Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Solving the sun's super-heating mystery with Parker Solar Probe

05.06.2019

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.


Alfven waves still.

Credit: Michigan Engineering

In roughly two years, the probe will be the first man-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.

Please add links at bottom:

Strong Preferential Ion Heating is Limited to within the Solar Alfven Surface: https://iopscience.iop.org/article/10.3847/2041-8213/ab1de5

Justin Kasper: https://clasp.engin.umich.edu/people/justin-kasper/

Media Contact

Nicole Casal Moore
ncmoore@umich.edu
734-647-7087

 @umich

http://www.umich.edu/ 

Nicole Casal Moore | EurekAlert!
Further information:
http://dx.doi.org/10.3847/2041-8213/ab1de5

More articles from Physics and Astronomy:

nachricht Immortal quantum particles: the cycle of decay and rebirth
14.06.2019 | Technische Universität München

nachricht Small currents for big gains in spintronics
13.06.2019 | University of Tokyo

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: MPSD team discovers light-induced ferroelectricity in strontium titanate

Light can be used not only to measure materials’ properties, but also to change them. Especially interesting are those cases in which the function of a material can be modified, such as its ability to conduct electricity or to store information in its magnetic state. A team led by Andrea Cavalleri from the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg used terahertz frequency light pulses to transform a non-ferroelectric material into a ferroelectric one.

Ferroelectricity is a state in which the constituent lattice “looks” in one specific direction, forming a macroscopic electrical polarisation. The ability to...

Im Focus: Determining the Earth’s gravity field more accurately than ever before

Researchers at TU Graz calculate the most accurate gravity field determination of the Earth using 1.16 billion satellite measurements. This yields valuable knowledge for climate research.

The Earth’s gravity fluctuates from place to place. Geodesists use this phenomenon to observe geodynamic and climatological processes. Using...

Im Focus: Tube anemone has the largest animal mitochondrial genome ever sequenced

Discovery by Brazilian and US researchers could change the classification of two species, which appear more akin to jellyfish than was thought.

The tube anemone Isarachnanthus nocturnus is only 15 cm long but has the largest mitochondrial genome of any animal sequenced to date, with 80,923 base pairs....

Im Focus: Tiny light box opens new doors into the nanoworld

Researchers at Chalmers University of Technology, Sweden, have discovered a completely new way of capturing, amplifying and linking light to matter at the nanolevel. Using a tiny box, built from stacked atomically thin material, they have succeeded in creating a type of feedback loop in which light and matter become one. The discovery, which was recently published in Nature Nanotechnology, opens up new possibilities in the world of nanophotonics.

Photonics is concerned with various means of using light. Fibre-optic communication is an example of photonics, as is the technology behind photodetectors and...

Im Focus: Cost-effective and individualized advanced electronic packaging in small batches now available

Fraunhofer IZM is joining the EUROPRACTICE IC Service platform. Together, the partners are making fan-out wafer level packaging (FOWLP) for electronic devices available and affordable even in small batches – and thus of interest to research institutes, universities, and SMEs. Costs can be significantly reduced by up to ten customers implementing individual fan-out wafer level packaging for their ICs or other components on a multi-project wafer. The target group includes any organization that does not produce in large quantities, but requires prototypes.

Research always means trying things out and daring to do new things. Research institutes, universities, and SMEs do not produce in large batches, but rather...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

SEMANTiCS 2019 brings together industry leaders and data scientists in Karlsruhe

29.04.2019 | Event News

Revered mathematicians and computer scientists converge with 200 young researchers in Heidelberg!

17.04.2019 | Event News

First dust conference in the Central Asian part of the earth’s dust belt

15.04.2019 | Event News

 
Latest News

Concert of magnetic moments

14.06.2019 | Information Technology

Materials informatics reveals new class of super-hard alloys

14.06.2019 | Materials Sciences

New imaging modality targets cholesterol in arterial plaque

14.06.2019 | Medical Engineering

VideoLinks
Science & Research
Overview of more VideoLinks >>>