The relatively low-energy components of cosmic rays are called galactic cosmic rays, and it is thought that they originate from shock waves (supernova remnant shock waves) generated by supernova explosions in our galaxy.Cosmic rays are composed of nuclei such as protons and electrons, and there is a standard model called Fermi acceleration, especially for the mechanism of acceleration of cosmic ray electrons in shock waves.It is said that acceleration can be explained naturally if there is an electron that becomes the "seed" of cosmic rays that has the same speed as the speed of light at the beginning, but it is a mystery how the "seed" is made. was.

　The group of Associate Professor Takanobu Amano of the University of Tokyo Graduate School of Science tackled the problem of "the first step" of cosmic ray electron acceleration, and analyzed the shock wave data near the earth observed by artificial satellites. , Succeeded in approaching the solution of this problem.The group recently proposed a new theoretical model of electron acceleration that takes into account the dynamics of micro-shock waves, which have been ignored so far, and the observation data proved the correctness of this new model.Then, it was found that when this model is applied to a supernova remnant shock wave, electrons can be accelerated to the speed of light, and the generation of particles that are the "seed" of cosmic rays can be theoretically explained.

　By clarifying the mechanism of the "first step" of cosmic ray acceleration in this way, it will be possible to conduct research to estimate the amount of "seed" of cosmic rays and, by extension, the total amount of cosmic rays.In the future, it is expected that the understanding of the whole picture of cosmic ray acceleration including not only electrons but also protons will progress.

Paper information:[Physical Review Letters] Observational Evidence for Stochastic Shock Drift Acceleration of Electrons at the Earth's Bow Shock