Posts Tagged ‘sun’

Solar Activity Could Cause Lightning Storms On Earth


A link has been found between storms in the atmosphere of the sun and those here on Earth, but not in the direction expected. The discovery could improve weather forecasting and save the lives of people who might otherwise be trapped in the open during electrical events.
The sun spits out charged particles that hit our atmosphere two to four days later at 1.5-.2.7million kph, but it does not do so evenly. “The solar wind is not continuous, it has slow and fast streams. Because the Sun rotates, these streams can be sent out behind each other – so if you have a fast solar wind catching up with a slow solar wind, it causes a concentration to occur,” says Dr Christ Scott of the University of Reading. The slow phase is composed similarly to the solar corona while fast particles have a composition close to that of the photosphere, the outer layer of the sun that produces the light.
The arrival of bursts of particles trigger the aurora borealis and australis, but Scott has found a correlation with lightning strikes as well, revealed in Environmental Research Letters. The connection may not been spotted before because electrical activity can last for more than a month after the arrival of a large dose of particles.
Scott found a 31% increase in average lightning strikes over central England (422 to 321) in the 40 days after major solar wind events compared to the days beforehand. Lightning peaked 12-18 days after the wind’s arrival. A matching increase in thundery days provided supporting evidence. Since satellite observations can pick up the conditions for such events weeks beforehand there is potential for long term forecasting of when the danger of lightning is highest.
“It’s unexpected,” Scott told the BBC. “Because these streams of particles bring with them an enhanced magnetic field – and this shields Earth from the very high-energy cosmic rays from outside of the Solar System.” The reduction in cosmic rays is only around 1%, but still noticeable. Cosmic rays emitted by supernovae are thought to trigger lighting strikes, and it was expected that the shielding effect of the solar wind would cause a reduction in lightning, rather than an increase. The solar wind particles, while more numerous, are also lower energy than those from cosmic rays, and therefore not as likely to have trigger the cascade of runaway electrons thought to link cosmic rays to lightning.  Moreover, past studies have found sunspot numbers negatively correlate with thunder days in other parts of the world.
If the relationship can be settled the implications are significant. Lightning is estimated to cause 24,000 deaths and ten times as many injuries each year worldwide. Even a small improvement in our capacity to predict it could save lives.
High speed streams were found to occur after periods when the sun was putting out less light, but sunspot numbers increased. Scott and his fellow authors attribute this to the streams coming from an active region appearing on the eastern side of the sun.
In addition to these puzzles Scott says we have plenty to learn about how solar energetic protons (SEPs) interact with the atmosphere. “We propose that these particles, while not having sufficient energies to reach the ground and be detected there, nevertheless electrify the atmosphere as they collide with it, altering the electrical properties of the air and thus influencing the rate or intensity at which lightning occurs,” Scott said.

Inevitably those who deny human involvement in climate change will seize on the findings as evidence that warming is driven by changes in the sun. However, such claims have been comprehensively refuted on numerous occasions. Sun spots and solar flares experience a strong 11 year cycle. If these, or anything correlating with them, were the major drivers of planet-wide temperature changes we would see a much stronger pattern over this cycle than we do.

Sun Could Unleash Devastating ‘Superflare’


The sun is capable of firing off an incredibly powerful superflare that could wreak havoc on Earth’s technology-dependent society, a new study suggests.

The same basic processes drive the “normal” flares of high-energy radiation emitted by the sun and superflares blasted out by faraway stars, which can be thousands of times more powerful, researchers found.

This result “supports the hypothesis that the sun is able to produce a potentially devastating superflare,” study co-author Anne-Marie Broomhall, from the University of Warwick in England, said in a statement.

The research team analyzed a superflare emitted by the binary star KIC9655129, which lies about 1,500 light-years from Earth, using NASA’s planet-hunting Kepler space telescope.

Kepler is sensitive enough to pick up tiny brightness fluctuations coming from stars. Indeed, that’s how the telescope finds planets. (Subtle brightness dips can be caused by orbiting worlds crossing their stars’ faces, as seen from Kepler’s perspective.)

Observations made using Kepler revealed key similarities between KIC9655129’s superflare and eruptions on Earth’s sun, researchers said.

“Occasionally, solar flares contain multiple waves superimposed on top of one another,” lead author Chloe Pugh, also of the University of Warwick, said in the same statement. “We have found evidence for multiple waves, or multiple periodicities, in a stellar superflare, and the properties of these waves are consistent with those that occur in solar flares.”

Strong solar flares can cause temporary radio blackouts, and they’re often accompanied by massive explosions of solar plasma called coronal mass ejections (CMEs) that can be even more disruptive. Powerful CMEs that hit Earth, for example, can trigger geomagnetic storms that affect GPS navigation, radio communications and power grids for extended periods of time.

So the consequences of a superflare (and possible associated super-CME) could be disastrous, Pugh said.

But you shouldn’t worry too much about this worst-case scenario, she added.

“Fortunately, the conditions needed for a superflare are extremely unlikely to occur on the sun, based on previous observations of solar activity,” Pugh said.

The new study was published in The Astrophysical Journal Letters.

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How Solar Flares Make Matter Move at (Nearly) the Speed of Light


Solar flares aren’t just fearsome displays of power capable of sending Earth’s technology back 200 years. They are also peculiar stellar phenomena that generate so much energy, they make particles move at nearly the speed of light. To that end, they may be models of future space travel. But how exactly they work that kind of magic stumps the scientific community.

A new study published Thursday in the journal Science might have some answers. Using data gathered by the National Science Foundations’ Karl G. Jansky Very Large Array radio telescope, Bin Chen and others at the Harvard-Smithsonian Center for Astrophysics have put forth a proposal involving something they call “termination shock.”

When solar flares erupt off the surface of the sun, they eject big amounts of material out into space. These eruptions are thought to be caused by the sudden reconfiguration of magnetic fields, but it was still unclear how and why magnetic behavior was responsible for firing charged particles off at such high speeds.

Through the VLA, Chen and his colleagues found that fast plasma flows during a solar fare can impact dense magnetic loops and create a stationery shock — or termination shock — that repeatedly hits particles and accelerates them to faster speeds.

“Our work made a significant progress in understanding this physical process,” says Chen. He says the findings also have “implications for other fields in space physics and astrophysics, because particle acceleration is not only an important aspect of solar flares, but also a fundamental physical process occurring throughout the universe.”

Chen emphasizes that these observations wouldn’t have been possible without recent upgrades to the VLA, allowing astronomers to take up to 40,000 individual radio images in a single second. “This raw power of the VLA is the key to probing the radio emission associated with the flare termination shock,” he says.


Though fascinating, the findings are just the first step for understanding the role of termination shock in solar flares. “We would like to observe more solar flare events like this to see whether or how the situation would change under different physical conditions,” says Chen.

Unfortunately, the VLA isn’t designed for such a high degree of solar research. Chen hopes to follow up on this reproach using the Owens Valley Solar Array operated by the New Jersey Institute of Technology, where he will be next spring.


NASA: Sun has Flipped Upside Down


The sun has fully “flipped upside down”, with its north and south poles reversed to reach the midpoint of Solar Cycle 24, Nasa has said.

Now, the magnetic fields have once again started moving in opposite directions to begin the completion of the 22 year long process which will culminate in the poles switching once again.

“A reversal of the sun’s magnetic field is, literally, a big event,” said Nasa’s Dr. Tony Phillips.

“The domain of the sun’s magnetic influence (also known as the ‘heliosphere’) extends billions of kilometers beyond Pluto. Changes to the field’s polarity ripple all the way out to the Voyager probes, on the doorstep of interstellar space.”

To mark the event, Nasa has released a visualisation of the entire process.

At the beginning, in 1997, the video shows the sun with its positive polarity on the top (the green lines), and the negative polarity on the bottom (the purple lines).

Over the next 11 years, each set of lines gradually move toward the opposite pole, eventually showing a complete flip.

By the end, both set of lines representing the opposing magnetic fields begin to work their way back, which will eventually culminate in the completion of the full 22 year magnetic solar cycle in approximately 11 years, before the whole process starts over again.

“At the height of each magnetic flip, the sun goes through periods of more solar activity, during which there are more sunspots, and more eruptive events such as solar flares and coronal mass ejections,” said Nasa’s Karen C. Fox.

“Cosmic rays are also affected,” added Dr. Phillips. “These are high-energy particles accelerated to nearly light speed by supernova explosions and other violent events in the galaxy.”


Does the Earth’s Magnetic Field Influence Suicide Rates?


Many animals can sense the Earth’s magnetic field, so why not people, asks Oleg Shumilov of the Institute of North Industrial Ecology Problems in Russia.

Shumilov looked at activity in the Earth’s geomagnetic field from 1948 to 1997 and found that it grouped into three seasonal peaks every year: one from March to May, another in July and the last in October.

Surprisingly, he also found that the geomagnetism peaks matched up with peaks in the number of suicides in the northern Russian city of Kirovsk over the same period.

Shumilov acknowledges that a correlation like this does not necessarily mean there is a causal link, but he points out that there have been several other studies suggesting a link between human health and geomagnetism.

For example, a 2006 review of research on cardiovascular health and disturbances in the geomagnetic field in the journal Surveys in Geophysics (DOI: 10.1007/s10712-006-9010-7) concluded that a link was possible and that the effects seemed to be more pronounced at high latitudes.

Twinned peaks

The review’s author, Michael Rycroft, formerly head of the European Geosciences Society, says that geomagnetic health problems affect 10 to 15% of the population.

“Others have found similar things [to Shumilov’s results] in independent sets of data,” says Rycroft. “It suggests something may be linking the two factors.”

A 2006 Australian study, for example, also found a correlation between peaks in suicide numbers and geomagnetic activity (Bioelectromagnetics, vol. 27 p 155).

Brain storms

Psychiatrists too have noticed a correlation between geomagnetic activity and suicide rates. A review of 13 years of South African data on suicides and magnetic storms in South African Psychiatry Review, vol. 6 p. 24) suggested a link.

Geomagnetic storms – periods of high geomagnetic activity caused by large solar flares – have also been linked to clinical depression.

In 1994, a study was published suggesting a 36.2% increase in the number of men admitted into hospital for depression in the second week after geomagnetic storms (British Journal of Psychiatry vol 164, p 403).

What may be the cause of the link, if there is one, remains unknown. “The intriguing correlation between geomagnetism and suicide justifies more research into its mechanism,” says Rycroft.

Environmental cue?

“The most plausible explanation for the association between geomagnetic activity and depression and suicide is that geomagnetic storms can desynchronise circadian rhythms and melatonin production,” says Kelly Posner, a psychiatrist at Columbia University in the US.

The pineal gland, which regulates circadian rhythm and melatonin production, is sensitive to magnetic fields. “The circadian regulatory system depends upon repeated environmental cues to [synchronise] internal clocks,” says Posner. “Magnetic fields may be one of these environmental cues.”

Geomagnetic storms could disrupt body clocks, precipitating seasonal affective disorder and therefore increase suicide risk, Posner told New Scientist.

There seems little doubt that the brain responds to electromagnetic fields – coils that generate electromagnetic fields can trigger muscular twitches when placed over a person’s skull.

However, Shumilov, who was presenting his data at the European Geoscience Union (EGU) annual meeting in Vienna, Austria, last week, does not believe geomagnetic activity influences everyone equally.

Suicide statistics

He also presented hospital data from 6000 pregnant women who had routine scans of their fetus’s heart rates between 1995 and 2003. In 15% of the fetuses, periods of disturbances in their heart rates coincided with periods of high geomagnetic activity.

Shumilov accepts that light levels in northern countries can influence depression, but believes that geomagnetism may be another factor, and one that is under-appreciated.

The trouble with studying the causes of suicide is that it is a rare condition, says Klaus Ebmeier, a psychiatrist at the University of Oxford. “You are bound to get spurious effects. A study of the causes would have to enrol a country’s entire population.”

Cosmo Hallstrom, a member of the Royal College of Psychiatrists, agrees. “You have to be very careful with suicide statistics,” he says. “Countries report them differently. Catholic countries are very reluctant to diagnose suicide. Scandinavian countries consider it a social injustice not to.”