SINUOUS AURORA AT MARS TRACES MAGNETOTAIL CURRENT SHEET: EMM AND MAVEN OBSERVATIONS

Sinuous aurorae are narrow, filamentary emission features on the Martian nightside that ex- tend across the terminator in an approximately anti-sunward direction. The Emirates Mars Ultraviolet Spectrometer (EMUS) onboard the Emirates Mars Mission (EMM) has captured synoptic images of this phenomenon in far-ultraviolet wavelengths, including the OI 130.4 nm and 135.6 nm emissions. We present the first observational evidence linking sinuous aurora to the magnetotail current sheet at Mars using near-simultaneous observations from EMM and MAVEN. During a conjunction event on January 12, 2025, EMUS imaged a sinuous aurora near the dawn terminator while MAVEN passed over the same region shortly before. MAVEN in-situ measurements reveal enhanced electron energy fluxes at tens of eV, a magnetic field rotation with a sign reversal in the sunward (Bx) component, and field line tracing connects the spacecraft location to the auroral emission altitudes. Minimum Variance Analysis indicates a current sheet crossing, with the aurora elongation direction aligning with the maximum magnetic variance direction, providing strong quantitative evidence that sinuous aurorae trace the magnetotail current sheet structure at Mars.