OBSERVATIONS OF ISOTROPIC INTERSTELLAR PICK-UP IONS AT 11 AND 17 AU FROM NEW HORIZONS

We report new observations by the Solar Wind Around Pluto (SWAP) instrument on the New Horizons spacecraft of an energy-per-charge (E/q) spectrum of interstellar pick-up ions (PUIs) from an unprecedented heliocentric distance of 17 AU. This E/q spectrum is fit well by an isotropic PUI distribution f...

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Bibliographic Details
Published in:The Astrophysical journal 2012-08, Vol.755 (1), p.1-7
Main Authors: RANDOL, B. M, ELLIOTT, H. A, GOSLING, J. T, MCCOMAS, D. J, SCHWADRON, N. A
Format: Article
Language:English
Subjects:
ACCELERATION
Analyzers
ASTRONOMY
ASTROPHYSICS
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
ATOMS
DATA ANALYSIS
DISTANCE
DISTRIBUTION FUNCTIONS
Earth, ocean, space
ELECTROSTATIC ANALYZERS
Electrostatics
ENERGY SPECTRA
Exact sciences and technology
HELIOSPHERE
Interstellar
INTERSTELLAR SPACE
IONS
New Horizons mission
Pluto
SOLAR WIND
Spacecraft
SUN
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Summary:We report new observations by the Solar Wind Around Pluto (SWAP) instrument on the New Horizons spacecraft of an energy-per-charge (E/q) spectrum of interstellar pick-up ions (PUIs) from an unprecedented heliocentric distance of 17 AU. This E/q spectrum is fit well by an isotropic PUI distribution function combined with the detailed response of the SWAP instrument. In contrast to earlier work, we are also able to fit an isotropic PUI model to an E/q spectrum measured by SWAP at 11.3 AU by explicitly including two additional effects. These are (1) the E/q-dependent geometric factor of SWAP, which increases with decreasing E/q owing to effects associated with the post-acceleration of particles exiting the electrostatic analyzer portion of the instrument; and (2) a solar wind distribution, the model spectrum of which contributes significantly to the low-E/q part of the overall model owing, presumably, to secondary particles produced within the instrument.
ISSN:0004-637X
1538-4357
DOI:10.1088/0004-637X/755/1/75