Japan Aerospace Exploration Agency

About: Japan Aerospace Exploration Agency is a facility organization based out in Tokyo, Japan. It is known for research contribution in the topics: Galaxy & Telescope. The organization has 4327 authors who have published 12054 publications receiving 208330 citations.

Magnetic flux cancellation associated with a recurring solar jet observed with Hinode, RHESSI, and STEREO/EUVI

Abstract: 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.

First Results from BISTRO : A SCUBA-2 Polarimeter Survey of the Gould Belt

Abstract: We present the first results from the B-fields In STar-forming Region Observations (BISTRO) survey, using the Sub-millimetre Common-User Bolometer Array 2 camera, with its associated polarimeter (POL-2), on the James Clerk Maxwell Telescope in Hawaii. We discuss the survey's aims and objectives. We describe the rationale behind the survey, and the questions that the survey will aim to answer. The most important of these is the role of magnetic fields in the star formation process on the scale of individual filaments and cores in dense regions. We describe the data acquisition and reduction processes for POL-2, demonstrating both repeatability and consistency with previous data. We present a first-look analysis of the first results from the BISTRO survey in the OMC 1 region. We see that the magnetic field lies approximately perpendicular to the famous "integral filament" in the densest regions of that filament. Furthermore, we see an "hourglass" magnetic field morphology extending beyond the densest region of the integral filament into the less-dense surrounding material, and discuss possible causes for this. We also discuss the more complex morphology seen along the Orion Bar region. We examine the morphology of the field along the lower-density northeastern filament. We find consistency with previous theoretical models that predict magnetic fields lying parallel to low-density, non-self-gravitating filaments, and perpendicular to higher-density, self-gravitating filaments.

First Detection of Photons with Energy beyond 100 TeV from an Astrophysical Source.

Abstract: We report on the highest energy photons from the Crab Nebula observed by the Tibet air shower array with the underground water-Cherenkov-type muon detector array. Based on the criterion of a muon number measured in an air shower, we successfully suppress 99.92% of the cosmic-ray background events with energies E>100 TeV. As a result, we observed 24 photonlike events with E>100 TeV against 5.5 background events, which corresponds to a 5.6σ statistical significance. This is the first detection of photons with E>100 TeV from an astrophysical source.

Rapid optical and X-ray timing observations of GX 339−4: multicomponent optical variability in the low/hard state

Abstract: A rapid timing analysis of Very Large Telescope (VLT)/ULTRACAM (optical) and RXTE (X- ray) observations of the Galactic black hole binary GX 339−4 in the low/hard, post-outburst state of 2007 June is presented. The optical light curves in the r � ,gand ufilters show slow (∼20 s) quasi-periodic variability. Upon this is superposed fast flaring activity on times approaching the best time resolution probed (∼50 ms inrandg � ) and with maximum strengths of more than twice the local mean. Power spectral analysis over ∼0.004-10 Hz is presented, and shows that although the average optical variability amplitude is lower than that in X-rays, the peak variability power emerges at a higher Fourier frequency in the optical. Energetically, we measure a large optical versus X-ray flux ratio, higher than that seen on previous occasions when the source was fully jet dominated. Such a large ratio cannot be easily explained with a disc alone. Studying the optical-X-ray cross-spectrum in Fourier space shows a markedly different behaviour above and below ∼0.2 Hz. The peak of the coherence function above this threshold is associated with a short optical time lag with respect to X-rays, also seen as the dominant feature in the time-domain cross-correlation at ≈150 ms. The rms energy spectrum of these fast variations is best described by distinct physical components over the optical and X-ray regimes, and also suggests a maximal irradiated disc fraction of 20 per cent around 5000 A. If the constant time delay is due to propagation of fluctuations to (or within) the jet, this is the clearest optical evidence to date of the location of this component. The low-frequency quasi-periodic oscillation is seen in the optical but not in X-rays, and is associated with a low coherence. Evidence of reprocessing emerges at the lowest Fourier frequencies, with optical lags at ∼10 s and strong coherence in the blue ufilter. Consistent with this, simultaneous optical spectroscopy also shows the Bowen fluorescence blend, though its emission location is