Understanding of radiation reaction force acting on charged particle in intense fields

2022 Fiscal Year Final Research Report

• Project/Area Number: 19K03786
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 14010:Fundamental plasma-related
• Research Institution: Fukuoka Institute of Technology
• Principal Investigator: Nakamura Tatsufumi 福岡工業大学, 情報工学部, 教授 (40318796)
• Project Period (FY): 2019-04-01 – 2023-03-31
• Keywords: 輻射反作用 / 高強度場 / LAD方程式 / 自己力 / 超高強度レーザー

Outline of Final Research Achievements

The Lorentz-Abraham-Dirac (LAD) equation is widely recognized as a correct equation of motion of charged particle, which includes the radiation reaction force. It is also known that the LAD equation has mathematical issues originating the Schott term which contains a third time-derivative term. Then other equations which do not suffer from the above issue such as the Landau-Lifshitz equation which is obtained by perturbative expansion of radiation reaction term in LAD equation, and others such as Mo-Papas equation. In this research, we obtained analytical solution of charged particle in relatively simple system by using the LAD and other equations, and compared them quantitatively. It was shown that there are some differences among solutions of those equations, such as the Lorentz factor, the differences are relatively small in the regime where the quantum effect is negligible and classical treatment is acceptable.

Free Research Field

プラズマ物理学

Academic Significance and Societal Importance of the Research Achievements

輻射を考慮した運動方程式として提案されているLAD方程式は、高階微分項を含むため解析的求解のみならず数値的球解も難しくこのためLAD方程式の近似方程式に相当する方程式を代用することが多い。そこでこれらの方程式を用いて運動の解析解を導出し、それらの定量的な比較を行った。その結果、量子電磁力学的な効果が無視できるような電磁場の強度領域においては、LAD方程式の解とLandau-Lifshitz方程式、Mo-Paras方程式、Ford-O’Connell方程式の解の相対的な誤差は10-6程度と小さいことが示された。このことは、数値積分が可能な上記の近似方程式を用いる際の妥当性を示す根拠の一つとなる。