Search

We report the critical behavior of the magnetization in Heusler alloy Co2TiGa0.8Sn0.2 as a potential candidate of high spin polarized materials with the characteristics of topological Weyl fermions. The Weyl semimetals are materials of great interest for applying spintronics devices, due to their unusual magnetoelectronic and magnetothermal properties. The magnetic properties of the synthesized Heusler alloy Co2TiGa0.8Sn0.2 are investigated around the Curie temperature TC. The magnetic isotherm measurements of Co2TiGa0.8Sn0.2 around TC exhibit that the critical exponent δ is deduced to be 4.455(4) in high maximum applied field of 50 kOe and 4.823(9) in low maximum applied field of 10 kOe, respectively. Both δ values are different from 3.0 derived by the conventional molecular field theory, but they are close to 5.0 predicted by the spin fluctuation theory for the itinerant electron ferromagnets. Possible origins for the discrepancy between experimental results and theoretical models are also discussed.

Background Carboplatin is a key drug for ovarian cancer. However, it sometimes induces hypersensitivity reactions (HSRs) that result in the discontinuation of the treatment. Although various desensitization protocols have been reported in previous retrospective studies, a limited number of prospective studies have analyzed these protocols. Methods Patients with platinum-sensitive relapsed ovarian cancer who experienced carboplatin-induced HSRs were treated with diluted solutions of 1/1000, 1/100, 1/10 and an undiluted solution of carboplatin over a 1-h period. If no HSRs occurred within the first two cycles, a short protocol regimen over a 30-min period per solution was followed. The primary endpoint was treatment completion rate. Results Between May 2015 and September 2018, 21 patients were enrolled from two institutions. One patient experienced platinum-sensitive recurrence after the desensitization protocol; thus, 22 sessions were analyzed. Epinephrine use, treatment-related death, and intensive care unit (ICU) admissions did not occur. The median number of desensitization cycles was 6 (range 1–6). Two sessions were discontinued early because of grade 2 dysgeusia and grade 2 malaise. Treatment in two (9.1%) patients was discontinued because of HSR development. The treatment completion rate was 90.9%. Six (27.3%) sessions met the criteria for transition to the short protocol regimen. In 14 (63.6%) sessions, HSRs were observed during infusion of the undiluted solution. The median progression-free survival and overall survival were 14.8 and 23.8 months, respectively. Conclusion This 4-step, 2-h carboplatin desensitization protocol is safe and feasible. Patients require careful monitoring with a rapid response to HSRs, especially during the administration of undiluted solutions.

The patient was an 81-year-old man who visited a clinic for fever and lower abdominal pain. He was subsequently diagnosed with prostatitis based on computed tomography (CT) findings that showed swelling of the prostate. Despite treatment with antibacterial therapy, his symptoms did not improve significantly. Since the patient also had myelodysplastic syndrome, he was transferred to our hospital and subsequently diagnosed with prostate abscess based on findings on magnetic resonance imaging (MRI). The abscess had spread widely from the dorsal side of the trigone of the bladder to anterior wall of the rectum. Transperineal drainage was performed to preserve the urethral mucosa of the prostatic urethra. Considering the shape of the abscess cavity, one pigtail catheter was placed in the prostate and another was placed transperineally on the dorsal side of the trigone of the bladder. Cystostomy was performed at the same time. Culture of the abscess revealed the presence of Staphylococcus aureus. As there was little exudate from the abscess 9 days after drainage, the pigtail catheter on the dorsal side of the trigone of the bladder was removed following an injection of minocycline into the abscess. CT showed shrinkage of the abscess 4 days later, and the remaining intraprostatic pigtail catheter was removed after an injection of minocycline. The cystostomy pigtail catheter was subsequently removed since the patient was able to urinate smoothly after clamping. MRI confirmed the disappearance of the abscess cavity 2 months later.

Magnetohydrodynamic (MHD) waves are candidates for heating the solar chromosphere, although it is still unclear which mode of the wave is dominant in heating. We perform two-dimensional radiative MHD simulation to investigate the propagation of MHD waves in the quiet region of the solar chromosphere. We identify the mode of the shock waves by using the relationship between gas pressure and magnetic pressure across the shock front and calculate their corresponding heating rate through the entropy jump to obtain a quantitative understanding of the wave heating process in the chromosphere. Our result shows that the fast magnetic wave is significant in heating the low-beta chromosphere. The low-beta fast magnetic waves are generated from high-beta fast acoustic waves via mode conversion crossing the equipartition layer. Efficient mode conversion is achieved by large attacking angles between the propagation direction of the shock waves and the chromospheric magnetic field., Accepted by ApJL

Solar magnetic fields comprise an 11-year activity cycle, represented by the number of sunspots. The maintenance of such a solar magnetic field can be attributed to fluid motion in the convection zone, i.e. a dynamo. This study conducts the mean-field analyses of the global solar dynamo simulation presented by Hotta et al. (2016). Although the study succeeds in producing coherent large-scale magnetic fields at high Reynolds numbers, the detailed physics of the maintenance of this field have not been fully understood. This study extracts the alpha-tensor and the turbulent magnetic diffusivity tensor through mean-field analyses. The turbulent magnetic diffusivity exhibits a significant decrease towards high Reynolds numbers. The decrease in the turbulent magnetic diffusivity suppresses the energy conversion of large-scale field to small-scale field. This implies that the decrease in the turbulent magnetic diffusivity contributes to the maintenance of a large-scale magnetic field at high Reynolds numbers. A significant downward turbulent pumping is observed; it is enhanced in the weak phase of the large-scale field. This study proposes a cyclic reversal process of a large-scale field which is dominantly driven by the alpha-effect and is possibly triggered by downward pumping., Comment: 17 pages, 20 figures, Accepted for publication in ApJ

Solar-C (EUVST) is the next Japanese solar physics mission to be developed with significant contributions from US and European countries. The mission carries an EUV imaging spectrometer with slit-jaw imaging system called EUVST (EUV High-Throughput Spectroscopic Telescope) as the mission payload, to take a fundamental step towards answering how the plasma universe is created and evolves and how the Sun influences the Earth and other planets in our solar system. In April 2020, ISAS (Institute of Space and Astronautical Science) of JAXA (Japan Aerospace Exploration Agency) has made the final down-selection for this mission as the 4th in the series of competitively chosen M-class mission to be launched with an Epsilon launch vehicle in mid 2020s. NASA (National Aeronautics and Space Administration) has selected this mission concept for Phase A concept study in September 2019 and is in the process leading to final selection. For European countries, the team has (or is in the process of confirming) confirmed endorsement for hardware contributions to the EUVST from the national agencies. A recent update to the mission instrumentation is to add a UV spectral irradiance monitor capability for EUVST calibration and scientific purpose. This presentation provides the latest status of the mission with an overall description of the mission concept emphasizing on key roles of the mission in heliophysics research from mid 2020s.

We perform magnetohydrodynamic (MHD) simulations to investigate the propagation of Alfven wave in magnetic chromosphere. We use the 1.5-dimensional expanding flux tube geometry setting and transverse perturbation at the bottom to generate the Alfven wave. Compared with previous studies, our expansion is that we include the radiative loss term introduced by Carlsson & Leenaarts (2012). We find that when an observation based transverse wave generator is applied, the spatial distribution of the time-averaged radiative loss profile in our simulation is consistent with that in the classic atmospheric model. In addition, the energy flux in the corona is larger than the required value for coronal heating in the quiet region. Our study shows that the Alfven wave driven model has the potential to explain chromospheric heating and transport enough energy to the corona simultaneously., Accepted by ApJ

We succeeded in observing two large spicules simultaneously with the Atacama Large Millimeter/submillimeter Array (ALMA), the Interface Region Imaging Spectrograph (IRIS), and the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory. One is a spicule seen in the IRIS Mg II slit-jaw images and AIA 304\AA\ images (MgII/304A spicule). The other one is a spicule seen in the 100GHz images obtained with ALMA (100GHz spicule). Although the 100GHz spicule overlapped with the MgII/304A spicule in the early phase, it did not show any corresponding structures in the IRIS Mg II and AIA 304A images after the early phase. It suggests that the spicules are individual events and do not have a physical relationship. To obtain the physical parameters of the 100GHz spicule, we estimate the optical depths as a function of temperature and density using two different methods. One is using the observed brightness temperature by assuming a filling factor, and the other is using an emission model for the optical depth. As a result of comparing them, the kinetic temperature of the plasma and the number density of ionized hydrogens in the 100GHz spicule are ~6800 K and 2.2 x 10^10 cm^-3. The estimated values can explain the absorbing structure in the 193A image, which appear as a counterpart of the 100GHz spicule. These results suggest that the 100GHz spicule presented in this paper is classified to a macrospicule without a hot sheath in former terminology., Comment: 8 pages, 4 figures, Accepted to ApJL

Solar-C EUVST (EUV High-Throughput Spectroscopic Telescope) is a solar physics mission concept that was selected as a candidate for JAXA competitive M-class missions in July 2018. The onboard science instrument, EUVST, is an EUV spectrometer with slit-jaw imaging system that will simultaneously observe the solar atmosphere from the photosphere/chromosphere up to the corona with seamless temperature coverage, high spatial resolution, and high throughput for the first time. The mission is designed to provide a conclusive answer to the most fundamental questions in solar physics: how fundamental processes lead to the formation of the solar atmosphere and the solar wind, and how the solar atmosphere becomes unstable, releasing the energy that drives solar flares and eruptions. The entire instrument structure and the primary mirror assembly with scanning and tip-tilt fine pointing capability for the EUVST are being developed in Japan, with spectrograph and slit-jaw imaging hardware and science contributions from US and European countries. The mission will be launched and installed in a sun-synchronous polar orbit by a JAXA Epsilon vehicle in 2025. ISAS/JAXA coordinates the conceptual study activities during the current mission definition phase in collaboration with NAOJ and other universities. The team is currently working towards the JAXA final down-selection expected at the end of 2019, with strong support from US and European colleagues. The paper provides an overall description of the mission concept, key technologies, and the latest status.

Using a three-dimensional compressible magnetohydrodynamic (MHD) simulation, we have reproduced the fast solar wind in a direct and self-consistent manner, based on the wave/turbulence driven scenario. As a natural consequence of Alfvenic perturbations at its base, highly compressional and turbulent fluctuations are generated, leading to heating and acceleration of the solar wind. The analysis of power spectra and structure functions reveals that the turbulence is characterized by its imbalanced (in the sense of outward Alfvenic fluctuations) and anisotropic nature. The density fluctuation originates from the parametric decay instability of outwardly propagating Alfven waves and plays a significant role in the Alfven wave reflection that triggers turbulence. Our conclusion is that the fast solar wind is heated and accelerated by compressible MHD turbulence driven by parametric decay instability and resultant Alfven wave reflection., published from The Astrophysical Journal Letters

Follicular dendritic cell sarcoma (FDCS) is a very rare malignant tumor derived from follicular dendritic cells. Radical resection is the standard therapy for patients with local disease, but an optimal chemotherapy regimen has not been determined for unresectable disease. We report our experience of an FDCS patient with multiorgan involvement. In the present case, disease was only located in the pancreas initially and radical resection was performed. Multiple metastasis developed after the treatment and several factors that indicated a poor prognosis were observed. The present case had a very poor prognostic disease but survived for a long time with a good performance status because of the multiple chemotherapy regimens, which follow therapeutic strategies for malignant lymphoma and soft tissue sarcoma. As far as we know, this is the first study reporting the indication of bendamustine for FDCS patients.

We propose a new lattice Boltzmann method (LBM) for two-phase fluid flows with high density ratios by improving Inamuro et al.’s method [13] without solving the pressure Poisson equation. In the proposed method, we use the lattice kinetic scheme (LKS, an extended scheme of LBM) in the same way as Inamuro et al.’s method. The velocity and pressure fields are computed by using a single equilibrium distribution function and by adjusting the speed of sound in a high density region to satisfy the incompressible continuity equation even for high density ratios. In addition, an improved LKS is used for eliminating dissipation errors, and the continuous surface force (CSF) model is used for modeling interfacial tension of thin interfaces accurately. In order to show the validity of the method, we apply the method to the simulations of a stationary drop, binary droplet collision, rising bubbles, and the impact of a drop on a thin liquid film (a milk crown). In a stationary drop, pressure and density profiles are computed, and the effect of sound speed on time evolution of the pressure field in the drop is illustrated. The stable computations can be performed for high density ratios up to 855. In the simulations of a binary droplet collision and rising bubbles, the computed results by the proposed method are compared with those by Inamuro et al.’s method in good agreement. Also, the computation time of the proposed method is about 50 times faster than that of Inamuro et al.’s method . In the simulation of a milk crown, the time evolution of the crown radius is in good agreement with theoretical predictions.

The 11-year solar magnetic cycle shows a high degree of coherence in spite of the turbulent nature of the solar convection zone. It has been found in recent high-resolution magnetohydrodynamics simulations that the maintenance of a large-scale coherent magnetic field is difficult with small viscosity and magnetic diffusivity ( ≲ 10 12 square centimenters per second). We reproduced previous findings that indicate a reduction of the energy in the large-scale magnetic field for lower diffusivities and demonstrate the recovery of the global-scale magnetic field using unprecedentedly high resolution. We found an efficient small-scale dynamo that suppresses small-scale flows, which mimics the properties of large diffusivity. As a result, the global-scale magnetic field is maintained even in the regime of small diffusivities—that is, large Reynolds numbers.

We report the results of the Atacama Large Millimeter/sub-millimeter Array (ALMA) observations of the solar chromosphere on the southern polar limb. Coordinated observations with the Interface Region Imaging Spectrograph (IRIS) are also conducted. ALMA provided unprecedented high spatial resolution in the millimeter band ($\approx$ 2.0 arcsec) at 100 GHz frequency with a moderate cadence (20 s). The results are as follows: (1) The ALMA 100 GHz images show saw-tooth patterns on the limb, and a comparison with SDO/AIA 171\AA\ images shows a good correspondence of the limbs with each other. (2) The ALMA 100 GHz movie shows a dynamic thorn-like structure elongating from the saw-tooth patterns on the limb, with lengths reaching at least 8 arcsec, thus suggesting jet-like activity in the ALMA microwave range. These ALMA jets are in good correspondence with IRIS jet clusters. (3) A blob ejection event is observed. By comparing with the IRIS Mg II slit-jaw images, the trajectory of the blob is located along the spicular patterns., Comment: Accepted for publication in The Astrophysical Journal

We conduct a three-dimensional magnetohydrodynamic (MHD) simulation of the parametric decay instability of Alfv\'en waves and resultant compressible MHD turbulence, which is likely to develop in the solar wind acceleration region. Because of the presence of the mean magnetic field, the nonlinear stage is characterized by filament-like structuring and anisotropic cascading. By calculating the timescales of phase mixing and the evolution of Alfv\'en wave turbulence, we have found that the early nonlinear stage is dominated by phase mixing, while the later phase is dominated by imbalanced Alfv\'en wave turbulence. Our results indicate that the regions in the solar atmosphere with large density fluctuation, such as the coronal bottom and wind acceleration region, are heated by phase-mixed Alfv\'en waves, while the other regions are heated by Alfv\'en wave turbulence., Comment: Accepted for publication in The Astrophysical Journal Letters

BACKGROUND Finding the correct medical information in a flood of information from the internet is a significant issue for patients with cancer. OBJECTIVE We investigated the reliability of the information on cancer treatment methods available on the internet based on an evaluation by medical oncologists, medical students, and cancer survivors. METHODS Using Google and Yahoo as the search engines, we carried out the information search using 2 keywords, “cancer treatment” and “cancer cure,” and the top 20 information sites were identified. A similar search was conducted on 5 types of cancer. The reliability of the information presented was rated on a 3-level scale (A, B, or C). Level A referred to reliable sites (providing information complying with the clinical practice guidelines for various types of cancer), Level B included sites not falling under either Level A or Level C, and Level C comprised dangerous or harmful sites (providing information on treatment not approved by the regulatory authority in Japan and bombastic advertisements without any relevant clinical evidence). The evaluation was conducted by medical oncologists, medical students, and cancer survivors. The consistency of the information reliability level rating between the medical students or cancer survivors with that of the medical oncologists was assessed by using the kappa value. RESULTS A total of 247 sites were evaluated for reliability. The ratings provided by the medical students’ group were as follows: Level A, 12.1% (30/247); Level B, 56.3% (139/247); and Level C, 31.6% (78/247). The ratings provided by the cancer survivors’ group were as follows: Level A, 16.8% (41/244); Level B, 44.7% (109/244); and Level C, 38.5% (94/244). The ratings provided by the oncologists’ group were as follows: Level A, 10.1% (25/247); Level B, 51.4% (127/247); and Level C, 38.5% (95/247). The intergroup rating consistency between the medical students’ group and oncologists’ group was 87.4% (216/247, kappa=0.77) and that between the cancer survivors’ group and oncologists’ group was 76.2% (186/244, kappa=0.61). CONCLUSIONS Of the investigated sites providing information on cancer treatment on the internet, the percentage of sites that seemed to provide harmful information was much higher than that of sites providing reliable information. The reliability level rating was highly consistent between the medical students’ group and the medical oncologists’ group and also between the cancer survivors’ group and the medical oncologists’ group.

Using numerical simulations, we investigate the onset and suppression of parametric decay instability (PDI) in the solar wind, focusing on the suppression effect by the wind acceleration and expansion. We also discuss the role of PDI in generating the density fluctuation in the solar wind and the cross-helicity evolution up to $1 {\rm \ au}$. Numerical simulations from the coronal base to 1 au are conducted in a self-consistent manner; we take into account the feedback of wave energy and pressure in the background. Monochromatic waves with various injection frequencies $f_0$ are injected to discuss the suppression of PDI, while broadband waves are applied to compare the numerical results with observation. We find, via the simulations with monochromatic waves, that high-frequency ($f_0 \gtrsim10^{-3} {\rm \ Hz}$) Alfv\'en waves are subject to PDI. Meanwhile, the maximum growth rate of the PDI of low-frequency ($f_0 \lesssim10^{-4} {\rm \ Hz}$) Alfv\'en waves becomes negative due to acceleration and expansion effects. Medium-frequency ($f_0 \approx 10^{-3.5} {\rm \ Hz}$) Alfv\'en waves have a positive growth rate but do not show the signature of PDI up to 1 au because the growth rate is too small. The medium-frequency waves experience neither PDI nor reflection so they propagate through the solar wind most efficiently. This is called the frequency-filtering mechanism of the solar wind. The simulations with broadband waves indicate that the observed trend of the density fluctuation is well explained by the evolution of PDI while the observed cross-helicity evolution is in agreement with low-frequency wave propagation., Comment: Accepted for publication in The Astrophysical Journal

The interiors of quiescent prominences are filled with turbulent flows. The evolution of upflow plumes, descending pillars, and vortex motions has been clearly detected in high-resolution observations. The Rayleigh-Taylor instability is thought to be a driver of such internal flows. Descending pillars are related to the mass budgets of prominences. There is a hypothesis of dynamic equilibrium where the mass drainage via descending pillars and the mass supply via radiative condensation are balanced to maintain the prominence mass; however, the background physics connecting the two different processes is poorly understood. In this study, we reproduced the dynamic interior of a prominence via radiative condensation and the mechanism similar to the Rayleigh-Taylor instability using a three-dimensional magnetohydrodynamic simulation including optically thin radiative cooling and nonlinear anisotropic thermal conduction. The process to prominence formation in the simulation follows the reconnection-condensation model, where topological change in the magnetic field caused by reconnection leads to radiative condensation. Reconnection is driven by converging motion at the footpoints of the coronal arcade fields. In contrast to the previous model, by randomly changing the speed of the footpoint motion along a polarity inversion line, the dynamic interior of prominence is successfully reproduced. We find that the mass condensation rate of the prominence is enhanced in the case with dynamic state. Our results support the observational hypothesis that the condensation rate is balanced with the mass drainage rate and suggest that a self-induced mass maintenance mechanism exists., Comment: Accepted for publication in ApJ, 26 pages, 12 figures

We propose a reconnection-condensation model in which topological change in a coronal magnetic field via reconnection triggers radiative condensation, thereby resulting in prominence formation. Previous observational studies have suggested that reconnection at a polarity inversion line of a coronal arcade field creates a flux rope that can sustain a prominence; however, they did not explain the origin of cool dense plasmas of prominences. Using three-dimensional magnetohydrodynamic simulations including anisotropic nonlinear thermal conduction and optically thin radiative cooling, we demonstrate that reconnection can lead not only to flux rope formation but also to radiative condensation under a certain condition. In our model, this condition is described by the Field length, which is defined as the scale length for thermal balance between radiative cooling and thermal conduction. This critical condition depends weakly on the artificial background heating. The extreme ultraviolet emissions synthesized with our simulation results have good agreement with observational signatures reported in previous studies., 22 pages, 11 figures, accepted to ApJ

The understanding of magnetic reconnection in three-dimension (3D) is far shallower than its counterpart in two-dimension (2D) due to its potential complication, not to mention the evolving of the spontaneously growing turbulence. We investigate the reason for reconnection acceleration on the characters and development of diffusion regions and sheared 3D energy modes (energy modes that are not parallel to the anti-parallel magnetic fields) during the turbulence building stage. We found that multiple reconnection layers emerge due to the growth of 3D sheared tearing instability. Diffusion regions on adjacent reconnection layers form an inflow-outflow coupling that enhances the local reconnection. Further coupling of the existing energy modes breeds new energy modes near the current sheet edge. As reconnection layers span and interact with each other across the whole current sheet, global magnetic energy consumption accelerates. The significant contribution of 3D energy modes and their interaction to the reconnection rate enhancement seems to be independent on magnetic diffusivity. On the other hand, the global guide field changes the layout of 3D reconnection layer thus determines whether the system is fast-reconnection-preferable., Comment: 13 pages, 14 figures

It has recently been recognized that the convective velocities achieved in the current solar convection simulations might be over-estimated. The newly-revealed effects of the prevailing small-scale magnetic field within the convection zone may offer possible solutions to this problem. The small-scale magnetic fields can reduce the convective amplitude of small-scale motions through the Lorentz-force feedback, which concurrently inhibits the turbulent mixing of entropy between upflows and downflows. As a result, the effective Prandtl number may exceed unity inside the solar convection zone. In this paper, we propose and numerically confirm a possible suppression mechanism of convective velocity in the effectively high-Prandtl number regime. If the effective horizontal thermal diffusivity decreases (the Prandtl number accordingly increases), the subadiabatic layer which is formed near the base of the convection zone by continuous depositions of low entropy transported by adiabatically downflowing plumes is enhanced and extended. The global convective amplitude in the high-Prandtl thermal convection is thus reduced especially in the lower part of the convection zone via the change in the mean entropy profile which becomes more subadiabatic near the base and less superadiabatic in the bulk., Comment: 17 pages, 13 figures, accepted for publication in ApJ

© 2017. The American Astronomical Society. All rights reserved. Magnetohydrodynamic (MHD) waves permeate the solar atmosphere and constitute potential coronal heating agents. Yet, the waves detected so far may be but a small subset of the true existing wave power. Detection is limited by instrumental constraints but also by wave processes that localize the wave power in undetectable spatial scales. In this study, we conduct 3D MHD simulations and forward modeling of standing transverse MHD waves in coronal loops with uniform and non-uniform temperature variation in the perpendicular cross-section. The observed signatures are largely dominated by the combination of the Kelvin-Helmholtz instability (KHI), resonant absorption, and phase mixing. In the presence of a cross-loop temperature gradient, we find that emission lines sensitive to the loop core catch different signatures compared to those that are more sensitive to the loop boundary and the surrounding corona, leading to an out-of-phase intensity and Doppler velocity modulation produced by KHI mixing. In all of the considered models, common signatures include an intensity and loop width modulation at half the kink period, a fine strand-like structure, a characteristic arrow-shaped structure in the Doppler maps, and overall line broadening in time but particularly at the loop edges. For our model, most of these features can be captured with a spatial resolution of 0.″33 and a spectral resolution of 25 km s-1, although we do obtain severe over-estimation of the line width. Resonant absorption leads to a significant decrease of the observed kinetic energy from Doppler motions over time, which is not recovered by a corresponding increase in the line width from phase mixing and KHI motions. We estimate this hidden wave energy to be a factor of 5-10 of the observed value. journal_title: The Astrophysical Journal article_type: paper article_title: Observational Signatures of Transverse Magnetohydrodynamic Waves and Associated Dynamic Instabilities in Coronal Flux Tubes copyright_information: © 2017. The American Astronomical Society. All rights reserved. date_received: 2016-11-23 date_accepted: 2017-02-02 date_epub: 2017-02-22 ispartof: Astrophysical Journal vol:836 issue:2 status: published

We propose a novel one-dimensional model that includes both shock and turbulence heating and qualify how these processes contribute to heating the corona and driving the solar wind. Compressible MHD simulations allow us to automatically consider shock formation and dissipation, while turbulent dissipation is modeled via a one-point closure based on Alfv\'en wave turbulence. Numerical simulations were conducted with different photospheric perpendicular correlation lengths $\lambda_0$, which is a critical parameter of Alfv\'en wave turbulence, and different root-mean-square photospheric transverse-wave amplitudes $\delta v_0$. For the various $\lambda_0$, we obtain a low-temperature chromosphere, high-temperature corona, and supersonic solar wind. Our analysis shows that turbulence heating is always dominant when $\lambda_0 \lesssim 1{\rm \ Mm}$. This result does not mean that we can ignore the compressibility because the analysis indicates that the compressible waves and their associated density fluctuations enhance the Alfv\'en wave reflection and therefore the turbulence heating. The density fluctuation and the cross helicity are strongly affected by $\lambda_0$, while the coronal temperature and mass loss rate depend weakly on $\lambda_0$., Comment: Accepted for publicaiton in The Astrophysical Journal

The main object of the paper is to present the condition of the non-diffusive part of the Reynolds stress for driving the double-cell structure of the solar meridional circulation, which has been revealed by recent helioseismic observations. By conducting a set of mean-field hydrodynamic simulations, we confirm for the first time that the double-cell meridional circulation can be achieved along with the solar-like differential rotation when the Reynolds stress transports the angular momentum upward in the lower part and downward in the upper part of the convection zone. It is concluded that, in a stationary state, the accumulated angular momentum via the Reynolds stress in the middle layer is advected to both the upper and lower parts of the convection zone by each of the two meridional circulation cells, respectively., 16 pages, 9 figures, accepted for publication in ApJ

In this paper, results of 2.5-dimensional magnetohydrodynamical simulations are reported for the magnetic reconnection of non-perfectly antiparallel magnetic fields. The magnetic field has a component perpendicular to the computational plane, that is, guide field. The angle theta between magnetic field lines in two half regions is a key parameter in our simulations whereas the initial distribution of the plasma is assumed to be simple; density and pressure are uniform except for the current sheet region. Alfven waves are generated at the reconnection point and propagate along the reconnected field line. The energy fluxes of the Alfven waves and magneto-acoustic waves (slow mode and fast mode) generated by the magnetic reconnection are measured. Each flux shows the similar time evolution independent of theta. The percentage of the energies (time integral of energy fluxes) carried by the Alfven waves and magneto-acoustic waves to the released magnetic energy are calculated. The Alfven waves carry 38.9%, 36.0%, and 29.5% of the released magnetic energy at the maximum (theta=80^\circ) in the case of beta=0.1, 1, and 20 respectively, where beta is the plasma beta (the ratio of gas pressure to magnetic pressure). The magneto-acoustic waves carry 16.2% (theta=70^\circ), 25.9% (theta=60^\circ), and 75.0% (theta=180^\circ) of the energy at the maximum. Implications of these results for solar coronal heating and acceleration of high-speed solar wind are discussed., Comment: Accepted for publication in PASJ. 24 pages, 11 figures

We investigated the dependence of the solar magnetic parity between the hemispheres on two important parameters, the turbulent diffusivity and the meridional flow, by means of axisymmetric kinematic dynamo simulations based on the flux-transport dynamo model. It is known that the coupling of the magnetic field between hemispheres due to turbulent diffusivity is an important factor for the solar parity issue, but the detailed criterion for the generation of the dipole field has not been investigated. Our conclusions are as follows. (1) The stronger diffusivity near the surface is more likely to cause the magnetic field to be a dipole. (2) The thinner layer of the strong diffusivity near the surface is also more apt to generate a dipolar magnetic field. (3) The faster meridional flow is more prone to cause the magnetic field to be a quadrupole, i.e., symmetric about the equator. These results show that turbulent diffusivity and meridional flow are crucial for the configuration of the solar global magnetic field., 19 pages, 5 figures

A cancellation is thought to be a basic process of the photospheric magnetic field and plays an important role in magnetic flux budget and in various solar activities. There are two major theoretical scenarios for this phenomena, the "U-loop emergence" and the "Ω-loop submergence" models. It is important to clarify which is the dominant process during the cancellation for the estimation of the solar magnetic flux transport through the surface. We study the vector magnetic field and velocity structures around a quiet-Sun cancellation by using the Solar Optical Telescope on board the Hinode satellite. Transverse magnetic field connecting the canceling magnetic features and strong long-lasting Doppler redshift signal are found. The transverse field is observed in the first spectropolarimetric observation after the occurrence of the cancellation while the redshift is clearly delayed to the cancellation by 20 minutes. These results indicate that the observed cancellation is an "Ω-loop submergence."

A revision to the flux-transport dynamo model for the solar sunspot cycle is proposed and is demonstrated by using the axisymmetric kinematic simulations. The flux-transport dynamo has succeeded to explain the general cyclic behaviors of the sunspots. It has been known, however, that previous models failed to avoid the strong polar surface field and the strong toroidal field at the base in the high latitude, both of which are not consistent with observations. We propose a new regime of the flux-transport dynamo model by assuming an additional intense diffusivity profile near the surface. The surface poloidal field generated by the α effect is transported down to the base of the convection zone not by the meridional flow but by the surface diffusion mainly in the mid-latitude. With a moderate α quenching, this prevents the concentration of the polar surface field and the amplification of the toroidal field at the high latitude. The condition to obtain the proper magnetic field strength near the pole is ηsurf/u 0>2 × 109 cm, where ηsurf and u 0 are the surface diffusivity and the meridional flow speed, respectively. We also do some parameter studies to ensure the importance of the surface strong diffusivity. In addition, the dependence of the cycle period on free parameters, the speed of meridional flow and the surface diffusivity, is investigated.

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

Aims. We study the physical properties of a recurring solar active region jet observed in X-rays and extreme-ultraviolet (EUV).Methods. Multi-wavelength data from all three instruments on board Hinode were analysed. X-ray imaging and spectroscopy of the microflaring emission associated with the jets was performed with the Reuven Ramaty High Energy Spectroscopic Imager (RHESSI ). Associated EUV jets were observed with the Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI)/Extreme Ultraviolet Imager (EUVI) on board STEREO .Results. We found a correlation between recurring magnetic flux cancellation close to a pore, the X-ray jet emission, and associated Ca II H ribbon brightenings. We estimated the lower limit for the decrease in magnetic energy associated with the X-ray jet emission at 3 1029 erg. The recurring plasma ejection was observed simultaneously at EUV and X-ray temperatures, associated with type III radio bursts and microflaring activity at the jet footpoint.Conclusions. The recurring jet (EUV and X-ray) emissions can be attributed to chromospheric evaporation flows due to recurring coronal magnetic reconnection. In this process, the estimated minimum loss in the magnetic energy is sufficient to account for the total energy required to launch the jet.

Aims. It is well known that convective motions in the photosphere are suppressed by magnetic fields. However, it has been difficult to study the interaction between convection and small magnetic features, such as G-band bright points (GBPs) or pores with polarimetric measurements, because of the available spatial resolution (∼1 �� ). This situation is changed by the advent of the SpectroPolarimeter (SP) aboard the Hinode satellite, which has 0. �� 3 spatial resolution. Methods. We analyzed the pore and its surrounding region in NOAA 10940 near the disk center. We obtained the field strength and filling factor through the Milne-Eddington inversion of the Stokes profiles. We also derived the line-of-sight velocity by the shift of the line core. Using these physical parameters, we investigated the physical conditions needed to suppress the convection. Results. We found that the convection is suppressed, not by the strength of the magnetic field itself, but by high concentration of magnetic flux tubes. We also found that GBPs and pores are distinguished in terms of the filling factor (f ); f � 0. 6f or GBPs and f = 0.8–0.9 for pores.

We study the non-thermal emissions in a solar flare occurring on 2003 May 29 by using RHESSI hard X-ray (HXR) and Nobeyama microwave observations. This flare shows several typical behaviors of the HXR and microwave emissions: time delay of microwave peaks relative to HXR peaks, loop-top microwave and footpoint HXR sources, and a harder electron energy distribution inferred from the microwave spectrum than from the HXR spectrum. In addition, we found that the time profile of the spectral index of the higher-energy ($\gsim 100$ keV) HXRs is similar to that of the microwaves, and is delayed from that of the lower-energy ($\lsim 100$ keV) HXRs. We interpret these observations in terms of an electron transport model called {\TPP}. We numerically solved the spatially-homogeneous {\FP} equation to determine electron evolution in energy and pitch-angle space. By comparing the behaviors of the HXR and microwave emissions predicted by the model with the observations, we discuss the pitch-angle distribution of the electrons injected into the flare site. We found that the observed spectral variations can qualitatively be explained if the injected electrons have a pitch-angle distribution concentrated perpendicular to the magnetic field lines rather than isotropic distribution.

Aims. We study the physical properties of an active region (AR) jet in order to probe the mechanisms responsible for it. Methods. We report 2007 January 15/16 observations of a recurring jet situated on the west side of NOAA AR 10938. Multiwavelength data from all three instruments onboard Hinode were analysed. This paper focuses on one instance of a jet observed with the Hinode/EUV Imaging Spectrometer (EIS). Using EIS raster data we measured the temperatures, Doppler shifts, density, and filling factor. Results. A strong blue-shifted component and an indication of a weak red-shifted component at the base of the jet was observed around Log Te = 6.2. The up-flow velocities exceeded 150 km s −1 . The jet component was seen over a range of temperatures between 5.4 and 6.4 in Log Te .U sing Fexii λ186 and λ195 line ratios, we measured densities above Log Ne = 11 for the high-velocity up-flow component. We found that the density of the high-velocity up-flow increases with velocity. We estimate the filling factor in the jet upflow to be

Specific cutting resistance was determined through airplane experiments under low relative gravity conditions such as μ G, 0.15 G, 0.3 G, 0.5 G, and 1 G. Results showed that the relationship between specific cutting resistance and relative gravity could be expressed as a linear function. As for numerical analysis by discrete element method (DEM), the data of spring constant in a contact model of DEM could be treated as constant in the analysis of specific cutting resistance under low gravity conditions from the viewpoint of stress-oriented soil-machine interaction. Moreover, the numerical analysis by DEM with change of relative gravity and the corresponding modification of consolidation time is found to be sufficient to obtain a specific cutting resistance at a given low gravity condition below 1 G.

著者人数：20名, Accepted: 2007-09-05, 資料番号: SA1000280000

On 2005 September 13 a filament eruption accompanied by a halo coronal mass ejection (CME) occurred in the most flare-productive active region, NOAA 10808, in solar cycle 23. Using multiwavelength observations before the filament eruption on September 13, we investigate the processes leading to the catastrophic eruption. We find that the filament slowly ascended at a speed of 0.1 km s-1 over 2 days before the eruption. During slow ascension, many small flares were observed close to the footpoints of the filament, where new magnetic elements were emerging. On the basis of the observational facts, we discuss the triggering mechanism leading to the filament eruption. We suggest that the process toward the eruption is as follows. First, a series of small flares played a role in changing the topology of the loops overlying the filament. Second, the small flares gradually changed the equilibrium state of the filament and caused the filament to ascend slowly over 2 days. Finally, a C2.9 flare that occurred when the filament was close to the critical point for loss of equilibrium directly led to the catastrophic filament eruption right after it.

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.

We consider MHD waves as a heating source of cool cores of galaxy clusters. In particular, we focus on transverse waves (Alfven waves), because they can propagate a longer distance than longitudinal waves (sound waves). Using MHD simulations, we found that the transverse waves can stably heat a cool core if the wave period is large enough (108 yr). Moreover, the longitudinal waves that are created as a by-product of the nonlinear evolution of the transverse waves could be observed as the "ripples" found in cool cores.

Aims. We study the solar flare on 28 August 1999 observed by the Nobeyama Radioheliograph at 17 and 34 GHz and analyze the unusual behavior of microwave source (a coronal loop) after injections of high-energy electrons. The observations reveal a propagation velocity of the emission front along the loop of about 10 4 km s -1 , which is 30 times less than the velocity of high-energy electrons generating gyrosynchrotron emission at 17 and 34 GHz. The main goal is to understand the physical origin of this electron propagation. Methods. We interpret this anomalous propagation in terms of the collective effects of relativistic electrons interacting with plasma turbulence. A cloud of highly energetic electrons responsible for microwave emission generates low-frequency whistler waves, and a turbulent "wall" in the loop is formed. Results. The electrons undergo strong resonant scattering due to wave-particle interaction, and the emission front propagates with the wave phase velocity, which is much lower than the particle velocity.

This paper describes how to predict the impact force and the penetration at landing on lunar sandy surface by SPH (Smoothed Particle Hydrodynamics) method. Before the calculations by SPH method, we conducted experiments about the landing on the lunar sandy surface. In experiment, 1/6 scale model of foot pad of landing gear, which was designed according to the 1/6 scaling laws, was dropped on the Regolith simulant foundation in vacuum chamber, and the impact acceleration and the penetration were measured. In calculations, the test bed of lunar simulant was modeled as Bingham fluid which had Mohr-Coulomb’s failure criteria and the impact acceleration and the penetration of foot pad model was calculated. The results of computations by SPH method are in good agreement with the experimental results.

In this paper we show that the phase mixing of continuum Alfv\'{e}n waves and/or continuum slow waves in magnetic structures of the solar atmosphere as, e.g., coronal arcades, can create the illusion of wave propagation across the magnetic field. This phenomenon could be erroneously interpreted as fast magnetosonic waves. The cross-field propagation due to phase mixing of continuum waves is apparent because there is no real propagation of energy across the magnetic surfaces. We investigate the continuous Alfv\'{e}n and slow spectra in 2D Cartesian equilibrium models with a purely poloidal magnetic field. We show that apparent superslow propagation across the magnetic surfaces in solar coronal structures is a consequence of the existence of continuum Alfv\'{e}n waves and continuum slow waves that naturally live on those structures and phase mix as time evolves. The apparent cross-field phase velocity is related to the spatial variation of the local Alfv\'{e}n/slow frequency across the magnetic surfaces and is slower than the Alfv\'{e}n/sound velocities for typical coronal conditions. Understanding the nature of the apparent cross-field propagation is important for the correct analysis of numerical simulations and the correct interpretation of observations., Comment: 41 pages, 7 figures, accepted for publication in ApJ