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The temperature of solar flares helps to understand the nature of solar plasma



Spectra of synthetic RADYN continuums in the range of 400–1000 Å showing the beginning of the He i continuum (<503.98 Å), LyC (<911.12 Å) and the tail of the Ca ii continuum (<1044.00 Å). The top row shows the spectra for a fixed EWith = 20 keV, with peak beam fluxes 3F9, 1F10, 3F10 and 1F11, all shown at peak in the LyC spectrum (between 9.7 and 13.6 s for all models). The black curve denotes the spectra before the outburst, and the colored curves are the spectra for spectral indices δ = 3–7. The bottom line shows the spectra, but at a fixed δ = 5, changing EWith = 15, 20 and 25 keV. Note 3F10, δ = 5, EWith = 20 keV and 1F10, δ = 5, EWith = 20 keV, the models have transient negative intensities in the tail of the LyC continuum during peak LyC emission. This is due to the numerical noise in the simulation at these times, which lasts for a very short time. Therefore, the spectra shown for these models were shifted by 1 s. Credit: Astrophysical journal (2023). DOI: 10.3847/1538-4357/acaf66

The rotation of the Sun causes changes in its magnetic field, which reverses approximately every 11 years, causing a phase of intense activity. Solar flares – huge eruptions from the surface of the Sun lasting minutes or hours – emit intense particle emissions and high levels of electromagnetic radiation. The release of energy during solar flares heats up the chromosphere, causing an almost complete ionization of the atomic hydrogen present in the region.

The chromosphere is a thin layer of plasma located at least 2000 km above the visible surface of the Sun (photosphere) and below the corona (upper layers of the Sun’s atmosphere). The plasma is very dense and the hydrogen recombines at a very high rate, resulting in a repetitive process of hydrogen ionization and recombination that produces a characteristic type of radiation in the ultraviolet known as the Lyman continuum (LyC) in memory of the American. physicist Theodore Lyman IV (1874-1954).

Theoretical descriptions suggest that the “color temperature” of LyC may be related to the temperature of the plasma causing the flare, and therefore the color temperature may be used to determine the temperature of the plasma during solar storms.

The new study simulated emissions from dozens of different solar flares and confirmed the relationship between the color temperature of LyC and the plasma temperature in the region from which the flare originated. This also confirms the existence of local thermodynamic equilibrium in the region between plasma and photons in LyC. An article about the study was published in Astrophysical journal.

The penultimate author of the article is Paulo José de Aguiar Simões, professor at Mackenzie Presbyterian University School of Engineering (EE-UPM) in São Paulo State, Brazil. “We show that LyC intensity increases significantly during solar flares and that Lyman spectrum analysis can indeed be used to diagnose plasma,” said Simoes, who is also a researcher at the Mackenzie Center for Radio Astronomy and Astrophysics (CRAAM).

The simulations confirmed an important result from the Solar Dynamics Laboratory by Argentinean astronomer Marcos Machado, showing that the color temperature, which is in the region of 9000 Kelvin (K) during quiet periods, rises to 12,000–16,000 K during flares.

V article in which he reported this result and was also co-authored by Simões, which was the last one published by Machado. A world-famous solar expert, he died in 2018 while the paper was under peer review.

solar dynamics

Here it is worth recalling a little of what is known about the structure and dynamics of the Sun. The vast amount of energy that provides the Earth with light and heat is mainly generated by converting hydrogen into helium in the process of nuclear fusion, which takes place deep inside the star. This vast region is not directly visible because the light does not cross the “surface” of the Sun, which is actually the photosphere.

“We can directly observe the region above the surface. The first layer, extending to an altitude of about 500 km, is the photosphere with a temperature of about 5800 K. It is here that we see sunspots, in places where the magnetic field of the field emanating from the sun interferes with convection and keeps the plasma relatively cool, creating dark areas, which we call sunspots,” Simones explained.

Above the photosphere, the chromosphere extends for about 2000 km. “The temperature of this layer is higher, exceeding 10,000 K, and the plasma is less dense. Due to these characteristics, atomic hydrogen is partially ionized, separating protons and electrons,” he said.

In a thin transition layer in the upper part of the chromosphere, the temperature rises sharply above 1 million K, and the plasma density drops by many orders of magnitude. This sudden heating during the transition from the chromosphere to the corona is a phenomenon contrary to common sense; it would be reasonable to expect the temperature to drop as the distance from the source increases.

“We don’t have an explanation yet. Solar physicists have submitted various proposals, but none of them has been accepted by the community without reservations,” Simones said.

The corona extends towards the interplanetary medium, without a clear transition region. The magnetic fields of the Sun have a strong effect on the corona, structuring the plasma, especially in active regions that are easily identified in ultraviolet images. Solar flares occur in these active regions.

“In these solar storms, energy stored in coronal magnetic fields is released abruptly, heating the plasma and accelerating particles. Electrons that have less mass can be accelerated up to 30% of the speed of light. These particles, moving along magnetic lines of force, are ejected into the interplanetary medium. Others move in the opposite direction, from the corona to the chromosphere, where they collide with dense plasma and transfer their energy to the medium. heats the local plasma, causing the ionization of atoms. The dynamics of ionization and recombination gives rise to the Lyman continuum,” Simoes said.

Solar bursts occur approximately every 11 years. During periods of intense activity, the effects on the Earth are significant, including more frequent aurora borealis, radio outages, increased scintillation effects on GPS signals, and increased drag on satellites, reducing their speed and hence their altitude. orbits. These phenomena and the physical properties of the near-Earth interplanetary medium are known as space weather.

“In addition to the fundamental knowledge they provide, solar flare physics research also improves our ability to predict space weather. These studies are going in two directions: direct observation and modeling based on computational models. Observational data in various ranges of the electromagnetic radiation spectrum allows us to better understand the evolution of solar flares and the physical properties of the plasma involved in these events. Computational models such as those used in our study serve to test hypotheses and test interpretations of observations because they give us access to quantities that cannot be obtained directly from analysis of observational data,” Simoins said.

Sean A. McLaughlin et al. Formation of the Lyman continuum during solar flares, Astrophysical journal (2023). DOI: 10.3847/1538-4357/acaf66

quotes: Solar Flare Temperature Helps Understand the Nature of Solar Plasma (2023 May 16), retrieved May 16, 2023 from .

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Surfing champion Lucy Campbell says her sport needs to be greener



Vaip Desai, the association’s chief executive, said businesses are “collaborating to address the environmental impact of the products the industry produces. These efforts have been and continue to be supported by consumers demanding that surf brands do more.”

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Who was Rube Goldberg and what are Rube Goldberg machines?



Rube Goldberg, born in San Francisco in 1883, was originally an engineer. In 1904 he graduated from the College of Mining at the University of California at Berkeley.

For six months he mapped water and sewer lines until he couldn’t take it anymore. He then took a low-paying job drawing cartoons for the San Francisco Chronicle.

“What he cared about the most was whether he made you laugh,” said his granddaughter Jennifer George, who we spoke to in 2018. Her 2013 book:Art by Rube Goldberg,” describes his extensive output of cartoons, writing and even sculpture until his death in 1970.

Goldberg left California for New York in 1907 and was hired by the New York Evening Mail. One of his early cartoons for a newspaper featured a badly injured man falling from a 50-story building and a woman asking, “Are you in pain?” The man replied: “No, I sleep with my beauty.”

It was a hit, and over the next two years he drew 449 more in the Silly Questions series. Readers loved to send suggestions.

He also created a TV series called I’m a Guy. It featured statements such as “I’m the guy who put the bum in Hoboken” and “I’m the guy who put the sand in the sandwich”, which started a national fad.

Among his cartoon characters was Bub McNutt.who always managed to screw up when he tried to help someone.

Drawings of Goldberg’s inventions began in 1912 and made him a household name, according to exhibition at the Contemporary Jewish Museum in San Francisco.

The first of his complex devices was “Simple mosquito repellentclassic Rube Goldberg machine. A mosquito climbs in through a window, walks along a board strewn with small pieces of steak, passes out from the chloroform fumes from a sponge, and falls onto the platform. He wakes up, looks through a spyglass to see the bald head’s reflection in the mirror, and jumps off a diving board in fear, killing himself when it hits the mirror, falling dead into a jar.

For the next 20 years, Goldberg delivered a new car to Rube Goldberg about every two weeks. He continued less frequently until 1964.

Hey invented character Professor Lucifer Gorgonzola Buttswho created his own machines to open screen doors, shine shoes, and find soap that has fallen out of the tub. According to The Art of Rube Goldberg, the character was inspired by two professors Goldberg found particularly boring at the College of Mining: Samuel B. Christie, who lectured extensively on the efficiency of time and motion, and Frederick Slate. who once showed students the “barodic”, an intricate machine designed to measure the weight of the earth.

The invention cartoons satirized the “complex world of machines,” wrote Adam Gopnik in the book’s preface, poking fun at “the broader idea of ​​efficiency.” Gopnik wrote that Goldberg had “the poetic intuition of all great cartoonists”.

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Get the best Hyrule experience with Samsung monitors up to 40% off.



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