Solar energetic particle anisotropies and insights into particle transport

Leske, R. A.; Cummings, A. C.; Cohen, C. M. S.; Mewaldt, R. A.; Labrador, A. W.; Stone, E. C.; Wiedenbeck, M. E.; Christian, E. R.; Rosenvinge, T. T. von

doi:10.1063/1.4943841

Cited by 3 publications

(5 citation statements)

References 13 publications

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“…This acceleration versus transport origin of widespread events also remains unsolved. New measurements at higher energies, with improved energy and angular resolution, along with direct particle anisotropies [55,56], will aid in addressing these research questions. Additionally, measurements of relativistic electrons hold value for in-situ forecasting of SEP protons [15].…”

Section: Solar Energetic Particle Acceleration and Transportmentioning

confidence: 99%

Galactic Cosmic Rays and Solar Energetic Particles in Cis-Lunar Space

Corti,

Whitman,

Desai

et al. 2023

Bulletin of the AAS

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The particle and radiation environment in cis-lunar space is becoming increasingly important as more and more hardware and human assets occupy various orbits around the Earth and space exploration efforts turn to the Moon and beyond. Since 2020, the total number of satellites in orbit has approximately doubled, highlighting the growing dependence on space-based resources. Through NASA's upcoming Artemis missions, humans will spend more time in cis-lunar space than ever before supported by the expansive infrastructure required for extended missions to the Moon, including a surface habitat, a communications network, and the Lunar Gateway -a space station which will orbit the Moon. Cis-lunar space starts at the top of the Earth's atmosphere and extends out to the orbit of the Moon, including the ionosphere, magnetosphere, free space, and the lunar surface. This paper focuses on galactic cosmic rays (GCRs) and solar energetic particles (SEPs) that create a dynamic and varying radiation environment within these regions. GCRs are particles of hundreds of MeV/nucleon (MeV/n) and above generated in highly energetic astrophysical environments in the Milky Way Galaxy, such as supernovae and pulsars, and beyond. These particles impinge isotropically on the heliosphere and are filtered down to 1 AU, experiencing modulation in energy and intensity on multiple timescales, from hours to decades, due to the solar magnetic cycle and other transient phenomena. SEPs are particles with energies up to thousands of MeV/n that are accelerated in eruptive events on the Sun and flood the inner heliosphere causing sudden and drastic increases in the particle environment on timescales of minutes to days. This paper highlights a current and prospective future gap in energetic particle measurements in the hundreds of MeV/n. We recommend key observations near Earth to act as a baseline as well as distributed measurements in the heliosphere, magnetosphere, and lunar surface to improve the scientific understanding of these particle populations and sources.

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Section: Solar Energetic Particle Acceleration and Transportmentioning

confidence: 99%

Galactic Cosmic Rays and Solar Energetic Particles in Cis-Lunar Space

Corti,

Whitman,

Desai

et al. 2023

Bulletin of the AAS

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“…This work makes use of techniques to infer Q from time-intensity profiles, which are particularly useful when direct charge state measurements or measurements based on the geomagnetic cutoff were not available. There was a report on peculiar anisotropy oscillations during the 2012 Jul 23 SEP event [48]. There was a study of how cosmogenic isotopics in lunar samples relate to the SEP flux [74].…”

Section: Other (4)mentioning

confidence: 99%

Solar-Heliospheric Physics

Ruffolo¹

2017

Proceedings of 35th International Cosmic Ray Conference — PoS(ICRC2017)

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This rapporteur paper summarizes the 99 presentations on solar-heliospheric physics at the 35th International Cosmic Ray Conference. These spanned a dizzying array of physical phenomena, especially time-dependent phenomena associated with solar storms, the 27-day solar rotation, the ∼11-year sunspot cycle, and the ∼22-year solar magnetic cycle. There was also work on composition-dependent effects and cosmic ray anisotropy involving transport effects. Topics included ground-and space-based instrumentation, solar energetic particles from solar storms (ranging from keV-range seed particles to GeV-range accelerated particles), interplanetary transport of energetic particles, Earth's radiation environment (including space weather and other effects of cosmic rays at Earth), the sun shadow in TeV-range Galactic cosmic rays (GCRs), and solar modulation of GCRs with the sunspot cycle and solar magnetic cycle.

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“…The peculiar shapes and rapid variability of the pitch-angle distributions (PADs) are more easily seen in the selected 1-minute samples in the bottom panel of Figure 1; at times the beam width fluctuated repeatedly by >25 • in a matter of minutes, and the distributions often tended to flatten at the peaks. In our earlier reports [7,8] we had failed to notice that changes in the variability of the PADs are well-correlated with changes in the variability of the magnetic field direction. Note that in the top panel of Figure 1 the magnetic field longitude varied over a range of >50 • between ∼5:30 and 6:10 UT (sometimes varying by 20 • or more from one minute to the next within this interval), exactly when the time intensity profiles in many µ bins (middle panel) were most variable.…”

Section: Observations and Analysismentioning

confidence: 99%

“…In previous reports, we have discussed LET/Ahead anisotropy observations in the 23 July 2012 event [7,8]. In particular, we noted puzzling oscillations in the width of a beamed distribution at the onset of this event and speculated as to their cause.…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, we had neglected the fact that LET 1-minute data are not aligned on minute boundaries, but rather have an offset varying throughout the mission as the instrument clock drifts slightly; for the period of interest here, this offset amounts to 58 seconds. Thus, in our previous reports [7,8] we were inadvertently comparing LET data with magnetic field directions measured 88 seconds earlier.…”

Section: Pos(icrc2017)144mentioning

confidence: 99%

See 1 more Smart Citation

Magnetic Fluctuations and Peculiar Anisotropy Oscillations in the 23 July 2012 SEP Event

Leske¹,

Cummings²,

Cohen³

et al. 2017

Proceedings of 35th International Cosmic Ray Conference — PoS(ICRC2017)

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The pitch-angle distributions of solar energetic particles (SEPs) provide a wealth of information about particle transport through interplanetary space, and depend on the magnetic field strength, topology, and turbulence at remote heliospheric locations. The Low Energy Telescope (LET) on STEREO measures angular distributions in the ecliptic for SEP ions from protons to iron with energies of about 2-12 MeV/nucleon. At the onset of the 23 July 2012 extreme SEP event, a beamed distribution was observed at STEREO-Ahead using LET. We have previously reported apparent "oscillations" in the pitch-angle width of this beam when using simultaneous particle and magnetic field measurements at a 1-minute cadence. We have now determined that this behavior is largely a result of the effects of magnetic turbulence on the calculated particle pitch angle distributions. The locally measured magnetic field direction varies relatively rapidly, while the energetic particle distribution is governed by magnetic fields averaged over much larger spatial and temporal scales than represented by solar wind measurements at the same cadence. Similar behavior in earlier events has been reported by others and analyzed in the framework of quasilinear theory.

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Solar energetic particle anisotropies and insights into particle transport

Cited by 3 publications

References 13 publications

Galactic Cosmic Rays and Solar Energetic Particles in Cis-Lunar Space

Galactic Cosmic Rays and Solar Energetic Particles in Cis-Lunar Space

Solar-Heliospheric Physics

Magnetic Fluctuations and Peculiar Anisotropy Oscillations in the 23 July 2012 SEP Event

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