11:15 AM - 11:30 AM
[PEM19-03] Density estimation utilizing the group-standing frequency of upstream whistlers in the solar wind
Based on statistical and comparative studies, we proposed that the waves are essentially group-standing, i.e., their group velocities become rather small in the body's rest frame [Tsugawa et al., JGR 2014]. In the group-standing condition, the waves can behave as if they are at a resonance frequency because the group refractive index approaches infinity in the spacecraft / solar system body rest frame. This suggests that the group-standing frequency can be utilized as an indicator of plasma parameters, in analogous to the upper-hybrid resonance frequency, which is used to determine the plasma density in the magnetosphere. We propose a method to estimate the plasma density utilizing the group-standing frequency and evaluate the feasibility of the proposed method by using Geotail in-situ observations. The method possibly estimates the absolute value of number density with an accuracy of <~0.1, although there remains some considerable difficulties. We discuss pros and cons of the proposed method.