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Flux enhancements of field‐aligned low‐energy O+ion (FALEO) are simultaneously observed by Arase, Van Allen Probes A and B in the nightside inner magnetosphere during 05–07 UT on September 22, 2018. FALEOs appear after a magnetic dipolarization signature with approximately 6–20 min delay. It has the energy‐dispersion signature from a few keV to ∼100 eV only in the direction parallel to the magnetic field at Arase, while it decreases its energy from a few keV down to 10 eV in both the parallel and antiparallel directions at Probes A and B. We perform a numerical simulation to trace trajectories of test O+ions in a model magnetosphere, which are launched from above the ionosphere 3–15 min after a substorm. Flying virtual satellites that have the same orbits as the real satellites, we create virtual energy‐time spectrograms of O+ions to compare with the observed ones. Results show a very good correspondence between them, indicating that FALEOs originate from ionospheric O+ions that are extracted from the upper ionosphere at substorm onset and flow along the magnetic field toward the geomagnetic equator. It is also revealed that 3–9 hr after their launch, test O+ions less than 400 eV have a spatial distribution in the inner magnetosphere which is similar to those of the warm plasma cloak and the oxygen torus. We therefore conclude that FALEO is a source of those cold ion populations. Flux enhancements of field‐aligned low‐energy O+ion (FALEO) are simultaneously observed by Arase, Van Allen Probes A and BNumerical simulation well reproduces observed energy‐time spectrograms of FALEO with the energy‐dispersed signature from 1 keV to 10 eVFALEO is a source of the warm plasma cloak and the oxygen torus that appear in the dawn to noon sectors Flux enhancements of field‐aligned low‐energy O+ion (FALEO) are simultaneously observed by Arase, Van Allen Probes A and B Numerical simulation well reproduces observed energy‐time spectrograms of FALEO with the energy‐dispersed signature from 1 keV to 10 eV FALEO is a source of the warm plasma cloak and the oxygen torus that appear in the dawn to noon sectors

We have developed a lightweight, compact, and highly sensitive Extreme ultraviolet (EUV) photometer for a space‐borne instrument. The photometer is onboard Japan's Mars orbiter, Planet‐B, which was successfully launched on July 4, 1998, and stayed in the parking orbits around the Earth for 6 months. The new photometer is designed for studying the spatial distribution of helium ions and atoms by detecting He II (304 Å) and He I (584 Å), which are major emission lines detectable around a planet. The photometer is a type of normal‐incidence telescope that consists of a mirror, filters, and a detector. The mirror employs a new technology of a molybdenum/silicon multilayer coating and is designed to have peak reflectivity at 304 Å. The photometer is capable of taking two‐dimensional images by using the spin and orbital motions of the spacecraft. There are open questions concerning the Earth's plasmasphere and plasma sheet that cannot be resolved by in situ observations alone (e.g., global shape of the plasmasphere and cold ions in the plasma sheet). Our observations with the EUV photometer over a reasonable number of orbits will answer them. The photometer also shows an outstanding performance of measuring the Martian helium.

The present study examines the low‐energy ion flux variations observed by the Arase satellite in the inner magnetosphere. From the magnetic field and ion flux data obtained by the fluxgate magnetometer and the low‐energy particle experiments–ion mass analyzer onboard Arase, we find 55 events of the low‐energy O+flux enhancement accompanied with magnetic field dipolarization in the periods of April 1–October 31, 2017 and July 1, 2018–January 31, 2019. The low‐energy O+flux enhancements (a) start a few minutes after the dipolarization onset, (b) have energy‐dispersed signatures with decreasing energy from a few keV down to ∼10 eV, (c) are observed in both storm and non‐storm periods, (d) have a field‐aligned distribution (α∼ 0° in the southern hemisphere and α∼ 180° in the northern hemisphere), (e) are accompanied by the low‐energy H+flux enhancements that have lower energies than O+by a factor of 3–10, and (f) increase the O+density and the O+/H+density ratio by ∼10 times and 4–5 times, respectively. We perform a numerical simulation to trace ion trajectories forward in time from the Arase positions. It is revealed that both H+and O+ions drift eastward and reach the dawn‐to‐morning sector without being lost in the ionosphere, if the pitch angle scattering effect is considered near the equatorial plane. This result suggests that these low‐energy field‐aligned ions can contribute to formation of the warm plasma cloak. O+flux enhancements that have energy‐dispersed signatures at <∼5 keV appear a few minutes after magnetic field dipolarizationThe lowest energy of ∼10 eV and a field‐aligned distribution of the O+flux enhancements suggest prompt extraction from the ionosphereThe field‐aligned low‐energy O+flux enhancements can be a source of the warm plasma cloak O+flux enhancements that have energy‐dispersed signatures at <∼5 keV appear a few minutes after magnetic field dipolarization The lowest energy of ∼10 eV and a field‐aligned distribution of the O+flux enhancements suggest prompt extraction from the ionosphere The field‐aligned low‐energy O+flux enhancements can be a source of the warm plasma cloak

We have built an X-ray ultraviolet (XUV) scanner on board Mars orbiter NOZOMI (Planet-B). This scanner has the He I and II emissions from the Martian atmosphere and ionosphere as its main target. These EUV emissions provide important information for the study of both Martian geological history and the interaction between solar wind and the Martian ionosphere. The XUV scanner will be operated in the parking orbit around the earth and also in the transfer orbit to Mars, where the terrestrial plasmasphere and interplanetary emissions will be studied.

The Ion Mass Imager (IMI) is a light-weight ion mass composition instrument for the Japanese Planet-B mission to be launched to Mars in 1998. The objective of the Planet-B mission is to study the Martian environment with emphasis on the upper atmosphere interaction with the solar wind. IMI measures positive ions with energies between 10 eV/q and 35 keV/q and with a mass resolution high enough to resolve the most important ion species (H+, He++, He+, O++, O+, O2+). The instrument has a 360° field-of-view aperture and uses the spacecraft spin to cover almost the full unit sphere to obtain three-dimensional distribution functions every 4 s (half a spacecraft spin period). Particles are energy-filtered by a spherical electrostatic analyzer, and then mass-analysed by the magnetic separation method. The ions hit a microchannel plate assembly with a position sensitive anode divided into 32 mass channels. Together with 16 angular sectors, this system “images” the direction of motion and mass of ions. A pre-acceleration voltage of 0–4000 V is used to select the mass range, e.g., modes optimized for light ions (up to O+) and heavy ions (O+to charged dust grains). A loss-less data compression algorithm is used in the in-flight processing software to optimize the amount of data that can be returned from Mars.

The Magnetospheric Multiscale (MMS) spacecraft observed many enhancements of electromagnetic ion cyclotron (EMIC) waves in an event in the late afternoon outer magnetosphere. These enhancements occurred mainly in the troughs of magnetic field intensity associated with a compressional ultralow frequency (ULF) wave. The ULF wave had a period of ∼2–5 min (Pc5 frequency range) and was almost static in the plasma rest frame. The magnetic and ion pressures were in antiphase. They are consistent with mirror‐mode type structures. We apply the Wave‐Particle Interaction Analyzer method, which can quantitatively investigate the energy transfer between hot anisotropic protons and EMIC waves, to burst‐mode data obtained by the four MMS spacecraft. The energy transfer near the cyclotron resonance velocity was identified in the vicinity of the center of troughs of magnetic field intensity, which corresponds to the maxima of ion pressure in the compressional ULF wave. This result is consistent with the idea that the EMIC wave generation is modulated by ULF waves, and preferential locations for the cyclotron resonant energy transfer are the troughs of magnetic field intensity. In these troughs, relatively low resonance velocity due to the lower magnetic field intensity and the enhanced hot proton flux likely contribute to the enhanced energy transfer from hot protons to the EMIC waves by cyclotron resonance. Due to the compressional ULF wave, regions of the cyclotron resonant energy transfer can be narrow (only a few times of the gyroradii of hot resonant protons) in magnetic local time. Electromagnetic ion cyclotron wave enhancements were detected in a compressional ultralow frequency (ULF) waveTroughs of magnetic field intensity of the ULF wave are preferential locations for the cyclotron resonant energy transferDue to compressional ULF wave, regions of the cyclotron resonant energy transfer can be narrow in magnetic local time Electromagnetic ion cyclotron wave enhancements were detected in a compressional ultralow frequency (ULF) wave Troughs of magnetic field intensity of the ULF wave are preferential locations for the cyclotron resonant energy transfer Due to compressional ULF wave, regions of the cyclotron resonant energy transfer can be narrow in magnetic local time