Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

NASA data shows surfer-shaped waves in near-Earth space

09.07.2015

The universe overflows with repeating patterns. From the smallest cells to the largest galaxies, scientists are often rewarded by observing similar patterns in vastly different places. One such pattern is the iconic surfer's waves seen on the ocean - a series of curled hills moving steadily in one direction. The shape has a simple cause. A fast fluid, say wind, moving past a slower one, say water, naturally creates this classic shape. Named Kelvin-Helmholtz waves in the late 1800s after their discoverers, these waves have since been discovered all over the universe: in clouds, in the atmospheres of other planets, and on the sun. Now two recently published papers highlight these shapely waves at the boundaries of near-Earth space.


This simulation shows the magnetic bubble around Earth, called the magnetosphere. As the the solar wind -- a steady flow of particles from the sun -- rushes by, it creates the shape of classic surfer waves known to scientists as Kelvin-Helmholtz waves.

Credits: S. Kavosi/J. Raeder/UNH

Scientists want to understand the details of what happens at those boundaries because various events there can disturb our space environment. When strong enough, this space weather can interrupt our communications systems or electronics on board satellites. While scientists have occasionally spotted Kelvin-Helmholtz waves at this boundary before - giving scientists reason to wonder if they could enhance or enable such space weather -- the new papers show the waves are much more common than expected. The second paper presents a case study describing a previously unobserved way in which the waves can be initiated. Together, the two sets of research suggest the waves may have more of an effect on our space environment than previously realized.

"We have known before that Kelvin-Helmholtz waves exist at the boundaries of Earth's magnetic environment - but they were considered relatively rare and thought to only appear under specialized conditions," said Shiva Kavosi, a space scientist at the University of New Hampshire in Durham, and first author on one of the papers, which appeared in Nature Communications on May 11, 2015. "It turns out they can appear under any conditions and are much more prevalent than we thought. They're present 20% of the time."

The waves are a direct result of the way our planet fits into the larger solar system. Planet Earth is a gigantic magnet and its magnetic influence extends outward in a large bubble called a magnetosphere. A constant flow of particles from the sun, called the solar wind, blows by the magnetosphere - not unlike a wind blowing over the surface of the ocean. During certain situations, particles and energy from the sun can breach the magnetosphere, crossing into near-Earth space. It is this influx that lies at the heart of the space weather events that can affect our technology closer to home.

To spot the frequency of the Kelvin-Helmholtz waves, the team relied on instrument data from two NASA spacecraft: the Advanced Composition Explorer, or ACE, and the Time History of Events and Macroscale Interactions during Substorms, or THEMIS. ACE sits between Earth and the sun, measuring the solar wind about 30-60 minutes before it makes contact with Earth's magnetosphere. THEMIS orbits Earth, regularly moving in and out of the magnetosphere boundaries. The researchers first established what the Kelvin-Helmholtz waves looked like with numerical simulations. They then used THEMIS observations to see when and where they occur. Next, they correlated what they saw at the magnetopause boundaries with what ACE measured in the solar wind. Previous theories suggested that the Kelvin-Helmholtz waves would only occur under very specific situations, such as when the solar wind's magnetic fields pointed in the same direction as Earth's. Unexpectedly, the team found that the Kelvin-Helmholtz waves appeared under a wide variety of conditions. Fast and slow winds and winds with magnetic fields pointed in any direction were all equally capable of producing these classic waves.

While the first paper compared Kelvin-Helmholtz waves to what was seen in the solar wind, the second team compared it to what was happening closer to Earth and provides a possible explanation as to why they may be observed so frequently. The second paper was released online in the Journal of Geophysical Research on June 26, 2015, and was conducted by Brian Walsh at Boston University and Evan Thomas, a student at Virginia Tech in Blacksburg, Virginia, who is collocated at NASA's Goddard Space Flight Center in Greenbelt, Maryland. Thomas works with data from a network of ground observatories known as SuperDARN, short for Super Dual Auroral Radar Network. These measure electric fields in near-Earth space. Walsh focuses on THEMIS data. Using the combined space- and ground-based observations, the team detected Kelvin-Helmholtz waves propagating down the side of the magnetosphere's boundary. THEMIS also spotted something else: Just before the waves began, a reservoir of charged gas around Earth - known as the plasmasphere - sent out a thin plume of plasma that traveled over 20,000 miles to contact the edges of the magnetosphere, depositing additional atoms into that crucial sun-Earth boundary.

Such plumes are fairly regular occurrences, but this is the first time they've been correlated with Kelvin-Helmholtz waves. This case study suggests that the plume itself may trigger the waves, perhaps because it increases the density at the magnetosphere boundary, thus creating a fluid that is substantially more sluggish than the faster solar wind blowing past - the necessary conditions for a Kelvin-Helmholtz wave.

"The theory of Kelvin-Helmholtz waves is well-developed, but we don't have many observations," said Thomas. "These new observations show that the waves are happening more often than expected and are probably more important than we thought - but we still don't know all the details."

Understanding that crucial magnetospheric boundary and how it can let in solar material requires an understanding of the variety of processes that can affect and disrupt it.

"There are a lot of processes proposed for how material enters into the magnetosphere," said Raeder. "And Kelvin-Helmholtz waves are one of them. Previously we thought the waves weren't happening often enough to have a strong effect, but if Kelvin-Helmholtz waves perturb the boundary and mix the solar material with near-Earth space, then that would be a way for the plasma from the solar wind to get into the magnetosphere."

Whether or not Kelvin-Helmholtz waves are a strong trigger for space weather events near Earth, these crucial details help paint a more complete picture of our magnetosphere, ultimately helping us to protect our home planet.

###

THEMIS and ACE are both operated under NASA's Explorer Program, which was conceived to provide frequent flight opportunities for world-class scientific investigations from space within the heliophysics and astrophysics science areas. NASA Goddard manages the program for the agency's Science Mission Directorate. SuperDARN is an international scientific radar network whose U.S. component is funded by the National Science Foundation under the Space Weather Research Program. The U.S. component is a collaboration between Virginia Tech as the lead institution and Dartmouth College, University of Alaska Fairbanks, and Johns Hopkins University Applied Physics Laboratory.

For more information about the THEMIS mission, visit:

http://www.nasa.gov/themis

For more information about the ACE mission, visit:

http://www.srl.caltech.edu/ACE/

Susan Hendrix | EurekAlert!

More articles from Physics and Astronomy:

nachricht NASA's fermi finds possible dark matter ties in andromeda galaxy
22.02.2017 | NASA/Goddard Space Flight Center

nachricht Tune your radio: galaxies sing while forming stars
21.02.2017 | Max-Planck-Institut für Radioastronomie

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: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Positrons as a new tool for lithium ion battery research: Holes in the electrode

22.02.2017 | Power and Electrical Engineering

New insights into the information processing of motor neurons

22.02.2017 | Life Sciences

Healthy Hiking in Smart Socks

22.02.2017 | Innovative Products

VideoLinks
B2B-VideoLinks
More VideoLinks >>>