A new simulation provides the first mechanism to explain why plasma from hypervelocity impacts generates electromagnetic radiation
When spacecraft and satellites travel through space they encounter tiny, fast moving particles of space dust and debris. If the particle travels fast enough, its impact appears to create electromagnetic radiation (in the form of radio waves) that can damage or even disable the craft's electronic systems.
A new study published this week in the journal Physics of Plasmas, from AIP Publishing, uses computer simulations to show that the cloud of plasma generated from the particle's impact is responsible for creating the damaging electromagnetic pulse. They show that as the plasma expands into the surrounding vacuum, the ions and electrons travel at different speeds and separate in a way that creates radio frequency emissions.
"For the last few decades researchers have studied these hypervelocity impacts and we've noticed that there's radiation from the impacts when the particles are going sufficiently fast," said lead author Alex Fletcher, now a postdoctoral researcher at the Boston University Center for Space Physics. "No one has really been able to explain why it's there, where it comes from or the physical mechanism behind it."
The study is a step towards verifying the theory of senior author Sigrid Close, associate professor of aeronautics and astronautics at Stanford University. In 2010, Close and colleagues published the initial hypothesis that hypervelocity impact plasmas are responsible for a few satellite failures.
To simulate the results from a hypervelocity impact plasma, researchers used a method called particle-in-cell simulation that allows them to model the plasma and the electromagnetic fields simultaneously. They fed the simulation details from a previously developed hydrocode -- a computational tool they used to model the fluid and solid dynamics of the impact. The researchers let the simulation evolve and calculated the radiation produced by the plasma.
When a particle hits a hard surface at high speeds, it vaporizes and ionizes the target, releasing a cloud of dust, gas and plasma. As the plasma expands into the surrounding vacuum (of space), its density drops and it enters a collisionless state where its particles no longer interact directly with one another.
In the current study, the researchers make the assumption that the electrons in this collisionless plasma then travel faster than the larger ions. Their simulation predicts that this large-scale charge separation generates the radiation. The model's results are consistent with Close's initial theory, but predict a higher frequency for the emission than researchers have detected experimentally.
The authors point out that the assumption that the electrons move en masse as they separate from the ions deserves more careful attention. The group is building new simulations to test whether the shift to a collisionless state is sufficient to create the separation.
Fletcher also notes that they have neglected to account for the dust.
"The impact creates dust particles that interact with the plasma," Fletcher said. The dynamics of these "dusty plasmas" are an area for future research.
The next step in the work is to use the simulation to quantify the radiation generated so they can assess the threat to satellites, and devise ways to protect satellites and spacecraft from meteoroids and orbital debris.
"More than half of electrical failures are unexplained because it's very hard to do diagnostics on a satellite that fails in orbit," Fletcher said. "We believe we can attribute some of these failures to this mechanism."
The article, "Particle-in-cell simulations of an RF emission mechanism associated with hypervelocity impact plasmas," is authored by Alex Fletcher and Sigrid Close. The article appears in Physics of Plasmas May 2, 2017 (DOI: 10.1063/1.4980833). After that date, it can be accessed http://aip.
ABOUT THE JOURNAL
Physics of Plasmas is devoted to the publication of original experimental and theoretical work in plasma physics, from basic plasma phenomena to astrophysical and dusty plasmas. See http://pop.
Julia Majors | EurekAlert!
Computer model predicts how fracturing metallic glass releases energy at the atomic level
20.07.2018 | American Institute of Physics
What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
20.07.2018 | Power and Electrical Engineering
20.07.2018 | Information Technology
20.07.2018 | Materials Sciences