Requirements and design of a dual, thermal ion-electron instrument for an outer heliosphere and interstellar mission

<p>We present the scientific rationale, and ensuing requirements, for the measurement of thermal ions and electrons in the solar wind (including pick-up ions), the inner and outer heliosphere, and the interstellar medium. We place these in the context of the interstellar missions being currently designed in the US and China. From these requirements, we propose an instrument concept that permits to measure both thermal ions (without composition) and electrons, alternatively, with low resources and high signal-to-noise ratio in accordance with the limited resources and large range of count rates, as expected over the course of such a mission.</p>

Understanding our global heliosphere with UV observations: Unique opportunities on Interstellar Probe

<p class="p1">Solar Lyman-a emission re-radiated from H atoms incoming to the heliosphere from interstellar medium is a powerful tool to probe globally plasma properties both at the heliosphere boundary and near the Sun. H Lyman-α line profiles reflect velocity distributions of low energy H atoms in the heliosphere which hold information about the plasma near the heliopause. H Lyman α intensities as observed at 1 AU serve as diagnostic of global properties of the solar wind. In this talk we will review what we have learned about the global heliospheric interaction from H Lyman-a observations from inside the heliosphere on SWAN/SOHO, Voyages/UVS and New Horizons/Alice missions. Outward trajectory of Interstellar Probe going through the outer heliosphere to the interstellar medium (ISM) up to 1000 AU enable unique science opportunities to explore global interaction between the solar wind and local ISM by observing for the first time Lyman-a emission from outside of the heliosphere. We will report a progress of UV working group in outlining primary science questions on the nature of the global heliosphere and Local Interstellar Cloud, planning observation strategy, measurement requirements and synergies with planetary UV observations for potential KBO fly-by.</p>

A Solar Cycle of Observations with the Interstellar Boundary Explorer (IBEX)

<p>The Interstellar Boundary Explorer (IBEX) was launched in 2008 and has now returned observations over a full 11-year solar cycle (Solar Cycle 24). IBEX remotely images global ion distributions via charge exchange Energetic Neutral Atoms (ENAs) propagating inward from the heliosheath – the region between the termination shock and heliopause – and beyond. These observations have led to numerous discoveries about the outer heliosphere and its interaction with the surrounding interstellar medium. Heliospheric ENAs arise largely from two sources: the IBEX Ribbon, which is likely generated beyond the heliopause, in the very local interstellar medium, and the globally distributed flux (GDF), which is primarily produced in the heliosheath. In this talk we summarize some of the critical advances driven by IBEX observations. We also examine how the heliosphere and its interstellar interaction have evolved over the past solar cycle. For most of IBEX’s 11 years of observations, there was an overall reduction and then flattening of the ENA fluxes at all energies, consistent with a generally deflating, or shrinking, heliosphere. Over the past few years, IBEX has been observing the progressive response of the heliosphere to a large persistent increase in the solar wind output that passed 1 AU in the second half of 2014. This enhancement arrived at the outer heliosphere as indicated by an increase in the ENAs returning from the closest region of the inner heliosheath, south of the upwind direction, starting in the second half of 2016. Since then, the region of enhanced ENA emissions has expanded progressively outward from there, exposing increasingly further away regions of the heliosheath. IBEX observations over the past 11-years have led to a true scientific revolution in our understanding of the outer heliosphere and its interstellar interaction.</p>