PAMELA results on the cosmic-ray antiproton flux from 60 MeV to 180 GeV in kinetic energy

The satellite-borne experiment PAMELA has been used to make a new measurement of the cosmic-ray antiproton flux and the antiproton-to-proton flux ratio which extends previously published measurements down to 60 MeV and up to 180 GeV in kinetic energy. During 850 days of data acquisition approximately 1500 antiprotons were observed. The measurements are consistent with purely secondary production of antiprotons in the galaxy. More precise secondary production models are required for a complete interpretation of the results.Comment: 11 pages, 3 figures, 1 table. Accepted for publication in Physical Review Letter

Gamma-Ray Sources Observed by Cos-B

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Correlations between earthquakes and anomalous particle bursts from SAMPEX/PET satellite observations.

In the last decades, a possible influence of electromagnetic fields of seismic origin in the ionosphere–magnetosphere transition region has been reported in the literature. In recent years, a few space experiments also revealed anomalous bursts of charged particles precipitating from the lower boundary of the inner radiation belt. They were thought to be caused by low-frequency seismo-electromagnetic emissions. A recent study [Aleksandrin et al., 2003. Annales Geophysicae 21, 597–602] seems to confirm that these particle bursts have a short-term preseismic character. The particle longitudinal drift should enhance the detectability of preseismic particle bursts, thus magnifying their importance in earthquake prediction studies. This paper takes into consideration the method introduced by Aleksandrin et al. (2003) to carry out a deeper investigation on the subject. In this sense, a method for the temporal correlation between continental earthquakes with MX5:0 and anomalous particle bursts collected by the PET- SAMPEX satellite mission is critically investigated and presented here. Several constraints and cuts have been applied to data in order to exclude, from the correlation, charged particles collected inside the SAA region and/or during ionospheric and magnetospheric perturbations caused by non-seismic sources. After the data have been detrended by these effects, a short-term seismic precursor of 4 h is observed in the histogram of the time difference between the time occurrence of earthquakes and that of particle burst events. The best correlation is obtained only when considering high-energy electrons (EX4 MeV) with pitch angles near the loss cone. Such a result confirms previous ones but also points out the importance of an ad hoc method of analysis. Results suggest the importance of coordinated and simultaneous ground-based and space investigations specifically dedicated to the subject. Also, a deeper investigation based on particle data prepared and analyzed as carefully as possible is requested to understand the physical mechanisms underlying the phenomenon under study

The possibilities of simultaneous detection of gamma rays, cosmic-ray electrons and positrons on the GAMMA-400 space observatory

The GAMMA-400 space observatory will provide precise measurements of gamma rays, electrons, and positrons in the energy range 0.1–3000 GeV. The good angular and energy resolutions, as well as identification capabilities (angular resolution ~0.01°, energy resolution ~1%, and proton rejection factor ~106) will allow us to study the main galactic and extragalactic sources, diffuse gamma-ray background, gamma-ray bursts, and to measure electron and positron fluxes. The peculiar characteristics of the experiment is simultaneous detection of gamma rays and cosmic-ray electrons and positrons, which can be connected with annihilation or decay of dark matter particles

Time Dependence of the electron and positron components of the cosmic radiation measured by the PAMELA experiment between July 2006 and December 2015

Cosmic-ray electrons and positrons are a unique probe of the propagation of cosmic rays as well as of the nature and distribution of particle sources in our Galaxy. Recent measurements of these particles are challenging our basic understanding of the mechanisms of production, acceleration, and propagation of cosmic rays. Particularly striking are the differences between the low energy results collected by the space-borne PAMELA and AMS-02 experiments and older measurements pointing to sign-charge dependence of the solar modulation of cosmic-ray spectra. The PAMELA experiment has been measuring the time variation of the positron and electron intensity at Earth from July 2006 to December 2015 covering the period for the minimum of solar cycle 23 (2006-2009) until the middle of the maximum of solar cycle 24, through the polarity reversal of the heliospheric magnetic field which took place between 2013 and 2014. The positron to electron ratio measured in this time period clearly shows a sign-charge dependence of the solar modulation introduced by particle drifts. These results provide the first clear and continuous observation of how drift effects on solar modulation have unfolded with time from solar minimum to solar maximum and their dependence on the particle rigidity and the cyclic polarity of the solar magnetic field