Mirror-mode Wave Identification Methods and Their Application to Martian Magnetosheath

Mirror-mode waves are structures usually seen in plasma with temperature anisotropy, identifiable through features in magnetic field and particle distribution and fluctuation. Two identification methods are analyzed and compared in this paper. Method A uses magnetic field data only, while Method B combines magnetic field and particle data. Method A is based mainly on features of magnetic field variation such as large amplitude fluctuation along background field direction, using magnitude of magnetic field fluctuation ΔB/|B| and angles between background field and maximum/minimum variation direction θ_max, θ_min as criteria. Method B is based on features such as wave compression, total pressure balance and zero velocity in plasma frame. Identification using data from MAVEN probe in the Martian magnetosheath shows that Method A can cause misidentification under certain circumstances, e.g. magneto-sonic waves. Results of identification using Method A with varying criteria ΔB/|B| and θ_min/θ_max are studied in the Martian magnetosheath, suggesting threshold values: θ_min> 40°, θ_max< 40° and ΔB/|B| > 80% can yield satisfying results.