Year: 2025
Type: article
Abstract: The stability of a realistic multicomponent pickup ion (PUI) velocity distribution derived from a global model of neutral atoms in the heliosphere, which treats hydrogen and helium atoms self-consistently and includes equations for electrons and helium ions, is investigated using linear instability analysis and hybrid simulations. Linear instability analysis shows that the excited oblique mirror waves and the parallel/quasi-parallel Alfvén-cyclotron (AC) waves have lower growth rates than those obtained previously by A. Mousavi et al. for the PUI velocity distributions given by J. Heerikhuisen et al. The PUI scattering by each of the two modes alone is studied. In contrast to the previous investigations, our current simulations using the updated realistic distributions indicate that mirror waves alone do not effectively scatter PUIs in pitch angle. Instead, they primarily contribute to reducing the thermal spread anisotropy of the PUIs originating from the neutral solar wind. The unstable AC waves exhibit lower growth rates but higher saturation levels than the mirror waves. Two-dimensional (2D) simulation results show that when all unstable waves are present, the predominant contributor to the fluctuating magnetic field energy is the AC mode. The AC waves quickly scatter the PUIs with pitch angles away from 90∘ toward isotropy, while the PUIs near 90∘ pitch angle maintain a degree of anisotropy within our simulation timeframe. Moreover, several 1D and 2D hybrid simulations with different numbers of particles per cell are performed to examine the impact of numerical noise on PUI scattering. Finally, the implications of these results for the Interstellar Boundary Explorer energetic neutral atom ribbon are discussed.
Source: The Astrophysical Journal
Institutions: Space Science Institute, University of Alabama in Huntsville
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $4,499
Awards: NSF-BSF: Collaborative Research: Rankine-Hugoniot Conditions Relating the Gyrotropic Regions of Collisionless Shocks in Non-Thermal Plasma, G250543480, G4393623358, WHILE VOYAGER 1 IS WIDELY BELIEVED TO BE MEASURING THE PROPERTIES OF THE LOCAL INTERSTELLAR MEDIUM (LISM) VOYAGER 2 IS DETECTING THE SOLAR WIND (SW) AND HELIOSPHERIC MAGNETIC FIELD (HMF) PROPERTIES IN THE INNER HELIOSHEATH (IHS) WHICH ARE MARKEDLY DIFFERENT FROM THOSE OBSERVED BY VOYAGER 1 AT THE SAME HELIOCENTRIC DISTANCE. THE GOAL OF THIS PROPOSAL TO INVESTIGATE THE FUNDAMENTAL PROPERTIES OF THE SW-LISM INTERACTION THAT ARE RELATED TO THE PRESENCE OF NON-THERMAL PICKUP IONS (PUIS) ARE RESPONSIBLE FOR THE SPACECRAFT OBSERVATIONS AND GENERATE CONTROVERSY IN THE LITERATURE RELATED TO PHYSICAL PROCESSES OCCURRING IN THE OUTER HELIOSPHERE. THE QUESTIONS THAT REQUIRE DEFINITIVE ANSWERS ARE THE FOLLOWING: (1) WHAT IS THE ROLE OF PUI IN THE STRESS BALANCE AT THE HELIOPAUSE? (2) HOW TO IMPLEMENT GENUINELY KINETIC BOUNDARY CONDITIONS FOR PUIS AT THE HELIOSPHERIC TERMINATION SHOCK IN A WAY APPROPRIATE FOR A GLOBAL-SCALE MODEL CAPABLE OF REPRODUCING VOYAGER AND IBEX OBSERVATIONS? (3) WHAT ARE THE PROPERTIES AND PHYSICAL CONSEQUENCES OF MICROSCOPIC TURBULENCE PRODUCED BY PUIS BEYOND THE HELIOPAUSE AND HOW DOES IT RELATE TO THE MACROSCOPIC LISM TURBULENCE? (4) WHAT IS THE ORIGIN OF THE HELIOSPHERIC BOUNDARY LAYER (HBL THE REGION OF DEPRESSED LISM PLASMA DENSITY EXTENDING A FEW TENS OF AU BEYOND THE HELIOPAUSE) IF IT EXISTS EVEN WITHOUT THE INTERSTELLAR MAGNETIC FIELD (ISMF)? (5) HOW CAN IBEX AND VOYAGER MEASUREMENTS VALIDATE THEORETICAL MODELS OF THE HELIOSPHERE THAT TAKE INTO ACCOUNT THE EFFECT OF PUIS SELF-CONSISTENTLY?, G5736577897, NSF-BSF: Collaborative Research: Rankine-Hugoniot Conditions Relating the Gyrotropic Regions of Collisionless Shocks in Non-Thermal Plasma, G7998775681, THE PLANNED PERIOD OF PERFORMANCE IS NOVEMBER 1 2017 THROUGH OCTOBER 31 2019. THE FOLLOWING ACTIVITIES WILL BE PERFORMED DURING THE EXTENDED MISSION BY PRINCETON. A. PROVIDE PI LEADERSHIP OF THE IBEX SCIENCE EFFORT THROUGHOUT THE EXTENDED MISSION B. MANAGE THE PRINCETON SCIENCE EFFORT THROUGHOUT THE EXTENDED MISSION C. PREPARE AND SUBMIT QUARTERLY TECHNICAL PROGRESS REPORTS D. SUPPORT TEAM TELECONS 1 TO 2 TIMES PER MONTH E. ATTEND SCIENCE TEAM MEETINGS AND SCIENTIFIC CONFERENCES AS CALLED BY THE PI F. DEVELOP ALGORITHMS AND SOFTWARE AS REQUEST BY THE PI IN SUPPORT OF IBEX DATA ANALYSIS OR THEORY EFFORTS G. ANALYZE AND PUBLISH IBEX INVESTIGATION SCIENCE DATA H. RECEIVE AND ANALYZE PAYLOAD SCIENCE DATA; WORK WITH THE IBEX TEAM TO DEVELOP MODELS ALGORITHMS ETC. TO ANALYZE THE SCIENCE DATA; PUBLISH IBEX SCIENCE RESULTS; SUPPORT THE ARCHIVAL OF SCIENCE DATA, Collaborative Research: Travel Supplement for Frontera's "Multi-scale, MHD-Kinetic Modeling of the Solar Wind and its Interaction with the Local Interstellar Medium"
OpenAlex ID: W4407194694