Data table of whistler-mode waves observed by Venus Express in the ionosphere of Venus
Description
This data table contains a list of whistler-mode waves observed by Venus Express in the ionosphere of Venus. It is provided as supplementary material for the Icarus paper "Statistical study of lightning-generated whistler-mode waves observed by Venus Express" accepted in 2022. Using the 128 Hz magnetometer data provided by the MAG instrument (Zhang, 2007), dynamic spectra were generated for all available data under 1100 km altitude. The spectra used to identify the whistlers include the coherence, ellipticity, propagation angle relative to the field, transverse power, and compressional power. The signals are logged in the table in 1 seconds steps. Other measured and derived values are included for purposes of statistical analysis. The columns in the table are as follows: 1. TIME - UTC date and time for the sample record ({YYYY}-{MM}-{DD}T{HH}:{MM}:{SS}.{MSEC}) 2. ALT - Altitude of the spacecraft in units of km. 3. SZA - Solar zenith angle of the spacecraft in units of degrees. 4. LAT - Geographic latitude of the spacecraft in unit of degrees. 5. LON - Geographic longitude of the spacecraft in unit of degrees. 6. LT - Local time of the spacecraft in fraction of an Earth day. 7. BR - Radial component of magnetic field value in REN coordinates in units of nT. 8. BE - East component of magnetic field value in REN coordinates in units of nT. 9. BN - North component of magnetic field value in REN coordinates in units of nT. 10. BT - Magnetic field magnitude in units of nT. 11. BX - X-axis magnetic field value in VSO coordinates in units of nT. 12. BY - Y-axis magnetic field value in VSO coordinates in units of nT. 13. BZ - X-axis magnetic field value in VSO coordinates in units of nT. 14. XVSO - X-axis position in VSO coordinates in units of km. 15. YVSO - Y-axis position in VSO coordinates in units of km. 16. ZVSO - Z-axis position in VSO coordinates in units of km. 17. RVSO - Radial distance of position in VSO coordinates in units of km. 18. B_AMP - Wave amplitude in units of nT. 19. POYNTING - Poynting flux in units of W m^-2. 20. REFRACT - Refractive index calculated from the electron density. 21. N_E - Electron density derived from the VIRA ionospheric model in units of m^-3. 22. PLASMA_E - Electron plasma frequency in units of Hz. 23. GYRO_E - Electron gyrofrequency in units of Hz. Zhang, T.L., et al. (2007). MAG: The Fluxgate Magnetometer of Venus Express. ESA Special Publication, 1295, 1–10.
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Steps to reproduce
The cleaned 128 Hz magnetometer data (Russell et al., 2022) were first rotated into a field-aligned coordinate system such that the Z-axis points the same direction as the background magnetic field. This has the effect of essentially separating the wave analysis into the transverse components and the longitudinal component (Z-axis), which improves the identification of transverse waves, such as whistler-mode waves. Following the method of Means (1972), we calculated and produced spectra for the coherence between the two transverse components, the ellipticity, the propagation angle relative to the ambient magnetic field, the transverse power, and the longitudinal power. To be identified as a whistler-mode wave in this study, we defined the following criteria: coherence > 0.3 ellipticity > 0.5 propagation angle < 45º transverse power > longitudinal power After the spectra are produced, a mask is created to filter out any portions that do not fulfill the criteria for at least 6 Hz in the frequency domain and 1 second in the time domain. The start and stop times of each signal are determined and the interval is recorded in 1 second steps in the data table. Along with other properties of the plasma and the wave. The electron density was used to calculate the refractive index and the Poynting flux, but there weren't sufficient in situ measurements so the Venus Atmospheric Reference Atmosphere (VIRA) model for the ionosphere was utilized (Brace et al. 1997). The model can scale using a power law to match the solar conditions during the observation times. Brace, L.H., J.M. Grebowsky, A.J. Kliore (1997). Pioneer Venus Orbiter contributions to a re-vised Venus reference atmosphere. Adv. Space Res., 19: 1203-1212, 10.1016/S0273-1177(97)00271-8. C.T. Russell, Hart, R.A., T.L. Zhang (2022). Venus Express Cleaned High-Resolution 128 Hz Magnetic Field Data Bundle. PDS Planetary Plasma Interactions Node, 10.17189/1522415. Means, J.D. (1972). Use of three-dimensional covariance matrix in analyzing the polarization properties of plane waves. J. Geophys. Res. 77, 5551-5559, 10.1029/JA077i028p05551.