Strong signals of neutral emissions were detected in association with a solar flare that occurred on 2005 September 7. They were produced by both relativistic ions and electrons. In particular, ...relativistic neutrons were observed with the solar neutron telescopes (SNTs) located at Mount Chacaltaya in Bolivia and Mount Sierra Negra in Mexico and with neutron monitors (NMs) at Chacaltaya and Mexico City with high statistical significances. At the same time, hard X-rays and g-rays, which were predominantly emitted by high-energy electrons, were detected by the Geotail and the INTEGRAL satellites. We found that a model of the impulsive neutron emission at the time of the X-ray/g-ray peak can explain the main peaks of all the detected neutron signals, but failed to explain the long tailed decaying phase. An alternative model, in which the neutron emission follows the X-ray/g-ray profile, also failed to explain the long tail. These results indicate that the acceleration of ions began at the same time as the electrons but that ions were continuously accelerated or trapped longer than the electrons in the emission site. We also demonstrate that the neutron data observed by multienergy channels of SNTs put constraints on the neutron spectrum.
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.
In search for clues towards the understanding of the cold plasma sheet formation under northward IMF, we study the temperature anisotropy of the two-component protons in the plasma sheet near the ...dusk low-latitude boundary observed by the Geotail spacecraft. The two-component protons result from mixing of the cold component from the solar wind and the hot component of the magnetospheric origin, and may be the most eloquent evidence for the transport process across the magnetopause. The cold component occasionally has a strong anisotropy in the dusk flank, and the sense of the anisotropy depends on the observed locations: the parallel temperature is enhanced in the tail flank while the perpendicular temperature is enhanced on the dayside. The hot component is nearly isotropic in the tail while the perpendicular temperature is enhanced on the dayside. We discuss possible mechanism that can lead to the observed temperature anisotropies.
We have investigated the feasibility of strong magnetic field generators composed of the high temperature superconducting (HTS) bulk magnet systems to the magnetic separation techniques for the waste ...water including thin emulsion bearing the cutting oil. Two types of the strong field generators were prepared by the face-to-face HTS bulk magnet systems, which emit the magnetic field density of 1 and 2
T in the open spaces between the magnetic poles activated by the pulsed field magnetization and the field cooling methods, respectively. A couple of water channels containing iron balls were settled in the strong field to trap the magnetized flocks in the waste water. The separation ratios of flocks containing 200
ppm magnetite powder were evaluated with respect to the flow rates of the waste water. The performances of bulk magnet system have kept showing values of around 100% until the flowing rate reached up to 18
l/min. This suggests that the magnetic separation by using bulk magnets is effective for the practical water purification systems.
The CALorimetric Electron Telescope (CALET) space experiment, which has been developed by Japan in collaboration with Italy and the United States, is a high-energy astroparticle physics mission on ...the International Space Station (ISS). The primary goals of the CALET mission include investigation of possible nearby sources of high-energy electrons, detailed study of galactic cosmic-ray acceleration and propagation, and search for dark matter signatures. With a long-term observation onboard the ISS, the CALET experiment measures the flux of cosmic-ray electrons (including positrons) up to 20 TeV, gamma-rays to 10 TeV, and nuclei up to 1,000 TeV based on its charge separation capability from Z = 1 to 40. Since the start of science operation in mid-October, 2015, a continuous observation has been maintained without any major interruptions. The number of triggered events over 10 GeV is nearly 20 million per month. By using the data obtained during the first two-years, here we present a summary of the CALET observations: 1) Electron+positron energy spectrum, 2) Nuclei analysis, 3) Gamma-ray observation with a characterization of the on-orbit performance. The search results for the electromagnetic counterparts of LIGO/Virgo gravitational wave events are also discussed.
Magnetic field observations made during 28 October to 1 November 2003, which included two fast interplanetary coronal mass ejections (ICMEs), allow a study of correlation lengths of magnetic field ...parameters for two types of interplanetary (IP) structures: ICMEs and ambient solar wind. Further, they permit the extension of such investigations to the magnetosheath and to a distance along the Sun‐Earth line (X) of about 400 RE. Data acquired by three spacecraft are examined: ACE, in orbit around the L1 point; Geotail, traveling eastward in the near‐Earth solar wind (at R ∼ 30 RE); and Wind, nominally in the distant geomagnetic tail (R ∼ −160 RE) but making repeated excursions into the magnetosheath/solar wind due to the flapping of the tail. Analyses are presented in both time and frequency domains. We find significant differences in the cross‐correlation/coherence properties of the ambient interplanetary magnetic field (IMF) and ICME parameters. For the ambient IMF, we find high coherence to be confined to low frequencies, consistent with other studies. In contrast, ICME magnetic field parameters remain generally coherent up to much higher frequencies. Scale lengths of ICME magnetic field parameters are in excess of 400 RE. High speeds of ∼1700 km s−1 are inferred from the plot of phase difference versus frequency, consistent with that obtained from plasma instruments. To strengthen these results and to extend them to include dependence on the distance perpendicular to the Sun‐Earth line (Y), we examine a 28‐day interval in year 2001 characterized by a sequence of 10 ICMEs and containing roughly equal ambient solar wind and ICME time intervals. ACE‐Wind X and Y separations were ∼220 and ∼250 RE, respectively. We find good coherence/correlation alternating with poor values. In particular, we find that in general ICME coherence/correlation lengths along Y are larger by a factor of 3–5 than those quoted in the literature for ambient solar wind parameters. Our findings are good news for the space weather effort, which depends crucially on predicting the arrival of large events, since they make possible the placement of upstream monitors to give a longer lead time than at L1.
Hybrid code simulations (ion particles, charge neutralizing electron fluid) of the MHD scale transverse Kelvin‐Helmholtz (K‐H) instability in a uniform plasma have been conducted. On a macroscopic ...scale the saturation states are found to be similar to the MHD result, even if the initial shear layer half thickness is as thin as twice the ion thermal Larmor radius. However, as opposed to the conventional belief based on the frozen‐in concept that a large‐scale mixing will be prohibited, an enhanced mixing of ions across the shear layer is found to occur inside the vortex. The temporal/spatial scales of the mixing process are determined by the fluid dynamical parameters and are anomalously quick/large compared to what can result from the mixing due to the finite Larmor radius overlapping at the interface. We propose that the low latitude boundary layer just inside the magnetopause is the mixing layer formed possibly by this mechanism.
In association with the large solar flare of April 15, 2001, the Chacaltaya neutron monitor observed a 3.6
σ enhancement of the counting rate between 13:51 and 14:15 UT. Since the enhancement was ...observed beginning 11
min before the GLE, solar neutrons must be involved in this enhancement. The integral energy spectrum of solar neutrons can be expressed by a simple power law in energy with the index
γ
=
-
3.0
±
1.0
. On the other hand, an integral energy spectrum of solar protons has been obtained in the energy range between 650
MeV and 12
GeV. The spectrum can also be expressed by a power law with the power index
γ
=
-
2.75
±
0.15
. The flux of solar protons observed at Chacaltaya (at ⩾12
GeV) was already one order less than the flux of the galactic cosmic rays. It may be the first simultaneous observation of the energy spectra of both high-energy protons and neutrons. Comparing the
Yohkoh soft X-ray telescope images with the observed particle time profiles, an interesting picture of the particle acceleration mechanism has been deduced.
The Earth’s bow shock is known to produce non-thermal electrons which are generally observed as a ‘spike’ in their flux profile. Here, in this paper, we present an analysis of electron and whistler ...wave properties for a quasi-perpendicular shock crossing that is supercritical, but subcritical to the so-called whistler critical Mach number, M
crit
w
, above which whistler waves cannot propagate upstream. We have found that the amplitudes of whistler waves increased exponentially as a function of time prior to the shock encounter, while the suprathermal (>2 keV) electron flux similarly increased with time, although with differing
e
-folding time scales. Comparison of the electron energy spectrum measured within the ramp with predictions from diffusive shock acceleration theory was poor, but the variation of pitch angle distribution showed scattering of non-thermal electrons in the upstream region. While not finding a specific mechanism to account for the electron diffusion, we suggest that the whistlers seen probably account for the differences observed between this ‘gradual’ event and the ‘spike’ events seen at shocks with no upstream whistlers.
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