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  1. Chemical release disasters have serious consequences, disrupting ecosystems, society, and causing significant loss of life. Mitigating the destructive impacts relies on identification and mapping, monitoring, and trajectory forecasting. Improvements in sensor capabilities are enabling airborne and space-based remote sensing to support response activities. Key applications are improving transport models in complex terrain and improved disaster response. Understanding urban atmospheric transport in the Los Angeles Basin, where topographic influences on transport patterns are significant, was improved by leveraging the Aliso Canyon leak as an atmospheric tracer. Plume characterization data was collected by the AutoMObile trace Gas (AMOG) Surveyor, a commuter carmore » modified for science. Mobile surface in situ CH 4 and winds were measured by AMOG Surveyor under Santa Ana conditions to estimate an emission rate of 365±30% Gg yr -1. Vertical profiles were collected by AMOG Surveyor by leveraging local topography for vertical profiling to identify the planetary boundary layer at ~700 m. Topography significantly constrained plume dispersion by up to a factor of two. The observed plume trajectory was used to validate satellite aerosol optical depth-inferred atmospheric transport, which suggested the plume first was driven offshore, but then veered back towards land. Numerical long-range transport model predictions confirm this interpretation. Lastly, this study demonstrated a novel application of satellite aerosol remote sensing for disaster response.« less
  2. The additional computing power offered by the planned exascale facilities could be transformational across the spectrum of plasma and fusion research — provided that the new architectures can be efficiently applied to our problem space. The collaboration that will be required to succeed should be viewed as an opportunity to identify and exploit cross-disciplinary synergies. To assess the opportunities and requirements as part of the development of an overall strategy for computing in the exascale era, the Exascale Requirements Review meeting of the Fusion Energy Sciences (FES) community was convened January 27–29, 2016, with participation from a broad range ofmore » fusion and plasma scientists, specialists in applied mathematics and computer science, and representatives from the U.S. Department of Energy (DOE) and its major computing facilities. This report is a summary of that meeting and the preparatory activities for it and includes a wealth of detail to support the findings. Technical opportunities, requirements, and challenges are detailed in this report (and in the recent report on the Workshop on Integrated Simulation). Science applications are described, along with mathematical and computational enabling technologies. Also see for more information.« less
  3. Recent efforts have shown that helicon waves (fast waves at >20 omega(ci)) may be an attractive option for driving efficient off-axis current drive during non-inductive tokamak operation for DIII-D, ITER and DEMO. For DIII-D scenarios, the ray tracing code, GENRAY, has been extensively used to study helicon current drive efficiency and location as a function of many plasma parameters. The full wave code, AORSA, which is applicable to arbitrary Larmor radius and can resolve arbitrary ion cyclotron harmonic order, has been recently used to validate the ray tracing technique at these high cyclotron harmonics. If the SOL is ignored, itmore » will be shown that the GENRAY and AORSA calculated current drive profiles are comparable for the envisioned high beta advanced scenarios for DIII-D, where there is high single pass absorption due to electron Landau damping and minimal ion damping. AORSA is also been used to estimate possible SOL effects on helicon current drive coupling and SOL absorption due to collisional and slow wave effects.« less
  4. We present the proof-of-principle KINETIC-J module for iterative addition of all-order kinetic effects (parallel and perpendicular) in both the IC and EC frequency ranges, to any existing FD or FE frequency-domain full-wave RF simulation. The module calculates the linear, kinetic plasma current, such that given f 0 (r,v) and the cold plasma solution as an initial guess at the wave electric field, iterating the KINETIC-J module and the existing code (its internal plasma current replaced with the output of the module) converges to the kinetic solution. Since KINETIC-J does not use the k-space representation of the hot plasma dielectric, inmore » favor of data parallel numeric integrals, implementing the module requires minimal code changes.« less
  5. Synchrotron emission has recently been detected in the jet of a massive protostar, providing further evidence that certain jet formation characteristics for young stars are similar to those found for highly relativistic jets from active galactic nuclei. We present data at 325 and 610 MHz taken with the Giant Metrewave Radio Telescope of the young, low-mass star DG Tau, an analog of the Sun soon after its birth. This is the first investigation of a low-mass young stellar object at such low frequencies. We detect emission with a synchrotron spectral index in the proximity of the DG Tau jet and interpretmore » this emission as a prominent bow shock associated with this outflow. This result provides tentative evidence for the acceleration of particles to relativistic energies due to the shock impact of this otherwise very low-power jet against the ambient medium. We calculate the equipartition magnetic field strength B {sub min} ≈ 0.11 mG and particle energy E {sub min} ≈ 4 × 10{sup 40} erg, which are the minimum requirements to account for the synchrotron emission of the DG Tau bow shock. These results suggest the possibility of low energy cosmic rays being generated by young Sun-like stars.« less
  6. Several experiments on different machines and in different fast wave (FW) heating regimes, such as hydrogen minority heating and high harmonic fast waves, have found strong interactions between radio-frequency (RF) waves and the scrape-off layer (SOL) region. This paper examines the propagation and the power loss in the SOL by using the full wave code AORSA, in which the edge plasma beyond the last closed flux surface (LCFS) is included in the solution domain and a collisional damping parameter is used as a proxy to represent the real, and most likely nonlinear, damping processes. 3D AORSA results for the Nationalmore » Spherical Torus eXperiment (NSTX), where a full antenna spectrum is reconstructed, are shown, confirming the same behavior found for a single toroidal mode results in Bertelli et al, Nucl. Fusion, 54 083004, 2014, namely, a strong transition to higher SOL power losses (driven by the RF field) when the FW cut-off is moved away from in front of the antenna by increasing the edge density. Additionally, full wave simulations have been extended to "conventional" tokamaks with higher aspect ratios, such as the DIII-D, Alcator C-Mod, and EAST devices. DIII-D results show similar behavior found in NSTX and NSTX-U, consistent with previous DIII-D experimental observations. In contrast, a different behavior has been found for Alcator C-Mod and EAST, which operate in the minority heating regime unlike NSTX/NSTX-U and DIII-D, which operate in the mid/high harmonic regime. A substantial discussion of some of the main aspects, such as (i) the pitch angle of the magnetic field; (ii) minority heating vs. mid/high harmonic regimes is presented showing the different behavior of the RF field in the SOL region for NSTX-U scenarios with different plasma current. Finally, the preliminary results of the impact of the SOL region on the evaluation of the helicon current drive efficiency in DIII-D is presented for the first time and briefly compared with the different regimes mentioned above.« less
  7. We report measurements of the X-ray expansion of the youngest Galactic supernova remnant, G1.9+0.3, using Chandra observations in 2007, 2009, and 2011. The measured rates strongly deviate from uniform expansion, decreasing radially by about 60% along the X-ray bright SE-NW axis from 0.84% ± 0.06% yr{sup –1} to 0.52% ± 0.03% yr{sup –1}. This corresponds to undecelerated ages of 120-190 yr, confirming the young age of G1.9+0.3 and implying a significant deceleration of the blast wave. The synchrotron-dominated X-ray emission brightens at a rate of 1.9% ± 0.4% yr{sup –1}. We identify bright outer and inner rims with the blast wavemore » and reverse shock, respectively. Sharp density gradients in either the ejecta or ambient medium are required to produce the sudden deceleration of the reverse shock or the blast wave implied by the large spread in expansion ages. The blast wave could have been decelerated recently by an encounter with a modest density discontinuity in the ambient medium, such as may be found at a wind termination shock, requiring strong mass loss in the progenitor. Alternatively, the reverse shock might have encountered an order-of-magnitude density discontinuity within the ejecta, such as may be found in pulsating delayed-detonation Type Ia models. We demonstrate that the blast wave is much more decelerated than the reverse shock in these models for remnants at ages similar to G1.9+0.3. Similar effects may also be produced by dense shells possibly associated with high-velocity features in Type Ia spectra. Accounting for the asymmetry of G1.9+0.3 will require more realistic three-dimensional Type Ia models.« less
  8. Recent efforts by Vdovin [1] and Prater [2] have shown that helicon waves (fast waves at ~30 ion cyclotron frequency harmonic) may be an attractive option for driving efficient off-axis current drive during non-inductive tokamak operation for DIIID, ITER and DEMO. For DIIID scenarios, the ray tracing code GENRAY has been extensively used to study helicon current drive efficiency and location as a function many plasma parameters. has some limitations on absorption at high cyclotron harmonics, so the full wave code AORSA, which is applicable to arbitrary Larmor radius and can therefore resolve high ion cyclotron harmonics, has been recentlymore » used to validate the GENRAY model. It will be shown that the GENRAY and AORSA driven current drive profiles are comparable for the envisioned high temperature and density advanced scenarios for DIIID, where there is high single pass absorption due to electron Landau damping. AORSA results will be shown for various plasma parameters for DIIID and for ITER. Computational difficulties in achieving these AORSA results will also be discussed. * Work supported by USDOE Contract No. DE-AC05-00OR22725 [1] V. L. Vdovin, Plasma Physics Reports, V.39, No.2, 2013 [2] R. Prater et al, Nucl. Fusion, 52, 083024, 2014« less
  9. Full wave simulations of fusion plasmas show a direct correlation between the location of the fast-wave cut-off, radiofrequency (RF) field amplitude in the scrape-off layer (SOL) and the RF power losses in the SOL observed in the National Spherical Torus eXperiment (NSTX). In particular, the RF power losses in the SOL increase significantly when the launched waves transition from evanescent to propagating in that region. Subsequently, a large amplitude electric field occurs in the SOL, driving RF power losses when a proxy collisional loss term is added. A 3D reconstruction of absorbed power in the SOL is presented showing agreementmore » with the RF experiments in NSTX. Loss predictions for the future experiment NSTX-Upgrade (NSTX-U) are also obtained and discussed.« less
  10. G1.9+0.3 is the youngest known Galactic supernova remnant (SNR), with an estimated supernova (SN) explosion date of {approx}1900, and most likely located near the Galactic center. Only the outermost ejecta layers with free-expansion velocities {approx}>18,000 km s{sup -1} have been shocked so far in this dynamically young, likely Type Ia SNR. A long (980 ks) Chandra observation in 2011 allowed spatially resolved spectroscopy of heavy-element ejecta. We denoised Chandra data with the spatio-spectral method of Krishnamurthy et al., and used a wavelet-based technique to spatially localize thermal emission produced by intermediate-mass elements (IMEs; Si and S) and iron. The spatialmore » distribution of both IMEs and Fe is extremely asymmetric, with the strongest ejecta emission in the northern rim. Fe K{alpha} emission is particularly prominent there, and fits with thermal models indicate strongly oversolar Fe abundances. In a localized, outlying region in the northern rim, IMEs are less abundant than Fe, indicating that undiluted Fe-group elements (including {sup 56}Ni) with velocities >18,000 km s{sup -1} were ejected by this SN. However, in the inner west rim, we find Si- and S-rich ejecta without any traces of Fe, so high-velocity products of O-burning were also ejected. G1.9+0.3 appears similar to energetic Type Ia SNe such as SN 2010jn where iron-group elements at such high free-expansion velocities have been recently detected. The pronounced asymmetry in the ejecta distribution and abundance inhomogeneities are best explained by a strongly asymmetric SN explosion, similar to those produced in some recent three-dimensional delayed-detonation Type Ia models.« less

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