| Popis: |
On Earth, electric discharges in thunderstorms produce ELF waves in the Earth-ionosphere waveguide that circles the globe. These waves give rise to Schumann resonances in the waveguide resonant cavity. These waves are also expected to occur at Venus, produced by strong lightning in the Venus atmosphere and at Mars produced by active dust devils or dust storms, during southern hemisphere summer, when the planet is near periapsis. Within dust storms, dust particles undergo triboelectric charging. The charge transfer leads to charge separation. A lightning discharge is expected to occur when the charge exceeds the breakdown strength of the media present. The transient electric discharge emits electromagnetic waves in the VLF/ELF range of frequency, leading to Schumann Resonance in the surface-ionospheric cavity. In a heterogeneous cavity, Schumann resonance modes are observable using an in-situ instrument. Recently has it been possible to search for these electromagnetic waves from the Mars surface using the UCLA-provided InSight fluxgate magnetometer. The weakness of the vertical component of ULF waves at Mars suggests that the subsurface is electrically conducting, allowing trapping of electromagnetic energy between the sub-surface and the ionosphere. The fundamental mode of Schumann resonance carries higher energy compared to there are more chances of observing the fundamental mode. Various values of the first mode are predicted in the literature for Mars like 13-14 Hz or between 9-14 Hz and 17.5 Hz. Even if the fundamental mode is above 10 Hz, the 20 Hz sampling rate will allow detection of an aliased signal. We examine the data obtained during Martian sandstorms for the possible existence of such waves. A large dust storm was detected on Mars beginning on InSight sols 40 to 50, and ending during sols 50 to 90. Examining the 20 Hz InSight magnetometer data during this period reveals no clearly identifiable Schumann Resonance signals within the bandwidth of the magnetometer. |
