The MAVEN Extreme Ultraviolet Monitor: Providing Solar EUV Irradiances for Mars Atmospheric Studies

Abstract:

The extreme ultraviolet (EUV) solar irradiance is one of the primary energy sources into the Mars atmosphere. Photons in this wavelength range heat, dissociate, and ionize the constituents of the upper atmosphere, hence knowledge of the solar irradiance is vital in determining not only the state of the planet’s atmosphere, but its variability and potential for atmospheric escape. The solar EUV irradiance varies on all timescales and is the result of the highly variable activity on the Sun. During the primary mission of the Mars Atmosphere Volatile Evolution Mission (MAVEN), the planet will be on a different side of the Sun than the Earth and will therefore be subjected to potentially very different irradiances than the standard Earth-based monitors can capture, particularly for short timescale variations such as on daily (active region evolution) or sub-daily (flares) scales. The EUV monitor on MAVEN measures the solar input to the Mars atmosphere with three broadband radiometers at 121-122 nm (H Ly-α), 17-22 nm, and 0-6 nm, capturing solar transition region, coronal, and flaring emissions. The EUV measurements will be at a 1-second cadence. The broadband measurements can be used as direct indicators of the timing and magnitude of solar irradiance variations. The EUV data will also be combined with interpolated Earth-based measurements using a proxy model to generate a full irradiance spectrum from 0-190 nm in1-nm bins at a 1-minute cadence for use in Mars atmospheric studies. This paper will present the EUV monitor measurements and data products and the synergies with the other MAVEN instruments and atmospheric studies.