Scientists look inside central engine of solar flare for first time

July 27, 2020


Massachusetts, Jul 27: Scientists from the Centre for Astrophysics, Harvard and Smithsonian and the New Jersey Institute of Technology on Monday announced the first successful measurement and characterisation of the 'central engine' of a large solar flare.

The findings have been published in the journal Nature Astronomy, reveal the source of the intense energy powering solar flares.

According to the study -- which closely examined a large solar flare accompanied by a powerful eruption captured on September 10, 2017, by the NJIT's Owens Valley Solar Array (EOVSA), at microwaves -- the intense energy powering the flare is the result of an enormous electric current 'sheet' stretching more than 40,000 kilometres -- greater than the length of three Earths placed side-by-side -- through the core flaring region, where opposing magnetic field lines approach, break, and reconnect.

"During large eruptions on the Sun, particles such as electrons can get accelerated to high energies. How exactly this happens is not clearly understood, but it is thought to be related to the Sun's magnetic field," said Kathy Reeves, astrophysicist, CfA, and co-author of the study.

"It has long been suggested that the sudden release of magnetic energy through the reconnection current sheet is responsible for these major eruptions, yet there has been no measurement of its magnetic properties," said Bin Chen, professor of physics at NJIT and lead author on the study.

"With this study, we have finally measured the details of the magnetic field of a current sheet for the first time, giving us a new understanding of the central engine of the Sun's solar flares," added Chen.

Measurements were taken during the study also indicate a magnetic, bottle-like structure located at the top of the flare's loop-shaped base, or flare arcade, at a height of nearly 20,000 kilometres above the surface of the Sun. The study suggests that this is the primary site where a solar flare's highly energetic electrons are trapped and accelerated to nearly the speed of light.

"We found that there were a lot of accelerated particles just above the bright, flaring loops," said Reeves.

"The microwaves, coupled with modeling, tells us there is a minimum in the magnetic field at the location where we see the most accelerated particles, and a strong magnetic field in the linear, sheet-like structure further above the loops," added Reeves.

The sheet-like structure and the loops seem to be working in concert, with significant magnetic energy being pumped into the current sheet at an estimated rate of 10-100 billion trillion joules per second, and 99 percent of the flare's relativistic electrons were observed congregating at the magnetic bottle.

"While the current sheet seems to be the place where the energy is released to get the ball rolling, most of the electron acceleration appears to be occurring in this other location, the magnetic bottle," said Dale Gary, director, EOVSA and co-author on the study.

"Others have proposed such a structure in solar flares before, but we can truly see it now in the numbers. What our data showed was a special location at the bottom of the current sheet -- the magnetic bottle -- appears to be crucial in producing or confining the relativistic electrons," Chen said.

The study results were achieved through a combination of microwave observations from EOVSA and extreme ultra-violet imaging observations from the Smithsonian Astrophysical Observatory's Atmospheric Imaging Assembly on the Solar Dynamics Observatory (SDO).

The observations were combined with analytical and numerical modeling -- based on a 1990s theoretical model of solar flare physics -- to help scientists understand the structure of the magnetic field during a large solar eruption.

"Our model was used for computing the physics of the magnetic forces during this eruption, which manifests as a highly twisted 'rope' of magnetic field lines, or magnetic flux rope," said Reeves.

"It is remarkable that this complicated process can be captured by a straightforward analytical model, and that the predicted and measured magnetic fields match so well," added Reeves.

Performed by Chengcai Shen, astrophysicist, CfA, the simulations allowed the team to resolve the thin reconnection current sheet and capture it in detail.

"Our simulation results match both the theoretical prediction on magnetic field configuration during a solar eruption and reproduce a set of observable features from this particular flare, including magnetic strength and plasma inflow/outflows around the reconnecting current sheet. It is a powerful tool to compare theoretical expectations and observations in detail," said Shen.

For the team, the study provides answers to long-unanswered questions about the Sun and its solar flares.

"The place where all the energy is stored and released in solar flares has been invisible until now," said Gary.

"To play on a term from cosmology, it is the Sun's 'dark energy problem,' and previously we've had to infer indirectly that the flare's magnetic reconnection sheet existed," added Gary.

For solar physics, the measurements represent a better understanding of the Sun, as well as providing a path to revealing the truth behind the current sheet, and the magnetic bottle and its role in particle acceleration.

"There are certainly huge prospects out there for us to study that address these fundamental questions," said Shen.

The current study builds on the team's quantitative measurements of the evolving magnetic field strength directly follow a solar flare's ignition, published in Science earlier this year. 


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September 27,2020


Washington, Sept 27: To understand how it functions and to shed light on what goes awry in cardiovascular disease, scientists have created a detailed cellular and molecular map of the healthy heart.

Scientists have created a detailed cellular and molecular map of the healthy human heart to understand how this vital organ functions and to shed light on what goes awry in cardiovascular disease.

The work, published in the journal Nature, was led by investigators at Harvard Medical School, Brigham and Women's Hospital, the Wellcome Sanger Institute, Max Delbruck Center for Molecular Medicine (MDC) in Germany, Imperial College London, and their global collaborators.

The team analysed almost a half-million individual cells to build the most extensive cell atlas of the human heart to date.

The atlas shows the huge diversity of cells and reveals heart muscle cell types, cardiac protective immune cells, and an intricate network of blood vessels. It also predicts how the cells communicate to keep the heart working.

The research is part of the Human Cell Atlas initiative to map every cell type in the human body.

The new molecular and cellular knowledge of the heart promises to enable a better understanding of heart disease and guide the development of highly individualized treatments.

The work also sets the stage for therapies based on regenerative medicine in the future, the researchers said.

Over a lifetime, the average human heart delivers more than 2 billion life-sustaining beats to the body. In doing so, it helps deliver oxygen and nutrients to cells, tissues and organs and enables the removal of carbon dioxide and waste products.

Each day, the heart beats around 100,000 times with a one-way flow through four different chambers, varying speed with rest, exercise, and stress. Every beat requires an exquisitely complex but perfect synchronization across various cells in different parts of the heart.

When this complex coordination goes bad, it can result in cardiovascular disease, the leading cause of death worldwide, killing an estimated 17.9 million people each year.

Detailing the molecular processes inside the cells of a healthy heart is critical to understanding how things go awry in heart disease. Such knowledge can lead to more precise, better treatment strategies for various forms of cardiovascular illness.

"Millions of people are undergoing treatments for cardiovascular diseases. Understanding the healthy heart will help us understand interactions between cell types and cell states that can allow lifelong function and how these differ in diseases," said study co-senior author Christine Seidman, professor of medicine in the Blavatnik Institute at Harvard Medical School and a cardiovascular geneticist at Brigham and Women's.

"Ultimately, these fundamental insights may suggest specific targets that can lead to individualized therapies in the future, creating personalized medicines for heart disease and improving the effectiveness of treatments for each patient," Seidman said.

The team studied nearly 500,000 individual cells and cell nuclei from six different regions of the heart obtained from 14 organ donors whose hearts were healthy but unsuitable for transplantation.

Using a combination of single-cell analysis, machine learning and imaging techniques, the team could see exactly which genes were switched on and off in each cell.

The researchers discovered major differences in the cells in different areas of the heart. They also observed that each area of the heart had specific subsets of cells--a finding that points to different developmental origins and suggests that these cells would respond differently to treatments.

"This project marks the beginning of new understandings into how the heart is built from single cells, many with different cell states," said study co-first author Daniel Reichart, research fellow in genetics at Harvard Medical School.

"With knowledge of the regional differences throughout the heart, we can begin to consider the effects of age, exercise and disease and help push the field of cardiology toward the era of precision medicine," added Reichart.

"This is the first time anyone has looked at the single cells of the human heart at this scale, which has only become possible with large-scale single-cell sequencing," said Norbert Hubner, co-senior author and professor at Max Delbruck Center for Molecular Medicine. "This study shows the power of single-cell genomics and international collaboration," he added.

"Knowledge of the full range of cardiac cells and their gene activity is a fundamental necessity to understand how the heart functions and to start to unravel how it responds to stress and disease," added Hubner.

As part of this study, the researchers also looked at blood vessels running through the heart in unprecedented detail. The atlas showed how the cells in these veins and arteries are adapted to the different pressures and locations and how this could help researchers understand what goes wrong in blood vessels during coronary heart disease.

"Our international effort provides an invaluable set of information to the scientific community by illuminating the cellular and molecular details of cardiac cells that work together to pump blood around the body," said co-senior author Michela Noseda of Imperial College, London.

"We mapped the cardiac cells that can be potentially infected by SARS-CoV-2 and found that specialized cells of the small blood vessels are also virus targets. Our datasets are a goldmine of information to understand subtleties of heart disease," she added.

The researchers also focused on understanding cardiac repair, looking at how the immune cells interact and communicate with other cells in the healthy heart and how this differs from skeletal muscle.

Further research will include investigating whether any heart cells could be induced to repair themselves.

"This great collaborative effort is part of the global Human Cell Atlas initiative to create a 'Google map' of the human body," said Sarah Teichmann of the Wellcome Sanger Institute, co-senior author of the study and co-chair of the Human Cell Atlas Organising Committee.

"Openly available to researchers worldwide, the Heart Cell Atlas is a fantastic resource, which will lead to a new understanding of heart health and disease, new treatments and potentially even finding ways of regenerating damaged heart tissue," she added.


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September 14,2020


Washington, Sept 14: A rare molecule -- phosphine -- has been detected in the atmosphere of Venus, an international team of astronomers announced today leading to speculation of life on Earth's nearest planetary neighbour.

On Earth, this gas is only made industrially or by microbes that thrive in oxygen-free environments.

Astronomers have speculated for decades that high clouds on Venus could offer a home for microbes -- floating free of the scorching surface but needing to tolerate very high acidity. The detection of phosphine could point to such extra-terrestrial "aerial" life.
"When we got the first hints of phosphine in Venus's spectrum, it was a shock!," says team leader Jane Greaves of Cardiff University in the UK, who first spotted signs of phosphine in observations from the James Clerk Maxwell Telescope, operated by the East Asian Observatory, in Hawaii.

The study was published today in a new paper in the journal Nature Astronomy

Confirming their discovery required using 45 antennas of the Atacama Large Millimeter/submillimeter Array (ALMA, in Chile, a more sensitive telescope in which the European Southern Observatory (ESO) is a partner. Both facilities observed Venus at a wavelength of about 1 millimetre, much longer than the human eye can see -- only telescopes at high altitude can detect it effectively.

The international team, which includes researchers from the UK, US and Japan, estimates that phosphine exists in Venus's clouds at a small concentration, only about 20 molecules in every billion.

Following their observations, they ran calculations to see whether these amounts could come from natural non-biological processes on the planet. Some ideas included sunlight, minerals blown upwards from the surface, volcanoes, or lightning, but none of these could make anywhere near enough of it. These non-biological sources were found to make at most one 10,000th of the amount of phosphine that the telescopes saw.

To create the observed quantity of phosphine (which consists of hydrogen and phosphorus) on Venus, terrestrial organisms would only need to work at about 10% of their maximum productivity, according to the team. Earth bacteria are known to make phosphine: they take up phosphate from minerals or biological material, add hydrogen, and ultimately expel phosphine. Any organisms on Venus will probably be very different to their Earth cousins, but they too could be the source of phosphine in the atmosphere.
While the discovery of phosphine in Venus's clouds came as a surprise, the researchers are confident in their detection.
"To our great relief, the conditions were good at ALMA for follow-up observations while Venus was at a suitable angle to Earth. Processing the data was tricky, though, as ALMA isn't usually looking for very subtle effects in very bright objects like Venus," says team member Anita Richards of the UK ALMA Regional Centre and the University of Manchester.

"In the end, we found that both observatories had seen the same thing -- faint absorption at the right wavelength to be phosphine gas, where the molecules are backlit by the warmer clouds below," adds Greaves, who led the study.

Another team member, Clara Sousa Silva of the Massachusetts Institute of Technology in the US, has investigated phosphine as a "biosignature" gas of non-oxygen-using life on planets around other stars, because normal chemistry makes so little of it. She comments: "Finding phosphine on Venus was an unexpected bonus! The discovery raises many questions, such as how any organisms could survive. On Earth, some microbes can cope with up to about 5% of acid in their environment -- but the clouds of Venus are almost entirely made of acid."

The team believes their discovery is significant because they can rule out many alternative ways to make phosphine, but they acknowledge that confirming the presence of "life" needs a lot more work. Although the high clouds of Venus have temperatures up to a pleasant 30 degrees Celsius, they are incredibly acidic -- around 90% sulphuric acid -- posing major issues for any microbes trying to survive there.

ESO astronomer and ALMA European Operations Manager Leonardo Testi, who did not participate in the new study, says: "The non-biological production of phosphine on Venus is excluded by our current understanding of phosphine chemistry in rocky planets' atmospheres. Confirming the existence of life on Venus's atmosphere would be a major breakthrough for astrobiology; thus, it is essential to follow-up on this exciting result with theoretical and observational studies to exclude the possibility that phosphine on rocky planets may also have a chemical origin different than on Earth."

More observations of Venus and of rocky planets outside our solar system, including with ESO's forthcoming Extremely Large Telescope, may help gather clues on how phosphine can originate on them and contribute to the search for signs of life beyond Earth. 


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News Network
September 20,2020


New Delhi, Sept 20: Scientists at the Council of Scientific & Industrial Research's (CSIR) Institute of Genomics and Integrative Biology have come up with a low-cost coronavirus test that will not require any expensive machines for detection of the pathogen.

Named after 'Feluda', the detective character in legendary filmmaker Satyajit Ray's stories, the test has been developed by Debojyoti Chakraborty and Souvik Maiti as a simpler way of detecting SARS-coV2 presence in clinical samples, IGIB Director Anurag Agarwal said.

CSIR is a department under the Union Ministry of Science and Technology.

It starts the same way as a normal real time reverse transcription- polymerase chain reaction (RT-PCR), which is extraction of ribonucleic acid (RNA) and its conversion to deoxyribonucleic acid (DNA), Agarwal said.

It then differs by using a specifically designed PCR reaction to amplify a part of the viral nucleic acid sequence. Then a highly specific CRISPR, FnCAS9, developed at IGIB, binds to that sequence, he added.

Using the innovative chemistry on a paper strip, the CRISPR complex, bound to that specific sequence, can be visualised as a positive band - like one sees in simple pregnancy tests.

The total time required for the test is less than one hour.

In the RT-PCR tests, the RNA is converted to DNA by using specific primers and probes, with fluorescent reporters, to amplify and detect viral nucleic acid presence. It requires expensive Real Time PCR machines which are available at specialised sites.

"If successfully commercialised, which depends upon all its components being available at scale and the commercial product being successfully validated by regulatory agencies, it would allow the test to be done in local path-labs that do not have expensive real time PCR machines, but simple cheap thermo-blocks used for conventional PCR," Agarwal said.

When asked why the test was named after Feluda, Agarwal said the researchers at MIT and University of California, Berkeley also use CRSIPR, but different technologies.

They have named the tests as 'Detector' and 'Sherlock', so Feluda was an Indian version, he added.


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