Detection and characterization of 0.5–8 MeV neutrons near Mercury: Evidence for a solar origin

Lawrence, D. J.; Feldman, W. C.; Goldsten, J.; Peplowski, P. N.; Rodgers, D. J.; Solomon, Sean C.

doi:10.1002/2013ja019037

Cited by 17 publications

(116 citation statements)

References 46 publications

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“…These events were caused by high energy solar neutrons with more than ∼ 100 MeV. On the other hand, low energy neutrons (< 100 MeV) have been detected by satellite-borne detectors ( [1], [2]). So far more than 10 solar neutron events have been detected on the ground by the network of solar neutron telescopes and neutron monitors ( [3], [4]).…”

Section: High Energy Solar Neutrons and Galactic Cosmic-ray Muonsmentioning

confidence: 99%

Upgrade of a data acquisition system for SciBar Cosmic Ray Telescope (SciCRT) at Mt. Sierra Negra, Mexico

Sasai¹,

Kawabata²,

Ikeno³

et al. 2016

Proceedings of the 34th International Cosmic Ray Conference — PoS(ICRC2015)

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SciCRT (SciBar Cosmic Ray Telescope) is a new project to observe cosmic rays via a full active scintillator tracker. Our aim is to detect high energy solar neutrons produced by the interaction between accelerated ions and the solar atmosphere and to observe muons to research anisotropy of Galactic Cosmic Rays (GCRs). In the previous ICRC in Brazil, we reported that the detector has been installed at Mt. Sierra Negra (4,600 m above sea level) in April 2013. We also reported that the current VME-based data acquisition (DAQ) system does not have enough capacity to deal with GCR-induced neutrons at such a high altitude mountain. Moreover noises produced by the VME readout prevent the DAQ system counting the trigger rate and make the current trigger process complicated. Therefore we have developed a fast readout DAQ system, optimized to our experimental environment within an Open-It project. We employed SiTCP, a hardware-based network processor, developed for high energy physics. We have developed a brand-new back-end board (BEB) based SiTCP and tested it at Mt. Sierra Negra in 2014. Then we determined the definitive design for the new BEB. We replaced the muon and a part of the neutron DAQ system with the new DAQ system in June, 2015. We will introduce the basic performance evaluation and the configuration of the new DAQ system which is operated at Mt. Sierra Negra.

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Section: High Energy Solar Neutrons and Galactic Cosmic-ray Muonsmentioning

confidence: 99%

Upgrade of a data acquisition system for SciBar Cosmic Ray Telescope (SciCRT) at Mt. Sierra Negra, Mexico

Sasai¹,

Kawabata²,

Ikeno³

et al. 2016

Proceedings of the 34th International Cosmic Ray Conference — PoS(ICRC2015)

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“…There is currently no capability to distinguish between energetic electrons and ions. The minimum energy thresholds to trigger the three types of events were initially estimated by Feldman et al [] and updated by Lawrence et al []. The updated minimum energy thresholds—based on the half‐maximum count rates for an isotropic energetic particle flux—are the following: singles, >15 MeV protons (or >1 MeV electrons); double coincidences, >45 MeV protons (or >10 MeV electrons); and triple coincidences, >125 MeV protons (or >30 MeV electrons).…”

Section: Cruise Particle Measurementsmentioning

confidence: 99%

“…The high‐energy GCR particles are themselves measurable in the NS by the double‐ and triple‐coincident energy deposition between the LG and BP detector components. The NS is also sensitive to solar energetic particles from solar flares and coronal mass ejections, such as those observed by MESSENGER on 31 December 2007 [ Feldman et al , ] and 4 June 2011 [ Lawrence et al , ].…”

Section: Cruise Particle Measurementsmentioning

confidence: 99%

“…The neutron count rate energy spectrum as a function of distance to the Sun, F ( E t , r ), is

F ((),, E_{t}, r) = ε ((), E_{t}) normalΔ normalΩ ((), r) true {true\int}_{0.5 M e V}^{9 M e V} Q ((), E) D ((),, E, r) T ((),, E, E_{t}) d E,

where E is the spacecraft‐incident neutron energy (MeV), E t is the NS‐incident neutron energy (MeV) after transport through the spacecraft, ε ( E t ) is a dimensionless neutron detection efficiency factor for the NS, and ΔΩ( r ) is the solid angle (sr) subtended by the 100 cm 2 NS detector area at a distance r (cm) from the Sun: ΔΩ( r ) = 100/ r 2 sr. Q ( E ) is the surface‐averaged neutron‐flux spectrum at the Sun (neutrons s −1 sr −1 MeV −1 ) and D ( E , r ) is a dimensionless factor accounting for the decay of nonrelativistic free neutrons with mean lifetime of 886 s. The quantity T ( E , E t ) is a transmission function (MeV −1 ) that incorporates neutron transport through MESSENGER to the NS. This function is calculated with the Monte Carlo N‐Particle extended (MCNPX) transport code and accounts for the full particle production and transport through the MESSENGER spacecraft [ Lawrence et al , ]. It was validated using measured neutron count rates and energy spectra from both Mercury and non‐Mercury neutron sources [ Lawrence et al , , ].…”

Section: Upper Limit On Quiescent Solar Neutron Productionmentioning

confidence: 99%

“…Identifying and characterizing solar neutrons are important goals of solar physics. As uncharged particles, they are unaffected by solar magnetic fields and can therefore provide key insight regarding solar acceleration processes [ Hua et al , ; Dorman , 2010; Vilmer et al , ; Feldman et al , ; Lawrence et al , ]. Prior studies have reported the detection of solar neutrons using MESSENGER NS data for specific times associated with enhanced solar activity [ Feldman et al , ; Lawrence et al , ], although the specific solar nature for one of these events has been disputed [ Share et al , ].…”

Section: Introductionmentioning

confidence: 99%

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Neutrons and energetic charged particles in the inner heliosphere: Measurements of the MESSENGER Neutron Spectrometer from 0.3 to 0.85 AU

et al. 2015

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Energetic charged particle and neutron data from the Neutron Spectrometer (NS) on board the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft have been acquired for solar distances ranging from 0.3 to 0.85 AU. The NS is sensitive to ions with energies greater than 120 MeV/nucleon and has made the first measurements of these energetic ions in the inner heliosphere since the mid-1970s. The high-energy ion measurements are well correlated with Earth-based neutron monitor measurements, which themselves provide a measure of the solar modulation of galactic cosmic rays (GCRs). These measurements provide an explicit demonstration of the expected GCR solar modulation for solar distances to 0.3 AU. These NS data also represent the first interplanetary neutron measurements in the inner heliosphere. The time variability of the neutron measurements are driven by two primary effects: time variable production of neutrons from GCRs interacting with local spacecraft material and small count rate changes due to temperature-driven gain changes in the NS instrument. When these time-dependent variations are removed from the neutron measurements, there is no statistically significant variation of neutron count rates versus solar distance. These data are used to derive an upper limit on solar neutron production of 10 24 neutrons [0.5 < E < 9 MeV] sr À1 s À1 during quiescent periods.

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Misidentification of the source of a neutron transient detected by MESSENGER on 4 June 2011

Murphy

Tylka

et al. 2015

JGR Space Physics

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Low‐energy (1–10 MeV) neutrons emanating from the Sun provide unique information about accelerated ions with steep energy spectra that may be produced in weak solar flares. However, observation of these solar neutrons can only be made in the inner heliosphere where measurement is difficult due to high background rates from neutrons produced by energetic ions interacting in the spacecraft. These ions can be from solar energetic particle events or produced in passing shocks associated with fast coronal mass ejections. Therefore, it is of the utmost importance that investigators rule out these secondary neutrons before making claims about detecting neutrons from the Sun. The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) neutron spectrometer recorded an hour‐long neutron transient beginning at 15:45 UTC on 4 June 2011 for which Lawrence et al. (2014) claim there is “strong evidence” that the neutrons were produced by the interaction of ions in the solar atmosphere. We studied this event in detail using data from the MESSENGER neutron spectrometer, gamma ray spectrometer, X‐ray Spectrometer, and Energetic Particle Spectrometer and from the particle spectrometers on STEREO A. We demonstrate that the transient neutrons were secondaries produced by energetic ions, probably accelerated by a passing shock, that interacted in the spacecraft. We also identify significant faults with the authors' arguments in favor of a solar neutron origin for the transient.

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Detection and characterization of 0.5–8 MeV neutrons near Mercury: Evidence for a solar origin

Cited by 17 publications

References 46 publications

Upgrade of a data acquisition system for SciBar Cosmic Ray Telescope (SciCRT) at Mt. Sierra Negra, Mexico

Upgrade of a data acquisition system for SciBar Cosmic Ray Telescope (SciCRT) at Mt. Sierra Negra, Mexico

Neutrons and energetic charged particles in the inner heliosphere: Measurements of the MESSENGER Neutron Spectrometer from 0.3 to 0.85 AU

Misidentification of the source of a neutron transient detected by MESSENGER on 4 June 2011

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