Based on the Van Allen Probe A observations from 2013 to 2015, we show the statistical relationship between exohiss waves and plasmaspheric hiss. Both hiss and exohiss waves have higher occurrence rates on the dayside (MLT = 8–20) and are positively correlated. The appearance of exohiss waves is nearly independent of the plasmapause density gradient at magnetic latitudes below 21°. Most exohiss waves (~ 68–88%) are propagating equatorward, and their amplitudes are generally smaller than those of hiss waves. This is consistent with the hiss leakage at high latitudes and associated energy dissipation. Less than 32% of exohiss waves are propagating poleward, probably due to multiple reflections of leaked hiss or excitation by equatorial instability. Although the inward reflection of chorus waves at high latitudes could produce equatorward propagating exohiss and hiss waves, this can explain only 10% of exohiss waves with larger amplitudes than hiss.

Based on the Neuber's rule and Walker equation, a new measurement method considering the influence of mean stress and stress gradient is proposed. A stress gradient factor is defined to correct the traditional Walker equation; thus, it is easy to estimate the life of the structural components only based on the purely elastic finite element analysis. The low‐cycle fatigue experiment was carried out by using the direct aging GH4169 notched specimen with different stress concentration factors under evaluated temperature. The fracture morphology of specimens was analyzed to determine the crack initiation position and the damage mechanism. The data points of the experiment life and the estimation life are correlated well within a three times scatter band. It indicates that the Walker equation corrected by introducing a new kind of measurement of stress gradient is reliable to estimate the notched specimen fatigue life.