Comparing Methods for Calculating Solar Energetic Particle Intensities: Rebinning versus Spectral Binning
Abstract
Solar energetic particle (SEP) events have been observed for decades in the interplanetary medium by spacecraft measuring the intensity of energetic ions and electrons. These intensities provide valuable information about particle acceleration, the effects of bulk plasma dynamics on particle transport, and the anisotropy of particle distributions. Since measured intensities are typically reported in narrow energy bins, it is common to rebin intensities over a wider energy range to improve counting statistics. We investigate two methods for calculating intensities across multiple energy bins: (a) rebinned intensity (j―linlin), which is calculated by integrating the intensity over energy space and corresponds to the intensity at an effective energy that depends on the time-varying spectral index, and (b) spectral binned intensity (j―loglog), calculated by integrating the log intensity in log–energy space, yielding the intensity at the log-centered energy that is independent of the spectral index and remains constant over time. We compare these methods using Parker Solar Probe (PSP) IS⊙IS measurements of energetic protons, and we prescribe criteria for selecting the appropriate method for different scenarios. Our results show that the rebinned intensity is consistently larger (up to a factor of 5) than the spectral binned intensity for two SEP events observed by PSP, although the time series of the two methods are strongly correlated. Overall, both measures are important for SEP spectral analysis, and the selection of the appropriate measure depends on whether a physical (spectral binned intensity) or a statistical (rebinned intensity) representation is needed for a given analysis.
Copyright and License
© 2025. The Author(s). Published by the American Astronomical Society.
Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
Acknowledgement
We thank the IS⊙IS team and everyone that made the PSP mission possible. The IS⊙IS data and visualization tools are available to the community at https://spacephysics.princeton.edu/missions-instruments/PSP. PSP was designed, built, and is operated by the Johns Hopkins Applied Physics Laboratory as part of NASA's Living with a Star (LWS) program (contract NNN06AA01C).
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Additional details
- Alternative title
- Comparing Methods for Calculating Solar Energetic Particle Intensities: Re-binning versus Spectral Binning
- National Aeronautics and Space Administration
- Living with a Star (LWS) NNN06AA01C
- Accepted
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2025-01-23Accepted
- Available
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2025-02-19Published
- Caltech groups
- Space Radiation Laboratory
- Publication Status
- Published