The Russian Academy of Sciences and Federal Space Agency, together with the participation of many international organizations, worked toward the launch of the RadioAstron orbiting space observatory with its onboard 10-m reflector radio telescope from the Baikonur cosmodrome on July 18, 2011. Together with some of the largest ground-based radio telescopes and a set of stations for tracking, collecting, and reducing the data obtained, this space radio telescope forms a multi-antenna groundspace radio interferometer with extremely long baselines, making it possible for the first time to study various objects in the Universe with angular resolutions a million times better than is possible with the human eye. The project is targeted at systematic studies of compact radio-emitting sources and their dynamics. Objects to be studied include supermassive black holes, accretion disks, and relativistic jets in active galactic nuclei, stellar-mass black holes, neutron stars and hypothetical quark stars, regions of formation of stars and planetary systems in our and other galaxies, interplanetary and interstellar plasma, and the gravitational field of the Earth. The results of ground-based and inflight tests of the space radio telescope carried out in both autonomous and ground-space interferometric regimes are reported. The derived characteristics are in agreement with the main requirements of the project. The astrophysical science program has begun.

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Using sixth degree simulations of the quiescent geomagnetic field, we have studied the vertical cutoff rigidities of more than three hundred positions on the earth's surface. Twenty‐six of these positions are near the South African magnetic anomaly, and six other points are in a region of the North Atlantic where Pomerantz and Agarwal have reported anomalous results. The cutoff rigidities have been obtained by detailed computation of the trajectories of cosmic rays at 0.01‐bv rigidity intervals to allow for the effects of the penumbra. Differences greater than 15% from the Quenby and Wenk threshold values have been found in the vicinity of South Africa, the South Atlantic, and the Canary Islands. Various latitude surveys are shown to exhibit consistency when plotted against the cutoff rigidities determined by this computational method. It is concluded that, though there is essentially no difference between the cutoff rigidities obtained using two currently accepted field models, these simulations of the geomagnetic field are not completely adequate over some parts of the earth to describe the cosmic‐ray effects in their entirety. Cutoff rigidities for a number of neutron monitors are listed.

The Pioneer 6 spacecraft was instrumented to provide detailed information on the magnetic field, plasma, and energetic particles pervading interplanetary space. Cosmic-ray and magnetic field measurements are complementary in that the cosmic rays can provide information regarding the magnetic field configuration over a large volume of space while the direct field measurements describe the local field near the spacecraft. Clearly, intercomparison of the two species of data adds considerably to the value of both types of observation. Cosmic rays released by solar flares are of particular value in such studies, for the point and time of injection of the particles into the solar system is known at least approximately, and hence a more precise specification of the magnetic field configuration traversed by the cosmic rays is possible. During the first thirty days of the flight of the Pioneer 6 spacecraft, three solar flares were observed, as detailed elsewhere [Bartley et al., 1966]. It is the purpose of this communication to compare a portion of the cosmic-ray and magnetic data observed during one of these flare events and lo demonstrate specific particle guidance properties of the interplanetary magnetic field. The data were obtained at a time when the spacecraft was 2.8 X 106 km from earth and at a sun-earth probe angle of 90 ø east of the sun and arc, therefore, unaffected by any terrestrial phenomena. It has been shown previously that both cosmic-ray observations [McCraken, 1962] and magnetic data [Ness et al., 1964] are in general agreement with the Archimedes spiral model for the interplanetary magnetic field [Parker, 1958]. In particular, if irregularities in the interplanetary field are of a scale size large compared to the cyclotron radius of the cosmic ray, the first adiabatic invariant of the particles' motion, sin g O/B, is conserved, where 0 is the pitch angle of the particles' motion. For a cosmic ray spiraling around an interplanetary line of force, B decreases by a factor of approximately 10' in traveling from the sun to the earth. Thus, pitch angles near the orbit of earth will be small (< 1ø), so that the solar cosmic radiation will be markedly anisotropic, and the particle flux will be observed streaming from a direction parallel to the interplanetary magnetic field vector. Irregularities in the magnetic field of a scale size comparable to the particle cyclotron radius will tend to scatter the cosmic rays and thereby destroy such an anisotropy.It has been shown [Bartley et al., 1966] that the solar-generated cosmic radiation arriving at the earth during the period December 29, 1965, through January 1, 1966, was markedly anisotropic. For any given period of time, the direction of the maximum cosmic-ray flux was determined (Figure 2, Bartley et al.) and was found to vary markedly with time. In particular, there were times at which the maximum cosmicray flux was arriving from directions 90 ø to 150 ø west of the earth-sun line. Such directions are not explicable on the basis of the simple Archimedes-spi...

[1] Worldwide observations of the cosmic ray ground level enhancement (GLE) of 20 January 2005 are used to investigate a commonly observed but poorly understood feature of this class of event. It is argued that the GLE comprised two distinctly different cosmic ray populations. The first resulted in an impulsive, highly anisotropic, field-aligned pulse with a relatively hard rigidity spectrum and significant velocity dispersion. The characteristics of the anisotropy were almost identical to those for similar impulsive increases observed during GLEs in 1960GLEs in , 1978GLEs in , and 1989. The p 0 g ray observations from the RHESSI and CORONAS-F spacecraft and Type III radio emissions yield a path length of 1.76 ± 0.1 AU to Earth for the first pulse. After the highest energies in the initial anisotropic pulse had passed Earth, another field-aligned but mildly anisotropic cosmic ray pulse developed slowly worldwide, exhibiting the characteristics of the conventional GLE. The risetime and anisotropy of this second population indicate substantial scattering, apparently at variance to the essentially scatter-free nature of the initial pulse. We show that the coexisting scatter-free initial impulsive increase and the diffusive character of the second pulse are consistent with the standard quasi-linear theory of pitch angle diffusion. Throughout the GLE, the anisotropy remained field-aligned, and a third maximum, seen by some stations, is shown to be due to changes in the direction of the heliospheric magnetic field (HMF). Examination of 22 large (>20%) GLEs in the historical record shows that the impulsive pulse never occurs after the commencement of the P2 pulse, indicating that the impulsive-gradual combination is not due to a chance sampling of differing scattering regions of the HMF. It is further shown that impulsive pulses, or their equivalents, have been observed in 13 out of the 15 GLEs associated with solar activity in the solar longitude range 24°-98°W, leading us to propose that the event of 20 January 2005 should be regarded as the defining example of the GLE. The observations lead us to propose two separate acceleration episodes in the typical GLE: (1) acceleration directly associated with the flare itself and located in the lower corona and (2) acceleration by a supercritical shock driven by the associated coronal mass ejection, located at $3-5 solar radii and farther in the upper corona. A one-to-one association with so-called impulsive and gradual solar energetic particle events at lower energies is proposed. On the basis of these observations, a generic model for the GLE is proposed.