The Heliosphere and Local Interstellar Medium from Neutral Atom Observations at Energies Below 10 keV.

As the heliosphere moves through the surrounding interstellar medium, a fraction of the interstellar neutral helium, hydrogen, and heavier species crossing the heliopause make it to the inner heliosphere as neutral atoms with energies ranging from few eV to several hundred eV. In addition, energetic neutral hydrogen atoms originating from solar wind protons and from pick-up ions are created through charge-exchange with interstellar atoms. This review summarizes all observations of heliospheric energetic neutral atoms and interstellar neutrals at energies below 10 keV. Most of these data were acquired with the Interstellar Boundary Explorer launched in 2008. Among many other IBEX breakthroughs, it provided the first ever all-sky maps of energetic neutral atoms from the heliosphere and enabled the science community to measure in-situ interstellar neutral hydrogen, oxygen, and neon for the first time. These observations have revolutionized and keep challenging our understanding of the heliosphere shaped by the combined forces of the local interstellar flow, the local interstellar magnetic field, and the time-dependent solar wind

Earth and Venus exospheres as seen by SWAN/SOHO and SPICAV/VEX

International audienc

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

International audienceSolar 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

The Discrepancy between Observed and Predicted Heliospheric Energetic Neutral Atoms below Solar Wind Energy

Measuring energetic neutral atoms (ENAs) allows for the remote observation of ion populations from the frontiers of our heliosphere. In this study, we compare the ENAs observed with the IBEX-Lo instrument onboard the Interstellar Boundary Explorer with ENA predictions from two heliosphere models. In contrast to previous studies, this paper presents model-data comparisons for the energy range 50 eV–2 keV over one full solar cycle not only in the upwind direction (Voyager 1 and Voyager 2 sky directions), but also for the north pole, south pole, port tail lobe, and downwind directions. The two heliosphere models produce the same basic result: there is a large gap (1 to 2 orders of magnitude in ENA intensity at 100 eV) between ENA data and model predictions between 100 and 500 eV for all sky directions. The reason for this gap is not understood yet. While some explanations are plausible and will be investigated in future studies, other explanations are excluded

SIHLA , a Mission of Opportunity to L1 to Map H Lyman Alpha Emissions from the Heliopause, the Interplanetary Medium, the Earth's Geocorona and Comets

International audienceSIHLA (Spatial/Spectral Imaging of Heliospheric Lyman Alpha pronounced as ‘Scylla’ [e.g. Homer, Odyssey, ~675-725 BCE] investigates fundamental physical processes that determine the interaction of the Sun with the interstellar medium (ISM); the Sun with the Earth; and the Sun with comets and their subsequent evolution. To accomplish these goals, SIHLA studies the shape of the heliosphere and maps the solar wind in 3D; characterizes changes in Earth’s extended upper atmosphere (the hydrogen ‘geocorona’); discovers new comets and tracks the composition changes of new and known ones as they pass near the Sun.SIHLA is a NASA Mission of Opportunity that has just completed its Phase A study (the Concept Study Report or CSR). At the time of the writing of this abstract NASA has not decided whether to fly this small satellite mission or its competitor (GLIDE: PI Prof. Lara Waldrop). SIHLA observes the ion-neutral interactions of hydrogen, the universe’s most abundant element, from the edge of the solar system to the Earth, to understand the fundamental properties that shaped our own home planet Earth and the heliosphere. From its L1 vantage point, well outside the Earth’s obscuring geocoronal hydrogen cloud, SIHLA maps the entire sky using a flight-proven, compact, far ultraviolet (FUV) hyperspectral imager with a Hydrogen Absorption Cell (HAC). The hyperspectral scanning imaging spectrograph (SIS) in combination with the spacecraft roll, creates 4 maps >87% of the sky each day, at essentially monochromatic lines over the entire FUV band (115 to 180nm) at every point in the scan. During half of these daily sky maps, the hydrogen absorption cell (HAC) provides a 0.001nm notch rejection filter for the H Lyman a. Using the HAC, SIHLA builds up the lineshape profile of the H Lyman a emissions over the course of a year. SIHLA’s SIS/HAC combination enables us to image the result of the ion-neutral interactions in the heliosheath, 100 AU away, in the lowest energy, highest density, part of the neutral atom spectrum – H atoms with energies below 10eV.The novel aspects of SIHLA are the scope of the science done within a MoO budget. The SIHLA projected costs were below the $75M cap with a 31.3% reserve for Phase B-D. The re-purposing of a spectrographic that was part of the DMSP SSUSI line (a copy was flown and NASA TIMED/GUVI and as NASA NEAR/NIS). Risk is extremely low in this Class-D mission with all major elements at least at TRL6 at this time.SIHLA has a high potential for discovery. We expect that we will 1) First detection of the hot H atoms produced directly from the ion-neutral interactions at the heliopause; 2) First detection of structures in Interplanetary Medium H emission, 3) First detection of response of the Earth’s extended (out to lunar orbit) geocorona to solar/geomagnetic drivers, 4) New UV-bright comets as they enter the inner solar system.SIHLA is a hyperspectral imager; at every point in the sky SIHLA obtains the entire FUV spectrum. This enables SIHLA to easily flag pixels contaminated by stars; obtain the spectrum of the Earth, viewed as an ‘exoplanet’ and observed the response of the exosphere and the thermosphere to solar/geomagnetic events; detect comets and determine their composition and how it varies at they enter and leave the inner solar system