Large coronal hole near the sun's north pole

The European Space Agency/NASA Solar and Heliospheric Observatory, or SOHO, captured this image of a gigantic coronal hole hovering over the sun’s north pole on July 18, 2013, at 9:06 a.m. EDT.
Credit: ESA & NASA/SOHO

The European Space Agency/NASA Solar and Heliospheric Observatory, or SOHO, captured this image of a gigantic coronal hole hovering over the sun's north pole on July 18, 2013, at 9:06 a.m. EDT. Coronal holes are dark, low density regions of the sun's outermost atmosphere, the corona. They contain little solar material, have lower temperatures, and therefore, appear much darker than their surroundings.

Coronal holes are a typical feature on the sun, though they appear at different places and with more frequency at different times of the sun's activity cycle. The activity cycle is currently ramping up toward what is known as solar maximum, currently predicted for late 2013. During this portion of the cycle, the number of coronal holes decreases. During solar max, the magnetic fields on the sun reverse and new coronal holes appear near the poles with the opposite magnetic alignment. The coronal holes then increase in size and number, extending further from the poles as the sun moves toward solar minimum again. At such times, coronal holes have appeared that are even larger than this one.

The holes are important to our understanding of space weather, as they are the source of a high-speed wind of solar particles that streams off the sun some three times faster than the slower wind elsewhere. While it's unclear what causes coronal holes, they correlate to areas on the sun where magnetic fields soar up and away, failing to loop back down to the surface, as they do elsewhere.

Source: NASA/Goddard Space Flight Center

NASA's SDO sees massive filament erupt on sun

Eruptive events on the sun can be wildly different. Some come just with a solar flare, some with an additional ejection of solar material called a coronal mass ejection (CME), and some with complex moving structures in association with changes in magnetic field lines that loop up into the sun's atmosphere, the corona. Credit: Image courtesy of NASA/Goddard Space Flight Center

Eruptive events on the sun can be wildly different. Some come just with a solar flare, some with an additional ejection of solar material called a coronal mass ejection (CME), and some with complex moving structures in association with changes in magnetic field lines that loop up into the sun's atmosphere, the corona.

On July 19, 2012, an eruption occurred on the sun that produced all three. A moderately powerful solar flare exploded on the sun's lower right limb, sending out light and radiation. Next came a CME, which shot off to the right out into space. And then, the sun treated viewers to one of its dazzling magnetic displays -- a phenomenon known as coronal rain.

Over the course of the next day, hot plasma in the corona cooled and condensed along strong magnetic fields in the region. Magnetic fields, themselves, are invisible, but the charged plasma is forced to move along the lines, showing up brightly in the extreme ultraviolet wavelength of 304 Angstroms, which highlights material at a temperature of about 50,000 Kelvin. This plasma acts as a tracer, helping scientists watch the dance of magnetic fields on the sun, outlining the fields as it slowly falls back to the solar surface.

Source: NASA/Goddard Space Flight Center

Origin of long-standing space mystery revealed: Origin of the 'theta aurora'

The night side of the terrestrial magnetosphere forms a structured magnetotail, consisting of a plasma sheet at low latitudes that is sandwiched between two regions called the magnetotail lobes. The lobes consist of the regions in which Earth's magnetic field lines are directly connected to the magnetic field carried by the solar wind. Different plasma populations are observed in these regions -- plasma in the lobes is very cool, whereas the plasma sheet is more energetic. The diagram labels by two red dots the location of an ESA Cluster satellite and NASA's IMAGE satellite on 15 September 2005, when particular conditions of the magnetic field configuration gave rise to a phenomenon known as 'theta aurora.'  Credit: ESA/NASA/SOHO/LASCO/EIT

University of Southampton researcher has helped solve a long-standing space mystery -- the origin of the 'theta aurora'.

Auroras are the most visible manifestation of the Sun's effect on Earth. They are seen as colourful displays in the night sky, known as the Northern or Southern Lights. They are caused by the solar wind, a stream of plasma -- electrically charged atomic particles -- carrying its own magnetic field, interacting with Earth's magnetic field.

Normally, the main region for this impressive display is the 'auroral oval', which lies at around 65-70 degrees north or south of the equator, encircling the polar caps.
However, auroras can occur at even higher latitudes. One type is known as a 'theta aurora' because seen from above it looks like the Greek letter theta -- an oval with a line crossing through the centre.

While the cause of the auroral oval emissions is reasonably well understood, the origin of the theta aurora was unclear until now.

Researchers observed particles in the two 'lobe' regions of the magnetosphere. The plasma in the lobes is normally cold, but previous observations suggested that theta auroras are linked with unusually hot lobe plasma.

Dr Robert Fear from the University of Southampton (formerly at the University of Leicester, where much of the research took place), and lead author of the paper published in Science this week, says: "Previously it was unclear whether this hot plasma was a result of direct solar wind entry through the lobes of the magnetosphere, or if the plasma is somehow related to the plasma sheet on the night side of Earth.

"One idea is that the process of magnetic reconnection on the night side of Earth causes a build-up of 'trapped' hot plasma in the higher latitude lobes."

The mystery was finally solved by studying data collected simultaneously by the European Space Agency's (ESA) Cluster and NASA's IMAGE satellites on 15 September 2005. While the four Cluster satellites were located in the southern hemisphere magnetic lobe, IMAGE had a wide-field view of the southern hemisphere aurora. As one Cluster satellite observed uncharacteristically energetic plasma in the lobe, IMAGE saw the 'arc' of the theta aurora cross the magnetic footprint of Cluster.

"We found that the energetic plasma signatures occur on high-latitude magnetic field lines that have been 'closed' by the process of magnetic reconnection, which then causes the plasma to become relatively hot," says Dr Fear.

"Because the field lines are closed, the observations are incompatible with direct entry from the solar wind. By testing this and other predictions about the behaviour of the theta aurora, our observations provide strong evidence that the plasma trapping mechanism is responsible for the theta aurora," he adds.

"The study highlights the intriguing process that can occur in the magnetosphere when the interplanetary magnetic field of the solar wind points northwards," adds Philippe Escoubet, ESA's Cluster project scientist.

"This is the first time that the origin of the theta aurora phenomenon has been revealed, and it is thanks to localised measurements from Cluster combined with the wide-field view of IMAGE that we can better understand another aspect of the Sun-Earth connection," he adds.

Source: University of Southampton

Physicist presents new observational solar weather model

An observation-based model presented in China by physicist Dr. S.T. Wu makes it possible to predict solar weather. Credit: Michael Mercier / UAH

Scientists now have an observational framework to help predict solar weather and how it will affect Earth.

"Now it's possible that we can have a space weather model that's like Earth's meteorology," says physicist Dr. S.T. Wu, distinguished professor emeritus of The University of Alabama in Huntsville (UAH) Department of Mechanical and Aerospace Engineering.

That's thanks to the observation-based model that predicts the occurrence and timing of solar mass ejections recently presented by Dr. Wu at the Scientific Committee on Solar-Terrestrial Physics' (SCOSTEP's) 13th Quadrennial Solar-Terrestrial Physics Symposium in Xi'An, China.

Being able to predict such events is important because a powerful direct hit by a coronal mass ejection (CME) is like a huge space hurricane that can deform Earth's magnetic field and fry the circuits of orbiting satellites, spacecraft and delicate terrestrial electronics.

In a large-scale storm, cell service would stop, air traffic control would lose its eyes and ears, and everything could be affected from traffic light control to the automated heating and cooling of buildings to the critical systems that control nuclear armaments. Earth would become largely dark as power grids blink offline.

The solar radiation could directly affect the health of humans, too, Dr. Wu says.

"If you travel to the Pacific, the airlines like to fly you there over the North Pole," he says. "That is the most direct route. But during a coronal event, the solar radiation can affect people, so the airlines try to avoid it by flying below the polar route."

Diverting around the polar route is necessary but costs extra time and money, Dr. Wu says, which is why the National Oceanic and Atmospheric Administration meets with airlines annually about possible upcoming events. Better predictions would help airlines.

The new predictive model is the culmination of decades of work by Dr. Wu, the founder and first director of UAH's Center for Space Plasma and Aeronomic Research (CSPAR). He wrote his first research paper on the subject of CME modeling in 1978.

The new model advances previous CME work by Dr. Wu and a global research group that includes his former students and post-doctoral students. Working with Dr. Wu are Dr. Chaowei Jiang of CSPAR and Dr. Xueshang Feng, Dr. Yufen Zhou and Dr. Qiang Hu of China's State Key Laboratory of Space Weather, Solar-Interplanetary-GeoMAgnetic Weather Group (SIGMA Weather Group).

In the previous work, Dr. Wu's team devised a model for the development of CMEs that was tested and proven against CMEs observed in the past. The scientists also modeled the conditions that are present in solar magnetic shear -- a sigmoidal twisting of the sun's magnetic field, flux emergence, null formation, torus instability, reconnection and free energy that can cause a CME. Their mathematical model of developing coronal mass ejections was shown to be accurate by comparison with actual observed phenomena from spacecraft tracking events on the sun's surface.

The researchers successfully performed a data-driven magnetohydrodynamic (MHD) simulation of a realistic CME initiation process, a step that helped lead to the predictive model and to better understanding the precursors to these solar storms. "Last time, we only modeled a coronal mass ejection," Dr. Wu says. "Now, we have put that eruption result into our propagation model. We have integrated what we did before into a global propagation model."

The predictive model can foresee the development and impacts of a CME from its genesis on the sun through its journey in the interplanetary medium and to its interaction with Earth.

The presentation was well received by the scientists at the conference because "I didn't use any theoretical inputs," says Dr. Wu.

"Others are doing this work, but they are still using theoretical models, but our work is observational, and that is the difference," he says. "It is more realistic because we start out from the sun and what you can see there, and then we work our way out."

The model provides important information to other scientists working on solar storm prediction.

"I've got the fram

ework that says it can be done, so now everybody can do it," says Dr. Wu. Further development of an accurate solar weather prediction system will take supercomputers and the efforts of many researchers and universities, he says. "Now, everybody can jump in with their own research."

Arriving at the working model caps took 36 years of research for Dr. Wu, a period of time he puts in perspective by talking about the development of meteorology.

"It took 60 years to develop accurate meteorology on Earth," he says. "Everybody knows we needed to do this, but finally we got a result. I feel really good about that I can get a handle on it."

Source:  University of Alabama Huntsville

The Fierce 2012 magnetic storm just missed us: Earth dodged huge magnetic bullet from the sun

This image captured on July 23, 2012, at 12:24 a.m. EDT, shows a coronal mass ejection that left the sun at the unusually fast speeds of over 1,800 miles per second. Credit: NASA/STEREO

Earth dodged a huge magnetic bullet from the sun on July 23, 2012.
According to University of California, Berkeley, and Chinese researchers, a rapid succession of coronal mass ejections -- the most intense eruptions on the sun -- sent a pulse of magnetized plasma barreling into space and through Earth's orbit. Had the eruption come nine days earlier, it would have hit Earth, potentially wreaking havoc with the electrical grid, disabling satellites and GPS, and disrupting our increasingly electronic lives.

The solar bursts would have enveloped Earth in magnetic fireworks matching the largest magnetic storm ever reported on Earth, the so-called Carrington event of 1859. The dominant mode of communication at that time, the telegraph system, was knocked out across the United States, literally shocking telegraph operators. Meanwhile, the Northern Lights lit up the night sky as far south as Hawaii.

In a paper appearing today (Tuesday, March 18) in the journal Nature Communications, former UC Berkeley postdoctoral fellow and research physicist Ying D. Liu, now a professor at China's State Key Laboratory of Space Weather, UC Berkeley research physicist Janet G. Luhmann and their colleagues report their analysis of the magnetic storm, which was detected by NASA's STEREO A spacecraft.
"Had it hit Earth, it probably would have been like the big one in 1859, but the effect today, with our modern technologies, would have been tremendous," said Luhmann, who is part of the STEREO (Solar Terrestrial Observatory) team and based at UC Berkeley's Space Sciences Laboratory.

A study last year estimated that the cost of a solar storm like the Carrington Event could reach $2.6 trillion worldwide. A considerably smaller event on March 13, 1989, led to the collapse of Canada's Hydro-Quebec power grid and a resulting loss of electricity to six million people for up to nine hours.
"An extreme space weather storm -- a solar superstorm -- is a low-probability, high-consequence event that poses severe threats to critical infrastructures of the modern society," warned Liu, who is with the National Space Science Center of the Chinese Academy of Sciences in Beijing. "The cost of an extreme space weather event, if it hits Earth, could reach trillions of dollars with a potential recovery time of 4-10 years. Therefore, it is paramount to the security and economic interest of the modern society to understand solar superstorms."

Based on their analysis of the 2012 event, Liu, Luhmann and their STEREO colleagues concluded that a huge outburst on the sun on July 22 propelled a magnetic cloud through the solar wind at a peak speed of more than 2,000 kilometers per second -- four times the typical speed of a magnetic storm. It tore through Earth's orbit but, luckily, Earth and the other planets were on the other side of the sun at the time. Any planets in the line of sight would have suffered severe magnetic storms as the magnetic field of the outburst tangled with the planets' own magnetic fields.

The researchers determined that the huge outburst resulted from at least two nearly simultaneous coronal mass ejections (CMEs), which typically release energies equivalent to that of about a billion hydrogen bombs. The speed with which the magnetic cloud plowed through the solar wind was so high, they concluded, because another mass ejection four days earlier had cleared the path of material that would have slowed it down.

"The authors believe this extreme event was due to the interaction of two CMEs separated by only 10 to 15 minutes," said Joe Gurman, the project scientist for STEREO at NASA's Goddard Space Flight Center in Greenbelt, Md.

One reason the event was potentially so dangerous, aside from its high speed, is that it produced a very long-duration, southward-oriented magnetic field, Luhmann said. This orientation drives the largest magnetic storms when they hit Earth because the southward field merges violently with Earth's northward field in a process called reconnection. Storms that normally might dump their energy only at the poles instead dump it into the radiation belts, ionosphere and upper atmosphere and create auroras down to the tropics.

"These gnarly, twisty ropes of magnetic field from coronal mass ejections come blasting from the sun through the ambient solar system, piling up material in front of them, and when this double whammy hits Earth, it skews the Earth's magnetic field to odd directions, dumping energy all around the planet," she said. "Some of us wish Earth had been in the way; what an experiment that would have been."
"People keep saying that these are rare natural hazards, but they are happening in the solar system even though we don't always see them," she added. "It's like with earthquakes -- it is hard to impress upon people the importance of preparing unless you suffer a magnitude 9 earthquake."

All this activity would have been missed if STEREO A -- the STEREO spacecraft ahead of us in Earth's orbit and the twin to STEREO B, which trails in our orbit -- had not been there to record the blast.

The goal of STEREO and other satellites probing the magnetic fields of the sun and Earth is to understand how and why the sun sends out these large solar storms and to be able to predict them during the sun's 11-year solar cycle. This event was particularly unusual because it happened during a very calm solar period.

"Observations of solar superstorms have been extremely lacking and limited, and our current understanding of solar superstorms is very poor," Liu said. "Questions fundamental to solar physics and space weather, such as how extreme events form and evolve and how severe it can be at the Earth, are not addressed because of the extreme lack of observations."

Source: University of California - Berkeley