Lab study creates artificial magnetosphere to explore spontaneous excitation of chorus emissions

A dipole magnetic field, produced by a ring current, is the most basic type of magnetic field found both in laboratories and in space. The magnetic fields of planets, such as Jupiter, effectively confine the plasma.

The RT-1 project aims to learn from nature and create a magnetosphere-type high-performance plasma to realize advanced fusion energy. At the same time, artificial magnetospheres provide a means of experimentally understanding the mechanisms of natural phenomena in a simple and controlled environment.

Ring Trap-1 (RT-1) is an experimental apparatus located at the University of Tokyo. Using high-temperature superconducting technology, a dipole field coil is levitated magnetically, which enables Plasma experiments To be performed in the near magnetosphere of the planets.

Whistler mode Course Emissions, observed in space around Earth, known as “geospace”, are an important phenomenon related to the aurora and space weather. Corsair emissions have been studied primarily through spacecraft observations, A theoretical studyand numerical simulations.

Although spacecraft are powerful tools for studying the real space environment, the planetary magnetosphere is a large and complex system that is difficult to fully understand. Also, manipulating the space environment is not easy for humans.

In contrast, laboratory settings allow us to create a simple research object that is extracted from the complexities of nature in a controlled environment. Therefore, empirical studies are expected to play a complementary role in the observation and theory of understanding course attrition. However, creating a magnetic environment in the laboratory is not straightforward. Laboratory experiments on course emission in a magnetospheric dipole Magnetic field has never been held so far.

A research team from the National Institute for Fusion Science in Tokyo, Japan, and the University of Tokyo Graduate School of Frontier Sciences in Kashiwa, Japan, successfully conducted a laboratory study on whistler mode course emissions using the RT-1 device. Is. This “artificial magnetic field” consists of a magnetically levitated superconducting coil to create a planetary magnetic field-type dipole magnetic field in the laboratory.

Using high-temperature superconducting technology, a 110 kg coil is magnetically levitated in a vacuum vessel, and the resulting magnetic field confines the plasma. This unique setup allows the coil to operate without any mechanical support structure, making it possible to generate plasma in an environment that resembles the planetary magnetosphere, even at a terrestrial facility. Inside too.

In this study, the research team filled RT-1’s vacuum vessel with hydrogen gas and injected microwaves to create a high-performance hydrogen plasma, essentially by heating electrons.

In the experiments, plasmas were created in different states and the generation of waves was investigated. Consequently, the spontaneous generation of Whistler wave chorus emission was observed when the plasma contained a substantial proportion of high-temperature electrons.

The force and frequency of the emission from the plasma were also measured, focusing on its density and state of high-temperature electrons.

gave ResultsPublished in Nature Communications, revealed that the generation of a chorus emission is driven by the addition of high-temperature electrons, which is responsible for the plasma pressure. Furthermore, an increase in overall plasma density had the effect of suppressing the generation of course emissions.

Through this study, it was demonstrated that course emission is a universal phenomenon that occurs in plasmas with high-temperature electrons in a simple dipole magnetic field. Characteristics that appear in experience, including apparent conditions and Wave propagationcan enhance our understanding of observed course discharges and related phenomena in geographic space.

The electromagnetic waves from the course emission have the ability to accelerate hot electrons to higher energy states, resulting in the formation of aurora and satellite failure. These electromagnetic waves, along with energetic particles, play an important role in space weather phenomena.

In geospace, when explosive events (flares) occur on the solar surface, they trigger magnetic storms, which cause large fluctuations in the electromagnetic field and produce large amounts of energetic particles. It not only causes satellite failure and affects the ozone layer, but is also known to disrupt power and communication networks on Earth.

With the expansion of human activities today, understanding space weather phenomena has become increasingly important. However, several mechanisms and phenomena in this area remain unresolved. The results of this study are expected to contribute to a better understanding of the mechanisms behind diverse space weather phenomena.

In the field of fusion plasma, which ultimately aims to solve energy problems, particle loss and structure formation due to interaction with waves is one of the central research problems. Achieving fusion requires a precise understanding of the complex interactions between spontaneous excited waves and plasma.

Wave phenomena with frequency variations have been widely observed in high-temperature plasmas for fusion, indicating the existence of a common physical mechanism with chorus emission.

The results of this study represent a step forward in understanding the common physical phenomena found in both fusion and space plasmas. It is anticipated that future research will advance further with increased collaboration between these two fields.

Whistler waves are one of the fundamental waves propagating in plasma. In geospace and observed course emissions around Jupiter, fluctuating events with frequency variations similar to birdsong are frequent. They are believed to be closely related to Aurora. the location Weathering phenomena, such as the production and transport of high-energy electrons.