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Duodenal obstruction is a rare event that is unlikely to be treated endoscopically. Herein, we describe the case of a 75-year-old woman who presented with vomiting and was diagnosed with food-induced duodenal obstruction. Impacted food was fragmented and removed by double-balloon enteroscopy, and the duodenal tract was reopened without any adverse events. Follow-up capsule endoscopy was performed one month after treatment to determine the obstruction etiology and it revealed a remarkably delayed passage of the capsule through the duodenum and excessive amounts of floating food residue in the third portion of the duodenum. Obstruction recurrence was not observed six months after endoscopic treatment. In conclusion, in our case, endoscopic treatment of duodenal obstruction prevented the unnecessary performance of surgery, suggesting its clinical utility for this condition.

A circular ribbon flare SOL2014-12-17T04:51 is studied using the 17/34 GHz maps from the Nobeyama Radioheliograph (NoRH) along with (E)UV and magnetic data from the Solar Dynamics Observatory (SDO). We report the following three findings as important features of the microwave CRF. (1) The first preflare activation comes in the form of a gradual increase of the 17 GHz flux without a counterpart at 34 GHz, which indicates thermal preheating. The first sign of nonthermal activity occurs in the form of stepwise flux increases at both 17 and 34 GHz about 4 min before the impulsive phase. (2) Until the impulsive phase, the microwave emission over the entire active region is in a single polarization state matching the magnetic polarity of the surrounding fields. During and after the impulsive phase, the sign of the 17 GHz polarization state reverses in the core region, which implies a magnetic breakout--type eruption in a fan-spine magnetic structure. (3) The 17 GHz flux around the time of the eruption shows quasi-periodic variations with periods of 1--2 min. The pre-eruption oscillation is more obvious in total intensity at one end of the flare loop, and the post-eruption oscillation, more obvious in the polarized intensity at a region near the inner spine. We interpret this transition as the transfer of oscillatory power from kink mode oscillation to torsional Alfv\'en waves propagating along the spine field after the eruption. We argue that these three processes are inter-related and indicate a breakout process in a fan-spine structure.

[Aims] In the presence of a sufficient amount of target material, γ-rays can be used as a tracer in the search for sources of Galactic cosmic rays (CRs). Here we present deep observations of the Galactic center (GC) region with the MAGIC telescopes and use them to infer the underlying CR distribution and to study the alleged PeV proton accelerator at the center of our Galaxy., [Methods] We used data from ≈100 h observations of the GC region conducted with the MAGIC telescopes over five years (from 2012 to 2017). Those were collected at high zenith angles (58−70 deg), leading to a larger energy threshold, but also an increased effective collection area compared to low zenith observations. Using recently developed software tools, we derived the instrument response and background models required for extracting the diffuse emission in the region. We used existing measurements of the gas distribution in the GC region to derive the underlying distribution of CRs. We present a discussion of the associated biases and limitations of such an approach., [Results] We obtain a significant detection for all four model components used to fit our data (Sgr A*, “Arc”, G0.9+0.1, and an extended component for the Galactic Ridge). We observe no significant difference between the γ-ray spectra of the immediate GC surroundings, which we model as a point source (Sgr A*) and the Galactic Ridge. The latter can be described as a power-law with index 2 and an exponential cut-off at around 20 TeV with the significance of the cut-off being only 2σ. The derived cosmic-ray profile hints to a peak at the GC position and with a measured profile index of 1.2 ± 0.3 is consistent with the 1/r radial distance scaling law, which supports the hypothesis of a CR accelerator at the GC. We argue that the measurements of this profile are presently limited by our knowledge of the gas distribution in the GC vicinity., The financial support of the German BMBF and MPG, the Italian INFN and INAF, the Swiss National Fund SNF, the ERDF under the Spanish MINECO (FPA2015-69818-P, FPA2012-36668, FPA2015-68378-P, FPA2015-69210-C6-2-R, FPA2015-69210-C6-4-R, FPA2015-69210-C6-6-R, AYA2015-71042-P, AYA2016-76012-C3-1-P, ESP2015-71662-C2-2-P, FPA2017-90566-REDC), the Indian Department of Atomic Energy, the Japanese JSPS and MEXT, the Bulgarian Ministry of Education and Science, National RI Roadmap Project DO1-153/28.08.2018 and the Academy of Finland grant nr. 320045 is gratefully acknowledged. This work was also supported by the Spanish Centro de Excelencia “Severo Ochoa” SEV-2016-0588 and SEV-2015-0548, and Unidad de Excelencia “María de Maeztu” MDM-2014-0369, by the Croatian Science Foundation (HrZZ) Project IP-2016-06-9782 and the University of Rijeka Project 13.12.1.3.02, by the DFG Collaborative Research Centers SFB823/C4 and SFB876/C3, the Polish National Research Center grant UMO-2016/22/M/ST9/00382 and by the Brazilian MCTIC, CNPq and FAPERJ.

形態: カラー図版あり, Physical characteristics: Original contains color illustrations, Accepted: 2017-07-05, 資料番号: PA1810064000

One of the most important products of solar flares are nonthermal energetic particles which may carry up to 50\% energy releasing in the flaring processes. In radio observations, nonthermal particles generally manifest as spectral fine structures with fast frequency drifting rates, named as solar fast drifting radio bursts (FDRBs). This work demonstrated three types of FDRBs, including type III pair bursts, narrow band stochastic spike bursts following the type III bursts and spike-like bursts superimposed on type II burst in an X1.3 flare on 2014 April 25. We find that although all of them have fast frequency drifting rates, but they are intrinsically different from each other in frequency bandwidth, drifting rate and the statistical distributions. We suggest that they are possibly generated from different accelerating mechanisms. The type III pair bursts may be triggered by high-energy electron beams accelerated by the flaring magnetic reconnection, spike bursts are produced by the energetic electrons accelerated by a termination shock wave triggered by the fast reconnecting plasma outflows impacting on the flaring looptop, and spike-like bursts are possibly generated by the nonthermal electrons accelerated by moving magnetic reconnection triggered by the interaction between CME and the background magnetized plasma. These results may help us to understand the generation mechanism of nonthermal particles and energy release in solar flares., 15 pages, 7 figures, and 1 table, accepeted by ApJ

Solar neutron observations are very important on understanding of particle acceleration mechanism in the Sun. However, previous ground-based observations with large area telescope ($\sim$10 m$^2$)at high latitude are not sensitive to solar neutrons due to attenuation in the earth atmosphere and roughly 10 detection since its discovery in 1980. From space, the SEDA-AP instrument with much smaller area (100 cm$^2$) onboard the International Space Station (ISS) monitored solar neutrons including charged particles, and successfully detected more than 30 detection since its launch in 2009. Unfortunately the SEDA-AP operation was stopped on March 2018. To overcome situation for no mission dedicated for solar neutrons, we have designed and developed a solar neutron and gamma-ray detector for a 3U cubesat with a size of 30$\times$10$\times$10 cm. Actually we launched the 50-kg class ChubuSat-2 satellite for solar neutron observations on February 2016, and have now been adjusting it to a 3U cubesat application. The solar neutron and gamma-ray detector consists of multi-layered plastic scintillator bars, and GAGG(Ce) scintillator array, and both of them are read out with silicon photo-multipliers (Si PMs). More than 600 signals from Si PMs are processed by ASICs. In this paper, we will describe details of the detector and perf\ ormance of its breadboard model (BBM).

An M6.5-class flare was observed at N12E56 on the solar surface at 16:06 UT on July 8, 2014. In association with the flare, two neutron detectors located at high mountains, Mt. Sierra Negra in Mexico and Mt. Chacaltaya in Bolivia, recorded two neutron pulses, separated approximately by 30 min. Moreover, enhancements were also observed by the solar neutron detector onboard the International Space Station. We analyzed these data combined with solar images from Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory. From these we noticed that the production mechanism of neutrons cannot be explained by a single model; at least one of the enhancements may be explained by an electric field generated by the collision of magnetic loops and the other by the shock acceleration mechanism at the front side of the CME.

PKS 1510-089 is a flat spectrum radio quasar strongly variable in the optical and GeV range. To date, very high-energy (VHE, > 100 GeV) emission has been observed from this source either during long high states of optical and GeV activity or during short flares. Aims. We search for low-state VHE gamma-ray emission from PKS 1510-089. We characterize and model the source in a broadband context, which would provide a baseline over which high states and flares could be better understood. Methods. PKS 1510-089 has been monitored by the MAGIC telescopes since 2012. We use daily binned Fermi-LAT flux measurements of PKS 1510-089 to characterize the GeV emission and select the observation periods of MAGIC during low state of activity. For the selected times we compute the average radio, IR, optical, UV, X-ray, and gamma-ray emission to construct a low-state spectral energy distribution of the source. The broadband emission is modeled within an external Compton scenario with a stationary emission region through which plasma and magnetic fields are flowing. We also perform the emission-model-independent calculations of the maximum absorption in the broad line region (BLR) using two different models. Results. The MAGIC telescopes collected 75 hr of data during times when the Fermi-LAT flux measured above 1 GeV was below 3? × 10 -8 ? cm -2 ? s -1 , which is the threshold adopted for the definition of a low gamma-ray activity state. The data show a strongly significant (9.5¿) VHE gamma-ray emission at the level of (4.27 ± 0.61 stat ) × 10 -12 ? cm -2 ? s -1 above 150 GeV, a factor of 80 lower than the highest flare observed so far from this object. Despite the lower flux, the spectral shape is consistent with earlier detections in the VHE band. The broadband emission is compatible with the external Compton scenario assuming a large emission region located beyond the BLR. For the first time the gamma-ray data allow us to place a limit on the location of the emission region during a low gamma-ray state of a FSRQ. For the used model of the BLR, the 95% confidence level on the location of the emission region allows us to place it at a distance > 74% of the outer radius of the BLR. © ESO 2018., The financial support of the German BMBF and MPG, the Italian INFN and INAF, the Swiss National Fund SNF, the ERDF under the Spanish MINECO (FPA2015-69818-P, FPA2012-36668, FPA2015-68378-P, FPA2015-69210-C6-2-R, FPA2015-69210-C6-4-R, FPA2015-69210-C6-6-R, AYA2015-71042-P, AYA2016-76012-C3-1-P, ESP2015-71662-C2-2-P, CSD2009-00064), and the Japanese JSPS and MEXT is gratefully acknowledged. This work was also supported by the Spanish Centro de Exce-lencia “Severo Ochoa” SEV-2012-0234 and SEV-2015-0548, and Unidad de Excelencia “María de Maeztu” MDM-2014-0369, by the Croatian Science Foundation (HrZZ) Project IP-2016-06-9782 and the University of Rijeka Project 13.12.1.3.02, by the DFG Collaborative Research Centers SFB823/C4 and SFB876/C3, the Polish National Research Centre grant UMO-2016/22/M/ST9/00382, and by the Brazilian MCTIC, CNPq and FAPERJ. IA acknowledges support from a Ramón y Cajal grant of the Ministerio de Economía, Industria, y Competitividad (MINECO) of Spain. Acquisition and reduction of the POLAMI and MAPCAT data was supported in part by MINECO through grants AYA2010-14844, AYA2013-40825-P, and AYA2016-80889-P, and by the Regional Government of Andalucía through grant P09-FQM-4784.

Astroparticle physics 102, 77 - 88 (2018). doi:10.1016/j.astropartphys.2018.05.002, A search for tau neutrino induced showers with the MAGIC telescopes is presented. The MAGIC telescopes located at an altitude of 2200 m a.s.l. in the Canary Island of La Palma, can point towards the horizon or a few degrees below across an azimuthal range of about 80°. This provides a possibility to search for air showers induced by tau leptons arising from interactions of tau neutrinos in the Earth crust or the surrounding ocean. In this paper we show how such air showers can be discriminated from the background of very inclined hadronic showers by using Monte Carlo simulations. Taking into account the orography of the site, the point source acceptance and the event rates expected have been calculated for a sample of generic neutrino fluxes from photo-hadronic interactions in AGNs. The analysis of about 30 h of data taken towards the sea leads to a 90% C.L. point source limit for tau neutrinos in the energy range from 1.0 × 10$^{15}$ eV to 3.0 × 10$^{18}$ eV of about $E^{2}_{\nu_{\tau}} \times \phi (E_{\nu_{\tau}}) < 2.0 \times 10^{-4}$ GeV cm$^{-2} s^{-1}$ for an assumed power-law neutrino spectrum with spectral index $\gamma =−2$. However, with 300 h and in case of an optimistic neutrino flare model, limits of the level down to $E^{2}_{\nu_{\tau}} \times \phi (E_{\nu_{\tau}}) < 8.4 \times 10^{-6}$ GeV cm$^{-2} s^{-1}$ can be expected., Published by Elsevier Science, Amsterdam [u.a.]

We have investigated the effect of moisture on current collapse of AlGaN/GaN high-electron mobility transistors (HEMTs) when using low dielectric constant (low-k) insulator films to reduce the parasitic capacitance of millimeter-wave amplifier monolithic microwave integrated circuits. We clarified that current collapse is caused by moisture uptake through the surface and the sidewall of low-k films. Moreover, the moisture resistance of conventional carbon-based low-k films, such as benzocyclobutene, are insufficient to suppress current collapse because of hydrophilic surface and highly hydrophilized sidewall by the contact hole etching. We proposed the use of methyl silsesquioxane (MSQ)-based low-k films to improve the moisture resistance because of methyl group's hydrophobic property. This is the first time that MSQ has been used in AlGaN/GaN HEMTs. After appling MSQ, the moisture resistance of low-k films at the surface and the sidewall improved, and current collapse due to humidification was successfully reduced. Our findings suggest that improving the moisture resistance with hydrophobic low-k films does play a key role in reducing current collapse of AlGaN/GaN HEMTs.

To understand the conditions that produce white-light (WL) enhancements in solar flares, a statistical analysis of visible continuum data as observed by Hinode/Solar Optical Telescope (SOT) was performed. In this study, approximately 100 flare events from M- and X-class flares were selected. The time period during which the data were recorded spans from January 2011 to February 2016. Of these events, approximately half are classified as white-light flares (WLFs), whereas the remaining events do not show any enhancements of the visible continuum (non-WLF; NWL). In order to determine the existence of WL emission, running difference images of not only the Hinode/SOT WL (G-band, blue, green, and red filter) data but also the Solar Dynamics Observatory/Helioseismic and Magnetic Imager continuum data are used. A comparison between these two groups of WL data in terms of duration, temperature, emission measure of GOES soft X-rays, distance between EUV flare ribbons, strength of hard X-rays, and photospheric magnetic field strength was undertaken. In this statistical study, WLF events are characterized by a shorter time-scale and shorter ribbon distance compared with NWL events. From the scatter plots of the duration of soft X-rays and the energy of non-thermal electrons, a clear distinction between WLF and NWL events can be made. It is found that the precipitation of large amounts of accelerated electrons within a short time period plays a key role in generating WL enhancements. Finally, it was demonstrated that the coronal magnetic field strength in the flare region is one of the most important factors that allow the individual identification of WLF events from NWL events., 17 pages, 9 figures, 3 tables, accepted for publication in ApJ

In association with strong solar flares, we sometimes observe enhancements of visible continuum radiation, which is known as a "white-light flare". As most white-light (WL) events show close correlations in time and location with hard X-rays and/or radio emission, there is some consensus that WL emission originates from accelerated particles, especially non-thermal electrons. One model proposes that WL is emitted near the photosphere; however, non-thermal electrons are thermalized in the chromosphere and cannot reach the photosphere. Thus, there is a problem: how can the energy of non-thermal electrons - and/or other accelerated particles such as high-energy protons - propagate to the photosphere and produce WL emission? In the present study, we investigate the possibility that accelerated protons may produce the WL emission of solar flares. We found 51 WL events observed by Hinode/SOT. Among them, gamma-rays with energies greater than 1MeV were observed only in the X1.8-class flare on October 23, 2012 and in the M7.9-class flare on June 25, 2015. Focusing on these flare events, we compare the energetics of WL emission and of accelerated ion fluxes. We find that it is difficult for accelerated ions to provide sufficient energy to account for WL emission.

At the 33rd ICRC, we reported the possible detection of solar gamma rays by a ground level detector and later re-examined this event. On March 7, 2011, the solar neutron telescope (SNT) located at Mt. Sierra Negra, Mexico (4,600 m) observed enhancements of the counting rate from 19:49 to 20:02 UT and from 20:50 to 21:01 UT. The statistical significance was 9.7sigma and 8.5sigma, respectively. This paper discusses the possibility of using this mountain detector to detect solar gamma rays. In association with this event, the solar neutron detector SEDA-FIB onboard the International Space Station has also detected solar neutrons with a statistical significance of 7.5sigma. The FERMI-LAT detector also observed high-energy gamma rays from this flare with a statistical significance of 6.7sigma. We thus attempted to make a unified model to explain this data. In this paper, we report on another candidate for solar gamma rays detected on September 25th, 2011 by the SNT located in Tibet (4,300 m) from 04:37 to 04:47 UT with a statistical significance of 8.0sigma (by the Li-Ma method)., 15 pages

SUMMARY Gallium nitride high electron mobility transistors (GaN HEMTs) were developed for millimeter-wave high power amplifier applications. The device with a gate length of 80 nm and an InAlN barrier layer exhibited high drain current of more than 1.2 A/ mm and high breakdown voltage of 73V. A cut-off frequency fT of 113GHz and maximum oscillation frequency fmax of 230GHz were achieved. The output power density reached 1 W/ mm with a linear gain of 6.4dB at load-pull measurements at 90GHz. And we extracted equivalent circuit model parameters of the millimeter-wave InAlN/ GaN HEMT and showed that the model was useful in simulating the millimeter-wave power performance. Also, we report a preliminary constant bias stress test result.

On 2011 September 6, we observed an X2.1-class flare in continuum and H$\alpha$ with a frame rate of about 30~Hz. After processing images of the event by using a speckle-masking image reconstruction, we identified white-light (WL) flare ribbons on opposite sides of the magnetic neutral line. We derive the lightcurve decay times of the WL flare kernels at each resolution element by assuming that the kernels consist of one or two components that decay exponentially, starting from the peak time. As a result, 42% of the pixels have two decay-time components with average decay times of 15.6 and 587 s, whereas the average decay time is 254 s for WL kernels with only one decay-time component. The peak intensities of the shorter decay-time component exhibit good spatial correlation with the WL intensity, whereas the peak intensities of the long decay-time components tend to be larger in the early phase of the flare at the inner part of the flare ribbons, close to the magnetic neutral line. The average intensity of the longer decay-time components is 1.78 times higher than that of the shorter decay-time components. If the shorter decay time is determined by either the chromospheric cooling time or the nonthermal ionization timescale and the longer decay time is attributed to the coronal cooling time, this result suggests that WL sources from both regions appear in 42% of the WL kernels and that WL emission of the coronal origin is sometimes stronger than that of chromospheric origin., Comment: 8 pages, 7 figures, and 1 table. Accepted by ApJ

A M-class behind-the-limb solar flare on 1 May 2013 (SOL2013-05-01T02:32), accompanied by a ($\sim$ 400 km/s) CME was observed by several space-based observatories with different viewing angles. We investigated the RHESSI-observed occulted hard X-ray emissions that originated at least 0.1 \solrad{} above the flare site. Emissions below $\sim$10 keV revealed a hot, extended (11 MK, >60 arcsec) thermal source from the escaping CME core, with densities around $10^{9}$ cm$^{-3}$. In such a tenuous hot plasma, ionization times scales are several minutes, consistent with the non-detection of the hot CME core in SDO/AIA's 131 \AA{} filter. The non-thermal RHESSI source originated from an even larger area ($\sim$100 arcsec) at lower densities ($10^{8}$ cm$^{-3}$) located above the hot core, but still behind the CME front. This indicates that the observed part of the non-thermal electrons are not responsible for heating the CME core. Possibly the hot core was heated by non-thermal electrons before it became visible from Earth, meaning that the un-occulted part of the non-thermal emission likely originates from a more tenuous part of the CME core, where non-thermal electrons survive long enough to became visible from Earth. Simultaneous hard X-ray spectra from the Mars Odyssey mission, which viewed the flare on disk, indicated that the number of non-thermal electrons $>$20 keV within the high coronal source is $\sim$0.1 - 0.5\% compared to the number within the chromospheric flare ribbons. The detection of high coronal hard X-ray sources in this moderate size event suggests that such sources are likely a common feature within solar eruptive events.

An M6.5-class flare was observed at N12E56 of the solar surface at 16:06 UT on July 8, 2014. In association with this flare, solar neutron detectors located on two high mountains, Mt. Sierra Negra and Chacaltaya and at the space station observed enhancements in the neutral channel. The authors analysed these data and a possible scenario of enhancements produced by high-energy protons and neutrons is proposed, using the data from continuous observation of a solar surface by the ultraviolet telescope onboard the Solar Dynamical Observatory (SDO).

The Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and the Nobeyama Radioheliograph (NoRH) are used to investigate coronal hard X-ray and microwave emissions in the partially disk-occulted solar flare of 2007 December 31. The STEREO mission provides EUV images of the flare site at different viewing angles, establishing a two-ribbon flare geometry and occultation heights of the RHESSI and NoRH observations of {approx}16 Mm and {approx}25 Mm, respectively. Despite the occultation, intense hard X-ray emission up to {approx}80 keV occurs during the impulsive phase from a coronal source that is also seen in microwaves. The hard X-ray and microwave source during the impulsive phase is located {approx}6 Mm above thermal flare loops seen later at the soft X-ray peak time, similar in location to the above-the-loop-top source in the Masuda flare. A single non-thermal electron population with a power-law distribution (with spectral index of {approx}3.7 from {approx}16 keV up to the MeV range) radiating in both bremsstrahlung and gyrosynchrotron emission can explain the observed hard X-ray and microwave spectrum, respectively. This clearly establishes the non-thermal nature of the above-the-loop-top source. The large hard X-ray intensity requires a very large number (>5 x 10{sup 35} above 16 keV for themore » derived upper limit of the ambient density of {approx}8 x 10{sup 9} cm{sup -3}) of suprathermal electrons to be present in this above-the-loop-top source. This is of the same order of magnitude as the number of ambient thermal electrons. We show that collisional losses of these accelerated electrons would heat all ambient electrons to superhot temperatures (tens of keV) within seconds. Hence, the standard scenario, with hard X-rays produced by a beam comprising the tail of a dominant thermal core plasma, does not work. Instead, all electrons in the above-the-loop-top source seem to be accelerated, suggesting that the above-the-loop-top source is itself the electron acceleration region.« less

We present a detailed examination on the coronal nonthermal emissions during the preflare phase of the X4.8 flare that occurred on 2002 July 23. The microwave (17 GHz and 34 GHz) data obtained with Nobeyama Radioheliograph, at Nobeyama Solar Radio Observatory and the hard X-ray (HXR) data taken with {\it Reuven Ramaty High Energy Solar Spectroscopic Imager} obviously showed nonthermal sources that are located above the flare loops during the preflare phase. We performed imaging spectroscopic analyses on the nonthermal emission sources both in microwaves and in HXRs, and confirmed that electrons are accelerated from several tens of keV to more than 1 MeV even in this phase. If we assume the thin-target model for the HXR emission source, the derived electron spectral indices ($\sim 4.7$) is the same value as that from microwaves ($\sim 4.7$) within the observational uncertainties, which implies that the distribution of the accelerated electrons follows a single power-law. The number density of the microwave-emitting electrons is, however, larger than that of the HXR-emitting electrons, unless we assume low ambient plasma density of about $1.0 \times 10^9$ cm$^{-3}$ for the HXR-emitting region. If we adopt the thick-target model for the HXR emission source, on the other hand, the electron spectral index ($\sim 6.7$) is much different, while the gap of the number density of the accelerated electrons is somewhat reduced., 21 pages, 6 figures, ApJ accepted

The Soft X-ray Telescope (SXT) onboard Yohkoh often observed large-scale coronal loops connecting two active regions situated in opposite hemispheres. These are the trans-equatorial loop systems (TLSs). The formation mechanism of TLSs is not yet known. We analyzed a TLS observed simultaneously with Yohkoh/SXT and a coronagraph (SOHO/LASCO-C1). SOHO/LASCO-C1 observed loop expansion and eruption at the west solar limb. Yohkoh/SXT observed a rising motion (chromospheric evaporation) of hot and dense plasmas from the active regions located at the footpoints of the loop. Important results of our analyses are that (1) the loop eruption and the rising motion of the plasmas were simultaneous, (2) the TLS had a cusp-like appearance, and (3) the highest temperature region of the TLS was located above the bright loop seen in soft X rays. These observational results (loop expansion, eruption, and chromospheric evaporation) suggest that this bright (high-density) TLS was created by the same mechanism by which a solar flare occurs, namely, magnetic reconnection. In this paper, we propose a formation mechanism of the TLS that forms between two independent active regions.

This review surveys hard X-ray emissions of non-thermal electrons in the solar corona. These electrons originate in flares and flare-related processes. Hard X-ray emission is the most direct diagnostic of electron presence in the corona, and such observations provide quantitative determinations of the total energy in the non-thermal electrons. The most intense flare emissions are generally observed from the chromosphere at footpoints of magnetic loops. Over the years, however, many observations of hard X-ray and even γ-ray emission directly from the corona have also been reported. These coronal sources are of particular interest as they occur closest to where the electron acceleration is thought to occur. Prior to the actual direct imaging observations, disk occultation was usually required to study coronal sources, resulting in limited physical information. Now RHESSI has given us a systematic view of coronal sources that combines high spatial and spectral resolution with broad energy coverage and high sensitivity. Despite the low density and hence low bremsstrahlung efficiency of the corona, we now detect coronal hard X-ray emissions from sources in all phases of solar flares. Because the physical conditions in such sources may differ substantially from those of the usual “footpoint” emission regions, we take the opportunity to revisit the physics of hard X-radiation and relevant theories of particle acceleration.

A new solar neutron telescope has been constructed at Yangbajing, Tibet (600 g/cm(2)) and has been successfully operated for 8 years. During this time several interesting events were observed in coincidence with large solar flares. In this paper the authors discuss a directional count rate enhancement 1998 November 28 as to whether it is related to solar phenomena or not. We use this event to evaluate the sensitivity of the solar neutron telescope and discuss the detection limit for solar neutrons and high energy solar protons of this detector. (C) 2007 Elsevier B.V. All rights reserved.

We present an examination of multiwavelength observations of an M8.2 long-duration flare which occurred on 2000 November 25. During the flare, we can see a hard X-ray (HXR) source on one Hα flare ribbon in the HXR images obtained with the Hard X-ray Telescope aboard Yohkoh, and a compact microwave emission source on the other flare ribbon in the data taken with the Nobeyama Radioheliograph, while we can also see an extended microwave emission source that connects both of these emission sources. The compact microwave and HXR sources clearly showed gradual hardening tendencies in their spectra. In addition, we found energy-dependent delays of the peak times in the HXR bursts and concluded that almost all of the accelerated electrons are trapped in magnetic loops to generate the extended microwave source and are dripping into the chromosphere at the compact microwave and the HXR emission sites. We then performed imaging spectroscopic analyses to the microwave emission sources. The temporal evolutions of the flux and the spectral index of the compact microwave footpoint source are quite similar to those of the HXR source, which is mainly emitted at the other footpoint, while those at the loop-top extended source do not show this similarity. Moreover, there is a constant gap between the electron spectral index derived from the microwave footpoint source and that from the HXR source. We also discuss the constant gap, based on the trapped and dripping model.

The flare catalogue of the Yohkoh mission is compiled and linked to this article as an electronic supplement. For showing flare characteristics over wide energy range concisely, we provide the images of Hard X-ray Telescope (HXT) and the Soft X-ray Telescope (SXT), and the spectra of Hard X-ray Spectrometer (HXS) and Gamma-Ray Spectrometer (GRS) with the Wide Band Spectrometer (WBS) time profiles. The energy versus pulse height (PH) data channels in HXS and GRS are re-calibrated by using the data of the whole mission period. Secular gain changes are recognized in HXS, and the characteristics of power-law flare spectra simultaneously observed by HXT and HXS confirms the trend. The GRS gains are different for the flare observations during the previous maximum and for the current maximum. The total of 33 γ -ray events are observed, and for 12 of them γ-ray flare spectra are obtained.

We report a detailed examination about the relationship between the evolution of the Hα flare ribbons and the released magnetic energy during the April 10 2001 flare. In the Hα images, several bright kernels are observed in the flare ribbons. We identified the conjugated foot-points, by analyzing the lightcurves at each Hα kernels, and showed their connectivities during the flare. Then, based on the magnetic reconnection model, we calculated quantitatively the released energy by using the photospheric magnetic field strengths and separation speeds of the Hα flare ribbons. Finally, we examined the downward motions which are observed at the Hα kernels. We found that the stronger the red-asymmetry tends to be associated with the brighter the Hα kernel.

We studied the 1998 November 28 X-class flare, which showed long-duration, two-ribbon H alpha emission. (1) A soft X-ray loop system developed along the major magnetic neutral line in the impulsive phase. Hard X-ray and microwave emissions due to nonthermal electrons were located in some limited regions. While the compact hard X-ray loop was associated with weak, diffuse soft X-ray emission, two large microwave loops did not have soft X-ray counterparts. (2) Time profiles of two large microwave loops were similar to that of hard X-ray total emission, which emanated mostly from the compact Source, even in the fine time Structure in the rising phase. (3) A super-hot thermal hard X-ray source appeared around the impulsive peak and was located along the major magnetic neutral line in the declining phase, coinciding with the bright soft X-ray emission. The thermal component can be explained within the standard reconnection model to the extent that the super-hot thermal plasma was heated in the large soft X-ray loop. However, the nonthermal electrons were accelerated in a localized region where three loops interacted with each other. The inferred configuration may be a more complicated form of the double-loop interaction model proposed by Hanaoka (1996) and Nishio et al. (1997).

Coronal hard X-ray (HXR) sources were discovered by the Yohkoh HXT telescope in about two dozen limb flares: Impulsive and gradual ones. On the basis of HXT data, we investigated the spatial evolution of coronal sources. Slow ascending motions of sources are seen in several flares. In five events, it was possible to estimate the velocity of the upward motion with values between 10 and 30 km/s. We present these observational results and conclude that coronal source motions should be studied statistically using the RHESSI high-resolution HXR imaging data. We discuss the possibility that coronal HXR emission is generated as bremsstrahlung of the fast electrons accelerated in collapsing magnetic traps due to joint action of the Fermi-type first-order mechanism and betatron acceleration.

Using the Yohkoh Hard X-Ray Telescope (HXT) data, we have examined motions of the hard X-ray (HXR) sources during 72 solar flares occurred from 1991 September to 2001 December. In these flares, we have found 198 intense sources that are presumably the chromospheric footpoints (FPs) of flare loops. The average velocity V and the velocity dispersion σ were determined by a linear regression for these sources. For 80% of them, the ratio of V to 3 σ is larger than 1, strongly suggesting that the regular motions of the HXR sources dominate their chaotic motions. For 43 of 72 flares, coalignment of the HXT images with the photospheric magnetograms allows us to consider the HXR sources located on the both sides of the photospheric neutral line (NL) as the FP sources, and to distinguish between three main types of the FP motions. The type I is the motions of the HXR sources preferentially away from and nearly perpendicular to the NL. Less than 5% of the flares show this pattern of motion. In the type II, the sources move mainly along the NL in anti-parallel directions. Such motions have been found in 26% of flares. The type III involves a similar pattern of motions as the type II but all the HXR sources move in the same direction along the NL. Flares of this type constitute 30% of the flares. About 19% of flares can be described as a combination of these basic types. The remaining 20% of flares seem to be more complicated or less regular in the motion scale under consideration. An interpretation of results is suggested.

We have examined the relation between the evolution of the Hα flare ribbons and the released magnetic energy in a solar flare that occurred on 2001 April 10. Based on the magnetic reconnection model, the released energy was quantitatively calculated by using the photospheric magnetic field strengths and separation speeds of the fronts of the Hα flare ribbons. We compared the variation of the released energy with the temporal and spatial fluctuations in the nonthermal radiation observed in hard X-rays and microwaves. These nonthermal radiation sources indicate when and where large energy releases occur. We also estimated the magnetic energy released during the flare. The estimated energy release rates in the Hα kernels associated with the hard X-ray sources are locally large enough to explain the difference between the spatial distributions of the Hα kernels and the hard X-ray sources. We also reconstructed the peaks in the nonthermal emission by using the estimated energy release rates.

This paper presents the recent progress in our project of estimating near real-time electric fields and currents in the ionosphere through our computer system called the Geospace Environment Data Analysis System (GEDAS). We show a new technique in which data from ground magnetometers are collected by the system and used as input for the KRM and AMIE programs to calculate the distribution of ionospheric electric fields and currents, as well as of other ionospheric parameters, such as electric potential patterns. One of the goals of this project is to specify ionospheric processes. Examples of the near real-time calculation and the data flow of our scheme are presented.

Solar neutrons have been detected using the neutron monitor located at Mt. Chacaltaya, Bolivia, in association with a large solar flare on November 24, 2000. This is the first detection of solar neutrons by the neutron monitor that have been reported so far in solar cycle 23. The statistical significance of the detection is 5.5 sigma. In this flare, the intense emission of hard X-rays and gamma-rays has been observed by the Yohkoh Hard X-ray Telescope (HXT) and Gamma Ray Spectrometer (GRS), respectively. The production time of solar neutrons is better correlated with those of hard X-rays and gamma-rays than with the production time of soft X-rays. The observations of the solar neutrons on the ground have been limited to solar flares with soft X-ray class greater than X8 in former solar cycles. In this cycle, however, neutrons were detected associated with an X2.3 solar flare on November 24, 2000. This is the first report of the detection of solar neutrons on the ground associated with a solar flare with its X-ray class smaller than X8.

An intense (X9.4/2B) flare, which occurred on 6 November 1997, was observed with the hard X-ray telescope on board Yohkoh . In the M2- (33 – 53 keV) and H-band (53 – 93 keV), This flare clearly show double footpoint sources during its impulsive phase. We have analyzed the locations and motions of these sources in detail. It is found that, at ∼ 11:53:06 UT, one of the footpoint sources in the M2-band moved to a new position earlier than the corresponding source in the H-band. The time-lag is about one second and the separation between the old and new positions is ∼ 5 arcsec. This happened between two major spikes in the time profile of hard X-ray intensity. This apparent motion might indicate that an epoch of energy release finished somewhere high in the corona and the next epoch started in another magnetic field system. This observation clearly shows that higher energy electrons precipitate into the footpoint region later . We try to interpret this particular phenomenon under the two assumptions, which are the direct precipitation model and the trap-and-precipitation model.

On the basis of Yohkoh Hard X-Ray Telescope data and the magnetograms taken by the SOHO Michelson Doppler Imager and the Solar Magnetic Field Telescope at Huairou Solar Observing Station, we suggest an interpretation of the well-observed "Bastille Day 2000" flare. The large-scale structure and dynamics of the flare, as seen in hard X-rays, can be explained in terms of the three-dimensional reconnection at a separator in the corona. More specifically, we suggest that before occurrence of two-ribbon flares with significant decrease of a distance between the hard X-ray (HXR) footpoints, like the Bastille Day flare, the bases of magnetic field separatrices are moved by the large-scale photospheric flows of two types. First, the shear flows, which are parallel to the photospheric neutral line, increase the length of field lines in the corona and produce an excess of magnetic energy. Second, the converging flows, i.e., the flows directed to the neutral line, create the preflare current layers in the corona and provide an excess of energy sufficient to produce a large flare. During the flare, both excesses of magnetic energy are released completely or partially. In the Bastille Day flare, the model describes two kinds of apparent motions of the HXR kernels. One is an increase of a distance between the flare ribbons in which the HXR kernels appear. The effect results from fast reconnection in a coronal current layer. The second effect is a decrease of the distance between the kernels moving to each other as a result of relaxation of magnetic tensions generated by the photospheric shear flows.

We present the relation of the spatial distribution of H-alpha kernels with the distribution of hard X-ray (HXR) sources seen during the 2001 April 10 solar flare. This flare was observed in H-alpha with the (Sartorius) telescope at Kwasan Observatory, Kyoto University, and in hard X-rays (HXRs) with the Hard X-ray Telescope (HXT) onboard Yohkoh. We compared the spatial distribution of the HXR sources with that of the H-alpha kernels. While many H-alpha kernels are found to brighten successively during the evolution of the flare ribbons, only a few radiation sources are seen in the HXR images. We measured the photospheric magnetic field strengths at each radiation source in the H-alpha images, and found that the H-alpha kernels accompanied by HXR radiation have magnetic strengths about 3 times larger than those without HXR radiation. We also estimated the energy release rates based on the magnetic reconnection model. The release rates at the H-alpha kernels with accompanying HXR sources are 16-27 times larger than those without HXR sources. These values are sufficiently larger than the dynamic range of HXT, which is about 10, so that the difference between the spatial distributions of the H$\alpha$ kernels and the HXR sources can be explained., Comment: 10 pages, 3 figures

Differential emission measure (DEM) derived from the extreme ultraviolet (EUV) lines of the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamic Observatory is used in the analysis of a solar flare observed by the Nobeyama Radioheliograph (NoRH). The target was a composite event consisting of an impulsive flare, SOL2015-06-21T01:42 (GOES class M2.0), and a gradual flare, SOL2015-06-21T02:36 (M2.6), for which separation of thermal plasma heating from nonthermal particle acceleration was of major interest. We have calculated the thermal free–free intensity maps with the AIA-derived DEM and compared them against the observed NoRH maps to attribute the difference to the nonthermal component. In this way, we were able to locate three distinct sources: the major source with thermal and nonthermal components mixed, a nonthermal source devoid of thermal particles, and a thermal source lacking microwave emission. Both the first and the second nonthermal sources produced impulsively rising 17 GHz intensities and moved away from the local magnetic polarization inversion lines in correlation with the flare radiation. In contrast, the thermal sources stay in fixed locations and show temporal variations of the temperature and emission measure uncorrelated with the flare radiation. We interpret these distinct properties as indicating that nonthermal sources are powered by magnetic reconnection and thermal sources passively receive energy from the nonthermal donor. The finding of these distinct properties between thermal and nonthermal sources demonstrates the microwave and EUV emission measure combined diagnostics.

There are high expectations for GaN high electron mobility transistors (GaN-HEMT) to serve as a key device in the production of a high power and high efficiency millimeter-wave amplifier. Until now, an extremely low three-terminal pinched-off-current of less than 10-6 A/mm was achieved by applying band engineering. It improved the on-state breakdown voltage to 50 V and the off-state breakdown voltage to over 100 V (Makiyama et al., Phys. Status Solidi C 6(S2), S1012 (2009) [1]). However, the output power of a GaN-HEMT decreases due to current collapse. In particular, the influence of current collapse increases in a GaN-HEMT with a short gate-length. In this work, technology was developed to reduce this amount of current collapse. By utilizing thin silicon nitride passivation film that contained many Si-H bonds, the current collapse was remarkably improved. A 3-stage common source amplifier MMIC was fabricated that used the current collapse reducing technology. The Pin vs. Pout characteristics were measured at the W-band. Excellent power characteristics, such as Pout of 1.3 W at 75 GHz at 35 V operation, and a frequency bandwidth of 13 GHz were demonstrated. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The Yohkoh hard X-ray telescope (HXT) observed hard X-rays from the impulsive phase of a long-duration event (LDE) occurring on 14 July 2000. The Yohkoh soft X-ray telescope (SXT) and other instruments observed a large arcade, with width and length ∼30 000 km and ∼120 000 km, respectively. In hard X-rays, for the first time, a two-ribbon structure was clearly observed in the energy range above 30 keV. This result suggests that electrons are in fact accelerated in the whole system of this arcade, not merely in a particular dominant loop. We analyzed the motions of bright kernels in the two hard X-ray ribbons in detail. Assuming these bright kernels to be footpoints of newly reconnected loops, we infer from their motions that the loops reconnecting early are highly sheared, while the loops reconnecting later are less sheared. We have also analyzed the hard X-ray spectra of the two ribbons independently. At the outer edge of a ribbon, the spectrum tends to be harder than that in the inner edge. This suggests that higher-energy electrons precipitate at the footpoints of outer loops and lower ones do at those of inner loops. We discuss what kind of model can support this tendency.

It is observed in impulsive flares with the Hard X-ray Telescope (HXT) onboard Yohkoh that a hard X-ray source is located above the apex of a soft X-ray flaring loop in addition to double footpoint sources (Masuda et al. 1994, 1995). This observation suggests that the flare energy-release, probably magnetic reconnection, takes place not in the soft X-ray loop, but above the loop. It is important to derive the hard X-ray spectrum of this source accurately in order to understand how electrons are energized there. Using an improved image-synthesis technique with new modulation patterns (Sato 1997), we obtained hard X-ray images of the 13 January 1992 flare in the four HXT energy bands with a common photon-accumulation time. The spectrum of the above-the-looptop source in the energy range of 14–93 keV seems to be well fit by emission from an isothermal plasma whose temperature is about 100 MK, rather than by a non-thermal, single power-law spectrum. Although this is consistent with the observational result that the density of the ambient plasma is not high enough to stop high energy electrons, we need to study other events, especially intense events from which more accurate spectra can be derived, in order to confirm this result.

We present hard X-ray imaging observations of impulsive solar flares with Yohkoh HXT, focusing on the evolution of hard X-ray double footpoint sources seen in the energy range above 30 keV. In 7 out of the 14 events studied, the separation between the double sources increases (at the 3σ confidence level) as the flare progresses, with the double sources moving nearly anti-parallel to each other in most cases. Implications of these results to the global magnetic field structure responsible for solar flare energy release / particle acceleration are discussed.

The imaging capability of the Hard X-ray Telescope (HXT) on board Yohkoh has been drastically improved by (1) adopting new instrumental response functions (modulation patterns) derived from a self-calibration procedure that makes use of solar flares themselves as calibration sources, (2) revising the Maximum Entropy (MEM) image synthesis procedure for better total flux estimation, and (3) incorporating in MEM properly estimated observation errors. One of the most intense flares so far observed with HXT, the 1997 November 6, X9 flare, has been analyzed with the new HXT imaging program. Two footpoint sources are clearly seen and show systematic motions during the impulsive phase. This may provide a new clue to understand the coronal magnetic field structure involved in the energy release process of flares.

Intense geomagnetic storms with DST index ≤-100 nT were recorded on 9 March and 11 March 1993 associated with solar activity on 6 March and 9-10 March, respectively. In this paper, we discuss the characteristic features of the solar origins of the two events that gave rise to coronal and interplanetary disturbances and as a consequence produced strong geomagnetic activity at the Earth. The source of the activity in one case is attributed to a major 3M7.0 flare that occurred on 6 March 1993 and in the other case, to two large filament disruptions on the disk during 9-10 March, 1993. Both these sources were found to be located near changing or varying low-latitude coronal holes. They were also located close to the heliospheric currents sheets. Distinct X-ray activity was observed for both the events as observed by the Yohkoh SXT telescope. The detailed evolution and a comparison of these events on the basis of Yohkoh soft X-ray observations are presented here.

We report the discovery of a high-temperature source above the soft X-ray loop of the impulsive limb flare on 1992 January 13 with the Yohkoh Soft X-ray Telescope (SXT). The hot source coincides in position with the loop-top impulsive hard X-ray source and continues to sit above the soft X-ray flare loop throughout the flare. The single high-temperature source in the initial phase evolves to the two high-temperature (15-20 MK) ridge structures in the peak and decay phases, and the compact hard X-ray source appears to be located in between the high-temperature ridges. We assume that the loop-top hard X-ray source is of thermal origin (superhot source). The loop-top hard X-ray source has an effective temperature of 100-150 MK and a total emission measure of ~10-4 of the hot source. The geometrical relationship between the superhot and the hot sources indicates that (1) the hot source is heated by the slow shocks associated with magnetic reconnection and that (2) the superhot source is heated with the fast bow shock owing to the collision of the supersonic downward outflow with the reconnected flux tube. The small emission measure of the superhot source indicates a narrow outflow jet in between the slow shocks. These observations suggest that there is no essential difference between the compact-loop (impulsive) and long-duration event (LDE) flares. The time coincidence of the loop-top hard X-ray source with the footpoint sources indicates that nonthermal electron acceleration is causally related to the formation of the fast shock rather than the slow shocks.

Imaging observations of solar flare hard X-ray sources with the Hard X-ray Telescope (HXT) aboard the Yohkoh satellite have revealed that hard X-ray emissions (greater than 30 ke V) originate most frequently from double sources. The double sources are located on both sides of the magnetic neutral line, suggesting that the bulk of hard X-rays is emitted from footpoints of flaring magnetic loops. We also found that hard X-rays from the double sources are emitted simultaneously within a fraction of second and that the weaker source tends to be located in the stronger magnetic field region, showing a softer spectrum. Physcial implications on the observed characteristics of the hard X-ray double sources are discussed.

Observations of a solar flare on 13 January, 1992 (17:25 UT) with the Hard X-ray Telescope (HXT; /1/) and the Soft X-ray Telescope (SXT; /2/) aboard Yohkoh /3/ clearly show an impulsive hard X-ray source well above a soft X-ray flaring loop. This source reveals that the primary energy release, maybe the magnetic reconnection, occurs well above the soft X-ray flaring loop. It is most plausible that this “loop-top” hard X-ray source represents the site where the down-ward plasma outflow, ejected from a reconnection point located above the hard X-ray source, collides with an underlying closed magnetic loop. This observation thus shows for the first time where the high-energy electrons are energized.

We studied electron spectral indices of nonthermal emissions seen in hard X-rays (HXRs) and in microwaves. We analyzed 12 flares observed by the Hard X-ray Telescope aboard {\it Yohkoh}, Nobeyama Radio Polarimeters (NoRP), and the Nobeyama Radioheliograph (NoRH), and compared the spectral indices derived from total fluxes of hard X-rays and microwaves. Except for four events, which have very soft HXR spectra suffering from the thermal component, these flares show a gap $\Delta\delta$ between the electron spectral indices derived from hard X-rays $\delta_{X}$ and those from microwaves $\delta_{\mu}$ ($\Delta\delta = \delta_{X} - \delta_{\mu}$) of about 1.6. Furthermore, from the start to the peak times of the HXR bursts, the time profiles of the HXR spectral index $\delta_{X}$ evolve synchronously with those of the microwave spectral index $\delta_{\mu}$, keeping the constant gap. We also examined the spatially resolved distribution of the microwave spectral index by using NoRH data. The microwave spectral index $\delta_{\mu}$ tends to be larger, which means a softer spectrum, at HXR footpoint sources with stronger magnetic field than that at the loop tops. These results suggest that the electron spectra are bent at around several hundreds of keV, and become harder at the higher energy range that contributes the microwave gyrosynchrotron emission., Comment: 24 pages, 6 figures, accepted for publication in ApJ

Molecular adlayers of doubly C(60)-conjugated phthalocyanine derivatives ((C(60))(2)NiPc) were examined on bare and zinc(II) octaethylporphyrin (ZnOEP)- and coronene-modified Au(111) surfaces. Electrochemical scanning tunneling microscopy (EC-STM) has revealed the structure of the (C(60))(2)NiPc adlayer at single molecular level. The (C(60))(2)NiPc adlayer is strongly influenced by the underlying organic layers, i.e., a disordered, a packed structure of (C(60))(2)NiPc was found on a clean Au(111) surface because of the strong interaction between (C(60))(2)NiPc molecule and Au(111) substrate, whereas a single (C(60))(2)NiPc molecule was clearly distinguished both on ZnOEP and coronene adlayers at a low coverage of (C(60))(2)NiPc molecules. The obtained results in the present study suggest that the underlying organic adlayers play an important role in the formation process of the (C(60))(2)NiPc molecule adlayer.

This paper presents two oscillators (OSCs) and a high power amplifier (PA) for millimeter-wave transceivers. The circuits were designed with a grounded coplanar waveguide (GCPW) and 0.12-μm GaN HEMT technology. One OSC, which was based on a simple series source feedback topology, oscillated at a frequency of 74.5 GHz with an output power of 2.2 mW (3.38 dBm). This oscillation frequency was the highest ever reported for GaN HEMT OSCs. Another OSC with a buffer delivered a record power of 85 mW (19.28 dBm) at 70.75 GHz. In addition, a single-chip PA with a 3-stage common source scheme delivered an output power of 1.3 W (31.13 dBm) at 75 GHz with a CW source module. The 3-dB bandwidth of the PA was 13 GHz from 67 to 80 GHz. The performance of these devices is sufficient for use in E-band fixed wireless access systems and automotive radar systems. The results demonstrate that the GaN HEMTs represent a feasible means of addressing the stringent demands imposed by various millimeter-wave applications.

We present a multi-wavelength observation of a solar flare occurring on 2006 December 13 with Hinode, RHESSI, and the Nobeyama Radio Observatory, to study the electron acceleration site and mechanism. The Solar Optical Telescope (SOT) on board Hinode observed elongated flare ribbons, and RHESSI observed double-footpoint hard X-ray (HXR) sources appearing in part of the ribbons. A photospheric vector magnetogram obtained from SOT reveals that the HXR sources are located at the region where horizontal magnetic fields change the direction. The region is interpreted as the footpoint of magnetic separatrix. Microwave images taken with the Nobeyama Radioheliograph show a loop structure connecting the HXR sources. The brighter parts of the microwave intensity are located between the top and footpoints of the loop. We consider these observations as an evidence of the electron acceleration near the magnetic separatrix and injection parallel to the field line., 20 pages, 7 figures, accepted by ApJ

著者人数：12名, 資料番号: SA1001982000