The Structure of the Large-Scale Heliosphere as Seen by Current Models.

This review summarizes the current state of research aiming at a description of the global heliosphere using both analytical and numerical modeling efforts, particularly in view of the overall plasma/neutral flow and magnetic field structure, and its relation to energetic neutral atoms. Being part of a larger volume on current heliospheric research, it also lays out a number of key concepts and describes several classic, though still relevant early works on the topic. Regarding numerical simulations, emphasis is put on magnetohydrodynamic (MHD), multi-fluid, kinetic-MHD, and hybrid modeling frameworks.

Shocks in the Very Local Interstellar Medium.

Large-scale disturbances generated by the Sun's dynamics first propagate through the heliosphere, influence the heliosphere's outer boundaries, and then traverse and modify the very local interstellar medium (VLISM). The existence of shocks in the VLISM was initially suggested by Voyager observations of the 2-3 kHz radio emissions in the heliosphere. A couple of decades later, both Voyagers crossed the definitive edge of our heliosphere and became the first ever spacecraft to sample interstellar space.

In Situ Observations of Interstellar Pickup Ions from 1 au to the Outer Heliosphere.

Interstellar pickup ions are an ubiquitous and thermodynamically important component of the solar wind plasma in the heliosphere. These PUIs are born from the ionization of the interstellar neutral gas, consisting of hydrogen, helium, and trace amounts of heavier elements, in the solar wind as the heliosphere moves through the local interstellar medium. As cold interstellar neutral atoms become ionized, they form an energetic ring beam distribution comoving with the solar wind.

Alfvénic velocity spikes and rotational flows in the near-Sun solar wind.

The prediction of a supersonic solar wind was first confirmed by spacecraft near Earth and later by spacecraft at heliocentric distances as small as 62 solar radii. These missions showed that plasma accelerates as it emerges from the corona, aided by unidentified processes that transport energy outwards from the Sun before depositing it in the wind. Alfvénic fluctuations are a promising candidate for such a process because they are seen in the corona and solar wind and contain considerable energy.

NEUTRAL ATOM PROPERTIES IN THE DIRECTION OF THE RIBBON.

In this paper, we present results from our three-dimensional (3D) simulations of the interaction between the solar wind and local interstellar medium with an emphasis on the phase-space properties of energetic neutral atoms (ENAs) along a sight line that intersects the ribbon of enhanced ENA flux seen by NASA's spacecraft. The majority of these ENAs have velocities directed away from the heliosphere, but it is believed that interactions between heliospheric ENAs and ions outside the heliosphere may result in a population of secondary ENAs that return to the heliosphere and generate the ribbon. While we do not consider the ion dynamics that result in secondary ENAs, our analysis is of key importance to the process since the heliospheric ENAs we consider form the source population for those ions.