(7 Oct 2015)Very high energy neutrino emission from the core of low luminosity AGNs triggered by magnetic reconnection acceleration(彼得後書)3:10但主的日子要像賊來到一樣。那日,天必大有響聲廢去,有形質的都要被烈火銷化,地和其上的物都要燒盡了。

Astrophysics > High Energy Astrophysical Phenomena

Very high energy neutrino emission from the core of low luminosity AGNs triggered by magnetic reconnection acceleration

The detection of astrophysical very high energy (VHE) neutrinos in the range of TeV-PeV energies by the IceCube observatory has opened a new season in high energy astrophysics. Energies ~PeV imply that the neutrinos are originated from sources where cosmic rays (CRs) can be accelerated up to ~ 10^{17}eV. Recently, we have shown that the observed TeV gamma-rays from radio-galaxies may have a hadronic origin in their nuclear region and in such a case this could lead to neutrino production. In this paper we show that relativistic protons accelerated by magnetic reconnection in the core region of these sources may produce VHE neutrinos via the decay of charged pions produced by photo-meson process. We have also calculated the diffuse flux of VHE neutrinos and found that it can be associated to the IceCube data.

Comments: 9 pages, 5 figures, Accepted for publication in the Monthly Notices of the Royal Astronomical Society (MNRAS)
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)
DOI: 10.1093/mnras/stv2337
Cite as: arXiv:1506.01063 [astro-ph.HE]
(or arXiv:1506.01063v2 [astro-ph.HE] for this version)

NASA launches 4 spacecraft to study magnetic reconnection

English.news.cn   2015-03-13 11:05:15  

WASHINGTON, March 12 (Xinhua) — U.S. space agency NASA on Thursday launched four identical spacecraft to study how magnetic fields like those around Earth and Sun interact as part of efforts to understand space weather events that could disrupt power grids, communications and navigation systems.

Known as the Magnetospheric Multiscale (MMS) mission, these spacecraft, stacked one atop the other, blasted off at 10:44 p.m. EDT (0244GMT Friday), from Cape Canaveral Air Force Station in Florida aboard an Atlas V rocket.

The 1.1-billion-U.S.-dollar project will study a phenomenon called magnetic reconnection, which occurs when magnetic fields connect and disconnect with an explosive release of energy that can accelerate particles up to nearly the speed of light.

Magnetic reconnection is a major driver of solar activity and space weather events such as solar flares and coronal mass ejections," NASA explained in its blog.

“These violent outbursts can be harmful to astronauts in orbit, and can affect our power grid and disrupt the satellites we use every day for communications, weather forecasting and navigation."

Unlike previous missions that have observed only evidence of magnetic reconnection events, MMS has sufficient resolution to observe and measure reconnection events as they occur, NASA said.

While MMS will fly through reconnection regions in less than a second, key sensors on each spacecraft are able to capture measurements 100 times faster than any previous mission, the space agency said.

The quartet will fly in a pyramid formation to provide the first three-dimensional view of magnetic reconnection. They will observe reconnection directly in Earth’s protective magnetic space environment known as the magnetosphere.

Each of the four MMS spacecraft is octagonal in shape, about 11 feet (3 meters) across by four feet (1 meter) high. They have 100 instruments on board, 25 on each unit.

“By studying reconnection in this local, natural laboratory, MMS helps us understand reconnection elsewhere, such as the atmosphere of the Sun, the vicinity of black holes and neutron stars, and the boundary between our solar system and interstellar space," NASA said.

The spacecraft will begin science operations in September after a six-month “checkout" period. Their primary mission is expected to last two years.

Solar Superstorms, Illustrated

An executive order calling for more preparedness and better forecasting for space weather is creating a buzz about electromagnetic storms. What are they?

  •  on November 17, 2016

Last month, … Obama signed an executive order to better prepare the nation for the potentially disastrous effects of of solar flares, solar energetic particles, and geomagnetic disturbances. Per the document:

Extreme space weather events—those that could significantly degrade critical infrastructure—could disable large portions of the electrical power grid, resulting in cascading failures that would affect key services such as water supply, healthcare, and transportation. Space weather has the potential to simultaneously affect and disrupt health and safety across entire continents. Successfully preparing for space weather events is an all-of-nation endeavor that requires partnerships across governments, emergency managers, academia, the media, the insurance industry, non-profits, and the private sector.”

How do these electromagnetic storms reach Earth? Here are the basics, as set forth in a graphic from “Bracing the Satellite Infrastructure for a Solar Superstorm,” by Sten Odenwald and James Green in the August 2008 issue of Scientific American.

Credit: Melissa Thomas

Want to dive in further? Check your local planetarium for screenings of the full-dome video Solar Superstorms. For more on forecasting space weather, and recent glitches experienced by the primary tool for tracking it—see “U.S. Sharpens Surveillance of Crippling Solar Storms” and “Cosmic Rays May Threaten Space-Weather Satellite.”

Neutrinos and solar storms

And now, the space-weather forecast

Can neutrinos be used to predict solar storms?

RADIOACTIVE materials decay at a predictable rate—so predictable, in fact, that scientists widely use them to date artefacts and geological objects. That, at least, is the received wisdom, which Jere Jenkins and Ephraim Fischbach, from Purdue University in Indiana, think may need revising. In 2006 Dr Jenkins noticed that the decay rate of the radioactive isotope manganese-54 dipped 39 hours before a solar flare came crashing into Earth’s protective magnetic field. Now it seems that the sun might affect other types of decay, too.

As the researchers report in Astroparticle Physics, the decay rate of chlorine-36 increases as Earth approaches the sun. The difference is tiny: the rate fluctuates by less than 1% between the aphelion and perihelion, the points on Earth’s orbit when it is farthest and closest to the sun, respectively. But it is discernible and persistent. As-yet-unpublished data for manganese-54 suggest that isotope follows a similar pattern. If confirmed, the insight might, among other things form the basis of a system for forecasting dangerous cosmic storms.

Solar flares, in which charged particles are ejected from the sun, can damage satellites and ground-based electronic infrastructure. In 2005 an unseasonal solar storm knocked out a number of Global Positioning System (GPS) birds, some of them for good. It also forced airliners to be redirected from Arctic routes, where Earth’s magnetic field provides least cover from the nefarious effects a hail of such particles can have on the people’s, and machines’, health. And that was a mere breeze compared with the solar storm of 1859, thought to have been many times more devastating on the basis of the disruption it caused to the nascent telegraph service. These days, another Carrington Event, as the 19th-century episode is known, risks crippling a planet increasingly reliant on all sorts of electronic gubbins.

A number of advance-warning systems, enabling countermeasures such as temporary shutdown of vulnerable electronics, are in the works. But reliable forecasts are scarce. This is because solar storms are not yet well understood. Paradoxically, Dr Jenkins and Dr Fischbach think this might change with the help of neutrinos, the ethereal particles which pervade the universe but rarely interact with anything—and themselves a cause of much head-scratching among physicists.

Neutrinos are a byproduct of the nuclear fusion which powers the sun. Earth’s elliptical orbit means that the flux of solar neutrinos which stream through it varies during the year. The changes in chlorine-36 and manganese-54 decay rates observed by the Purdue team, including the dip prior to the flare in 2006, mirror the changes in neutrino flux detected by other experiments. Unlike their tiny radioactive sample, though, those existing neutrino detectors are vast (to shorten the odds that the elusive particles deign to react with at least one atom inside it) and often sit deep underground (to shield the detectors from other particles which leave neutrino-like traces; only neutrinos, thanks to their signature unwillingness to react, are able to penetrate ). As a result, any system based on such detectors would be hard to scale up.

If Dr Fischbach and Dr Jenkins are right about neutrinos affecting radioactive decay, it would herald a new era in neutrino physics, not just space-weather forecasting. That is still a prodigious if. For a start, like many things neutrino-related, the mechanism through which the particles might affect decay rates remains a mystery. On the rare occasions that they do interact, neutrinos do so via the weak nuclear force, which is also responsible for the sorts of radioactivity present in chlorine-36 and manganese-54. Physicists critical of the work point out that in the Purdue team’s proposal the strength of the force, which can be calculated from the observed changes in decay rates, is much larger than established particle theory would have it.

Such discrepancies might be explained if a neutrino somehow amplifies the decay rates. In the conventional view, most neutrinos pass through matter without so much as a shudder. Those that do interact tend to do so only once; the likelihood of a single neutrino scattering off one atom and then another in short order is infinitesimal. However, rather controversially, Dr Fischbach thinks that the large number of neutrinos that seem not to be interacting may in fact be doing so, just that the effects of these interactions in stable matter are too small to see. In an unstable radioactive sample, he speculates, they might come to light, because decay rates are known to be extremely sensitive to the energy released in the process. As a result, if solar neutrinos transferred a mere millionth of their energy to a decaying nucleus, that might have a big effect on the rate at which it breaks up.

Whatever the mechanism, the correlation between radioactive decay rates and neutrino flux looks striking, and has been observed in a number of samples in different laboratories. Wary neutrino physicists warn that it could all yet prove to be an artefact of the way the experiments were conducted. That was the case in 2011, when their colleagues in Italy clocked neutrinos travelling faster than light, only to discover that the result, at odds with Einstein’s cherished theory of relativity, was down to a loose cable.

Even if this time all cables were taut, many hurdles remain. Dr Fischbach admits that while whatever process generated the flare in 2006 also caused a dip in neutrino flux, and a corresponding drop in radioactive decay rates, other processes seem to have the opposite effect. For example, a storm in 2008 was preceded by a spike in manganese-54 decay rates.He suspects that what is loosely termed a “solar storm" may in fact be a number of distinct processes whose common feature is that they affect neutrino production in one way or another. That is a far cry from a reliable space-weather forecast. But it has not stopped the university from applying for a patent on a decay-based neutrino detector technology, just in case.

Astrophysics > High Energy Astrophysical Phenomena

On the detection of neutrinos from solar flares using pion-decay photons to provide a time window template

(on 21 May 2015)

Since the end of the eighties and in response to a reported increase in the total neutrino flux in the Homestake experiment in coincidence with solar flares, solar neutrino detectors have searched for solar flare signals. Even though these detectors have used different solar flare samples and analyses, none of them has been able to confirm the possible signal seen by Homestake. Neutrinos from the decay of mesons, which are themselves produced in collisions of accelerated ions with the solar atmosphere would provide a novel window on the underlying physics of the hadronic acceleration and interaction processes during solar flares. Solar flare neutrino flux measurements would indeed help to constrain current parameters such as the composition of the accelerated flux, the proton/ion spectral index and the high energy cutoff or the magnetic configuration in the interaction region. We describe here a new way to search for these neutrinos by considering a specific solar flare sample and a data driven time window template which will improve the likelihood of neutrino detection.

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)
Cite as: arXiv:1505.05837 [astro-ph.HE]
(or arXiv:1505.05837v1 [astro-ph.HE] for this version)

(帖撒羅尼迦前書) 5:2-3Chinese Union Version Modern Punctuation (Traditional) (CUVMPT)2 因為你們自己明明曉得,主的日子來到好像夜間的賊一樣3 人正說平安穩妥的時候,災禍忽然臨到他們,如同產難臨到懷胎的婦人一樣,他們絕不能逃脫(彼得後書) 3:10 但主的日子要像賊來到一樣。那日,天必大有響聲廢去,有形質的都要被烈火銷化,地和其上的物都要燒盡了End of CIA Training Program Removes Roadblock to Real Peace in Syria.02:56 21.07.2017.Trump, CIA Abandon US Arming of al-Qaeda in Syria(10:58 21.07.2017)White House Admits Defeat in Syria(18:08 20.07.2017)President Trump’s announcement this week to end the CIA’s covert arming of militants in Syria is an admission of defeat. The US has lost its six-year war for regime change in the Arab country. It’s time to wrap it up.Donald Trump’s decision to end CIA training for US-backed rebel groups in Syria opens the way for peace at last and humanitarian relief for the suffering people of that country, analysts told Sputnik.




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