Evidence for Solar-Cycle Changes in the Inner-Belt Protons

Nakano, G. H.; Heckman, H. H.

doi:10.1103/physrevlett.20.806

Cited by 21 publications

(12 citation statements)

References 6 publications

(3 reference statements)

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“…They reported a high degree of stability during that period. As solar activity increased after mid-1966, these same authors observed a decrease in the 63-MeV proton population [Nakano and Heckman, 1968] and by mid-1969 (solar maximum) this same population had decreased by about a factor 2 relative to the solar minimum period.…”

Section: Introductionmentioning

confidence: 87%

Solar cycle induced modulation of the 55‐MeV proton fluxes at low altitudes

Parsignault¹,

Holeman²

1981

J. Geophys. Res.

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Experiments flown on U.S. Air Force Satellites from 1961 until 1976 have measured the 55-MeV proton flux at low altitudes, between 275 km and 600 km. The analysis of these data shows that in spite of all the uncertainties involved, the agreement obtained between the theoretical calculations and the data is quite good. We conclude that the major determining factors of the 55-MeV proton fluxes in the inner zone are a nearly constant source coupled with a solar cycle varying atmospheric ionization loss process. to a minimum flux around 1968-69. day duration of the Air Force Satellite flights from 1961-1971. THE EXPERIMENTS The measurements of the 55-MeV proton fluxes from 1961-1971 involved the use of emulsions carried on oriented, recov-

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Section: Introductionmentioning

confidence: 87%

Solar cycle induced modulation of the 55‐MeV proton fluxes at low altitudes

Parsignault¹,

Holeman²

1981

J. Geophys. Res.

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“…A typical temporal variation in this region is the solar cycle variation [ Nakano and Heckman , ; Dragt , ]. The proton flux variation was first substantiated to be anticorrelated with solar cycle changes in density of the upper atmosphere on the basis of experimental data [ Nakano and Heckman , ]. Using data from the TIROS/NOAA spacecraft, Huston et al [, ] found a definite phase lag when examining the anticorrelation relationship between the F 10.7 flux and the proton flux.…”

Section: Introductionmentioning

confidence: 99%

“…A typical temporal variation in this region is the solar cycle variation [Nakano and Heckman, 1968;Dragt, 1971]. The proton flux variation was first substantiated to be anticorrelated with solar cycle changes in density of the upper atmosphere on the basis of experimental data [Nakano and Heckman, 1968].…”

Section: Introductionmentioning

confidence: 99%

Solar cycle variations of trapped proton flux in the inner radiation belt

Qin

Zhang

et al. 2014

JGR Space Physics

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Trapped proton population in the inner radiation belt is highly dense, posing a potential danger to astronauts and man-made space assets traversing through this region. While being significantly stable within timescales up to hundreds of days, inner zone proton fluxes can exhibit considerable solar cycle variations, which has not been investigated comprehensively yet. To analyze the long-term variation of the South Atlantic Anomaly (SAA), we adopt the proton flux data measured by NOAA 15 from 1999 through 2009 and perform statistical analyses on the basis of reasonable Gaussian fits. We report that the variation of the peak proton flux in the SAA is anticorrelated with that of F 10.7 during a solar cycle. There also exists a phase lag of 685 days between the solar F 10.7 flux and the proton flux. Similar features are seen for changes of the SAA distribution area, which in addition shows a rapid decrease during the solar maximum and a slow increase during the solar minimum. We also find that the region where the proton flux peaks drifts westward year by year with larger drift rates during the solar minimum. The peak region shifts southward during the solar maximum but in the opposite direction during the solar minimum with higher shift speed. Enhancements in solar wind dynamic pressure can favor the north-south drift of the SAA.

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“…Moreover, at the minima of solar activity, the inner edge of a proton flux radial profiles with E > 1 MeV is less steep and achieves smaller L shells. Solar-cyclic (11-year) variations of proton fluxes with E > 1 MeV in the inner region of the ERB connected mainly with the variations in the concentrations of atoms in the atmosphere (see, e.g., Pizzella et al, 1962;Hess, 1962;Blanchard and Hess, 1964;Filz, 1967;Nakano and Heckman, 1968;Vernov, 1969;Dragt, 1971;Huston et al, 1996;Vacaresse et al, 1999;Kuznetsov et al, 2010;Qin et al, 2014). These variations achieves one order of magnitude at L = 1.14 and reduced rapidly with increasing L (see, e.g., Vacaresse et al, 1999).…”

Section: Invariants Of the Ion Earth's Radiation Belts Structurementioning

confidence: 99%

Invariants of the Spatial-Energy Structure and Modeling of the Earth's Ion Radiation Belts

Kovtyukh

2019

Preprint

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Abstract. The spatial-energy distributions of proton fluxes in the Earth's radiation belts (ERB) are well studied and the NASA averaged empirical models constructed for them (the latest versions are AP8 and AP9). These models are widely used in space research. However, for heavier ERB ions (helium, oxygen, etc.), much less measurements were made on satellites, especially in the energy range from tens to hundreds of MeV, and there are no sufficiently complete and reliable models for them. Meanwhile, such ions, although there are much smaller than protons, play a very important role in the physics of ERB, especially in their dynamics, as well as in solving problems of ensuring the safety of space flights. The data on such ions represent a rather fragmentary picture, in which there are significant white spots. Using the methods considered in this paper, these fragmentary data can be streamlined, linked to each other and get a regular picture that has a simple physical meaning. Spatial-energy distributions of the stationary fluxes of protons, helium ions and ions of the CNO group with energy from 100 keV to 200 MeV at L ~ 1–8 considered here on the data of the satellites for 1961–2017. It is found, that results of the measurements of the ion fluxes are arrange in certain regular patterns in the spaces {E, L} and {L, B/B0}. This effect connected with the existence of invariant parameters of these distributions of ion fluxes. These invariant parameters are very useful and necessary for constructing the ion models of the ERB. The physical mechanisms leading to formation spatial-energy structure of the ERB ion fluxes and the values of its invariant parameters discussed here. In the course of this work, solar-cyclic (11-year) variations in the distributions of helium and carbon-nitrogen-oxygen ions fluxes in the ERB studied for the first time. It shown that, as compared with such variations in the proton fluxes studied earlier, the amplitude of the variations of heavier ions is much larger and increases with increasing their mass.

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Evidence for Solar-Cycle Changes in the Inner-Belt Protons

Cited by 21 publications

References 6 publications

Solar cycle induced modulation of the 55‐MeV proton fluxes at low altitudes

Solar cycle induced modulation of the 55‐MeV proton fluxes at low altitudes

Solar cycle variations of trapped proton flux in the inner radiation belt

Invariants of the Spatial-Energy Structure and Modeling of the Earth's Ion Radiation Belts

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