The EUV Spectral Irradiance at Mars: It’s Not Just About Solar Variability

Abstract:

The solar EUV spectral irradiance is an important energy input to the atmosphere of Mars resulting in heating, photoionization, photodissociation, and escape. The solar EUV spectral output varies differently and significantly in both magnitude and wavelength as a function of solar activity on the timescales of solar cycle, solar rotation, and flares. However, for Mars with its eccentric orbit, the changing distance from the Sun plays an equally significant role as solar activity in the final spectral irradiance at the top of the Mars atmosphere. In this presentation we will demonstrate how both solar activity and the Mars orbit affect the spectral distribution of EUV energy input to the Mars system. We will give an overview of the observations of the EUV Monitor on the Mars Atmosphere and Volatile Evolution (MAVEN) mission from October 2014 to the present, spanning from the maximum of Solar Cycle 24 through the declining phase and to the current solar minimum. We will also present spectral irradiance model products for use at Mars.