Lab simulation sheds light on solar wind-induced comet X-ray mechanism
Researchers from the Institute of Modern Physics (IMP) of the Chinese Academy of Sciences (CAS) recently set up an experimental platform to simulate the X-ray emission of comets irradiated by ions from the solar wind. With this platform, they studied the emission of X-rays produced by highly charged ions bombarding the surface of nickel. The results were published in European Physical Journal Plus on September 7.
Comets are one of the coolest stars in the solar system. The X-radiation mechanism of comets has been a controversial issue as it was explained by different physical mechanisms. The reason is mainly related to the measurement of X-ray yield and cross section in experiments. The difficulty of accurately measuring the intensity of the collision current leads to the inaccuracy of the X-ray yield and cross-section, thus causing great uncertainty in fitting the comet X-ray energy spectrum.
To accurately measure the intensity of the incident current, IMP researchers built a simulation platform on a 14.5 GHz electron cyclotron resonance ion source (ECRIS), which performed live monitoring. real-time and accurate measurement of collision current intensity, laying a good foundation for clarifying the physics mechanism of cometary X-ray emission.
Based on this platform, the researchers studied the X-ray emission caused by the interaction of highly charged nitrogen and oxygen ions with the surface of metallic nickel. They obtained precise data on the production of X-rays by precisely measuring the intensity of the collision current.
Additionally, the researchers found that the X-ray cross section was quite different from the existing theoretical expectation when the incident energy of the ions was below 5 keV/q. They proposed an inner shell multi-electron transition model which successfully explained the phenomenon.
The aforementioned platform construction and research has laid the foundation for laboratory simulations of comet X-rays caused by the solar wind and provides new insights into the physical mechanism of cometary X-ray radiation.
X-ray cross section of high charge nitrogen and oxygen ions colliding with nickel surface. When the energy of the incident ions is less than 5 keV/q, the experimental results deviate significantly from the theoretical expectations. (Picture by WANG Wei)