G. A. Bazilevskaya

Solar and Heliospheric Phenomena in October-November 2003: Causes and Effects

We present new observational data on the phenomena of extremely high activity on the Sun and in the heliosphere that took place in October–November 2003. A large variety of solar and heliospheric parameters give evidence that the interval under consideration is unique over the entire observation time. Based on these data, comparing them with similar situations in the past and using available theoretical concepts, we discuss possible cause-and-effect connections between the processes observed. The paper includes the first results and conclusions derived by the collaboration “Solar Extreme Events-2003” organized in Russia for detailed investigations of these events. As a result of our consideration, it is beyond question that the physical causes of solar and heliospheric phenomena in October–November 2003 are not exclusively local and do not belong only to the active regions and solar atmosphere above them. The energy reservoirs and driving forces of these processes have a more global nature. In general, they are hidden from an observer, since ultimately their sources lie in the subphotospheric layers of the Sun, where changes that are fast and difficult to predict can sometimes take place (and indeed they do). Solar flares can serve as sufficiently good tracers of these sudden changes and reconstructions on the Sun, although one can still find other diagnostic indicators among the parameters of magnetic fields, motions of matter, and emission characteristics.

Measurement of the flux of primary cosmic ray antiprotons with energies of 60 MeV to 350 GeV in the PAMELA experiment

It is interesting to measure the antiproton galactic component in cosmic rays in order to study the mechanisms by which particles and antiparticles are generated and propagate in the Galaxy and to search for new sources of, e.g., annihilation or decay of dark matter hypothetical particles. The antiproton spectrum and the ratio of the fluxes of primary cosmic ray antiprotons to protons with energies of 60 MeV to 350 GeV found from the data obtained from June 2006 to January 2010 in the PAMELA experiment are presented. The usage of the advanced data processing method based on the data classification mathematical model made it possible to increase statistics and analyze the region of higher energies than in the earlier works.

Upper limit on the antihelium flux in primary cosmic rays

The explanation of the observed baryon asymmetry, i.e., the almost complete absence of antimatter in the visible part of the universe, is one of the most important problems in cosmology. The real asymmetry value can be determined by direct measurements of the fluxes of antinuclei with charges |Z| ⩾ 2 in primary cosmic rays near the Earth. The results of the search for antihelium using data from the PAMELA experiment obtained from June 2006 to December 2009 are presented. No events with a charge of −2 have been detected in the rigidity range of 0.6–600 GV. An upper limit on the antihelium/helium flux ratio

Solar Proton Events in Solar Activity Cycles 21–24

overline {He} /He

New measurements of the energy spectra of high-energy cosmic-ray protons and helium nuclei with the calorimeter in the PAMELA experiment

has been presented as a function of the energy. An integral upper level of 4.7 × 10−7 is the lowest limit at rigidities above 14 GV.

Measurement of galactic cosmic-ray deuteron spectrum in the PAMELA experiment

It is shown that the number of solar proton events (SPEs) with proton energies (E) higher than 10 and 100 MeV in the current solar cycle (cycle 24) differs slightly from the number of the same events in earlier cycles (cycles 21–23), even though solar activity was low during the growth and maximum phase in cycle 24. A deficit was in this case observed for the most powerful GLE events, which are characterized by high proton fluxes with E > 100 MeV. The ratio of the number of SPEs with E > 10 and 100 MeV to the number of sunspots in cycle 24 doubled, compared to the same ratio in cycles 21–23, and the relative number of GLEs fell by more than half. The characteristics of flares and coronal mass ejections associated with proton events with E > 100 MeV in cycle 24 were virtually the same as the analogous parameters in cycle 23.

Positrons and electrons in primary cosmic rays as measured in the PAMELA experiment

New measurements of the energy spectra of cosmic-ray protons and helium nuclei with significantly increased statistics owing to an improvement of the event selection technique and the involvement of all data over the period 2006–2013 in the analysis have been made at energies above 0.8 TeV/nucleon with a position-sensitive calorimeter based on data from the PAMELA satellite-borne experiment.

Secondary electron and positron fluxes in the near-Earth space observed in the ARINA and PAMELA experiments

This work presents the results of measuring the deuteron spectrum of Galactic cosmic rays (GCRs) with the PAMELA experiment. The PAMELA is an international experiment. Its main objectives are to search for antimatter and measure proton, helium nuclei, electron, and positron spectra over a wide range of energies. In addition, the experimental setup allows the detection of deuterons and the reconstruction of their spectra at low energies. Cosmic ray deuteron spectrum and the deuteron-proton ratio measured in the PAMELA experiment in the energy range of 50–650 MeV/nucleon are presented below.

Secondary positrons and electrons in near-Earth space in the PAMELA experiment

The PAMELA experiment is being carried out on board the Russian satellite Resurs DK1 placed in the near-earth near-polar orbit on June 15, 2006. The apparatus comprising a silicon-strip magnetic spectrometer and an electromagnetic calorimeter allows measurement of electron and positron fluxes in cosmic rays in a wide energy interval from ∼100 MeV to hundreds of GeV. The high-energy electron and positron separation technique is discussed and the data on positron-to-electron ratio in primary cosmic rays up to E ≈ 10 GeV from the 2006–2007 measurements are reported in this work.

Measurement of the large-scale anisotropy of cosmic rays in the PAMELA experiment

Secondary electron and positron fluxes in the energy range from 3 MeV to 7 GeV were measured with the ARINA and PAMELA spectrometers onboard the Resurs-DK satellite launched on June 15, 2006 into an elliptical orbit with an inclination of 70.4° and an altitude of 350–600 km. It is shown that positrons dominate over electrons by a factor of up to 4–5 in the geomagnetic equator region (L < 1.2 and B > 0.25).