G. I. Pugacheva

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 Earths 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 π± → μ± → 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 ≥8 GeV. Our numerical computations for the resulting e+/e− fluxes provide ratio values of ∼4 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.

Antiprotons confined in the earth’s inner magnetosphere

Abstract The possible existence of noticeable fluxes of antiparticles in the Earth magnetosphere is considered theoretically in this article. These antiparticles (antiprotons in this paper) that are confined by geomagnetic field at the altitudes of several hundred kilometers are predominantly not of immediate extraterrestrial origin, but rather are the products of nuclear reactions of the high energy primary cosmic rays (CR) with constituents of the terrestrial atmosphere. Direct extraterrestrial antiprotons impinging upon the Earth’s magnetosphere are themselves also secondary in origin, i.e. they are born in nuclear reactions of the same CR passing through 5–7 g/cm 2 of interstellar matter. These exhibit lower fluxes compared to the magnetospheric antiprotons that are born at a pass length of hundreds g/cm 2 in the residual Earth atmosphere. Such locally generated antiprotons can be confined by the magnetic field of the Earth (or equivalently by another planet) and so accumulated in the magnetosphere. We here present the results of numerical simulation of antiproton fluxes in the energy range from 10 MeV to several GeV produced by CR in the Earth’s atmosphere at altitudes of about 1000 km, and we compare this to antiprotons born in interstellar matter. The estimates presented herein show a significant (up to two orders of magnitude) excess of magnetospheric antiproton fluxes over those formed in the interstellar media at energies

Trapped positron flux formation in the innermost magnetosphere of the Earth

The possible existence of a positron radiation belt in the inner magnetosphere of the Earth, its space location, flux, energy distribution and the ratio of e+/e− fluxes is considered. The source of the positrons/electrons is assumed to be the decay of charged pions (π - μ - e decay chain) produced, in the nuclear interactions between protons and the neutral constituents of the atmosphere. The production of excess positron fluxes over electron ones through this process is examined for two different proton populations and their atmospheric interactions in the altitude range of 80 to 1000 km. Monte Carlo simulations of intranuclear cascade process through SHIELD code was utilized to simulate these interactions. Considering the trapped proton fluxes in the inner magnetosphere as a source, the simulations for interactions in rarified atmosphere shows excess of positrons over electrons with ratios above 2 for proton energies below 2.5 GeV. Although, protons above this energy do not produce excess of positrons compared to electrons in atmospheric interactions, we assumed the primary cosmic rays with the energy greater than 8–10 GeV also as a source for these interactions, and utilizing the east-west asymmetry in the arrival directions of these primary cosmic rays combined with the exponential nature of the atmosphere density we also obtained an excess of positrons over electrons escaping from the atmosphere to the altitudes of satellite orbits. A comparison is attempted with the recent data of AMS experiment on board the space shuttle.

Antiproton radiation belt produced by cosmic rays in the Earth magnetosphere

[1]xa0The possible existence of noticeable fluxes of antiparticles in the Earth magnetosphere has been predicted on theoretical considerations in this article. The antiprotons expected at several hundred kilometers of altitudes, we do not believe are of direct extraterrestrial origin, but are the natural products of nuclear reactions of the high-energy primary cosmic rays (CR) with the constituents of the terrestrial atmosphere. Extraterrestrial, galactic antiprotons are themselves of secondary in origin, i.e. they are born in nuclear reactions of the same CR particles passing through 5–7 g/cm2 of interstellar matter encountered during their lifetime in the Galaxy. We expect that the fluxes of magnetospheric antiprotons to be higher compared to the interstellar fluxes because the fluxes get accumulated due to confinement by the magnetic field of the Earth. We present the results of the computations of the antiproton fluxes at 50 MeV to several GeV energies due to the CR particle interactions with the matter in the interstellar space, and also with the residual atmosphere at altitudes of ∼1000 km over the Earths surface. The estimates show that the magnetospheric antiproton fluxes are two orders of magnitude greater compared to the interstellar fluxes measured at energies < 1 GeV.

Natural Sources of Antiparticles in the Solar System and the Feasibility of Extraction for High Delta‐V Space Propulsion

Antiparticles have a mass‐based energy density nearly 10 orders of magnitude greater than the best chemical propellants. This attribute, particularly with antiprotons, enables exciting new approaches to spacecraft propulsion and design. However, these advantages have not been realized due to the inherent limitations associated with the artificial production and storage of the antiparticles. In comparison, antiparticles are produced and trapped naturally in the space environment due to the interaction of high‐energy galactic cosmic rays (GCR) with residual matter in the interstellar medium and around solar system bodies. We assess the stable and transient antiparticle content of these sources and subsequently consider their capture and application to high delta‐v space propulsion.The magnetosphere surrounding a planet offers a unique environment for the generation and trapping of antiprotons. Using Earth’s magnetic field as an example, we have considered the various source mechanisms that are applicable to...

Ring current ion motion in the disturbed magnetosphere with non-equipotential magnetic field lines

Transport of ring current ions during the main phase of the geomagnetic storm is modeled. Particle trajectories are simulated by the Lorentz equation for dipole and Tsyganenko magnetic field models. The convection electric field is described by variations on the Kp dependent Volland–Stern model structure in the equatorial plane. Out of that plane the electric field is assumed to be the same as in the equatorial plane at least at the low latitudes. This consideration implies the possibility of non-equipotentiality of geomagnetic field lines at least for L⩾6 during strong magnetic storms. In our modeling energetic protons, typically of several tens of keV, start on the night side at L=4 or at L=7, and move initially under gradient magnetospheric drift largely confined to the equatorial plane. However, soon after crossing the noon–night meridian, the protons rather abruptly depart from the equatorial plane and deviate towards high latitude regions. This latter motion is essentially confined to a plane perpendicular to the equator, and it is characterized by finite periodic motion. The calculations indicate a slow violation of the first adiabatic invariant at the point of ion departure from the equatorial region, with slower non-adiabatic variation later along the orbit. The greater the convection electric field, the higher is the energy of the protons participating in this off equatorial divergent flow. The more energetic ions, of hundreds of keV and higher, however, rather continue their magnetic drift around the Earth uninterruptedly and these ions form the symmetric ring current ion population. The numerical calculations described herein explicitly indicate that the perpendicular divergent ion flow can contribute to the morning–evening component of the magnetic field perturbation during magnetic storm conditions, and can result in populating the high latitude and tail regions by the energetic protons.

Antiparticles and light element isotope ions in the earth's magnetosphere

Abstract The ratio of positron/electron fluxes originating in nuclear reactions in the Earths Magnetosphere is considered. It is supposed that positrons as well as electrons are mainly produced in the decay of charged pions π ± → μ ± → e ± born in nuclear collisions of trapped relativistic inner zone protons and of cosmic rays with the residual atmosphere. These positrons and electrons are captured in the magnetosphere and create a positron and electron radiation belt of nuclear origin. The positron/electron trapped magnetospheric fluxes formed with this mechanism from radiation belt proton source are simulated and the resulting computed e + / e − flux ratio ≈4 appears to be in agreement with the recent observations made by the Alpha Magnetic Spectrometer (AMS) ( The AMS collaboration, 1999 ). A >200 MeV positron flux with an intensity about 4 times higher than the electron flux of the same energy was registered in the equatorial region at the altitude of ≈400 km . This ratio is significantly different from the computed ratio ≈1 obtained from the primary cosmic ray source through the same mechanism. As our modeling of nuclear spallation reaction shows, in the same reaction nuclei of isotopes of hydrogen and helium are also produced, which are the source of light element isotope radiation belts of D, T, 3 He and 4 He with a significant excess of 3 He over 4 He fluxes. The AMS instrument, as we have known, also looked at the distribution of helium nuclei and only 3 He was observed, which is one more evidence in favor of the above hypothesis.

FEM code simulation of the magnetospheric proton fluxes

We report a study of the numeric solution to the diffusive transport equation for energetic protons magnetically trapped in the Earths equatorial magnetosphere. The analysis takes into account the pertinent physical processes in this region, including deceleration of protons by Coulomb collisional interactions with free and bound electrons, the charge exchange process, cosmic ray albedo neutron decay source, and electric and magnetic radial diffusion. These results were obtained using the Finite Element Method with magnetic moment and geomagnetic L-shell as free variables. Steady state boundary conditions were imposed at L=1 as zero distribution function and at L=7 with proton distribution function extracted from ATS 6 satellite observations. The FEM-code yields unidirectional proton flux in the energy range of 0.1–1000 MeV at the equatorial top of the geomagnetic lines, and the results are found to be in satisfactorily agreement with the empirical NASA AP-8 model proton flux within the energy range of 0.5–100 MeV. Below 500 keV, the empirical AP-8 model proton fluxes are several orders of magnitude greater than those computed with the FEM-code at L<3. This discrepancy is difficult to explain by uncertainties of boundary spectrum parameters or transport coefficients.

Seasonal polar cap radiation zones in dayside magnetosphere

The phenomenon of quasi-stable trapping of charged particles in the keV to MeV energy range within the polar cusp region of the Earth’s magnetosphere is explored. The remote equatorial magnetic field lines on the dayside magnetosphere are compressed by the solar wind and exhibit two local minima in the geomagnetic field strength along the field line in high latitudes. These minima, on both sides of the equator, result in stable confinement structures. Numerical modeling of charged particle orbits that pass through the regions of these local field minima has been carried out using different seasonal Earth tilt and different magnetospheric disturbance level. These orbit tracings show when and where these off-equatorial trapped radiation zones would be situated. The existence and extent of these confinement zones depend on the tilt angle. Indeed, the northern cusp confinement zone appears only at the northern summer solstice, while the southern cusp particle capture zone appears around winter solstice. The particle orbits that pass through opposite off-equatorial field minimum during solstices reveal a bound of the geomagnetic equatorial plane on the day sector. During equinox, the particle confinement zones exist in both cusps at times of disturbed magnetosphere conditions. The trapped particles drift within the trapping zones with periods of the several minutes, conserving the 1st and 2nd adiabatic invariants.

Seasonal cusp radiation belt on dayside magnetosphere

The possibility of quasi-stable trapping of charged particles of hundreds keV to MeV energy on the frontside Earth magnetosphere is explored in by numerical modeling of the single particle orbits in the geomagnetic field utilizing empirical Tsyganenko magnetic field model. Due to solar wind pressure the remote magnetic field lines on the frontside of the magnetosphere exhibit two minima in the geomagnetic field strength along the field line in high latitudes on the both sides of the equator. These minima may result in stable confinement structures, a kind of radiation belts, in the northern or/and the southern hemispheres, providing energetic particle trapping for times from several minutes to duration of seasonal scale. Simulation of energetic proton orbits passing through the regions of the magnetic field minima with different disturbance level and the Earth’s tilt reveals conditions in which these trapped radiation zones could result. It is shown that the existence of the adiabatic confinement zones strongly depends on the seasonal inclination of the Earth’s rotation axis. As a result the northern cusp confinement zone appears only in a summer solstice and similarly the southern cusp capture zone appears only in a winter solstice. In equinox time the confinement zones exist in both hemispheres in the disturbed magnetospheric conditions, however, they are less pronounced. The zones are essentially restricted to the sunlit magnetosphere. They form a kind of cusp radiation ring/belt, where a proton drifts with a period of several minutes, conserving its 1 st and the 2 nd adiabatic invariants. The latitudinal width of the ring is very thin, about 2-5 latitudinal degrees. The proton orbits passing through the off-equatorial field minimum opposite to those cusp belts reveal another interesting effect: a bound of the geomagnetic equatorial plane on the day sector. These and other features of the confinement zones in the two minima off-equatorial magnetic field regions are discussed.