Extreme Magnetic Storm: Red Aurora Over Kyoto In 1770

Auroras are lightshows that typically occur at high latitudes such as the Arctic and Antarctic; however, they expand equatorward under severe magnetic storms. Past observations of such unusual auroras can therefore allow us to determine the frequency and severity of magnetic storms. The more information that can be gathered about historic intense magnetic storms, the greater the opportunity to mitigate disruption of power grids in a future event.

Historical documents are becoming much more accessible for research as newly discovered records surface from private collections across the world. Researchers centered at Tokyo’s National Institute of Japanese Literature (NIJL) and National Institute for Polar Research (NIPR) examined a detailed painting from a Japanese manuscript Seikai (“understanding comets”) with associated commentary describes a red aurora occurring over Kyoto on 17 September 1770. Also investigated were detailed descriptions of the event from a newly discovered diary of the Higashi-Hakura family of Kyoto.

“The enthusiasm and dedication of amateur astronomers in the past provides us an exciting opportunity,” Kiyomi Iwahashi of NIJL says. “The diary was written by a kokugakusha [scholar of ancient Japanese culture], and provides a sophisticated description of the red aurora, including a description of the position of the aurora relative to the Milky Way.”

Using astrometric calculations of the elevations of the Milky Way as it would have been viewed from Kyoto on 17 September 1770, the researchers were able to calculate the geometry of the red aurora and check the results against the details from the Seikai painting and the diary. The success of the description of the aurora according to the historical documents allowed the researchers to estimate the strength of the magnetic storm that caused the September 1770 aurora.

“The magnetic storm on 17 September 1770 was comparable with or slightly larger than the September 1859 magnetic storm that occurred under the influence of the Carrington solar flare. The 1859 storm was the largest magnetic storm on record, in which technological effects were widely observed, “Ryuho Kataoka of NIPR says.” It was lucky for us that the 1770 storm predated our reliance on electricity.”

So how likely are such magnetic storms? ” We are currently within a period of decreasing solar activity, which may spell the end for severe magnetic storms in the near future,” Kataoka says. “However, we actually witnessed an extremely fast coronal mass ejection only several days ago [10 September 2017], which might be powerful enough to cause extreme storms. Fortunately, it just missed the Earth.”

Regardless of the specific likelihood of another perfect magnetic storm, interdisciplinary historical and scientific collaborations are invaluable in providing important physical details that could help us to understand the greatest magnetic storms in history and prepare for any potential future event.

Computer Simulations Provide Preview Of Upcoming Eclipse

A research team from Predictive Science Inc. (PSI) used the Stampede2 supercomputer at The University of Texas at Austin’s Texas Advanced Computing Center (TACC) to forecast the corona of the sun during the upcoming eclipse. The findings shed light on what the eclipse of the sun might look like Aug. 21 when it will be visible across much of the U.S., tracing a 70-mile-wide band across 14 states.

Beyond their rarity, solar eclipses help astronomers better understand the sun’s structure, inner workings and the space weather it generates.

The researchers completed a series of highly detailed solar simulations timed to the moment of the eclipse using TACC’s Stampede2, Comet at the San Diego Supercomputer Center, and NASA’s Pleiades supercomputer. They modeled the Sun’s surface and predicted what the solar corona—the aura of plasma that surrounds the sun and extends millions of kilometers into space—will look like during this eclipse.

“Advanced computational resources are crucial to developing detailed physical models of the solar corona and solar wind,” said Jon Linker, president and senior research scientist of PSI. “The growth in the power of these resources in recent years has fueled an increase in not only the resolution of these models, but the sophistication of the way the models treat the underlying physical processes as well.”

The researchers’ computer simulations were converted into scientific visualizations that approximate what the human eye might see during the solar eclipse.

The simulations are among the largest the research group has performed, using 65 million grid points to provide great accuracy and realism.

The team used data collected by the Helioseismic and Magnetic Imager aboard NASA’s Solar Dynamics Observatory and a combination of magnetic field maps, solar rotation rates and mathematical models of how magnetohydrodynamics (the interplay of electrically conducting fluids such as plasmas and magnetic fields) affect the corona.

Predictions about the appearance of the corona during an eclipse test complex, three-dimensional computational models of the Sun against visible reality.

Doing so improves the accuracy of predicting space weather, which could have important practical ramifications. If a powerful solar storm such as the 1859 Carrington Event—which led to auroras being visible as far south as the Caribbean and caused telegraphs to short and catch fire—were to hit Earth today, it would cause more than $2 trillion in damages, according a National Academy of Sciences report.

Predicting the arrival of such a solar storm in advance would allow officials to take the most critical electronic infrastructure offline and limit the storm’s impact. But doing so requires understanding how the visible surface of the Sun (the corona) relates to the mass ejections of plasma that cause space weather.

“With the ability to more accurately model solar plasmas, researchers will be able to better predict and reduce the impacts of space weather on key pieces of infrastructure that drive today’s digital world,” said Niall Gaffney, a former Hubble Space Telescope scientist and director of data intensive computing at TACC.

Day To Night And Back Again: Earth’s Ionosphere During The Total Solar Eclipse

On Aug. 21, 2017, the Moon will slide in front of the Sun and for a brief moment, day will melt into a dusky night. Moving across the country, the Moon’s shadow will block the Sun’s light, and weather permitting, those within the path of totality will be treated to a view of the Sun’s outer atmosphere, called the corona.

But the total solar eclipse will also have imperceptible effects, such as the sudden loss of extreme ultraviolet radiation from the Sun, which generates the ionized layer of Earth’s atmosphere, called the ionosphere. This ever-changing region grows and shrinks based on solar conditions, and is the focus of several NASA-funded science teams that will use the eclipse as a ready-made experiment, courtesy of nature.

NASA is taking advantage of the Aug. 21 eclipse by funding 11 ground-based science investigations across the United States. Three of these will look to the ionosphere in order to improve our understanding of the Sun’s relationship to this region, where satellites orbit and radio signals are reflected back toward the Earth.

“The eclipse turns off the ionosphere’s source of high-energy radiation,” said Bob Marshall, a space scientist at University of Colorado Boulder and principal investigator for one of the studies. “Without ionizing radiation, the ionosphere will relax, going from daytime conditions to nighttime conditions and then back again after the eclipse.”

Stretching from roughly 50 to 400 miles above Earth’s surface, the tenuous ionosphere is an electrified layer of the atmosphere that reacts to changes from both Earth below and space above. Such changes in the lower atmosphere or space weather can manifest as disruptions in the ionosphere that can interfere with communication and navigation signals.

“In our lifetime, this is the best eclipse to see,” said Greg Earle, an electrical and computer engineer at Virginia Tech in Blacksburg, Virginia, who is leading another of the studies. “But we’ve also got a denser network of satellites, GPS and radio traffic than ever before. It’s the first time we’ll have such a wealth of information to study the effects of this eclipse; we’ll be drowning in data.”

Pinning down ionospheric dynamics can be tricky. “Compared to visible light, the Sun’s extreme ultraviolet output is highly variable,” said Phil Erickson, a principal investigator of a third study and space scientist at Massachusetts Institute of Technology’s Haystack Observatory in Westford, Massachusetts.

“That creates variability in ionospheric weather. Because our planet has a strong magnetic field, charged particles are also affected along magnetic field lines all over the planet—all of this means the ionosphere is complicated.”

But when totality hits on Aug. 21, scientists will know exactly how much solar radiation is blocked, the area of land it’s blocked over and for how long. Combined with measurements of the ionosphere during the eclipse, they’ll have information on both the solar input and corresponding ionosphere response, enabling them to study the mechanisms underlying ionospheric changes better than ever before.

Tying the three studies together is the use of automated communication or navigation signals to probe the ionosphere’s behavior during the eclipse. During typical day-night cycles, the concentration of charged atmospheric particles, or plasma, waxes and wanes with the Sun.

“In the daytime, ionospheric plasma is dense,” Earle said. “When the Sun sets, production goes away, charged particles recombine gradually through the night and density drops. During the eclipse, we’re expecting that process in a much shorter interval.”

The denser the plasma, the more likely these signals are to bump into charged particles along their way from the signal transmitter to receiver. These interactions refract, or bend, the path taken by the signals. In the eclipse-induced artificial night the scientists expect stronger signals, since the atmosphere and ionosphere will absorb less of the transmitted energy.

“If we set up a receiver somewhere, measurements at that location provide information on the part of the ionosphere between the transmitter and receiver,” Marshall said. “We use the receivers to monitor the phase and amplitude of the signal. When the signal wiggles up and down, that’s entirely produced by changes in the ionosphere.”

Using a range of different electromagnetic signals, each of the teams will send signals back and forth across the path of totality. By monitoring how their signals propagate from transmitter to receiver, they can map out changes in ionospheric density. The teams will also use these techniques to collect data before and after the eclipse, so they can compare the well-defined eclipse response to the region’s baseline behavior, allowing them to discern the eclipse-related effects.

Probing the Ionosphere

The ionosphere is roughly divided into three regions in altitude based on what wavelength of solar radiation is absorbed: the D, E and F, with D being the lowermost region and F, the uppermost. In combination, the three experiment teams will study the entirety of the ionosphere.

Marshall and his team, from the University of Colorado Boulder, will probe the D-region’s response to the eclipse with very low frequency, or VLF, radio signals. This is the lowest and least dense part of the ionosphere—and because of that, the least understood.

“Just because the density is low, doesn’t mean it’s unimportant,” Marshall said. “The D-region has implications for communications systems actively used by many military, naval and engineering operations.”

Marshall’s team will take advantage of the U.S. Navy’s existing network of powerful VLF transmitters to examine the D-region’s response to changes in solar output. Radio wave transmissions sent from Lamoure, North Dakota, will be monitored at receiving stations across the eclipse path in Boulder, Colorado, and Bear Lake, Utah. They plan to combine their data with observations from several space-based missions, including NOAA’s Geostationary Operational Environmental Satellite, NASA’s Solar Dynamics Observatory and NASA’s Ramaty High Energy Solar Spectroscopic Imager, to characterize the effect of the Sun’s radiation on this particular region of the ionosphere.

Erickson and team will look further up, to the E- and F-regions of the ionosphere. Using over 6,000 ground-based GPS sensors alongside powerful radar systems at MIT’s Haystack Observatory and Arecibo Observatory in Puerto Rico, along with data from several NASA space-based missions, the MIT-based team will also work with citizen radio scientists who will send radio signals back and forth over long distances across the path.
MIT’s science team will use their data to track travelling ionospheric disturbances—which are sometimes responsible for space weather patterns in the upper atmosphere—and their large-scale effects. These disturbances in the ionosphere are often linked to a phenomenon known as atmospheric gravity waves, which can also be triggered by eclipses.

“We may even see global-scale effects,” Erickson said. “Earth’s magnetic field is like a wire that connects two different hemispheres together. Whenever electrical variations happen in one hemisphere, they show up in the other.”

Earle and his Virginia Tech-based team will station themselves across the country in Bend, Oregon; Holton, Kansas; and Shaw Air Force Base in Sumter, South Carolina. Using state-of-the-art transceiver instruments called ionosondes, they will measure the ionosphere’s height and density, and combine their measurements with data from a nation-wide GPS network and signals from the ham radio Reverse Beacon Network. The team will also utilize data from SuperDARN high frequency radars, two of which lie along the eclipse path in Christmas Valley, Oregon, and Hays, Kansas.

“We’re looking at the bottom side of the F-region, and how it changes during the eclipse,” Earle said. “This is the part of the ionosphere where changes in signal propagation are strong.” Their work could one day help mitigate disturbances to radio signal propagation, which can affect AM broadcasts, ham radio and GPS signals.

Ultimately, the scientists plan to use their data to improve models of ionospheric dynamics. With these unprecedented data sets, they hope to better our understanding of this perplexing region.

“Others have studied eclipses throughout the years, but with more instrumentation, we keep getting better at our ability to measure the ionosphere,” Erickson said. “It usually uncovers questions we never thought to ask.”

Sun’s Core Rotates Four Times Faster Than Its Surface

The Sun’s core rotates nearly four times faster than the sun’s surface, according to new findings by an international team of astronomers. Scientists had assumed the core was rotating like a merry-go-round at about the same speed as the surface.

“The most likely explanation is that this core rotation is left over from the period when the Sun formed, some 4.6 billion years ago,” said Roger Ulrich, a UCLA professor emeritus of astronomy, who has studied the sun’s interior for more than 40 years and co-author of the study that was published today in the journal Astronomy and Astrophysics. “It’s a surprise, and exciting to think we might have uncovered a relic of what the Sun was like when it first formed.”

The rotation of the solar core may give a clue to how the sun formed. After the Sun formed, the solar wind likely slowed the rotation of the outer part of the Sun, he said. The rotation might also impact sunspots, which also rotate, Ulrich said. Sunspots can be enormous; a single sunspot can even be larger than the Earth.

The researchers studied surface acoustic waves in the Sun’s atmosphere, some of which penetrate to the Sun’s core, where they interact with gravity waves that have a sloshing motion similar to how water would move in a half-filled tanker truck driving on a curvy mountain road. From those observations, they detected the sloshing motions of the solar core. By carefully measuring the acoustic waves, the researchers precisely determined the time it takes an acoustic wave to travel from the surface to the center of the Sun and back again. That travel time turns out to be influenced a slight amount by the sloshing motion of the gravity waves, Ulrich said.

The researchers identified the sloshing motion and made the calculations using 16 years of observations from an instrument called GOLF (Global Oscillations at Low Frequency) on a spacecraft called SoHO (the Solar and Heliospheric Observatory)—a joint project of the European Space Agency and NASA. The method was developed by the researchers, led by astronomer Eric Fossat of the Observatoire de la Côte d’Azur in Nice, France. Patrick Boumier with France’s Institut d’Astrophysique Spatiale is GOLF’s principal investigator and a co-author of the study.

The idea that the solar core could be rotating more rapidly than the surface has been considered for more than 20 years, but has never before been measured.

The core of the Sun differs from its surface in another way as well. The core has a temperature of approximately 29 million degrees Fahrenheit, which is 15.7 million Kelvin. The sun’s surface is “only” about 10,000 degrees Fahrenheit, or 5,800 Kelvin.

Ulrich worked with the GOLF science team, analyzing and interpreting the data for 15 years. Ulrich received funding from NASA for his research. The GOLF instrument was funded primarily by the European Space Agency.

SoHO was launched on Dec. 2, 1995 to study the Sun from its core to the outer corona and the solar wind; the spacecraft continues to operate.

Eclipse On August 21 Offers Unique Research Opportunities

In a briefing today on solar eclipse science, leading U.S. scientists highlighted research projects that will take place across the country during the upcoming August 21 solar eclipse. The research will advance our knowledge of the sun’s complex and mysterious magnetic field and its effects on Earth’s atmosphere and land.

Experts at the National Science Foundation (NSF), the National Aeronautics and Space Administration (NASA) and the National Center for Atmospheric Research (NCAR) discussed how scientists from coast to coast are preparing to deploy an array of technologies and methodologies to gain unprecedented views of the sun.

The experiments, led by specialized researchers, will also draw on observations by amateur sky watchers and students.

“This total solar eclipse across the United States is a unique opportunity in modern times, enabling the entire country to be engaged through modern technology and social media,” said Carrie Black, a program director in NSF’s Division of Atmospheric and Geospace Sciences. “Images and data from as many as millions of people will be collected and analyzed by scientists for years to come.”

“This is a generational event,” agreed Madhulika Guhathakurta, NASA lead scientist for the 2017 Eclipse. “This is going to be the most documented, the most appreciated, eclipse ever.”

The scientific experiments will take place along the path of totality, a 70-mile-wide ribbon where the moon will completely cover the sun; it stretches from Oregon to South Carolina.

Viewers in any one location may experience the total eclipse for as long as two minutes and 40 seconds. It will take about an hour and a half for the eclipse to travel across the sky from the Pacific Coast to the Atlantic.

For scientists, the celestial event is a rare opportunity to observe the elusive solar corona, the sun’s outer atmosphere, which is usually obscured by the sun’s bright surface.

Many scientific questions focus on the corona: Why is it much hotter than the sun’s surface? What role does it play in spewing large streams of charged particles, known as coronal mass ejections, which strike Earth’s atmosphere and can disrupt GPS systems and other sensitive technologies?

Black noted that during the eclipse the moon will align exactly with the sun’s surface and enable observations of the entire corona, including regions that are rarely detectable. “The moon is about as perfect an occulter as one can get,” she said.

Obtaining observations from the ground will play a particularly important part in the experiments, she explained, because far more data can be transmitted than would be possible from space-based instruments.

In addition to focusing ground-based instruments on the sun, scientists will also deploy aircraft to follow the eclipse, thereby increasing the amount of time they can make observations.

An NCAR research team, for example, will use the NSF/NCAR Gulfstream-V research aircraft to take infrared measurements for about four minutes, helping scientists better understand the solar corona’s magnetism and thermal structure.

Scientists at the Southwest Research Institute in Boulder, Colorado, will use visible and infrared telescopes on NASA’s twin WB-57 airplanes to enable a unique look at both the solar corona and Mercury for about eight minutes. The goals are to better understand the movement of energy through the corona and to learn more about the composition and properties of Mercury’s surface.

During the eclipse, scientists will also study Earth’s outer atmosphere, the ionosphere, a region of the atmosphere containing particles that are charged by solar radiation. Disturbances in the ionosphere can affect radio waves. Because the eclipse blocks energy from the sun, scientists can study the ionosphere’s response to a sudden drop in solar radiation.

For example, a Boston University research team will use off-the-shelf cellphone technology to construct a single-frequency GPS array of sensors to study the ionospheric effects of the eclipse. This project could lay the foundation for using consumer smartphones to help monitor the outer atmosphere for disturbances caused by solar storms.

In another experiment, a Virginia Tech team will use a network of radio receivers and transmitters across the country to observe the ionosphere, while researchers at the University of Virginia and George Mason University will use transmitters broadcasting at low frequencies to probe various regions of the ionosphere.

Citizen scientists are expected to play a major role in making valuable observations during the eclipse. “This is a social phenomenon, and we have a significant opportunity to promote this and do all the science we can,” Guhathakurta said. Black added, “What makes this an even more valuable opportunity is that everyone has access to it.”

The Citizen Continental-America Telescopic Eclipse (CATE) Experiment by the National Solar Observatory, for example, will rely on volunteers from universities, high schools, informal education groups, and national labs for an eclipse “relay race.” Participants spaced along the path of totality will use identical telescopes and digital camera systems to capture high-quality images that will result in a dataset capturing the entire 93-minute eclipse across the country.

And a project led by the University of California, Berkeley, will assemble a large number of solar images, obtained along the eclipse path by students and amateur observers, to create educational materials as part of an “Eclipse Megamovie.”

“As these projects show, the eclipse will place the sun firmly in the forefront of the national eye,” said Scott McIntosh, director of NCAR’s High Altitude Observatory. “This is a unique opportunity to communicate the fact that our star is complex, beautiful and mysterious. At the same time, it’s more critical than ever to study it, as solar activity can pose significant threats to our technologically driven society.”