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[en] Interstellar neutral helium streams into the heliosphere and is focused strongly by the solar gravitation in the anti-apex direction of the streaming motion relative to the sun. Due to this effect relatively high interplanetary helium concentrations are predicted for a distance of about 1 AU from the sun near the ecliptic plane. The earth moves through this helium bulge in winter. The velocity of the helium flux is added to the orbital velocity of the earth. The particle stream is estimated to be above 107 particles/cm2/sec during winter and 106 during summer. As the helium in neutral, it passes through the magnetosphere undisturbed. The energy of each atom is sufficient to ionize several neutral atoms of terrestrial atmosphere, but due to elastic collissions which compete very effectively with ionizing collisions only about 0.23 ionizations per incoming helium atom actually occur. This ionization source must be taken into account for the winter ionization balance, especially at night in the height region above 200 km. For the He+ ion balance this source is of importance even during daylight hours over the whole year
[en] Knowledge of the history of the interplanetary environment is linked to that of the formation and evolution of the lunar regolith. The major importance of the various space flights was the collection of almost 400 kg of lunar soil and rock samples, the study of which, thanks to isotopic dating methods, enabled the main lines of the history of the moon to be retraced. Since the ending of magma activity (three thousand million years ago), only the impacts of meteorites have modified the appearance of the lunar surface; the data acquired on their flow provide the explanation of the essential characteristics of the lunar regolith. The processing of the core particles and the samples has contributed to the determination of the history of the flow of particles and matter in the interplanetary environment
[fr]La connaissance de l'histoire du milieu interplanetaire est liee a celle de la formation et de l'evolution du regolith lunaire. L'interet majeur des differentes missions spatiales a ete la collecte de pres de 400 kg d'echantillons de sols et de roches lunaires dont l'etude, grace a des methodes de datation isotopique, a permis de retracer les grandes lignes de l'histoire de la lune. Depuis la fin de l'activite magmatique (3 milliards d'annees), seuls les impacts des meteorites ont modifie l'aspect de la surface lunaire; les donnees acquises sur leur flux apportent l'explication des caracteristiques essentielles du regolithe lunaire. L'exploitation des grains de carottes et des echantillons a contribue a la determination de l'histoire des flux de particules et de matiere dans le milieu interplanetaire
[en] Kinetic equation is used to examine the angular distribution of cosmic rays in interplanety space. The case has been analyzed where the particle radius of gyration in Interplanetary magnetic field is much smaller than the particle transport path. The second spherical harmonic has been shown to account for the maximum of cosmic ray intensity at the Earth's orbit in the direction perpendicular to the interplanetary force line if the heliolatitude distribution of cosmic rays exhibits a minimum in the helioequator plane
[en] One of the goals of the NASA Solar TErestrial RElations Observatory (STEREO) mission is to study the feasibility of forecasting the direction, arrival time, and internal structure of solar coronal mass ejections (CMEs) from a vantage point outside the Sun-Earth line. Through a case study, we discuss the arrival time calculation of interplanetary CMEs (ICMEs) in the ecliptic plane using data from STEREO/SECCHI at large elongations from the Sun in combination with different geometric assumptions about the ICME front shape [fixed-Φ (FP): a point and harmonic mean (HM): a circle]. These forecasting techniques use single-spacecraft imaging data and are based on the assumption of constant velocity and direction. We show that for the slow (350 km s-1) ICME on 2009 February 13-18, observed at quadrature by the two STEREO spacecraft, the results for the arrival time given by the HM approximation are more accurate by 12 hr than those for FP in comparison to in situ observations of solar wind plasma and magnetic field parameters by STEREO/IMPACT/PLASTIC, and by 6 hr for the arrival time at Venus Express (MAG). We propose that the improvement is directly related to the ICME front shape being more accurately described by HM for an ICME with a low inclination of its symmetry axis to the ecliptic. In this case, the ICME has to be tracked to >300 elongation to obtain arrival time errors < ± 5 hr. A newly derived formula for calculating arrival times with the HM method is also useful for a triangulation technique assuming the same geometry.
[en] The modulation of galactic cosmic rays has been studied for the case where the energy distribution of particles in interstellar space is characteristized by a pronounced maximum. The dependence of the radial gradient of cosmic ray density on particle energy has been examined
[en] The numerous recent works devoted to the study of cosmic ray fluctuations and the analysis of reliability of their regularities has given rise to the urgent necessity that the methods for discriminating such fluctuations against the noise background and their possible nature should be studied in detail. Such study is actually divided into quite a number of independent problems relevant to the origin and development of the fluctuations depending on the processes in interplanetary space
[en] The study of cosmic rays in space has acquired a unique importance in recent years, due to the fact that they are a powerful tool for understanding the mechanisms of the origin of the Universe or the nature of dark matter. Experiments already flown or currently in orbit, conducted on balloons, satellites and ISS, allowed to make huge strides in understanding the mechanisms of production and acceleration of cosmic rays, and have posed new questions to which we hope to answer in the near future.