Abstract.The suprathermal electrons of _>20 keV that extend from the hot thermal electron with 2 -3 keV temperature are sometimes observed in Earth's magnetosphere in association with reconnection. We study the origin of the hot and suprathermal electrons in terms of the kinetic magnetic reconnection process by using the two-dimensional particle-in-cell simulation. We find that the hot and suprathermal electrons can be formed in the nonlinear evolution of a large-scale magnetic reconnection. The electrons are, at the first stage, accelerated in the elongated, thin, X-type current sheet. Next the preheated/accelerated electrons are transported to the stronger magnetic field region produced by piling up of magnetic field lines due to colliding of the fast reconnection outflow with the preexisting plasma. In this region they are further accelerated owing to the X7B drift and the curvature drift. The mirror fbrce of the reconnecting magnetic fields, the effective pitch angle scattering that occurs when the Larmor radius is comparable to the magnetic field line curvature radius, and the broadband waves excited by the Hall electric current are the other important agents to control the particle acceleration.

Abstract. A series of bursty bulk flow events (BBFs) were observed by GEOTAIL and WIND in the geomagnetotail. IMP8 at the solar wind showed significant energy coupling into the magnetosphere, while the UVI instrument on POLAR evidenced significant energy transfer to the ionosphere during two substorms. There was good correlation between B BFs and ionospheric activity observed by UVI even when ground magnetic signatures were absent, suggesting that low ionospheric conductivity at the active sector may be responsible for this observation. During the second substorm no significant flux transport was evidenced past WIND in stark contrast to GEOTAIL and despite the small intexsatellite separation ((3.54, 2.88,-0.06) RE). Throughout the intervals studied there were significant differences in the individual flow bursts at the two satellites, even during longitudinally extended ionospheric activations. We conclude that the half-scale-size of transportbeating flow bursts is less than 3 RE.

On the basis of wave and plasma observations of the Geotail satellite, the instability mode of low‐frequency (1–10 Hz) electromagnetic turbulence observed at the neutral sheet during substorms has been examined. Quantitative estimation has also been made for the anomalous heating and resistivity resulting from the electromagnetic turbulence. Four possible candidates of substorm onset sites, characterized by the near‐Earth neutral line, are found in the data sets obtained at substorm onset times. In these events, wave spectra obtained by the search‐coil magnetometer and the spherical double‐probe instrument clearly show the existence of electromagnetic wave activity in the lower hybrid frequency range at and near the neutral sheet. The linear and quasi‐linear calculations of the lower hybrid drift instability well explain the observed electromagnetic turbulence quantitatively. The calculated characteristic electron heating time is comparable to the timescale of the expansion onset, while that of ion heating time is much longer. The estimated anomalous resistivity fails to supply enough dissipation for the resistive tearing mode instability.

We discuss the electron heating in the course of magnetic reconnection by using both the Geotail observation and the particle-in-cell simulation. Geotail observes several unique non-Maxwellian velocity distribution functions during the plasma sheet crossing in association with a fast plasma flow. We find that the observed distributions can be classified into four different types depending on the position in the plasma sheet. In the boundary between the lobe and the plasma sheet, the distribution consists of the cold plasma flowing toward the X-type region and the hot plasma escaping from the X-type region along the magnetic field. In the plasma sheet side of the boundary, the distribution becomes bi-Maxwellian distribution with T > T ⊥ . Inside the plasma sheet, the distribution is deformed into a hot and isotropic distribution. We discuss the physical mechanism responsible for those electron heating in a thin plasma sheet by using the kinetic reconnection simulation. We find that the dawn-dusk reconnection electric field as well as the turbulent waves excited by the strong Hall electric currents play an important role on the strong electron heating and acceleration.

Abstract. This paper describes the development of a major space storm during November 2-11, 1993. We discuss the history of the contributing high-speed stream, the powerful combination of solar wind transients and a corotating interaction region which initiated the storm, the high-speed flow which prolonged the storm and the near-Earth manifestations of the storm. The 8-day storm period was unusually long; the result of a high-speed stream (maximum speed 800 km/s) emanating from a distended coronal hole. Storm onset was accompanied by a compression of the entire dayside magnetopause to within geosynchronous Earth orbit (GEO). For nearly 12 hours the near-Earth environment was in a state of tumult. A super-dense plasma sheet was observed at GEO, and severe spacecraft charging was reported. The effects of electrons precipitating into the atmosphere penetrated into the stratosphere. Subauroral electron content varied by 100% and F layer heights oscillated by 200 km. Equatorial plasma irregularities extended in plumes to heights of 1400 km. Later, energetic particle fluxes at GEO recovered and rose by more than an order of magnitude. A satellite anomaly was reported during the interval of high energetic electron flux. Model results indicate an upper atmospheric temperature increase of 200øK within 24 hours of storm onset. Joule heating for the first 24 hours of the storm was more than 3 times that for typical active geomagnetic conditions. We estimate that total global ionospheric heating for the full storm interval was-190 PJ, with 30% of that generated within 24 hours of storm onset.

Abstract. Initial ENA images obtained with the MENA imager on the IMAGE observatory show that ENAs emanating from Earth's magnetosphere at least crudely track both Dst and Kp. Images obtained during the storm of August 12, 2000, clearly show strong ring current asymmetry during storm main phase and early recovery phase, and a high degree of symmetry during the late recovery phase. Thus, these images establish the existence of both partial and complete ring currents during the same storm. Further, they suggest that ring current loss through the day side magnetopause dominates other loss processes during storm main phase and early recovery phase.

We present a statistical study of elevated (bimodal) ion conics observed by the Exos D (Akebono) satellite from 0900 to 1500 magnetic local time (MLT). We especially focus on a comparative analysis of elevated conics with standard conics and ion beams. Elevated conics are observed mainly above 6,000 km, while standard conics begin to appear at lower altitudes. The energy of elevated conics is usually higher than that of standard ion conics. This is consistent with the idea that the elevated conics evolve from standard conics through some acceleration process while they flow up to high altitudes. Since the elevated conics studied here received additional energization as they evolve from standard conics, the velocity filter mechanism previously invoked to explain elevated conics is inconsistent with our results. Our observation suggests that two kinds of acceleration processes are responsible for the upward shift in the velocity distribution of elevated conics. The elevated conics with a large cone angle and small upward shift in velocity space are most likely to be caused by the perpendicular energization extended along the field line. The MLT occurrence of this subset of elevated conics is similar to that of standard conics. The ion conics with a cone angle near 60° are found to be the most energetic, which strongly suggests the extended energization. On the other hand, the elevated conics with a small cone angle and large upward shift are mainly due to the parallel acceleration acting in tandem with perpendicular energization. This subset of elevated conics is found more often in the afternoon sector than are standard conics, which evokes rather some similarity to ion beams.

The altitude dependence of ion conics is investigated by using EXOS D observations on the dayside below 10,000 km altitude. The cone angle of ion conics tends to decrease with increasing altitude, but not so much as expected from a simple adiabatic model. The conic temperature, on the other hand, tends to increase with increasing altitude. The occurrence frequency of ion conics increases with altitude below 6000 km but is approximately constant above 6000 km. The appearance of newly born conics and the extinction of old conics in the statistics at any altitude could make some contribution, if the appearance and the extinction are large enough, to the observation results: less significant change in cone angle and increasing temperature with altitude, but this effect alone hardly provides a full explanation for the differences in the conic characteristics between the observations and the simple adiabatic model. The results rather seem to reflect the real evolution of an ion conic as ions flow up along the field line, suggesting nonconservation of the adiabatic invariant and the height-integrated transverse acceleration of ion conics over a wide range of altitude. 11,127