A SupraThermal Ion Spectrometer for future Heliospheric (STISH) missions

Recent studies have revealed that suprathermal ions may significantly contribute as seed particles for acceleration either close to the Sun in solar energetic particle (SEP) events, locally at 1 AU in energetic storm particle (ESP) events, and outside 1 AU as ions accelerated in corotating interaction regions (CIRs). Measurement of the suprathermal ions in the heliosphere has always been a difficult challenge. Situated in the energy regime of a few times the solar wind plasma and below the threshold of the state-of-art solid-state detectors, there was, until recently with the Solar Orbiter Heavy Ion Sensor (HIS) instrument, no dedicated instrument to measure this energy range. All the current measurements in the suprathermal energy range have been obtained with instruments that are optimized to operate in the solar wind (~keV/q) energy range. All these instruments require long-term integration (~weeks) to acquire statistics. Hence, short-term (~hours) variations of these particles remain largely unexplored and could play an important role in particle acceleration processes. We are developing a new suprathermal ion spectrograph that measure energetic ions from 3 to 150 keV/q. The proposed instrument concept will use a new E/Q disperser design that allows us to cover the entire energy range in 5 voltage steps, hence dramatically enhancing the duty cycle of the instrument. Two TOF sections (one with position sensitive anode) will be used to augment the E/Q measurement to resolve charge and element.