The necessary condition of external oscillations is the existence of closedgeodesic lines on the surface of scatterers.
外部振荡存在的必要条件是散射体表面有闭合测地线。
2
The existence of closedgeodesic lines (oscillate loci) is proved. Although there are infinite closed loci on the surface of scatterer, they yield same result in determining SEM poles.