The cosmic-ray proton and helium spectra from 0.2 GeV nucleon~1 to about 200 GeV nucleon~1 have been measured with the balloon-borne experiment Isotope Matter-Antimatter Experiment (IMAX) launched from Lynn Lake, Manitoba, Canada, in 1992. IMAX was designed to search for antiprotons and light isotopes using a superconducting magnet spectrometer together with scintillators, a time-of-Ñight system, and Cherenkov detectors. Using redundant detectors, an extensive examination of the instrument efficiency was carried out. We present here the absolute spectra of protons and helium corrected to the top of the atmosphere and to interstellar space. If demodulated with a solar modulation parameter of / \ 750 MV, the measured interstellar spectra between 20 and 200 GV can be represented by a power law in rigidity, with (1.42^0.21) ] 104R~2.71B0.04 (m2 GV s sr)~1 for protons and (3.15^1.03) ] 103R~2.79B0.08 (m2 GV s sr)~1 for helium. Subject headings : cosmic rays È elementary particles È ISM : abundances

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The Modular Multispectral Imaging Array (MMIA) is a suite of optical sensors mounted on an external platform of the European Space Agency's Columbus Module on the International Space Station. The MMIA, together with the Modular X-and Gamma-ray Sensor (MXGS), are the two main instruments forming the Atmosphere-Space Interactions Monitor (ASIM). The primary scientific objectives of the ASIM mission are to study thunderstorm electrical activity such as lightning, Transient Luminous Emissions (TLEs) and Terrestrial Gamma-ray Flashes (TGFs) by observing the associated emissions in the UV, near-infrared, x-and gamma-ray spectral bands. The MMIA includes two cameras imaging in 337 nm and 777.4 nm, at up to 12 frames per second, and three high-speed photometers at 180-230 nm, 337 nm and 777.4 nm, sampling at rates up to 100 kHz. The paper describes the MMIA and the aspects that make it an essential tool for the study of thunderstorms. The mission architecture is described in Neubert et al.

During the Northern Hemisphere summer of 2003 a sprite observation campaign was conducted from Southern Europe and the magnetically conjugate region in South Africa. The campaign brought together a wide variety of instrumentation to investigate the effects of sprites on the mesosphere, and to search for signatures of the relativistic electron acceleration process in the magnetically conjugate hemisphere. Measurements in Europe included optical video imaging from a remote-controlled, semi-automatic camera system located at the Observatoire du Pic du Midi in the Pyre´ne´es mountains in Southern France, infrasound observations from France, and ULF-HF electromagnetic observations from a number of locations. The measurements in South Africa included observations of optical emissions and VLF electromagnetic waves. The campaign was successful, with more than 100 sprites observed during 10 storms. The paper will give an overview of the campaign and some results. They include: (1) the first clear identification of infrasound from sprites, allowing independent (of optical observations) estimates of the energy input to the mesosphere, (2) the first detection of sprites triggered by intra-cloud lightning, a result that underscores the need for considering the complete thunderstorm source field resulting from both cloud-to-ground discharges and the intra-cloud discharges feeding them, and (3) a clear one-to-one relationship with sprites and early VLF events, suggesting that VLF ground transmitter signals can be an important tool for estimating ionisation and relaxation of ionised structures in sprites. No signatures of relativistic electrons were identified during the campaign. r

Abstract. The JEM-X monitor provides X-ray spectra and imaging with arcminute angular resolution in the 3 to 35 keV band. The good angular resolution and the low energy response of JEM-X plays an important role in the identification of gamma ray sources and in the analysis and scientific interpretation of the combined X-ray and gamma ray data. JEM-X is a coded aperture instrument consisting of two identical, coaligned telescopes. Each of the detectors has a sensitive area of 500 cm 2 , and views the sky through its own coded aperture mask. The two coded masks are inverted with respect to each other and provides an angular resolution of 3 across an effective field of view of about 10• diameter.

Terrestrial gamma-ray flashes (TGFs) are transient gamma-ray emissions from thunderstorms, generated by electrons accelerated to relativistic energies in electric fields. Elves are ultraviolet and optical emissions excited in the lower ionosphere by electromagnetic waves radiated from lightning current pulses. We observe a TGF and an associated Elve using the Atmosphere-Space Interactions Monitor on the International Space Station. The TGF occurs at the onset of a lightning current pulse that generates an Elve, in the early stage of a lightning flash. Our measurements suggest that the current onset is fast and has a high amplitude, a prerequisite for Elves, and that the TGF is generated in the electric fields associated with the lightning leader.

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The balloon-borne Isotope Matter-Antimatter Experiment (IMAX) was flown from Lynn Lake, Manitoba, Canada on 16 -17 July 1992. Using velocity and magnetic rigidity to determine mass, we have directly measured the abundances of cosmic ray antiprotons and protons in the energy range from 0.25 to 3.2 GeV. Both the absolute flux of antiprotons and the antiproton͞proton ratio are consistent with recent theoretical work in which antiprotons are produced as secondary products of cosmic ray interactions with the interstellar medium. This consistency implies a lower limit to the antiproton lifetime of ϳ10 7 yr.PACS numbers: 98.70. Sa, 14.20.Dh, 95.85.Ry Measurement of the antiproton abundance in the cosmic radiation bears strongly on questions ranging from the possibility of a baryon symmetric universe to characterizing the origin and transport of the cosmic rays. However, the interpretation of cosmic ray antiproton measurements has been very uncertain ever since their discovery by Golden et al. [1]. While antiprotons in the cosmic radiation are expected as "secondary" products of interactions of the primary cosmic radiation, principally protons, with the ambient interstellar medium (ISM) [2][3][4], the first positive measurements [1,5,6] reported higher antiproton fluxes than predicted by contemporary models of cosmic ray transport. Of the numerous explanations proposed (reviewed in Stephens and Golden [7]), one class assumed that secondary antiprotons are produced by cosmic ray protons and helium which have passed through more matter than implied by measured secondary͞primary ratios of heavier elements (e.g., boron͞carbon). Others considered "exotic" sources such as the evaporation of primordial black holes, the decay of dark matter, or acceleration in relativistic plasmas. It was also suggested that the excess could be a manifestation of a baryon symmetric cosmology [8]. The largest discrepancy was at ϳ200 MeV [6], where antiproton production in p-p interactions is heavily suppressed [7,9]; however, later measurements gave corresponding upper limits which were significantly lower [10,11]. The Isotope Matter-Antimatter Experiment (IMAX) [12] and other recent experiments [13] were designed to clarify these issues.The fluxes of antiprotons and protons from ϳ0.2 to 3.2 GeV were measured by IMAX using magnetic rigidity, ionization energy loss, and velocity measurements to determine the charge (from energy loss and b) and mass (from Z, b, and rigidity) of incident particles. Data were taken for ϳ16 h at an average altitude of 36 km C2 and C3) [17] with n 1.043 silica-aerogel radiators (giving b Ck ). A third Cherenkov counter (C1) was not used in the current analysis. For Z 1, b 1 particles, the TOF resolution (s) was 122 ps and the yields from C2 and C3 were 11 and 13 photoelectrons. The sum of the signals expected from C2 and C3 for a Z 1, b 1 particle was normalized to 1. Energy loss was measured by the TOF and scintillators S1 and S2. Agreement was required among the four resulting charge measurements.Tracking quali...