M. Fujimoto
A5101503839- Ionosphere and magnetosphere dynamics
- Solar and Space Plasma Dynamics
- Astro and Planetary Science
- Geomagnetism and Paleomagnetism Studies
- Planetary Science and Exploration
- Magnetic confinement fusion research
- Earthquake Detection and Analysis
- Plasma Diagnostics and Applications
- Space Exploration and Technology
- Geophysics and Gravity Measurements
- Space Science and Extraterrestrial Life
- Astrophysics and Cosmic Phenomena
- Gamma-ray bursts and supernovae
- Stellar, planetary, and galactic studies
- Spacecraft and Cryogenic Technologies
- Spacecraft Design and Technology
- Isotope Analysis in Ecology
- Space exploration and regulation
- Astrophysics and Star Formation Studies
- Nuclear Physics and Applications
- Atmospheric Ozone and Climate
- Laser-induced spectroscopy and plasma
- GNSS positioning and interference
- Fluid Dynamics and Turbulent Flows
- Particle Detector Development and Performance
Japan Aerospace Exploration Agency
2015-2024
Institute of Space and Astronautical Science
2015-2024
Tokyo Metropolitan University
2023
National Sagamihara Hospital
2007-2022
Tokyo Institute of Technology
2007-2019
Life Science Institute
2013-2019
Lancaster University
2018
Goddard Space Flight Center
2018
RIKEN Nishina Center
2018
Prefectural University of Hiroshima
2016-2017
Fast tailward ion flows with strongly southward magnetic fields are frequently observed near the neutral sheet in premidnight sector of magnetotail at 20–30 R E for substorm onsets Geotail observations. These fast occasionally accompanied by a few keV electrons. With these events, we study structure and dynamics reconnection. The plasma reconnection site can be divided into three regions: region (near absolute magnitude B x < 5 nT), boundary sheet/tail lobe is or > 10 off‐equatorial...
The Hayabusa2 spacecraft arrived at the near-Earth carbonaceous asteroid 162173 Ryugu in 2018. We present observations of Ryugu's shape, mass, and geomorphology. has an oblate "spinning top" with a prominent circular equatorial ridge. Its bulk density, 1.19 ± 0.02 grams per cubic centimeter, indicates high-porosity (>50%) interior. Large surface boulders suggest rubble-pile structure. Surface slope analysis shows shape may have been produced from having once spun twice current rate. Coupled...
Hayabusa2 at the asteroid Ryugu Asteroids fall to Earth in form of meteorites, but these provide little information about their origins. The Japanese mission is designed collect samples directly from surface an and return them for laboratory analysis. Three papers this issue describe team's study near-Earth carbonaceous 162173 Ryugu, which spacecraft arrived June 2018 (see Perspective by Wurm). Watanabe et al. measured asteroid's mass, shape, density, showing that it a “rubble pile” loose...
Abstract C-type asteroids 1 are considered to be primitive small Solar System bodies enriched in water and organics, providing clues the origin evolution of building blocks life. asteroid 162173 Ryugu has been characterized by remote sensing 2–7 on-asteroid measurements 8,9 with Hayabusa2 (ref. 10 ). However, ground truth provided laboratory analysis returned samples is invaluable determine fine properties other planetary bodies. We report preliminary results analyses on from particle size...
Presented here are the observations and interpretations from a comprehensive analysis of 16 representative particles returned C-type asteroid Ryugu by Hayabusa2 mission. On average consist 50% phyllosilicate matrix, 41% porosity 9% minor phases, including organic matter. The abundances 70 elements in close agreement with those CI chondrites. Bulk show higher δ18O, Δ17O, ε54Cr values than As such, sampled most primitive least-thermally processed protosolar nebula reservoirs. Such finding is...
The Hayabusa2 spacecraft investigated the C-type (carbonaceous) asteroid (162173) Ryugu. mission performed two landing operations to collect samples of surface and subsurface material, latter exposed by an artificial impact. We present images second touchdown site, finding that ejecta from impact crater was at sample location. Surface pebbles both sites show morphological variations ranging rugged smooth, similar Ryugu's boulders, shapes quasi-spherical flattened. were returned Earth on 6...
Abstract Volatile and organic-rich C-type asteroids may have been one of the main sources Earth’s water. Our best insight into their chemistry is currently provided by carbonaceous chondritic meteorites, but meteorite record biased: only strongest types survive atmospheric entry are then modified interaction with terrestrial environment. Here we present results a detailed bulk microanalytical study pristine Ryugu particles, brought to Earth Hayabusa2 spacecraft. particles display close...
Abstract Martian moons exploration, MMX, is the new sample return mission planned by Japan Aerospace Exploration Agency (JAXA) targeting two with scheduled launch in 2024 and to Earth 2029. The major scientific objectives of this are determine origin Phobos Deimos, elucidate early Solar System evolution terms volatile delivery across snow line terrestrial planets having habitable surface environments, explore evolutionary processes both Mars environment. To achieve these objectives, during a...
In a two‐fluid picture of magnetic reconnection, inflow electrons flow with the field line to diffusion region, whereas ions cannot reach region and rest around distance ion inertial length. The relative motion results in electric currents, that is, Hall currents. current system produces quadrupole structure cross‐tail component near reconnection region. Furthermore, this forms field, whose direction is toward equatorial plane (midplane). We have investigated plasma magnetotail Geotail...
A statistical survey of GEOTAIL observations reveals the following properties near‐Earth plasma sheet (−15 < X GSM′ −50 Re): During periods when northward IMF dominates, (1) becomes significantly cold and dense, (2) best correlations between parameters occur latter quantities are averaged over 9 −4 +3 hours prior to observations, (3) temperatures diminish densities increase near dawn dusk flanks sheet. We suggest that during prolonged (∼ several hours) there is a slow diffusive transport...
Geotail observations of the low‐latitude boundary layer (LLBL) in near–Earth tail flanks are reported. Cold‐dense stagnant ions, which likely to be magnetosheath origin, detected this region magnetosphere. Charge neutrality is maintained by accompanying dense thermal (< 300 eV) electrons presumably also from magnetosheath. Compared component, however, anisotropically heated have enhanced bidirectional flux along field lines. The well balanced, and fact, together with slow convection,...
Interaction between the solar wind and objects in system varies largely according to settings, such as existence of a global intrinsic magnetic field and/or thick atmosphere. The Moon's case is characterized by absence both them. Low energy ion measurements on lunar orbit realized more than 30 years after Apollo period low charged particle analyzers MAP‐PACE board SELENE(KAGUYA). sensors have found that 0.1%∼1% protons are reflected back from Moon instead being absorbed surface. Some ions...
Energetic electrons of up to tens MeV are created during explosive phenomena in the solar corona. While many theoretical models consider magnetic reconnection as a possible way generating energetic electrons, precise roles acceleration and heating still remain unclear. Here, we show from two-dimensional particle-in-cell simulations that coalescence islands naturally form consequence tearing mode instability associated leads efficient energization electrons. The key process is secondary at...
Recent numerical simulations suggest that as soon the Kelvin‐Helmholtz instability (KHI) has grown nonlinearly to form a highly rolled‐up vortex, plasma mixing is inevitably achieved within vortex. Identification of vortices by in situ measurements therefore an important task step establish mechanism which solar wind plasmas enter magnetosphere and understand conditions under form. In present study we show are detectable even from single‐spacecraft measurements. Numerical KHI indicate vortex...
We examine traversals on 20 November 2001 of the equatorial magnetopause boundary layer simultaneously at ∼1500 magnetic local time (MLT) by Geotail spacecraft and ∼1900 MLT Cluster spacecraft, which detected rolled‐up MHD‐scale vortices generated Kelvin‐Helmholtz instability (KHI) under prolonged northward interplanetary field conditions. Our purpose is to address excitation process KHI, ion‐scale structures vortices, formation mechanism low‐latitude (LLBL). The observed KH wavelength...
We have performed a statistical study of THEMIS spacecraft crossings the asymmetric dayside magnetopause to test prediction that diamagnetic drift X‐line due plasma pressure gradient across can suppress magnetic reconnection. The includes both when reconnection exhausts were present and they absent in current sheet. When we restrict survey subsolar region (10 < MLT 14), find for low Δ β (the difference on two sides sheet) majority events occurred over large range shears, whereas was high...
Abstract We surveyed 79 magnetopause reconnection exhausts detected by the THEMIS spacecraft to investigate how amount and anisotropy of electron bulk heating produced depend on inflow boundary conditions. find that heating, ΔT e , is correlated with asymmetric Alfvén speed, V AL,asym based reconnecting magnetic field plasma density measured in both high‐density magnetosheath low‐density magnetospheric regions. Best fit data produces empirical relation = 0.017 m i 2 indicating proportional...
Hayabusa2 is an asteroid exploration mission to return surface samples of a near-Earth C-type (162173) 1999 JU3. Because asteroids are the evolved remnants planetesimals that were building blocks planets, detailed observation by spacecraft and analysis returned will provide direct evidence regarding planet formation dynamic evolution solar system. Moreover, expected preserve most pristine materials in system, mixture minerals, ice, organic matter interact with each other. Space missions only...