Solving The Sun’s Super-Heating Mystery With Parker Solar Probe

It’s one of the greatest and longest-running mysteries surrounding, quite literally, our sun — why is its outer atmosphere hotter than its fiery surface?

University of Michigan researchers believe they have the answer, and hope to prove it with help from NASA’s Parker Solar Probe.

In roughly two years, the probe will be the first human-made craft to enter the zone surrounding the sun where heating looks fundamentally different that what has previously been seen in space. This will allow them to test their theory that the heating is due to small magnetic waves traveling back and forth within the zone.

Solving the riddle would allow scientists to better understand and predict solar weather, which can pose serious threats to Earth’s power grid. And step one is determining where the heating of the sun’s outer atmosphere begins and ends — a puzzle with no shortage of theories.

“Whatever the physics is behind this superheating, it’s a puzzle that has been staring us in the eye for 500 years,” said Justin Kasper, a U-M professor of climate and space sciences and a principal investigator for the Parker mission. “In just two more years, Parker Solar Probe will finally reveal the answer.”

The U-M theory, and how the team will use Parker to test it, is laid out in a paper published June 4 in The Astrophysical Journal Letters.

In this “zone of preferential heating” above the sun’s surface, temperatures rise overall. More bizarre still, individual elements are heated to different temperatures, or preferentially. Some heavier ions are superheated until they’re 10 times hotter than the hydrogen that is everywhere in this area — hotter than the core of the sun.

Such high temperatures cause the solar atmosphere to swell to many times the diameter of the sun and they’re the reason we see the extended corona during solar eclipses. In that sense, Kasper says, the coronal heating mystery has been visible to astronomers for more than a half millenium, even if the high temperatures were only appreciated within the last century.

This same zone features hydromagnetic “Alfvén waves” moving back and forth between its outermost edge and the sun’s surface. At the outermost edge, called the Alfvén point, the solar wind moves faster than the Alfvén speed, and the waves can no longer travel back to the sun.

“When you’re below the Alfvén point, you’re in this soup of waves,” Kasper said. “Charged particles are deflected and accelerated by waves coming from all directions.”

In trying to estimate how far from the sun’s surface this preferential heating stops, U-M’s team examined decades of observations of the solar wind by NASA’s Wind spacecraft.

They looked at how much of helium’s increased temperature close to the sun was washed out by collisions between ions in the solar wind as they traveled out to Earth. Watching the helium temperature decay allowed them to measure the distance to the outer edge of the zone.

“We take all of the data and treat it as a stopwatch to figure out how much time had elapsed since the wind was superheated,” Kasper said. “Since I know how fast that wind is moving, I can convert the information to a distance.”

Those calculations put the outer edge of the superheating zone roughly 10 to 50 solar radii from the surface. It was impossible to be more definitive since some values could only be guessed at.

Initially, Kasper didn’t think to compare his estimate of the zone’s location with the Alfvén point, but he wanted to know if there was a physically meaningful location in space that produced the outer boundary.

After reading that the Alfvén point and other surfaces have been observed to expand and contract with solar activity, Kasper and co-author Kristopher Klein, a former U-M postdoc and new faculty at University of Arizona, reworked their analysis looking at year-to-year changes rather than considering the entire Wind Mission.

“To my shock, the outer boundary of the zone of preferential heating and the Alfvén point moved in lockstep in a totally predictable fashion despite being completely independent calculations,” Kasper said. “You overplot them, and they’re doing the exact same thing over time.”

So does the Alfvén point mark the outer edge of the heating zone? And what exactly is changing under the Alfvén point that superheats heavy ions? We should know in the next couple of years. The Parker Solar Probe lifted off in August 2018 and had its first rendezvous with the sun in November 2018 — already getting closer to the sun than any other human-made object.

In the coming years, Parker will get even closer with each pass until the probe falls below the Alfvén point. In their paper, Kasper and Klein predict it should enter the zone of preferential heating in 2021 as the boundary expands with increasing solar activity. Then NASA will have information direct from the source to answer all manner of long-standing questions.

“With Parker Solar Probe we will be able to definitively determine through local measurements what processes lead to the acceleration of the solar wind and the preferential heating of certain elements,” Klein said. “The predictions in this paper suggest that these processes are operating below the Alfvén surface, a region close to the sun that no spacecraft has visited, meaning that these preferential heating processes have never before been directly measured.”

Kasper is the principal investigator of the Solar Wind Electrons Alphas and Protons Investigation on the Parker Solar Probe. SWEAP’s sensors scoop up the solar wind and coronal particles during each encounter to measure velocity, temperature and density, and shed light on the heating mystery.

The research is funded by NASA’s Wind Mission.

VLT Observes A Passing Double Asteroid Hurtling By Earth At 70 000 Km/h

The unique capabilities of the SPHERE instrument on ESO’s Very Large Telescope have enabled it to obtain the sharpest images of a double asteroid as it flew by Earth on 25 May. While this double asteroid was not itself a threatening object, scientists used the opportunity to rehearse the response to a hazardous Near-Earth Object (NEO), proving that ESO’s front-line technology could be critical in planetary defence.

The International Asteroid Warning Network (IAWN) coordinated a cross-organisational observing campaign of the asteroid 1999 KW4 as it flew by Earth, reaching a minimum distance of 5.2 million km on 25 May 2019. 1999 KW4 is about 1.3 km wide, and does not pose any risk to Earth. Since its orbit is well known, scientists were able to predict this fly-by and prepare the observing campaign.

ESO joined the campaign with its flagship facility, the Very Large Telescope (VLT). The VLT is equipped with SPHERE—one of the very few instruments in the world capable of obtaining images sharp enough to distinguish the two components of the asteroid, which are separated by around 2.6 km.

SPHERE was designed to observe exoplanets; its state-of-the-art adaptive optics (AO) system corrects for the turbulence of the atmosphere, delivering images as sharp as if the telescope were in space. It is also equipped with coronagraphs to dim the glare of bright stars, exposing faint orbiting exoplanets.

Taking a break from its usual night job hunting exoplanets, SPHERE data helped astronomers characterise the double asteroid. In particular, it is now possible to measure whether the smaller satellite has the same composition as the larger object.

“These data, combined with all those that are obtained on other telescopes through the IAWN campaign, will be essential for evaluating effective deflection strategies in the event that an asteroid was found to be on a collision course with Earth,” explained ESO astronomer Olivier Hainaut. “In the worst possible case, this knowledge is also essential to predict how an asteroid could interact with the atmosphere and Earth’s surface, allowing us to mitigate damage in the event of a collision.”

“The double asteroid was hurtling by the Earth at more than 70 000 km/h, making observing it with the VLT challenging,” said Diego Parraguez, who was piloting the telescope. He had to use all his expertise to lock on to the fast asteroid and capture it with SPHERE.

Bin Yang, VLT astronomer, declared “When we saw the satellite in the AO-corrected images, we were extremely thrilled. At that moment, we felt that all the pain, all the efforts were worth it.” Mathias Jones, another VLT astronomer involved in these observations, elaborated on the difficulties. “During the observations the atmospheric conditions were a bit unstable. In addition, the asteroid was relatively faint and moving very fast in the sky, making these observations particularly challenging, and causing the AO system to crash several times. It was great to see our hard work pay off despite the difficulties!”

While 1999 KW4 is not an impact threat, it bears a striking resemblance to another binary asteroid system called Didymos which could pose a threat to Earth sometime in the distant future.

Didymos and its companion called “Didymoon” are the target of a future pioneering planetary defence experiment. NASA’s DART spacecraft will impact Didymoon in an attempt to change its orbit around its larger twin, in a test of the feasibility of deflecting asteroids. After the impact, ESA’s Hera mission will survey the Didymos asteroids in 2026 to gather key information, including Didymoon’s mass, its surface properties and the shape of the DART crater.

The success of such missions depends on collaborations between organisations, and tracking Near-Earth Objects is a major focus for the collaboration between ESO and ESA. This cooperative effort has been ongoing since their first successful tracking of a potentially hazardous NEO in early 2014.

“We are delighted to be playing a role in keeping Earth safe from asteroids,” said Xavier Barcons, ESO’s Director General. “As well as employing the sophisticated capabilities of the VLT, we are working with ESA to create prototypes for a large network to take asteroid detection, tracking and characterization to the next level.”

This recent close encounter with 1999 KW4 comes just a month before Asteroid Day, an official United Nations day of education and awareness about asteroids, to be celebrated on 30 June.

Italy’s Mount Etna Volcano Spews Lava In New Active Phase

CATANIA, Sicily – Mount Etna, the largest of Italy’s three active volcanoes, is spewing ash and lava once again, but officials say the activity is taking place at its summit and does not pose a risk to people and towns.

Etna began a new phase of eruptions on Thursday as two new cracks in the volcano opened up, sending lava down its flank.

The volcano previously erupted in December. That eruption was linked to an earthquake which caused injuries and extensive damage to buildings on and near the volcano’s slopes.

Eugenio Privitera, the director in Catania of Italy’s National Institute of Geophysics and Volcanology, says this eruption is taking place at Etna’s summit and does not pose risks to residents. But he says visitors to Etna must stay away from the summit for their own safety.

Bali Volcano Spews Ash In New Eruption

A volcano on the Indonesian island of Bali erupted Friday, spewing a plume of ash and smoke more than 2,000 metres (6,500 feet) into the sky.

Mount Agung, about 70 kilometres from the tourist hub of Kuta, has been erupting periodically since it rumbled back to life in 2017, sometimes grounding flights and forcing residents to flee their homes.

The latest eruption shortly before noon on Friday shot a cloud of volcanic ash high into the sky, but caused no disruption to flights, Indonesia’s geological agency said.

Agung remained at the second highest danger warning level, and there is a four-kilometre no-go zone around the crater.

Last summer, dozens of flights were cancelled after Agung erupted, while tens of thousands of locals fled to evacuation centres after an eruption in 2017.

The last major eruption of Agung in 1963 killed around 1,600 people.

Indonesia is situated on the Pacific “Ring of Fire”, a vast zone of geological instability where the collision of tectonic plates causes frequent quakes and major volcanic activity.

Scientists Find Telling Early Moment That Indicates A Coming Megaquake

Scientists combing through databases of earthquakes since the early 1990s have discovered a possible defining moment 10-15 seconds into an event that could signal a magnitude 7 or larger megaquake.

Likewise, that moment—gleaned from GPS data on the peak rate of acceleration of ground displacement—can indicate a smaller event. GPS picks up an initial signal of movement along a fault similar to a seismometer detecting the smallest first moments of an earthquake.

Such GPS-based information potentially could enhance the value of earthquake early warning systems, such as the West Coast’s ShakeAlert, said Diego Melgar, a professor in the Department of Earth Sciences at the University of Oregon.

The physics-heavy analyses of two databases maintained by co-author Gavin P. Hayes of the U.S. Geological Survey’s National Earthquake Information Center in Colorado detected a point in time where a newly initiated earthquake transitions into a slip pulse where mechanical properties point to magnitude.

Melgar and Hayes also were able to identify similar trends in European and Chinese databases. Their study was detailed in the May 29 issue of the online journal Science Advances.

“To me, the surprise was that the pattern was so consistent, Melgar said. “These databases are made different ways, so it was really nice to see similar patterns across them.”

Overall, the databases contain data from more than 3,000 earthquakes. Consistent indicators of displacement acceleration that surface between 10-20 seconds into events were seen for 12 major earthquakes occurring in 2003-2016.

GPS monitors exist along many land-based faults, including at ground locations near the 620-mile-long Cascadia subduction zone off the U.S. Pacific Northwest coast, but their use is not yet common in real time hazard monitoring. GPS data shows initial movement in centimeters, Melgar said.

“We can do a lot with GPS stations on land along the coasts of Oregon and Washington, but it comes with a delay,” Melgar said. “As an earthquake starts to move, it would take some time for information about the motion of the fault to reach coastal stations. That delay would impact when a warning could be issued. People on the coast would get no warning because they are in a blind zone.”

This delay, he added, would only be ameliorated by sensors on the seafloor to record this early acceleration behavior.

Having these capabilities on the seafloor and monitoring data in real time, he said, could strengthen the accuracy of early warning systems. In 2016, Melgar, as a research scientist at Berkeley Seismological Laboratory in Berkeley, California, led a study published in Geophysical Research Letters that found real time GPS data could provide an additional 20 minutes of warning of a possible tsunami.

Japan already is laying fiber optic cable off its shores to boost its early warning capabilities, but such work is expensive and would be more so for installing the technology on the seafloor above the Cascadia fault zone, Meglar noted.

Melgar and Hayes came across the slip-pulse timing while scouring USGS databases for components that they could code into simulations to forecast what a magnitude 9 rupture of the Cascadia subduction zone would look like.

The subduction zone, which hasn’t had a massive lengthwise earthquake since 1700, is where the Juan de Fuca ocean plate dips under the North American continental plate. The fault stretches just offshore of northern Vancouver Island to Cape Mendocino in northern California.

6.6 Magnitude Earthquake Hits Off Coast Of El Salvador

A strong earthquake has hit off the coast of El Salvador, sending frightened residents running out of their homes in the predawn hours.

The U.S. Geological Survey says the quake had a preliminary magnitude of 6.6. Its epicenter was about 17 miles south-southeast of La Libertad, a suburb of the regional capital, Santa Tecla, and it was recorded at a depth of 65 kilometers (40 miles).

The earthquake was felt strongly in the capital, San Salvador, Thursday morning. People left their homes with flashlights, and power was knocked out in at least some areas.

At least seven aftershocks of between magnitude 4.1 and 5.0 were recorded, while El Salvador’s Ministry of Environment and Natural Resources warned of a possible tsunami and advised people to stay away from the Pacific Ocean for the next four hours.

Peru Earthquake Leaves One Dead And Several Injured

One person was killed and at least 11 people have been injured in Peru, with a further seven injuries in neighboring Ecuador, after an 8.0 magnitude earthquake struck northern Peru on Sunday morning.

Graphic shows large earthquake logo over broken earth and Richter scale reading

Peru’s National Emergency Operations Center reported the death of a 48-year-old man from the Cajamarca region in northwestern Peru following an earthquake in the country’s Amazon region.

The earthquake’s epicenter was at an approximate depth of 115 km, according to preliminary readings from the United States Geological Survey, and it was felt as far afield as Lima, Peru; Caracas, Venezuela; and Quito, Ecuador.

Ricardo Seijas, head of the emergency operations center, said the number of injured had risen to at least 11 people.

The emergency operations center reported numerous damages to buildings including five schools; two religious temples; and four health centers. Two additional health centers collapsed, said Seijas.

Peruvian President Martin Vizcarra has traveled to Yurimaguas, a city in the Peruvian Amazon that was among the hardest hit by the earthquake.

Vizcarra arrived with other top government officials, and said they are coordinating with local leaders to evaluate the damage.

The president said he himself, along with his transportation minister, will evaluate damage to roadways.

Other officials will evaluate damages to structures and any effect on a nearby reservoir, Vizcarra said.

Earlier in the day Vizcarra reported injuries as well as damages to homes and roadways, in a statement on state TV.

“We already have reports of injuries, of affected homes, collapsed highways and a bridge that connects Yurimaguas with Tarapoto has also collapsed,” Vizcarra said.

The country’s civil protection agency is sending teams to the affected areas, he added.

Five injuries were confirmed by the country’s health ministry on Twitter.

Two of the injured are from the city of Yurimaguas, and the other injuries were from other provinces in the Amazon region, the ministry said.

Ecuador’s Vice President Otto Sonnenholzner confirmed at least 7 injuries in the country as a result of the earthquake.

There are no immediate reports of infrastructure damage, he added.

Landslides have been reported in various parts of the country, according to Ecuador’s emergency management agency.

“The strong earthquake that occurred early this morning was felt in several regions of the country,” Peru’s Vizcarra tweeted earlier Sunday.

“We are evaluating the affected areas. I ask all of our citizens to remain calm.”

The earthquake was the strongest in Peru in 12 years, Vizcarra said.

Peru’s National Emergency Operations Center tweeted that the earthquake was felt in several regions of the country, and monitoring continues.

The country’s interior ministry tweeted photos of damaged houses in the northern Amazonas region, adding that police were on site to protect affected areas.

Ecuador’s President Lenín Moreno also tweeted: “I am awaiting of the information about the strong earthquake recorded this morning.”

In January 2018 a 7.1-magnitude earthquake hit southern Peru, killing two people.

At least 65 people were injured in the cities of Arequipa, Ica and Ayacucho in southern Peru, the National Civil Defense Institute reported.

On August 15, 2007 a magnitude 8.0 earthquake struck about 100 miles south of the Peruvian capital of Lima, killing approximately 514 people.