ZPEnergy.com - Magnetic whirlpools over Earth; A new particle; Novel Magnets

Magnetic whirlpools feed Earth's magnetosphere Giant whirlpools of electrically charged gas, some 40 000 kilometres across, have been witnessed above the Earth by a team of European and American scientists. Using data from ESA's Cluster quartet of spacecraft, the researchers have shown that these whirlpools inject electrified gas into the magnetic environment of the Earth.

The magnetic field generated inside the Earth protects the planet from the electrically charged particles given out by the Sun. However, it is only a partially effective shield.

In the same way that a car can only travel along roads, electrically charged gas, known as plasma, can only travel along magnetic field lines, never across them. For a car to suddenly change direction, it has to use a road junction.

For a particle of plasma to suddenly jump onto a different field line, there has to be a reconnection event. In a reconnection, magnetic fields lines spontaneously break and then join up with other nearby lines. In doing so, the plasma is suddenly redirected along new routes.

Scientists know this happens in Earth's magnetosphere because of changes to the plasma sheet. This is one of the inner regions of the Earth's magnetic field. Plasma in the sheet is usually hot and tenuous, whereas the solar wind is cooler and denser. At certain times, the sheet fills with cooler and denser plasma over the course of a few hours.

For this to happen, the solar wind plasma must somehow be able to cross the Earth’s magnetic boundary, known as the magnetopause. Yet, until now scientists had no observational evidence that reconnection inside whirlpools contribute to this process. "Wondering how the solar wind could get into the plasma sheet is how I became interested in this problem," says Katariina Nykyri, lead author of the results, from the Imperial College, London, UK.

Together with colleagues, Nykyri began investigating a strange event recorded by Cluster on 3 July 2001. At this time, Cluster was passing the dawn side of the Earth. In this region of space, the solar wind is sliding past the Earth's magnetopause, in roughly the same way as wind blows across the surface of an ocean.

A previous Cluster observation had shown that whirlpools of plasma can be whipped up by this configuration. Such whirlpools are known as Kelvin-Helmholtz instabilities and scientists suspected them of being the location of magnetic reconnection but no one had found any conclusive evidence that this was the case.

Cluster can recognise magnetic reconnection because of what researchers call 'rotational discontinuities'. These show up as sudden changes in the direction of the plasma flow and magnetic field. After a painstaking analysis, Nykyri found just such rotational discontinuities in the data for 3 July 2001. To be certain of her result, she reanalysed the data four times.

Then she developed a computer model to simulate the event. The computer showed that the Cluster data was only understandable if the whirlpools were causing magnetic reconnection to take place. In these reconnections, plasma was being fed down through the magnetic boundary of Earth and into the magnetosphere.

The work does not stop there. Nykyri and colleagues are now developing more sophisticated computer simulations to understand the whirlpools’ three-dimensional behaviour. "This is a very big challenge," she says, because of the additional numerical processes involved.

She also plans to search the Cluster data archive for more examples of these events.

Source: European Space Agency
Story: http://www.physorg.com/news84626761.html
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Long the fixation of physicists worldwide, a tiny particle is found

After decades of intensive effort by both experimental and theoretical physicists worldwide, a tiny particle with no charge, a very low mass and a lifetime much shorter than a nanosecond, dubbed the "axion," has now been detected by the University at Buffalo physicist who first suggested its existence in a little-read paper as early as 1974.

The finding caps nearly three decades of research both by Piyare Jain, Ph.D., UB professor emeritus in the Department of Physics and lead investigator on the research, who works independently -- an anomaly in the field -- and by large groups of well-funded physicists who have, for three decades, unsuccessfully sought the recreation and detection of axions in the laboratory, using high-energy particle accelerators.

The paper, available online in the British Journal of Physics G: Nuclear and Particle Physics at http://www.iop.org/EJ/abstract/0954-3899/34/1/009 , will be published in the January 2007 issue.

Results first were presented during a two-day symposium held in October at UB that celebrated Jain’s 50-year career in the physics department in the College of Arts and Sciences.

During that symposium, the world-renowned and Nobel Prize-winning scientists in attendance expressed astonishment and delight that the axion finally might have been found.

The axion has been seen as critical to the Standard Model of Physics and is believed to be a component of much of the dark matter in the universe.

"These results show that we have detected axions, part of a family of particles that likely also includes the very heavy Higgs-Boson particle, which at present is being sought after at different laboratories," said Jain.

The story of the search for the axion particle in high-energy physics -- not to be confused with the search by cosmologists and astrophysicists for axions produced by the sun -- reads almost like a novel,

with veritable armies of physicists committing many years of research and passion to its discovery starting in the 1970s.

In 1977, theoretical physicists predicted that there should exist a particle with characteristics very similar to those described in Jain’s papers; in that publication, the term "axion" was coined. After that theoretical work, there was a mushrooming of papers from both theoretical and experimental physicists all chasing the axion using low-, medium- and high-energy accelerator beams from different laboratories worldwide.

But when it proved to be too elusive, many in the physics community then abandoned the search in the 1990s, based on puzzling evidence that perhaps this tantalizing particle didn’t exist after all. Some groups flatly denied its existence and began referring to it as a "phantom."

Jain’s initial interest in the elusive particles originated with work he began publishing in 1974 in Physical Review Letters and other journals that demonstrated evidence for particles with very low mass and very short lifetimes during particle accelerator experiments he conducted at Fermilab and Brookhaven National Laboratory.

At the time, Jain’s papers elicited little interest from other physicists.

"This particle was there in my original paper in 1974," he said. "The experiment gave a hint that these particles existed but did not generate sufficient statistics to prove it. I knew I had to wait until a heavy ion beam at very high energy was available at a new accelerator."

As recently as 1999, a project called the CERES experiment at CERN in Geneva again focused on attempting to detect the axion, but that project also was unsuccessful.

The problem, according to Jain, was with their detector, which was electronic, the standard used in high-energy physics experiments today.

"They didn’t know how to handle the detector for short-lived particles," Jain said. "I knew that for this very short-lived particle -- 10-13 seconds -- the detector must be placed very near the interaction point where the collision between the projectile beam and the target takes place so that the produced particle doesn’t run away too far; if it does, it will decay quickly and it will be completely missed. That is what happened in most of the unsuccessful experiments." Instead, Jain used a visual detector, made of three-dimensional photographic emulsions, which act as both target and detector and that therefore can detect very short-lived particles, such as the axion. However, use of such a detector is so specialized that to be successful, it requires intensive training and experience. In the 1950s, Jain was trained to use this type of detector by its developer, the Nobel laureate, British physicist Cecil F. Powell. Jain has used it throughout his career to successfully detect other exotic

phenomena, such as the charm particle, the anomalon, the quark-gluon plasma and the nuclear collective flow. In Jain’s successful experiment, the axions were produced under extreme conditions of high temperature and high pressure, using a heavy ion lead beam with a total energy of 25 trillion electron volts at CERN in Geneva.

His experiments generated 1,220 electron pairs with identified vertices, the origin of each pair. They peaked at a distance of just 200-300 microns from the interaction point where the collisions take place in the emulsion.

"Only at that very short distance did I find the peak signal of this very-low-mass, short-lived particle with a neutral charge," he said.

After they are produced, axions rapidly decay into two electron pairs, the electron and the positron, he explained.

"We identified each vertex for each electron pair and we would not accept any electron pair unless we knew its vertex," he said. "There was a congestion of all kinds of low mass particles, including axions, near the detector. The background has to be filtered out from this congestion in order to obtain the signal of the axion."

Jain’s co-author on the paper is Gurmukh Singh, then a post-doctoral researcher at UB and now a visiting assistant professor in the Department of Computer and Information Sciences at the State University of New York at Fredonia.

During Jain’s long and illustrious career at UB, he published 175 scientific papers on a wide variety of physics topics, ranging from cosmic ray research performed on balloon flights to National Institutes of Health-funded studies on bone tissue to find more effective cancer therapies. "After half a century as a scientist at UB, I find that with the discovery of this axion, my mission is complete," he concluded.

Source: University at Buffalo

Story: http://www.physorg.com/news84633896.html
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Novel magnets made from the strongest known hydrogen bond

A team of scientists from the US, the UK and Germany has been the first to make a magnetic material constructed from nature's strongest known hydrogen bond. Hydrogen bonds are responsible for many of the properties of water and for holding together the DNA double helix.

However, hydrogen bonds are normally rather weak but the new compound contains the bifluoride ion in which a hydrogen atom is tightly bound to two fluorine atoms. This leads to the new magnet being stable up to 200 degrees Celsius.

The work is published in the latest issue of the journal Chemical Communications, where it features on its cover.

The magnetic properties of the material were measured using muons by a team at Oxford University, headed by Stephen Blundell, Professorial Fellow in Physics at Mansfield College. He said: ‘Muons are tiny, sub-atomic particles which can be implanted into materials. They behave like tiny gyroscopes and spin round when they experience a magnetic field.’

Using this method, which is uniquely sensitive to magnetism in these types of magnetic material, the researchers found that there is no overall magnetism at room temperature; however, as the temperature is lowered, copper magnetic moments begin to align, producing a microscopic magnetic field visible to the implanted muons below a temperature of 1.54 Kelvin.

These experiments were performed at ISIS, the world's most intense source of pulsed muons, located in Oxfordshire, UK.

The team hopes that the magnetic studies will help them understand to what extent bifluoride units and their hydrogen bonds influence the spin arrangement on neighbouring magnetic centres.

Source: University of Oxford
Story: http://www.physorg.com/news84643085.html