[en] A microwave-induced plasma (MIP) reactor has been constructed from a domestic microwave oven (DMO) and applied to the bulk synthesis of solid state compounds. Low pressure MIP can be initiated and maintained using a range of gases including Ar, N₂, NH₃, O₂, Cl₂, and H₂S. In order to obtain reproducible synthesis conditions the apparatus is designed to allow control of gas flow rate, gas composition, and pressure. The use of the reactor is demonstrated by the synthesis of three binary metal nitrides formed in a NH₃ MIP. The reactions are rapid and the products show good crystallinity and phase purity as judged by powder x-ray diffraction

[en] We present new measurements of the time variability of intensity, Doppler, and nonthermal velocities in moss in an active region core observed by the EUV Imaging Spectrometer on Hinode in 2007 June. The measurements are derived from spectral profiles of the Fe XII 195 A line. Using the 2'' slit, we repeatedly scanned 150'' by 150'' in a few minutes. This is the first time it has been possible to make such velocity measurements in the moss, and the data presented are the highest cadence spatially resolved maps of moss Doppler and nonthermal velocities ever obtained in the corona. The observed region produced numerous C- and M-class flares with several occurring in the core close to the moss. The magnetic field was therefore clearly changing in the active region core, so we ought to be able to detect dynamic signatures in the moss if they exist. Our measurements of moss intensities agree with previous studies in that a less than 15% variability is seen over a period of 16 hr. Our new measurements of Doppler and nonthermal velocities reveal no strong flows or motions in the moss, nor any significant variability in these quantities. The results confirm that moss at the bases of high temperature coronal loops is heated quasi-steadily. They also show that quasi-steady heating can contribute significantly even in the core of a flare productive active region. Such heating may be impulsive at high frequency, but if so it does not give rise to large flows or motions.

[en] The cocaine analogue RTI-121 (3β-(4-iodophenyl)tropane-2β-carboxylic acid isopropyl ester), when labeled with carbon-11, was evaluated in rats as a potential PET ligand for the dopamine transporter. The compound gave in vivo striatum:cerebellum ratios that were similar to those obtained with the related ligand [¹¹C]RTI-55 (2↔-(4-iodophenyl)tropane-2β-carboxylic acid methyl ester) but showed a much greater selectivity for the dopamine compared with the 5-HT uptake site. The results indicate that [¹¹C]RTI-121 could be used in preference to [¹¹C]RTI-55 in man. Experimentally, [¹¹C]RTI-121 has potential in the quantification of dopamine terminal function in rat models of disease, using a combination of autoradiography, postmortem sampling, and in vivo tomography

[en] Spectral line widths are often observed to be larger than can be accounted for by thermal and instrumental broadening alone. This excess broadening is a key observational constraint for both nanoflare and wave dissipation models of coronal heating. Here we present a survey of non-thermal velocities measured in the high temperature loops (1–4 MK) often found in the cores of solar active regions. This survey of Hinode Extreme Ultraviolet Imaging Spectrometer (EIS) observations covers 15 non-flaring active regions that span a wide range of solar conditions. We find relatively small non-thermal velocities, with a mean value of 17.6 ± 5.3 km s"−"1, and no significant trend with temperature or active region magnetic flux. These measurements appear to be inconsistent with those expected from reconnection jets in the corona, chromospheric evaporation induced by coronal nanoflares, and Alfvén wave turbulence models. Furthermore, because the observed non-thermal widths are generally small, such measurements are difficult and susceptible to systematic effects

[en] Measurements of the temperature and density structure of the solar corona provide critical constraints on theories of coronal heating. Unfortunately, the complexity of the solar atmosphere, observational uncertainties, and the limitations of current atomic calculations, particularly those for Fe, all conspire to make this task very difficult. A critical assessment of plasma diagnostics in the corona is essential to making progress on the coronal heating problem. In this paper, we present an analysis of temperature and density measurements above the limb in the quiet corona using new observations from the EUV Imaging Spectrometer (EIS) on Hinode. By comparing the Si and Fe emission observed with EIS we are able to identify emission lines that yield consistent emission measure distributions. With these data we find that the distribution of temperatures in the quiet corona above the limb is strongly peaked near 1 MK, consistent with previous studies. We also find, however, that there is a tail in the emission measure distribution that extends to higher temperatures. EIS density measurements from several density sensitive line ratios are found to be generally consistent with each other and with previous measurements in the quiet corona. Our analysis, however, also indicates that a significant fraction of the weaker emission lines observed in the EIS wavelength ranges cannot be understood with current atomic data.

[en] Recent observations from the Interface Region Imaging Spectrograph ( IRIS ) have discovered a new class of numerous low-lying dynamic loop structures, and it has been argued that they are the long-postulated unresolved fine structures (UFSs) that dominate the emission of the solar transition region. In this letter, we combine IRIS measurements of the properties of a sample of 108 UFSs (intensities, lengths, widths, lifetimes) with one-dimensional non-equilibrium ionization simulations, using the HYDRAD hydrodynamic model to examine whether the UFSs are now truly spatially resolved in the sense of being individual structures rather than being composed of multiple magnetic threads. We find that a simulation of an impulsively heated single strand can reproduce most of the observed properties, suggesting that the UFSs may be resolved, and the distribution of UFS widths implies that they are structured on a spatial scale of 133 km on average. Spatial scales of a few hundred kilometers appear to be typical for a range of chromospheric and coronal structures, and we conjecture that this could be an important clue for understanding the coronal heating process.

[en] The timescale for energy release is an important parameter for constraining the coronal heating mechanism. Observations of 'warm' coronal loops (∼1 MK) have indicated that the heating is impulsive and that coronal plasma is far from equilibrium. In contrast, observations at higher temperatures (∼3 MK) have generally been consistent with steady heating models. Previous observations, however, have not been able to exclude the possibility that the high temperature loops are actually composed of many small-scale threads that are in various stages of heating and cooling and only appear to be in equilibrium. With new observations from the EUV Imaging Spectrometer and X-ray Telescope (XRT) on Hinode we have the ability to investigate the properties of high temperature coronal plasma in extraordinary detail. We examine the emission in the core of an active region and find three independent lines of evidence for steady heating. We find that the emission observed in XRT is generally steady for hours, with a fluctuation level of approximately 15% in an individual pixel. Short-lived impulsive heating events are observed, but they appear to be unrelated to the steady emission that dominates the active region. Furthermore, we find no evidence for warm emission that is spatially correlated with the hot emission, as would be expected if the high temperature loops are the result of impulsive heating. Finally, we also find that intensities in the 'moss', the footpoints of high temperature loops, are consistent with steady heating models provided that we account for the local expansion of the loop from the base of the transition region to the corona. In combination, these results provide strong evidence that the heating in the core of an active region is effectively steady, that is, the time between heating events is short relative to the relevant radiative and conductive cooling times.

[en] High-resolution spectra from the Hinode EUV Imaging Spectrometer have revealed that coronal spectral line profiles are sometimes asymmetric, with a faint enhancement in the blue wing on the order of 100 km s^–1. These asymmetries could be important since they may be subtle yet diagnostically useful signatures of coronal heating or solar wind acceleration processes. It has also been suggested that they are signatures of chromospheric jets supplying mass and energy to the corona. Until now, however, there have been no studies of the physical properties of the plasma producing the asymmetries. Here we identify regions of asymmetric profiles in the outflows of AR 10978 using an asymmetric Gaussian function and extract the intensities of the faint component using multiple Gaussian fits. We then derive the temperature structure and chemical composition of the plasma producing the asymmetries. We find that the asymmetries are dependent on temperature, and are clearer and stronger in coronal lines. The temperature distribution peaks around 1.4-1.8 MK with an emission measure at least an order of magnitude larger than that at 0.6 MK. The first ionization potential bias is found to be 3-5, implying that the high-speed component of the outflows may also contribute to the slow-speed wind. Observations and models indicate that it takes time for plasma to evolve to a coronal composition, suggesting that the material is trapped on closed loops before escaping, perhaps by interchange reconnection. The results, therefore, identify the plasma producing the asymmetries as having a coronal origin.

[en] One of the most interesting discoveries from Hinode is the presence of persistent high-temperature high-speed outflows from the edges of active regions (ARs). EUV imaging spectrometer (EIS) measurements indicate that the outflows reach velocities of 50 km s^-1 with spectral line asymmetries approaching 200 km s^-1. It has been suggested that these outflows may lie on open field lines that connect to the heliosphere, and that they could potentially be a significant source of the slow speed solar wind. A direct link has been difficult to establish, however. We use EIS measurements of spectral line intensities that are sensitive to changes in the relative abundance of Si and S as a result of the first ionization potential (FIP) effect, to measure the chemical composition in the outflow regions of AR 10978 over a 5 day period in 2007 December. We find that Si is always enhanced over S by a factor of 3-4. This is generally consistent with the enhancement factor of low FIP elements measured in situ in the slow solar wind by non-spectroscopic methods. Plasma with a slow wind-like composition was therefore flowing from the edge of the AR for at least 5 days. Furthermore, on December 10 and 11, when the outflow from the western side was favorably oriented in the Earth direction, the Si/S ratio was found to match the value measured a few days later by the Advanced Composition Explorer/Solar Wind Ion Composition Spectrometer. These results provide strong observational evidence for a direct connection between the solar wind, and the coronal plasma in the outflow regions.

[en] With the aim of studying active region fan loops using observations from the Hinode EUV Imaging Spectrometer (EIS) and Solar Dynamics Observatory Atmospheric Imaging Assembly (AIA), we investigate a number of inconsistencies in modeling the absolute intensities of Fe VIII and Si VII lines, and address why spectroheliograms formed from these lines look very similar despite the fact that ionization equilibrium calculations suggest that they have significantly different formation temperatures: log(T_e /K) = 5.6 and 5.8, respectively. It is important to resolve these issues because confidence has been undermined in their use for differential emission measure (DEM) analysis, and Fe VIII is the main contributor to the AIA 131 A channel at low temperatures. Furthermore, the strong Fe VIII 185.213 A and Si VII 275.368 A lines are the best EIS lines to use for velocity studies in the transition region, and for assigning the correct temperature to velocity measurements in the fans. We find that the Fe VIII 185.213 A line is particularly sensitive to the slope of the DEM, leading to disproportionate changes in its effective formation temperature. If the DEM has a steep gradient in the log(T_e /K) = 5.6-5.8 temperature range, or is strongly peaked, Fe VIII 185.213 A and Si VII 275.368 A will be formed at the same temperature. We show that this effect explains the similarity of these images in the fans. Furthermore, we show that the most recent ionization balance compilations resolve the discrepancies in absolute intensities. With these difficulties overcome, we combine EIS and AIA data to determine the temperature structure of a number of fan loops and find that they have peak temperatures of 0.8-1.2 MK. The EIS data indicate that the temperature distribution has a finite (but narrow) width < log (σ_Te/K) = 5.5 which, in one detailed case, is found to broaden substantially toward the loop base. AIA and EIS yield similar results on the temperature, emission measure magnitude, and thermal distribution in the fans, though sometimes the AIA data suggest a relatively larger thermal width. The result is that both the Fe VIII 185.213 A and Si VII 275.368 A lines are formed at log(T_e /K)∼ 5.9 in the fans, and the AIA 131 A response also shifts to this temperature.