To investigate the cold plasma sheet formation under northward IMF, we study the temperature anisotropies of electrons and two-component protons observed by the Geotail spacecraft. The two-component ...protons, which are occasionally observed in the dusk plasma sheet near the low-latitude boundary, are the result of spatial mixing of the hot protons of the magnetosphere proper and the cold protons from the solar wind. Recent research focusing on the two-component protons reported that the cold proton component at times has a strong anisotropy, and that the sense of the anisotropy depends on the observed locations. Since electrons have been known to possess a strong parallel anisotropy around the low-latitude boundary layer, we compare anisotropies of electrons and protons to find that the strengths of parallel anisotropies of electrons and the cold proton component are in good correlation in the tail flank. The parallel anisotropy of electrons is stronger than that of the cold proton component, which is attributed to selective heating of electrons. We further find that the strengths of the parallel anisotropies in the tail flank depend on the latitudinal angle of the IMF; strong parallel anisotropies occur under strongly northward IMF. We discuss that the Kelvin-Helmholtz vortices, which developed under strongly northward IMF, and the resultant magnetic reconnection therein may lead to the strong parallel anisotropies observed in the tail flank.
The Mercury Magnetopsheric Orbiter (MMO) is one of the spacecraft of the BepiColombo mission; the mission is scheduled for launch in 2014 and plans to revisit Mercury with modern instrumentation. MMO ...is to elucidate the detailed plasma structure and dynamics around Mercury, one of the least-explored planets in our solar system. The Mercury Plasma Particle Experiment (MPPE) on board MMO is a comprehensive instrument package for plasma, high-energy particle, and energetic neutral particle atom measurements. The Mercury Ion Analyzer (MIA) is one of the plasma instruments of MPPE, and measures the three dimensional velocity distribution of low-energy ions (from 5
eV to 30
keV) by using a top-hat electrostatic analyzer for half a spin period (2
s). By combining both the mechanical and electrical sensitivity controls, MIA has a wide dynamic range of count rates for the proton flux expected around Mercury, which ranges from 10
6 to 10
12
cm
−2
s
−1
str
−1
keV
−1, in the solar wind between 0.3 and 0.47
AU from the sun, and in both the hot and cold plasma sheet of Mercury’s magnetosphere. The geometrical factor of MIA is variable, ranging from 1.0
×
10
−7
cm
2
str
keV/keV for large fluxes of solar wind ions to 4.7
×
10
−4
cm
2
str
keV/keV for small fluxes of magnetospheric ions. The entrance grid used for the mechanical sensitivity control of incident ions also work to significantly reduce the contamination of solar UV radiation, whose intensity is about 10 times larger than that around Earth’s orbit.
To systematically review the prognostic accuracy of fluorine-18-fluorodeoxyglucose positron emission tomography (FDG-PET) for interim response assessment of patients with untreated advanced-stage ...Hodgkin's lymphoma (HL) or diffuse large B-cell lymphoma (DLBCL).
MEDLINE, EMBASE, SCOPUS, and Biologic Abstracts were searched for relevant studies. Two assessors independently reviewed studies for inclusion and extracted data. Relevant unpublished data were requested from the investigators if unavailable from publications. A meta-analysis of the prognostic accuracy was performed.
Thirteen studies involving 360 advanced-stage HL patients and 311 DLBCL patients met our inclusion criteria. Advanced-stage HL studies included few unfavorable-risk patients. DLBCL studies were heterogeneous. FDG-PET had an overall sensitivity of 0.81 (95% CI, 0.72 to 0.89) and a specificity of 0.97 (95% CI, 0.94 to 0.99) for advanced-stage HL, and a sensitivity of 0.78 (95% CI, 0.64 to 0.87) and a specificity of 0.87 (95% CI, 0.75 to 0.93) for DLBCL. Meta-regression and subgroup analyses did not identify factors that affect prognostic accuracy.
For low- to intermediate-risk advanced-stage HL, FDG-PET performed after a few cycles of standard chemotherapy seems to be a reliable prognostic test to identify poor responders, warranting prospective studies to assess PET-based treatment strategies. For DLBCL, no reliable conclusions can be drawn due to heterogeneity. Interim PET remains an unproven test for routine clinical practice. Its use should be reserved for research settings where treatment regimens and imaging conditions are standardized.
In this paper, we present the analysis and results of a direct measurement of the cosmic-ray proton spectrum with the CALET instrument onboard the International Space Station, including the detailed ...assessment of systematic uncertainties. The observation period used in this analysis is from October 13, 2015 to August 31, 2018 (1054 days). We have achieved the very wide energy range necessary to carry out measurements of the spectrum from 50 GeV to 10 TeV covering, for the first time in space, with a single instrument the whole energy interval previously investigated in most cases in separate subranges by magnetic spectrometers (BESS-TeV, PAMELA, and AMS-02) and calorimetric instruments (ATIC, CREAM, and NUCLEON). The observed spectrum is consistent with AMS-02 but extends to nearly an order of magnitude higher energy, showing a very smooth transition of the power-law spectral index from -2.81±0.03 (50-500 GeV) neglecting solar modulation effects (or -2.87±0.06 including solar modulation effects in the lower energy region) to -2.56±0.04 (1-10 TeV), thereby confirming the existence of spectral hardening and providing evidence of a deviation from a single power law by more than 3σ.
The outer shells of young supernova remnants (SNRs) are the most plausible acceleration sites of high-energy electrons with the diffusive shock acceleration (DSA) mechanism. We studied spatial and ...spectral properties close to the shock fronts in four historical SNRs (Cas A, Kepler's remnant, Tycho's remnant, and RCW 86) with excellent spatial resolution of Chandra. In all of the SNRs, hard X-ray emissions were found on the rims of the SNRs, which concentrate in very narrow regions (so-called filaments); apparent scale widths on the upstream side are below or on the order of the point-spread function of Chandra, while they are 0".5-40" (0.01-0.4 pc) on the downstream side with most reliable distances. The spectra of these filaments can be fitted with both thermal and nonthermal (power law and SRCUT) models. The former requires unrealistic high temperature ( 2 keV) and low abundances ( 1 solar) for emission from young SNRs and may be thus unlikely. The latter reproduces the spectra with best-fit photon indices of 2.1-3.8, or roll-off frequencies of (0.1-28) x 10 super(17) Hz, which reminds us of the synchrotron emission from electrons accelerated via DSA. We consider various physical parameters as functions of the SNR age, including the previous results on SN 1006; the filament width on the downstream side increases with the SNR age, and the spectrum becomes softer, keeping a nonthermal feature. It was also found that a function, that is, the roll-off frequency divided by the square of the scale width on the downstream side, shows negative correlation with the age, which might provide us some information on the DSA theory.
Extended results on the cosmic-ray electron + positron spectrum from 11 GeV to 4.8 TeV are presented based on observations with the Calorimetric Electron Telescope (CALET) on the International Space ...Station utilizing the data up to November 2017. The analysis uses the full detector acceptance at high energies, approximately doubling the statistics compared to the previous result. CALET is an all-calorimetric instrument with a total thickness of 30 X_{0} at normal incidence and fine imaging capability, designed to achieve large proton rejection and excellent energy resolution well into the TeV energy region. The observed energy spectrum in the region below 1 TeV shows good agreement with Alpha Magnetic Spectrometer (AMS-02) data. In the energy region below ∼300 GeV, CALET's spectral index is found to be consistent with the AMS-02, Fermi Large Area Telescope (Fermi-LAT), and Dark Matter Particle Explorer (DAMPE), while from 300 to 600 GeV the spectrum is significantly softer than the spectra from the latter two experiments. The absolute flux of CALET is consistent with other experiments at around a few tens of GeV. However, it is lower than those of DAMPE and Fermi-LAT with the difference increasing up to several hundred GeV. The observed energy spectrum above ∼1 TeV suggests a flux suppression consistent within the errors with the results of DAMPE, while CALET does not observe any significant evidence for a narrow spectral feature in the energy region around 1.4 TeV. Our measured all-electron flux, including statistical errors and a detailed breakdown of the systematic errors, is tabulated in the Supplemental Material in order to allow more refined spectral analyses based on our data.
We investigate statistical properties of cold O+ beams (COBs) streaming tailward at the velocity nearly equal to the major H+ component, which were observed by Geotail/low‐energy particle (LEP) ...instrument in the tail lobe/mantle regions at geocentric distance between 8 and 210 RE (Earth radii) during the solar‐minimum period (October 1993 to March 1995). The average O+ density is ∼1.3×10−3 cm−3, which corresponds to ∼1.2 % of the proton component. Properties of the flow velocity show that it is not the weakening of the magnetospheric convection but the large parallel velocity which enables the O+ ions to remain still in the distant lobe/mantle regions. The occurrence frequency of COBs suggests that O+ ions tend to exist in the mantle‐like region rather than tenuous “pure lobe” and that their existence has a clear correlation with the geomagnetic activity. On the basis of the EMF By dependence of the double‐peaked COB distribution along dawn‐dusk direction, it is shown that COBs exist mostly on loaded quadrants in the north–south and dawn‐dusk asymmetry of sheath plasma entry caused by the IMF By effect on the dayside reconnection process. The concentration on the loaded quadrants can be seen even in geomagnetic storms. It suggests that frequent COB occurrence at active times is mainly due to the southward orientation of IMF rather than the increase of dynamic pressure itself during the geomagnetic storms. That is, the statistics show that COBs are abundant at geomagnetically active times on loaded quadrants resulting from the dayside reconnection process, where the ions of solar wind origin bear the major component, and their field‐aligned velocity is larger than usual. These COBs should originate in the dayside magnetosphere and/or the polar cap regions. From the COB energy of several keV, which is rather higher than that of cusp/cleft ion outflows, the necessity of extra energization(s) to elevate parallel velocity is suggested. Clear IMF By dependence, on one hand, provides other possibilities of the COB's source such as the energetic UFI beams and the equatorially trapped ions. The requirements for each candidate so as to be a main contributor to COBs are also discussed.
First results of a cosmic-ray electron and positron spectrum from 10 GeV to 3 TeV is presented based upon observations with the CALET instrument on the International Space Station starting in ...October, 2015. Nearly a half million electron and positron events are included in the analysis. CALET is an all-calorimetric instrument with total vertical thickness of 30 X_{0} and a fine imaging capability designed to achieve a large proton rejection and excellent energy resolution well into the TeV energy region. The observed energy spectrum over 30 GeV can be fit with a single power law with a spectral index of -3.152±0.016 (stat+syst). Possible structure observed above 100 GeV requires further investigation with increased statistics and refined data analysis.
We study a very fast interplanetary shock (IP shock) event observed on 29 October 2003 based on the Geotail particle and field measurements in the solar wind. During this event the intensity of ...high‐energy solar energetic particles (greater than several to several tens of MeV) was quite high, causing a serious background problem for plasma particle measurements on Geotail as well as on the other spacecraft. The magnetic/electric field measurements and the plasma wave measurement aboard Geotail, on the other hand, were free from such a background problem and provided a reliable estimate for the local plasma parameters including the plasma density. From these measurements, our best estimation for the local shock velocity is ∼2000 km/s in the observer's rest frame or ∼1400 km/s in the upstream plasma rest frame. The corresponding Alfvén Mach number is ∼12. It is found that the timing analysis of the shock arrivals at ACE and Geotail gives a shock velocity significantly lower than the above value. We argue that this difference is due to the shock surface rippling by 15–20 deg. We also comment that this IP shock had a property of “cosmic‐ray‐mediated” shock, namely a shock having a spatial structure affected by pressures exerted by nonthermal particles accelerated by the shock itself.
The π+π− photoproductions on the proton and deuteron have been studied in a photon energy range of 0.8–1.1 GeV at the Laboratory of Nuclear Science, Tohoku University. Charged pions and protons were ...detected using Neutral Kaon Spectrometer. We obtained the cross sections for the p(γ,pπ+π−) and d(γ,pπ+π−)n. The quasi-free process with a neutron spectator was extracted by the neutron momentum cut of pn>0.3 GeV/c. The cross section for the Δ++Δ− production was deduced in the non-quasi-free process of the γd→pnπ+π−. It was 13.4±0.4 μb at Eγ=0.82 GeV.
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