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STEREO-A PLasma and Supra-Thermal Ion Composition (PLASTIC) He⁺ Counts and Relative Energy Flux in four Velocity Ranges normalized by the Solar Wind Speed, Level 3 (L3), Daily Data

Published by NASA Space Physics Data Facility (SPDF) Coordinated Data Analysis Web (CDAWeb) Data Services;STEREO Science Center;SSC | National Aeronautics and Space Administration | Metadata Last Checked: February 21, 2026 | Last Modified: 2026-02-17
STEREO-A Plasma and Suprathermal Ion Composition, Singly-charged Helium, He⁺, counts and relative differential energy fluxes binned by the ion speed relative to the solar wind bulk speed, four speed ratio bins. STEREO PLASTIC daily suprathermal He⁺ pickup ion signatures include He⁺ energy spectra, directional information, and contenxt information, such as the H⁺ plasma velocity. The four speed ratio, V/Vsw, bin ranges of are: 1.44 to 1.85, 1.85 to 2.50, 2.50 to 3.50, and 3.50 to 8.00. The identification of He⁺ is based on the measurement of energy per charge, E/q, time-of-flight, TOF, and total energy deposited in the solid state detector, SSD. These data include double coincidence measurements by using E/Qi and TOF and triple coincidence measurements by using E/Q, TOF, and SSD, see for example Galvin et al., Space Sci. Rev. 136, p 437-468, 2008. The proton bulk parameters including speed, Vsw, thermal velocity, Vth, and Density, Np, in this file are derived from a one-deminsional, 1-D, Maxwellian fit to a single detector rate with no coincidence required. These proton bulk parameters are corrected for background and dead time. The software version number used to derive the proton bulk parameters is shown in the file header and is described in the section on file formats. The most recent update of the proton bulk parameters can be found on the following STEREO website: http://stereo-ssc.nascom.nasa.gov/data/ins_data/plastic/level2/Protons/ For a full explanation, see the description at: https://stereo-ssc.nascom.nasa.gov/data/ins_data/plastic/level3/HePlus/HePlus_flux/READ_ME_PLASTIC_HePlus_Fluxes.pdf The singly-charged Helium, He⁺, flux data are also available from the STEREO Science Center in ASCII format via: https://stereo-ssc.nascom.nasa.gov/data/ins_data/plastic/level3/HePlus/ Note that this SPASE Numerical Description only describes the MESSENGER Magnetometer data stored in Common Data Files.

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