TY - GEN
T1 - The role of pickup ions in the solar wind and its interaction with the local interstellar medium
AU - Pogorelov, Nikolai
AU - Zhang, Ming
AU - Gedalin, Michael
AU - Kim, Tae
AU - Roytershteyn, Vadim
AU - Renfroe, Kyle
PY - 2021/1/1
Y1 - 2021/1/1
N2 - The role of pickup ions in the solar wind and its interaction with the
local interstellar medium The structure and dynamical evolution of the
heliosphere, our home in the universe, is governed by a number of
fundamental physical processes that define how plasma and magnetic
fields of solar origin interact with the local interstellar medium
(LISM). The solar plasma is accelerated near the Sun and creates a solar
wind (SW), which is collisionless with respect to Coulomb collisions.
The SW--LISM interaction creates a heliospheric termination shock (TS)
and the heliopause (HP), both observed in situ by the Voyager 1 (V1) and
Voyager 2 (V2) spacecraft. The LISM plasma is partially ionized, so
charge exchange between ions and atoms plays a major role in the
SW--LISM interaction. New populations of neutral atoms are born in the
SW and LISM. Some of them propagate far upstream into the LISM and
modify it to such an extent that the existence of a bow shock cannot be
confirmed knowing the properties of the unperturbed LISM only. In
addition, nonthermal (pickup) ions (PUIs) are created. They
energetically dominate the SW at large heliocentric distances, create
turbulence, affect the properties of the TS and HP, and are further
accelerated to create anomalous cosmic rays. PUIs are measured in situ
by Ulysses and New Horizons (NH). Charge exchange with PUIs creates
energetic neutral atoms (ENAs), which may propagate to near-Earth
distances. Fluxes of ENAs were measured in the past by SOHO and Cassini,
and have been mapped by the Interstellar Boundary Explorer (IBEX) since
2009. NASA's IMAP mission, scheduled for launch in 2024, will measure
ENAs even more accurately. It is crucial to extract the 3-D properties
of the heliosphere and LISM from ENA data. Parker Solar Probe is
measuring kinetic properties of the SW plasma and is expected to answer
the fundamental questions related to SW acceleration and transport. Most
observational data cannot be explained satisfactorily without
time-dependent, data-driven models. These investigations require an
integrated approach based on the combination of MHD and kinetic scales.
We discuss a systematic approach for acquiring a quantitative
understanding of the dynamical heliosphere affected by PUIs. Our
heliospheric model comprehensively describes the relevant physical
processes and helps interpret spacecraft observations of turbulent
plasma in the SW and LISM. Our simulation results along the NH and
Voyager trajectories show a good agreement with measurements both for
PUIs and thermal plasma. We discuss physical phenomena affecting the
measured ENA fluxes and their evolution in time. Both the charge
exchange and PUI transport phenomena are kinetic processes. Shock
crossing by a non-Maxwellian, collisionless plasma is a fundamental,
unresolved problem of plasma physics. Our kinetic modeling allows us to
develop proper boundary conditions at collisional shocks, which are used
in our global SW-LISM interaction calculations. Presented results help
build a framework for the interpretation of future IMAP observations.
AB - The role of pickup ions in the solar wind and its interaction with the
local interstellar medium The structure and dynamical evolution of the
heliosphere, our home in the universe, is governed by a number of
fundamental physical processes that define how plasma and magnetic
fields of solar origin interact with the local interstellar medium
(LISM). The solar plasma is accelerated near the Sun and creates a solar
wind (SW), which is collisionless with respect to Coulomb collisions.
The SW--LISM interaction creates a heliospheric termination shock (TS)
and the heliopause (HP), both observed in situ by the Voyager 1 (V1) and
Voyager 2 (V2) spacecraft. The LISM plasma is partially ionized, so
charge exchange between ions and atoms plays a major role in the
SW--LISM interaction. New populations of neutral atoms are born in the
SW and LISM. Some of them propagate far upstream into the LISM and
modify it to such an extent that the existence of a bow shock cannot be
confirmed knowing the properties of the unperturbed LISM only. In
addition, nonthermal (pickup) ions (PUIs) are created. They
energetically dominate the SW at large heliocentric distances, create
turbulence, affect the properties of the TS and HP, and are further
accelerated to create anomalous cosmic rays. PUIs are measured in situ
by Ulysses and New Horizons (NH). Charge exchange with PUIs creates
energetic neutral atoms (ENAs), which may propagate to near-Earth
distances. Fluxes of ENAs were measured in the past by SOHO and Cassini,
and have been mapped by the Interstellar Boundary Explorer (IBEX) since
2009. NASA's IMAP mission, scheduled for launch in 2024, will measure
ENAs even more accurately. It is crucial to extract the 3-D properties
of the heliosphere and LISM from ENA data. Parker Solar Probe is
measuring kinetic properties of the SW plasma and is expected to answer
the fundamental questions related to SW acceleration and transport. Most
observational data cannot be explained satisfactorily without
time-dependent, data-driven models. These investigations require an
integrated approach based on the combination of MHD and kinetic scales.
We discuss a systematic approach for acquiring a quantitative
understanding of the dynamical heliosphere affected by PUIs. Our
heliospheric model comprehensively describes the relevant physical
processes and helps interpret spacecraft observations of turbulent
plasma in the SW and LISM. Our simulation results along the NH and
Voyager trajectories show a good agreement with measurements both for
PUIs and thermal plasma. We discuss physical phenomena affecting the
measured ENA fluxes and their evolution in time. Both the charge
exchange and PUI transport phenomena are kinetic processes. Shock
crossing by a non-Maxwellian, collisionless plasma is a fundamental,
unresolved problem of plasma physics. Our kinetic modeling allows us to
develop proper boundary conditions at collisional shocks, which are used
in our global SW-LISM interaction calculations. Presented results help
build a framework for the interpretation of future IMAP observations.
M3 - Conference contribution
T3 - 43rd COSPAR Scientific Assembly. Held 28 January - 4 February, 2021
SP - 892
BT - 43rd COSPAR Scientific Assembly. Held 28 January - 4 February, 2021
ER -