On the chaos and stability problem in the trapping of anomalous cosmic ray heavy ions by the Earth's magnetosphere

Ions of nitrogen, oxygen and neon have been observed in detectable quantities in the Earth's inner radiation zone between L-shells of 1.2 and 2.4. Russian and American spacecraft observations of these ions pertain to low altitudes near the top of the atmosphere. Because of large loss rates during cross-field diffusion, the source of these ions cannot simply be radial transport from the outer radiation zone, but rather must be an effective local source at low L-shells. This source is now believed to be the direct entry of anomalous cosmic ray ions in low charge states and thus high geomagnetic rigidity. These ions call charge exchange with atmospheric particles to become multiply charged and thus instantaneously trapped by the geomagnetic field. The energies of these ions are sufficiently high to violate the strict adiabaticity criterion of trapped particles, and thus their bounce motion and azimuthal drift-like transport will be at least partially non-adiabatic and may be considered chaotic in nature. The stability and chaos-like pitch angle scattering process expected for such inner radiation zone energetic heavy ions are discussed. From the theory considered, the ACR ions of energy about tens of MeV nucleon(-1) could be trapped only when they have atomic mass A greater than or equal to 7 and arrive at the Earth from the westward direction.44326727

Nuclear reactions in the uppermost Earth atmosphere as a source of the magnetospheric positron radiation belt

A physical mechanism for the formation of a natural positron belt in the Earth's magnetosphere is considered. It is assumed that a natural source of energetic positrons as well as electrons can be created owing to the decay of charged pions pi (+/-) --> mu (+/-) --> e(+/-), which have their origin in nuclear collisions between energetic trapped inner zone protons and heavier atoms (He and O) in the upper atmosphere of the Earth. Simulations of these processes demonstrate that there is a predominant production of positive pions over negative pions, and consequently the decays result in a substantial excess of positrons over electrons at energies greater than tens of MeV. This positron excess is found to be energy-dependent and to decrease with increasing incident proton energy; this excess is essentially absent at proton energies corresponding to cosmic ray primaries of greater than or equal to8 GeV. Our numerical computations for the resulting e(+)/e(-) fluxes provide ratio values of similar to4 at multi-MeV energies and at L = 1.2 +/- 0.1. The simulation results presented herein are compared to the existing and recent experimental evidence.O TEXTO COMPLETO DESTE ARTIGO, ESTARÁ DISPONÍVEL À PARTIR DE FEVEREIRO DE 2015.106A11261112611

On the natural energetic positron population in the Earth's inner radiation belt

Anti-particles may coexist with particles in the rarefied energetic particle and plasma environments of the magnetized planets. We consider here the possibility that a naturally generated belt of positrons may be part of the terrestrial radiation environment. It is suggested that energetic positrons of MeV energies can be produced in inelastic nuclear reactions resulting from energetic collisions between the geomagnetically confined population of relativistic protons and the residual terrestrial atmosphere and exosphere. The spatial location of the production of these positrons would thus most likely be the inner radiation zone on L-shells well below L = 2.0. In this work we present a computed positron source function, and we assess the longevity and probable ambient abundance of these positrons in the 10-100 MeV energy range around L = 1.2. The theoretical predictions are then compared with available experimental measurements of magnetospheric positrons. Copyright (C) 1996 Elsevier Science Ltd.59336336

Energetic-positron population in the inner zone

The possibility of the existence of a natural positron belt in the Earth's magnetosphere is considered. It is suggested that the positrons can be produced in the nuclear reactions of trapped relativistic protons of the inner zone with the residual atmosphere. The positron spectrum in the range of 10-100 MeV at the top of L = 1.2 is calculated and compared with the experimental results.19446146

The temporal evolution of 3-9 MeV/nucleon He flux trapped in the magnetosphere

Results of measurements of the absolute values and long term temporal evolution of the spatial distribution of trapped He ion fluxes of 3.2 - 9.2 MeV/nucleon energy at L < 4 obtained by the OHZORA satellite are reported. The annually aver aged radial profile exhibits one persistently present peak at L = 1.3 - 1.5 as well as very significant transient trapped fluxes at L = 1.4 - 4.0 during the period 1984-1986. Together the absolute values of the fluxes measured by OHZORA and S72-1, SAMPEX, and CRRES spacecrafts may approximately be described by a power spectrum with index of -8.0 +/- 1.0 at L = 1.9 - 2.3 within the energy range of 3 - 100 MeV/nucleon.O TEXTO COMPLETO DESTE ARTIGO, ESTARÁ DISPONÍVEL À PARTIR DE FEVEREIRO DE 2015.23202793279

Dynamics of the low-altitude energetic proton fluxes beneath the main terrestrial radiation belts

At the interface between the upper atmosphere and the radiation belt region there exists a secondary radiation belt consisting mainly of energetic ions that have become neutralized in the ring current and in the main radiation belt and then re-ionized by collisions in the inner exosphere. The time history of the proton fluxes in the 0.64-35 MeV energy range was traced in the equatorial region beneath the main radiation belts during the 3-year period from February 21, 1984, to March 26, 1987, using data obtained with the High-Energy Particle experiment on board the Japanese OHZORA satellite. During most of this period a fairly small proton flux of similar to 1.2 cm(-2) s(-1) sr was detected on geomagnetic field lines in the range 1.05 < L < 1.15. We report a few surprisingly deep and rapid flux decreases (flux reduction by typically 2 orders of magnitude). These flux decreases were also long in duration (lasting up to 3 months). We also registered abrupt flux increases, such that magnitude of the proton flux enhancements could reach 3 orders of magnitude and with an enhancement duration of 1-3 days. Possible reasons for these unexpected phenomena are discussed.O TEXTO COMPLETO DESTE ARTIGO, ESTARÁ DISPONÍVEL À PARTIR DE FEVEREIRO DE 2015.101A9196591966

On synchrotron radiation energy losses of trapped magnetospheric electrons

Using an energy balance equation it is explicitly demonstrated that synchrotron radiation (SR) significantly decelerates several MeV electrons confined on geomagnetic L-shells below 2 during their radial diffusive transport into inner magnetosphere. SR losses from the ambient electrons are found to be comparable in importance with Coulomb friction energy losses, a well-known and much modeled cause of energy degradation in the radiation belts. It may also be true that, under some geophysical conditions and at some electron energies, the effective electron lifetime due to wave-induced pitch-angle scattering can be shorter than both the Coulomb and the SR lifetimes. But even when this holds true, the effect of the competing SR energy loss process can substantially influence the outcome of model computations of the ambient inner zone electron flux, pitch angle, spatial and energy distributions. We find that in the inner radiation zone of the Earth, care must be exercised to include the simultaneous effects of all three competing electron loss mechanisms. (C) 1998 Elsevier Science Ltd. All rights reserved.60111159116

Space weather impact on magnetosphere: New helium radiation belt storm time formation

The consequences of the March 1991 storm oil the Earth's radiation environment are now well known through many in-situ magnetospheric observations. Measurement from the CRRES spacecraft show the sudden formation of a new Helium ion structure deep within the magnetosphere. In that event, two additional new radiation belts were created, one containing large fluxes of 10 MeV electrons, and the other forming a structure containing 30 MeV protons. These sudden space weather phenomena appear to be due the conjunction of the two occurrences: (1) a solar energetic particle (SEP) event arriving in the vicinity of the Earth, and (2) a very intense magnetic storm within the Earth's magnetosphere. Attempts to reproduce the appearance of storm time helium belt by computational modeling are made using a three-dimensional charged particle code (Salammbo code) incorporating Helium ion charge exchange and post-event classical diffusion theory. We have extended the capabilities of the code to Helium ions, and we show that these physical phenomena can also lead to a build-up of a new Helium belt in the 30 MeV range. Detailed modeling predictions of the location of this belt and computed flux levels will be presented and discussed in the context of space weather phenomena in the Earth's magnetosphere.322BSI62463