The SIXS Instrument on Bepicolumbo, and Its Use for Space Weather Observations, and in Conjunction with MIXS

Abstract

The Solar Intensity X-ray and particle Spectrometer (SIXS) on BepiColumbo Mercury Planetary Orbiter (MPO) will investigate the direct solar X-rays and protons and electrons which pass the spacecraft on their way to Mercury. It has an innovative compact design, and the Mercury Imaging X-ray Spectrometer, with which it is paired, is similarly highly innovative. The SIXS measurements are vitally important for understanding quantitatively that make Mercury's surface fluoresce in X-rays, since all X-rays from Mercury are due to these energetic incoming photons and particles. SIXS data also can provide unique insights into the space weather at Mercury. Moreover, since it will explore the solar wind in the inner solar system, it is ideally suited to improve our understanding of Space Weather propagation to the Earth. Mercury and the Moon are examples of terrestrial bodies which lack an atmosphere and therefore have surfaces which interact directly with the space environment. Thus the surfaces can be reprocessed by plasma impact, and in the process can emit X-rays via the Particle Induced X-ray Emission (PIXE) process. We will present and review existing measurements, particularly from SMART-1 and Chandrayaan at the Moon, and Messenger and Mercury, in order to predict opportunities for new science at Mercury by BepiColumbo. We will present predictions of PIXE signals from different regions of the Mercury surface, and examine the possibility of using the signal for direct diagnosis of particle interactions with the surface. These include the auroral signatures of substorm like behaviour, and interactions with coronal mass ejections.