On the Magnetic-Field Dependence of the Longitudinal Ultrasonic Attenuation in a Type-II Superconductor

We propose a simple method by which we can explain the magnetic-field dependence of the longitudinal ultrasonic attenuation in a type-II superconductor. It gives a curve which is in good agreement with experimental data, in paticular, near the lower critical field H_c1. We compare it with conventional methods, which is not in good agreement with the experimental data near H_c1 but near the upper critical field H_c2.