NASA Finds Unusual Origins Of High-Energy Electrons
Mysterious ‘megafast electrons’ are accelerated to the speed of light
just outside Earth’s magnetic field and scientists say strange
discovery could change particle physics forever
Findings change the accepted theories on how electrons can be accelerated not only in shocks near Earth, throughout the universe
‘Affects pretty much every field that deals with high-energy particles’
Astronomers have discovered electrons just outside the Earth’s magnetic field travelling at almost the speed of light and don’t know why.
This
image represents one of the traditional proposed mechanisms for
accelerating particles across a shock, called a shock drift
acceleration. The electrons (yellow) and protons (blue) can be seen
moving in the collision area where two hot plasma bubbles collide (red
vertical line). The cyan arrows represent the magnetic field and the
light green arrows, the electric field.
Nasa admits the the new results ‘provide the first steps towards an answer, while opening up more questions’.
The particles are disturbed in regions just outside of Earth’s magnetic field, and some are reflected into a turbulent region called the foreshock, where they are somehow ‘super accelerated’.
‘This affects pretty much every field that deals with high-energy particles, from studies of cosmic rays to solar flares and coronal mass ejections, which have the potential to damage satellites and affect astronauts on expeditions to Mars,’ said Lynn Wilson, lead author of the paper on these results at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
High above the surface, Earth’s magnetic field constantly deflects incoming supersonic particles from the sun.
High above the surface, Earth’s magnetic field constantly deflects incoming supersonic particles from the sun
What is EARTH’S MAGNETIC FIELDS:
High above the surface, Earth’s magnetic field constantly deflects incoming supersonic particles from the sun.
New observations from NASA’s THEMIS – short for Time History of Events and Macroscale Interactions during Substorms – mission show that this turbulent region can accelerate electrons up to speeds approaching the speed of light.
Such extremely fast particles have been observed in near-Earth space and many other places in the universe, but the mechanisms that accelerate them have never been understood.
Now, the researchers found electrons can be accelerated to extremely high speeds in a near-Earth region farther from Earth than previously thought possible – leading to new inquiries about what causes the acceleration.
HOW THE SOLAR WIND IS FORMED
The sun and its atmosphere are made of plasma – a mix of positively and negatively charged particles which have separated at extremely high temperatures, that both carries and travels along magnetic field lines.
Material from the corona streams out into space, filling the solar system with the solar wind.
But scientists found that as the plasma travels further away from the sun, things change. The sun begins to lose magnetic control, forming the boundary that defines the outer corona – the very edge of the sun.
The breakup of the rays is similar to the way water shoots out from a squirt gun.
First, the water is a smooth and unified stream, but it eventually breaks up into droplets, then smaller drops and eventually a fine, misty spray.
The images in a Nasa study capture the plasma at the same stage where a stream of water gradually disintegrates into droplets.
If charged particles from solar winds hit Earth’s magnectic field, this can cause problems for satellite and communication equipment.
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
THE THEMIS MISSION
The observations that led to this discovery were taken from one of the THEMIS – short for Time History of Events and Macroscale Interactions during Substorms mission satellites.
The five THEMIS satellites circled Earth to study how the planet’s magnetosphere captured and released solar wind energy, in order to understand what initiates the geomagnetic substorms that cause aurora.
The THEMIS orbits took the spacecraft across the foreshock boundary regions.
The new observations from NASA’s THEMIS short for Time History of Events and Macroscale Interactions during Substorms mission show that this turbulent region can accelerate electrons up to speeds approaching the speed of light.
These extremely fast particles have previously been observed in near-Earth space and many other places in the universe, but the mechanisms that accelerate them have never been understood.
Now, the researchers found electrons can be accelerated to extremely high speeds in a near-Earth region farther from Earth than previously thought possible – leading to new questions over how they become so fast.
These findings may change the accepted theories on how electrons can be accelerated not only in shocks near Earth, but also throughout the universe, Nasa says.
Having a better understanding of how particles are energized will help scientists and engineers better equip spacecraft and astronauts to deal with these particles, which can cause equipment to malfunction and affect space travelers.
The results, published in Physical Review Letters, describe how such particles may get accelerated in specific regions just beyond Earth’s magnetic field.
Typically, a particle streaming toward Earth first encounters a boundary region known as the bow shock, which forms a protective barrier between the solar wind, the continuous and varying stream of charged particles flowing from the sun, and Earth.
The magnetic field in the bow shock slows the particles, causing most to be deflected away from Earth, though some are reflected back towards the sun.
These reflected particles form a region of electrons and ions called the foreshock region.
Some of those particles in the foreshock region are highly energetic, fast moving electrons and ions.
Historically, scientists have thought one way these particles get to such high energies is by bouncing back and forth across the bow shock, gaining a little extra energy from each collision.
However, the new observations suggest the particles can also gain energy through electromagnetic activity in the foreshock region itself.
‘This is a puzzling case because we’re seeing energetic electrons where we don’t think they should be, and no model fits them,’ said David Sibeck, co-author and THEMIS project scientist at NASA Goddard.
‘There is a gap in our knowledge, something basic is missing.’
The electrons also could not have originated from the bow shock, as had been previously thought, the researchers say.
If the electrons were accelerated in the bow shock, they would have a preferred movement direction and location – in line with the magnetic field and moving away from the bow shock in a small, specific region.
However, the observed electrons were moving in all directions, not just along magnetic field lines.
Additionally, the bow shock can only produce energies at roughly one tenth of the observed electrons’ energies.
Instead, the cause of the electrons’ acceleration was found to be within the foreshock region itself.
‘It seems to suggest that incredibly small scale things are doing this because the large scale stuff can’t explain it,’ Wilson said.
Next, the researchers intend to gather more observations from THEMIS to determine the specific mechanism behind the electrons’ acceleration.
Findings change the accepted theories on how electrons can be accelerated not only in shocks near Earth, throughout the universe
‘Affects pretty much every field that deals with high-energy particles’
Astronomers have discovered electrons just outside the Earth’s magnetic field travelling at almost the speed of light and don’t know why.
This
image represents one of the traditional proposed mechanisms for
accelerating particles across a shock, called a shock drift
acceleration. The electrons (yellow) and protons (blue) can be seen
moving in the collision area where two hot plasma bubbles collide (red
vertical line). The cyan arrows represent the magnetic field and the
light green arrows, the electric field.Nasa admits the the new results ‘provide the first steps towards an answer, while opening up more questions’.
The particles are disturbed in regions just outside of Earth’s magnetic field, and some are reflected into a turbulent region called the foreshock, where they are somehow ‘super accelerated’.
‘This affects pretty much every field that deals with high-energy particles, from studies of cosmic rays to solar flares and coronal mass ejections, which have the potential to damage satellites and affect astronauts on expeditions to Mars,’ said Lynn Wilson, lead author of the paper on these results at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
High above the surface, Earth’s magnetic field constantly deflects incoming supersonic particles from the sun.
High above the surface, Earth’s magnetic field constantly deflects incoming supersonic particles from the sunWhat is EARTH’S MAGNETIC FIELDS:
High above the surface, Earth’s magnetic field constantly deflects incoming supersonic particles from the sun.
New observations from NASA’s THEMIS – short for Time History of Events and Macroscale Interactions during Substorms – mission show that this turbulent region can accelerate electrons up to speeds approaching the speed of light.
Such extremely fast particles have been observed in near-Earth space and many other places in the universe, but the mechanisms that accelerate them have never been understood.
Now, the researchers found electrons can be accelerated to extremely high speeds in a near-Earth region farther from Earth than previously thought possible – leading to new inquiries about what causes the acceleration.
HOW THE SOLAR WIND IS FORMEDThe sun and its atmosphere are made of plasma – a mix of positively and negatively charged particles which have separated at extremely high temperatures, that both carries and travels along magnetic field lines.
Material from the corona streams out into space, filling the solar system with the solar wind.
But scientists found that as the plasma travels further away from the sun, things change. The sun begins to lose magnetic control, forming the boundary that defines the outer corona – the very edge of the sun.
The breakup of the rays is similar to the way water shoots out from a squirt gun.
First, the water is a smooth and unified stream, but it eventually breaks up into droplets, then smaller drops and eventually a fine, misty spray.
The images in a Nasa study capture the plasma at the same stage where a stream of water gradually disintegrates into droplets.
If charged particles from solar winds hit Earth’s magnectic field, this can cause problems for satellite and communication equipment.
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 wavesTHE THEMIS MISSION
The observations that led to this discovery were taken from one of the THEMIS – short for Time History of Events and Macroscale Interactions during Substorms mission satellites.
The five THEMIS satellites circled Earth to study how the planet’s magnetosphere captured and released solar wind energy, in order to understand what initiates the geomagnetic substorms that cause aurora.
The THEMIS orbits took the spacecraft across the foreshock boundary regions.
The new observations from NASA’s THEMIS short for Time History of Events and Macroscale Interactions during Substorms mission show that this turbulent region can accelerate electrons up to speeds approaching the speed of light.
These extremely fast particles have previously been observed in near-Earth space and many other places in the universe, but the mechanisms that accelerate them have never been understood.
Now, the researchers found electrons can be accelerated to extremely high speeds in a near-Earth region farther from Earth than previously thought possible – leading to new questions over how they become so fast.
These findings may change the accepted theories on how electrons can be accelerated not only in shocks near Earth, but also throughout the universe, Nasa says.
Having a better understanding of how particles are energized will help scientists and engineers better equip spacecraft and astronauts to deal with these particles, which can cause equipment to malfunction and affect space travelers.
The results, published in Physical Review Letters, describe how such particles may get accelerated in specific regions just beyond Earth’s magnetic field.
Typically, a particle streaming toward Earth first encounters a boundary region known as the bow shock, which forms a protective barrier between the solar wind, the continuous and varying stream of charged particles flowing from the sun, and Earth.
The magnetic field in the bow shock slows the particles, causing most to be deflected away from Earth, though some are reflected back towards the sun.
These reflected particles form a region of electrons and ions called the foreshock region.
Some of those particles in the foreshock region are highly energetic, fast moving electrons and ions.
Historically, scientists have thought one way these particles get to such high energies is by bouncing back and forth across the bow shock, gaining a little extra energy from each collision.
However, the new observations suggest the particles can also gain energy through electromagnetic activity in the foreshock region itself.
‘This is a puzzling case because we’re seeing energetic electrons where we don’t think they should be, and no model fits them,’ said David Sibeck, co-author and THEMIS project scientist at NASA Goddard.
‘There is a gap in our knowledge, something basic is missing.’
The electrons also could not have originated from the bow shock, as had been previously thought, the researchers say.
If the electrons were accelerated in the bow shock, they would have a preferred movement direction and location – in line with the magnetic field and moving away from the bow shock in a small, specific region.
However, the observed electrons were moving in all directions, not just along magnetic field lines.
Additionally, the bow shock can only produce energies at roughly one tenth of the observed electrons’ energies.
Instead, the cause of the electrons’ acceleration was found to be within the foreshock region itself.
‘It seems to suggest that incredibly small scale things are doing this because the large scale stuff can’t explain it,’ Wilson said.
Next, the researchers intend to gather more observations from THEMIS to determine the specific mechanism behind the electrons’ acceleration.
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