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Interstellar He + ring‐beam distributions: Observations and implications
Author(s) -
Drews C.,
Berger Lars,
WimmerSchweingruber Robert F.,
Galvin Antoinette B.
Publication year - 2013
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/grl.50368
Subject(s) - solar wind , physics , ion , pitch angle , plasma , heliosphere , flux (metallurgy) , pickup , spectrometer , interplanetary magnetic field , energetic neutral atom , atomic physics , interstellar medium , astrophysics , astronomy , optics , materials science , nuclear physics , quantum mechanics , artificial intelligence , galaxy , computer science , metallurgy , image (mathematics)
We report systematic measurements of the distribution of the incident angle of interstellar pickup He + ions as observed by STEREO/Plasma and Supra‐Thermal Ion Composition (PLASTIC). We have organized these observations according to the angle spanned by the Interplanetary Magnetic Field (IMF),B → , and the bulk solar wind velocity,v sw→ . Our measurements show clear evidence of a relatively local injection of He + pickup ions into the solar wind, which are then seen as a ring distribution perpendicular toB → . Changes of the spectral shape and a reduced flux of interstellar He + during radial IMF configuration, as observed by, e.g., Ulysses/Solar Wind Ion Composition Spectrometer (SWICS), SOHO/Charge Time‐Of‐Flight (CTOF), Active Magnetospheric Particle Tracer Explorers/SUprathermaL Energy Ionic Charge Analyzer (SULEICA), have generally been attributed to inefficient scattering across 90° pitch‐angle. Our observations of the pitch‐angle distribution of interstellar He + suggest that these changes are instead a result of locally injected pickup ions that escape detection for IMF configuration in which the Solar Wind Sector of PLASTIC, as well as SWICS, CTOF, and SULEICA, are not sensitive to the measurement of the locally injected pickup ion ring.