Magnetic field lines that wrap around the Earth protect our planet from cosmic rays. PPPL researchers have now found that beams of fast-moving particles launched from a satellite could help map the precise shape of the field, helping scientists predict how plasma belched from the sun can disrupt telecommunications satellites, cell phone service, and global positioning systems.

The mapping could provide insight into the magnetosphere, the region of outer space affected by the field. “Understanding space weather — the behavior of hot, charged particles from the sun as they interact with the Earth’s immediate environment — is critically important,” said Andrew Powis, a graduate student in Princeton University’s Department of Mechanical and Aerospace Engineering and lead author of a paper reporting the results. “Developing a better fundamental understanding of how the magnetosphere operates is going to improve our ability to predict how it affects life on Earth.”

Powis and PPPL physicist Igor Kaganovich, deputy head of the PPPL Theory Department, ran computer simulations to determine the feasibility of using a beam of electrons to measure the magnetic field. They sought to answer two questions: First, would changing conditions in the magnetosphere affect where in the Earth’s atmosphere the electron beam would strike? And Second: Would the electron beam stay focused enough to produce a strong-enough signal when hitting the atmosphere for ground-based instruments to detect?

“For these beams to teach us something about the magnetosphere, changing conditions in the magnetosphere must cause a change in the electron beam’s strike point,” Powis said. “Our research has confirmed that this is the case.”

Using codes on PPPL computers, the scientists also confirmed that the electron beam would remain focused enough to create an observable signal. Powis now hopes that a satellite with the electron beam technology will fly in the near future. “There is uncertainty about magnetospheric storms and how they affect telecommunications satellites and the electric grid,” he said. “This tool would be able to settle some of the uncertainty.”

When fast-moving particles from the sun strike the Earth’s magnetic field, they set off reactions that could disrupt communications satellites and power grids. Now, scientists at PPPL have learned new details of this process that could lead to better forecasting of this so-called space weather.

The findings indicate how these regular blasts of fast-moving particles from the sun interact with the magnetic fields surrounding Earth in a region known as the magnetosphere. During these solar outpourings, the sun’s and Earth’s magnetic field lines collide. The field lines break and then reattach, releasing huge amounts of energy in a process known as magnetic reconnection. That energy disperses through the magnetosphere and into Earth’s upper atmosphere.

The scientists developed a computer program that analyzed information gathered by NASA’s Magnetospheric Multiscale (MMS) mission, a group of four spacecraft launched in 2015 to study reconnection in the magnetosphere. “Exactly how reconnection begins and releases energy is still an open question,” said Kendra Bergstedt, a graduate student in the Princeton Program in Plasma Physics at PPPL and lead author of the paper reporting the results in Geophysical Research Letters. “Getting a better understanding of this process could help us forecast how solar storms affect us here on Earth. We could also get better insight into how reconnection impacts fusion reactions.”

The findings shed new light on the emergence of particle energy during reconnection. “There is ongoing debate about what parts of the reconnecting region contribute the most to particle energization and how,” Bergstedt said. “We found that the smaller-scale plasmoids [bubble-like structures] that we studied in the reconnection region didn’t make a large contribution to the total energy imparted from the magnetic fields to the particles.”

The findings were notable because the physics is so complex. While scientists have made significant progress in understanding reconnection, there is still a lot to learn. “And understanding the connection between turbulence and reconnection is even harder,” said Jongsoo Yoo, a PPPL physicist and co-author of the paper. “Kendra did a good job getting some new insights into the process.”

An invention to apply plasma to frequently touched items for continuous disinfection could provide a safe, effective, non-chemical way to reduce pathogens on various surfaces such as keypads, escalator handrails, and other high-touch surfaces, PPPL inventors say.

The invention, which is in the patent pending phase of the process, would provide “cold” plasma, or room-temperature plasma, from different positional orientations, and would keep surfaces disinfected without the need to use hand sanitizer, sprays, ultraviolet light, or other liquid or chemical-based solutions.

“This is a continuous, in-situ answer to disinfecting surfaces that people touch frequently,” said Charles Gentile, a PPPL inventor who developed the technology with Kenneth Silber, a 38-year professional in PPPL Information Technology’s department. “The technology provides for a compact, efficient, and inexpensive method of plasma generation for the purpose of disinfecting surfaces,” the inventors said.

The idea came to Silber when he was trying to find a way to keep hand sanitizer applications automated at PPPL so that surfaces in bathrooms and entrance door handles/push bars would be disinfected when people used them. After talking with Gentile, now retired from PPPL, the inventors came up with the idea of using a novel method to deploy cold plasma on targeted surfaces. (Click here for a description of the method.)

“Employing our approach you don’t have to keep wiping it down,” Silber said. “It’s continuously disinfecting. Imagine, every night, not having to wipe down subway car poles and handles that people hold on to.”

The plasma in this invention is room temperature, unlike the plasma used at PPPL for fusion energy research that is heated to many times the temperature of the center of the sun in order to fuse light elements to produce energy, like the sun and stars. “You wouldn’t even feel it,” Gentile said of the room-temperature plasma.

“We know plasma will kill viruses,” he said. “We know how to make inexpensive plasma, and we know how to make low-temperature plasma. “The challenge is to engineer an in-situ deployment configuration that will work in multiple applications. That’s the technology we have developed.” Adds Silber: “There are some 30,000 escalators in the United States, with two handrails each. That’s 60,000 handrails touched daily. Imagine if we could keep those constantly disinfected.”

The Princeton University Office of Technology Licensing is actively discussing with multiple parties how to move the invention from lab to market.

A new method for verifying a widely held but unproven theoretical explanation of the formation of stars and planets has been proposed by PPPL researchers. The method grows from simulation of the Princeton Magnetorotational Instability (MRI) Experiment, a unique laboratory device that aims to demonstrate the MRI process that is believed to have filled the cosmos with celestial bodies.

The novel device, designed to duplicate the process that causes swirling clouds of cosmic dust and plasma to collapse into stars and planets, consists of two fluid-filled concentric cylinders that rotate at different speeds. The device seeks to replicate the instabilities that are thought to cause the swirling clouds to gradually shed what is called their angular momentum and collapse into the growing bodies that they orbit. Angular momentum keeps the Earth and other planets firmly within their orbits.

“In our simulations we can actually see the MRI develop in experiments,” said Himawan Winarto, a graduate student in the Princeton Program in Plasma Physics at PPPL and lead author of a paper that reports the findings. “We also are proposing a new diagnostic system to measure MRI,” he said.

The suggested system would measure the strength of the circular magnetic field that the rotating inner cylinder generates in experiments. Since the strength of the field correlates strongly with expected turbulent instabilities, the measurements could help pinpoint the source of the turbulence.

“Our overall objective is to show the world that we’ve unambiguously seen the MRI effect in the lab,” said physicist Erik Gilson, one of Himawan's mentors on the project and a coauthor of the paper. “What Himawan is proposing is a new way to look at our measurements to get at the essence of MRI.”

As the Earth orbits the sun, it plows through a stream of fast-moving particles that can interfere with satellites and global positioning systems. Scientists at PPPL and Princeton University have reproduced a process that occurs in space to deepen understanding of what happens when the Earth encounters this solar wind.

The team used computer simulations to model a jet of plasma, the state of matter that makes up the sun and stars and fuels fusion reactions. Many cosmic events can produce plasma jets, from relatively small star burps to gigantic stellar explosions known as supernovae. When fast-moving plasma jets pass through the slower plasma that exists in the void of space, it creates what is known as a collision-less shock wave.

Understanding these shock waves could help scientists forecast the space weather that develops when the solar wind swirls into the magnetic field that surrounds the Earth and thereby enable the researchers to protect satellites that allow people to communicate across the globe.

The simulations revealed several telltale signs indicating when a shock is forming along with phenomena that could be mistaken for a shock. “By being able to distinguish a shock from other phenomena, scientists can feel confident that what they are seeing in an experiment is what they want to study in space,” said Derek Schaeffer, an associate research scholar in the Princeton University Department of Astrophysics and lead author of a paper that followed up on previous research reported here and here.

When fast and slow plasma particles interact to produce shock waves in space, the process occurs without the particles touching one another. “Think of a boulder in the middle of fast-moving stream,” Schaeffer said. “The water will come right up to the front of the boulder, but not quite reach it. The transition area between quick motion and zero [standing] motion is the shock.”

In the future, the researchers aim to make the simulations more realistic by adding more detail and making the plasma density and temperature less uniform. They would also like to run experiments to determine whether the phenomena predicted by the simulations can in fact occur in a physical apparatus. “We’d like to put the ideas we talk about in the paper to the test,” Schaeffer said.

Mercury, the planet nearest the sun, shares with Earth the distinction of being one of the two mountainous planets in the solar system with a global magnetic field that shields it from cosmic rays and the solar wind. Now researchers, led by physicist Chuanfei Dong of PPPL and the Princeton University Center for Heliophysics, have developed the first detailed model of the interaction between the magnetized wind and the magnetic field, or magnetosphere, that surrounds the planet.

Dong used a new three-dimensional simulation code called “Gkeyll” that will deliver a basic tool to the twin-satellite BepiColombo mission en route to Mercury, for which Dong is co-investigator of a suite of four instruments on board the spacecraft. The international mission, named for the late mathematician Giuseppe (Bepi) Colombo and launched by European and Japanese space agencies in 2018, is scheduled to reach Mercury and begin orbiting in 2025.

“We will supply numerical information based on the model that will help the mission understand its findings,” said Dong, lead author of a paper describing the model.

A peculiarity of Mercury is that its magnetic field is some three times stronger in the northern hemisphere than in the southern, contrary to Earth’s, where the fields are basically the same. Generating the fields in both planets is the shifting liquid iron in their electrically conducting molten cores. In Mercury the unusually large core extends over 80 percent of the radius of the interior, tightly coupling the field to the core that creates it.

The new model enabled Dong and his team to explore many key features of the Mercury magnetosphere. These include the unusual back-and-forth cycling of the magnetic field between the front, or dayside of the magnetosphere and the rear, or nightside, and the fact that the tight coupling between the planet’s magnetosphere and large iron core helps to protect Mercury from erosion by the solar wind.

These findings, said Dong, “represent a crucial step toward establishing an innovative revolutionary approach” to improved understanding of the physics behind the contact of the solar wind with the lopsided magnetosphere of the planet closest to the sun.”

A long-standing puzzle in space science is what triggers fast magnetic reconnection, an explosive process that unfolds throughout the universe more rapidly than theory says it should. Solving the puzzle could enable scientists to better understand and anticipate the process, which ignites solar flares and magnetic space storms that can disrupt cell phone service and black out power grids on Earth.

Researchers at PPPL and Princeton University have now produced a formula for tracking the development of what are called “plasmoid-instability-mediated disruptions” in plasma that trigger the transition from slow to fast reconnection. The research traces the dependence of the instability on conditions ranging from the electrical conductivity of the plasma — measured by what is called the Lundquist number — to the natural noise of the system.

“You give me the Lundquist number and system noise and I can fit it into the formula that will spit out the answer,” said physicist Yi-Min Huang, a Princeton University member of the PPPL Theory Department and lead author of a paper describing the process.

The calculation tracks the evolution of plasmoids, bubbles that form in current-carrying sheets of plasma. When the bubbles are large enough, they trigger disruptions that cause fast reconnection. “We are interested in finding out when the plasmoids will disrupt the current sheet and the number of plasmoids when disruptions happen,” Huang said.

The versatile new formula tracks the dependence of disruptions on a broad range of high Lundquist numbers. Results can be compared with simulations of laboratory experiments and used to describe the development of plasmoid instabilities in natural systems. Such detailed tracking of the dependence of disruptions can provide fresh insight into the onset of fast magnetic reconnection.