by the electric field around the comet’s nucleus.
However, because Comet 67P does not have its own magnetic field, its aurora is in a diffuse state, in sharp contrast to the “closed aurora” stimulated by the solar wind on Earth and Mars. The researchers pointed out that the acceleration and excitation process of comet 67P aurora makes this auroral phenomenon unique in the solar system.
This discovery may provide new clues for understanding how aurora is generated in the entire solar system, but comet aurora can be used as a tool for cognition of space weather. By detecting the glow of the sun at different distances, astronomers can learn a lot about electronic changes in the solar wind information. Currently, this latest research report is published in the recently published “Natural Astronomy” magazine.
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