Variability of the Proton Radiation Belt

Selesnick, R. S.; Albert, J. M.

doi:10.1029/2019ja026754

Cited by 20 publications

(63 citation statements)

References 35 publications

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“…Its solar cycle variation is only obvious at L < 1.2, which is also confirmed by recent measurements from the Van Allen Probes (2012–2019) in geo‐transfer‐like orbit. It is remarkable that the general model simulations, in which the decay of the proton fluxes is mainly due to energy loss to free and bound electrons in the local plasma and neutral atmosphere and is solar cycle dependent (Selesnick & Albert, 2019), reproduce the measurement well. This leads to a consolidated understanding that the solar cycle variation of the ionospheric and atmospheric density dominates the observed solar cycle variation of trapped inner belt proton flux.…”

Section: Introductionmentioning

confidence: 94%

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New Insights From Long‐Term Measurements of Inner Belt Protons (10s of MeV) by SAMPEX, POES, Van Allen Probes, and Simulation Results

Xiang

Zhang

et al. 2020

JGR Space Physics

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The Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX) mission provided long‐term measurements of 10s of megaelectron volt (MeV) inner belt (L < 2) protons (1992–2009) as did the Polar‐orbiting Operational Environmental Satellite‐18 (POES‐18, 2005 to present). These long‐term measurements at low‐Earth orbit (LEO) showed clear solar cycle variations which anticorrelate with sunspot number. However, the magnitude of the variation is much greater than the solar cycle variation of galactic cosmic rays (>GeV) that are regarded as a source of these trapped protons. Furthermore, the proton fluxes and their variations sensitively depend on the altitude above the South Atlantic Anomaly (SAA) region. With respect to protons (>36 MeV) mirroring near the magnetic equator, both POES measurements and simulations show no obvious solar cycle variations at L > 1.2. This is also confirmed by recent measurements from the Van Allen Probes (2012–2019), but there are clear solar cycle variations and a strong spatial gradient of the proton flux below L = 1.2. A direct comparison between measurements and simulations leads to the conclusion that energy loss of trapped protons due to collisions with free and bound electrons in the ionosphere and atmosphere is the dominant mechanism for the strong spatial gradient and solar cycle variation of the inner belt protons. This fact is also key of importance for spacecraft and instrument design and operation in near‐Earth space.

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Section: Introductionmentioning

confidence: 94%

“…Nonetheless, it is still uncertain how many solar protons can become trapped in the magnetosphere for a given SEP event (Selesnick et al, 2010). It was also recognized that the SEP contribution to trapped protons inside L < 1.3 through radial diffusion is insignificant (e.g., Jentsch, 1981; Selesnick & Albert, 2019).…”

Section: Introductionmentioning

confidence: 99%

New Insights From Long‐Term Measurements of Inner Belt Protons (10s of MeV) by SAMPEX, POES, Van Allen Probes, and Simulation Results

Xiang

Zhang

et al. 2020

JGR Space Physics

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“…Therefore, the solar-cyclic variations of Z ≥ 2 ion fluxes can be motivated only under the assumption that the effect related to an increase in the ionization losses of such ions significantly exceeds the effect connected with the possible enhancement of radial diffusion of ions during the rising phase of solar activity. For example, when comparing the empirical model of the inner belt (L < 2.4) of protons with E ∼ 19-200 MeV, constructed on the data from Van Allen Probes, with the mathematical model of radial diffusion of protons in this region, it was assumed that D LL increases by only ∼ 2 times on the phase of growth of solar activity from 2013 to 2015 (Selesnick and Albert, 2019).…”

Section: Discussionmentioning

confidence: 99%

“…4). If one takes into account that the average charge Q i = +2 for helium ions with E > 0.2 MeV/n at L < 6 (see, e.g, Spjeldvik, 1979), we get µ b ∼ 1.4 × Q i keV nT −1 for the boundary considered at the maximum of solar activity and µ b ∼ 1.4 × M i keV nT −1 at the minimum of solar activity (for the dipole magnetic field region). The isolines of helium ion fluxes in Figs.…”

Section: Spatial-energy Structure Of the Helium Ion Fluxesmentioning

confidence: 99%

Earth's radiation belts' ions: patterns of the spatial-energy structure and its solar-cyclic variations

Kovtyukh

2020

Ann. Geophys.

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Abstract. Spatial-energy distributions of the stationary fluxes of protons, helium, and ions of the carbon–nitrogen–oxygen (CNO) group, with energy from E ∼100 keV to 200 MeV, in the Earth's radiation belts (ERBs), at L∼1–8, are considered here using data from satellites during the period from 1961 to 2017. It has been found that the results of these measurements line up in the {E,L} space, following some regular patterns. The ion ERB shows a single intensity peak that moves toward Earth with increasing energy and decreasing ion mass. Solar-cyclic (11-year) variations in the distributions of protons, helium, and the CNO group ion fluxes in the ERB are studied. In the inner regions of the ERB, it has been observed that fluxes decrease with increasing solar activity and that the solar-cyclic variations of fluxes of Z≥2 ions are much greater than those for protons; moreover, it seems that they increase with increasing atomic number Z. It is suggested that heavier ion intensities peak further from the Earth and vary more over the solar cycle, as they have more strong ionization losses. These results also indicate that the coefficient DLL of the radial diffusion of the ERB ions changes much less than the ionization loss rates of ions with Z≥2 due to variations in the level of solar activity.

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“…Escoubet et al [2015]). The findings from the Van Allen Probes, in particular, have led to many breakthrough discoveries and have evolved the state of the art of radiation belts' research to a new level [Shprits et al 2016;Ozeke et al 2017;Baker et al 2018;Selesnick and Albert, 2019]. The remarkable increase of refereed publications on the subject after 2000 ( Figure 11) and the launch of follow-up missions like Arase, the China Seismo-Electromagnetic Satellite, Lomonosov and others [Alfonsi et al 2017;Shprits et al 2018b;Miyoshi et al 2017], are representative of the aforementioned, rapid progress and increased interest in the field.…”

Section: Multi-point Investigations Of Planetary Magnetospheresmentioning

confidence: 99%

The in-situ exploration of Jupiter's radiation belts

Roussos¹

2020

Preprint

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<p>Jupiter has the most energetic and complex radiation belts in our solar system. Their hazardous environment is the reason why so many spacecraft avoid rather than investigate them, and explains how they have kept many of their secrets so well hidden, despite having been studied for decades. We believe that these secrets are worth unveiling, as Jupiter&#8217;s radiation belts and the vast magnetosphere that encloses them constitute an unprecedented physical laboratory, suitable for both interdisciplinary and novel scientific investigations: From studying fundamental high energy plasma physics processes which operate throughout the universe, such as adiabatic charged particle acceleration and nonlinear wave-particle interactions; to exploiting the astrobiological consequences of energetic particle radiation. The in-situ exploration of the uninviting environment of Jupiter&#8217;s radiation belts presents us with many challenges in mission design, science planning, instrumentation and technology development. We address these challenges by reviewing the different options that exist for direct and indirect observation of this unique system. We stress the need for new instruments, the value of synergistic Earth and Jupiter-based remote sensing and in-situ investigations, and the vital importance of multi-spacecraft, in-situ measurements. While simultaneous, multi-point in-situ observations have long become the standard for exploring electromagnetic interactions in the inner solar system, they have never taken place at Jupiter or any strongly magnetized planet besides Earth. We conclude that a dedicated multi-spacecraft mission to Jupiter&#8217;s radiation belts is an essential and obvious way forward. Besides guaranteeing many discoveries and outstanding progress in our understanding of planetary radiation belts, it offers a number of opportunities for interdisciplinary science investigations. For all these reasons, the exploration of Jupiter&#8217;s radiation belts deserves to be given a high priority in the future exploration of our solar system. A White Paper on this subject was submitted in response to ESA's Voyage 2050 call.</p>

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Variability of the Proton Radiation Belt

Cited by 20 publications

References 35 publications

New Insights From Long‐Term Measurements of Inner Belt Protons (10s of MeV) by SAMPEX, POES, Van Allen Probes, and Simulation Results

New Insights From Long‐Term Measurements of Inner Belt Protons (10s of MeV) by SAMPEX, POES, Van Allen Probes, and Simulation Results

Earth's radiation belts' ions: patterns of the spatial-energy structure and its solar-cyclic variations

The in-situ exploration of Jupiter's radiation belts

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