Yoshizumi Miyoshi

We show evidence that left‐hand polarised electromagnetic ion cyclotron (EMIC) plasma waves can cause the loss of relativistic electrons into the atmosphere. Our unique set of ground and satellite observations shows coincident precipitation of ions with energies of tens of keV and of relativistic electrons into an isolated proton aurora. The coincident precipitation was produced by wave‐particle interactions with EMIC waves near the plasmapause. The estimation of pitch angle diffusion coefficien

The Exploration of energization and Radiation in Geospace (ERG) project explores the acceleration, transport, and loss of relativistic electrons in the radiation belts and the dynamics for geospace storms. This project consists of three research teams for satellite observation, ground-based network observation, and integrated data analysis/simulation. This synergetic approach is essential for obtaining a comprehensive understanding of the relativistic electron generation/loss processes of the ra

Using the data from the NOAA and Exos‐D satellites during the 3 November 1993 magnetic storm, the dynamic behavior of electrons with energies from a few tens of kiloelectronvolts to a few and its relation to plasma waves were examined. After the late main phase, relativistic electron flux started to recover from the heart of the outer radiation belt, where the cold plasma density was extremely low, and intense whistler mode chorus emissions were detected. The phase space density showed a peak in

Abstract Pulsating auroras show quasi‐periodic intensity modulations caused by the precipitation of energetic electrons of the order of tens of keV. It is expected theoretically that not only these electrons but also subrelativistic/relativistic electrons precipitate simultaneously into the ionosphere owing to whistler mode wave‐particle interactions. The height‐resolved electron density profile was observed with the European Incoherent Scatter (EISCAT) Tromsø VHF radar on 17 November 2012. Elec

The Exploration of energization and Radiation in Geospace (ERG) Science Center serves as a hub of the ERG project, providing data files in a common format and developing the space physics environment data analysis software and plug-ins for data analysis. The Science Center also develops observation plans for the ERG (Arase) satellite according to the science strategy of the project. Conjugate observations with other satellites and ground-based observations are also planned. These tasks contribut

Superposed epoch analyses of ring current (RC) ions and radiation belt (RB) electrons are conducted for geomagnetic storms with Dst < −100 nT during solar cycle 23. As a new approach, the storms are categorized into three groups in terms of the solar wind structures; storms with Dst > −130 nT associated with corotating interaction regions (CIRs), storms with Dst > −130 nT driven by coronal mass ejections (CMEs), and CME‐driven great storms with Dst < −130 nT. The flux enhancements of

Abstract Relativistic electron flux in the outer radiation belt tends to increase during the high‐speed solar wind stream (HSS) events. However, HSS events do not always cause large flux enhancement. To determine the HSS events that cause such enhancement and the mechanisms that are responsible for accelerating the electrons, we analyzed long‐term plasma data sets, for periods longer than one solar cycle. We demonstrate that during HSS events with the southward interplanetary magnetic field (IMF

We propose a model for the energy dispersion of electron precipitation associated with pulsating auroras, considering the wave‐particle interactions with propagating whistler mode waves from the equator. Since the resonant energy depends on the magnetic latitude, the pitch angle scattering of different energy electrons can occur continuously along the field line. Considering the energy‐dependent path length and the precipitation start time of the precipitating electrons, the transit time of whis

Abstract In this study, by simulating the wave‐particle interactions, we show that subrelativistic/relativistic electron microbursts form the high‐energy tail of pulsating aurora (PsA). Whistler‐mode chorus waves that propagate along the magnetic field lines at high latitudes cause precipitation bursts of electrons with a wide energy range from a few kiloelectron volts (PsA) to several megaelectron volts (relativistic microbursts). The rising tone elements of chorus waves cause individual microb

The Earth's outer radiation belt electrons increase when the magnetosphere is surrounded by the high‐speed solar wind stream, while the southward interplanetary magnetic field (IMF) is also known as an important factor for the flux enhancement. In order to distinguish the two different kinds of solar wind parameter dependence statistically, we investigate the response of the outer belt to stream interaction regions (SIRs). A total of 179 SIR events are identified for the time period from 1994 to

Abstract We investigate the origin of the fine structure of the energy spectrum of precipitating electrons for the pulsating aurora (PsA) observed by the low‐altitude Reimei satellite. The Reimei satellite achieved simultaneous observations of the optical images and precipitating electrons of the PsA from satellite altitude (~620 km) with resolution of 40 ms. The main modulation of precipitation, with a few seconds, and the internal modulations, with a few hertz, that are embedded inside the mai

We examined and simulated the dynamics of energetic electrons during the October 2001 magnetic storm with the relativistic RAM electron model for a wide range of energies. The storm had a rapid main phase followed by a day of strong geomagnetic activity that produced a second Dst minimum and then a very quiet recovery phase. During the main phase and the period of intense activity, the observed hot electron flux ( E = 30 keV) increased at low L while decreasing at large L and then decayed abrupt

Pulsating aurorae (PsA) are caused by the intermittent precipitations of magnetospheric electrons (energies of a few keV to a few tens of keV) through wave-particle interactions, thereby depositing most of their energy at altitudes ~ 100 km. However, the maximum energy of precipitated electrons and its impacts on the atmosphere are unknown. Herein, we report unique observations by the European Incoherent Scatter (EISCAT) radar showing electron precipitations ranging from a few hundred keV to a f

Long‐term variations of energetic particles in the radiation belts were examined using data from the NOAA (1979–2003) satellites. A significant flux variation with solar cycle was detected together with both semiannual and recurrent flux variations. It was revealed that the phase of flux variations for the solar cycle depends on both particle energy and distance from the Earth; the outer belt shifted inward during the solar active period and outward during the solar quiet period. The numerical s

Evolution of energetic electron fluxes, related solar wind conditions, and relevant plasma waves in the inner magnetosphere are examined during the two corotating interaction region (CIR)‐driven magnetic storms in November 1993. In this paper we focus on the fact that the flux of the outer radiation belt electrons increased significantly during the 3 November storm, while it did not increase above the prestorm level during the 18 November storm. The recovery phase of the 3 November storm is asso