Search Publications
Anisotropies of the Magnetic Field Fluctuations at Kinetic Scales in the Solar Wind: Cluster Observations
Alexandrova, Olga; Matteini, Lorenzo; Lacombe, Catherine
We present the first statistical study of the anisotropy of the magnetic field turbulence in the solar wind between 1 and 200 Hz, I.e., from proton to sub-electron scales. We consider 93 ten-minute intervals of the Cluster/STAFF measurements. We find that the fluctuations δ {B}\perp 2 are not gyrotropic at a given frequency f…
The Presence of Thermally Unstable X-Ray Filaments and the Production of Cold Gas in the NGC 5044 Group
Jones, Christine; David, Laurence P.; Sun, Ming +3 more
We present the results of a deep Chandra observation of the X-ray bright moderate-cooling flow group NGC 5044 along with the observed correlations between the ionized, atomic, and molecular gas in this system. The Chandra observation shows that the central AGN has undergone two outbursts in the past 108 years, based on the presence of t…
Testing the Recovery of Intrinsic Galaxy Sizes and Masses of z ∼ 2 Massive Galaxies Using Cosmological Simulations
Barro, Guillermo; Faucher-Giguère, Claude-André; Kriek, Mariska +5 more
Accurate measurements of galaxy masses and sizes are key to tracing galaxy evolution over time. Cosmological zoom-in simulations provide an ideal test bed for assessing the recovery of galaxy properties from observations. Here, we utilize galaxies with {M}* ∼ {10}10{--}{10}11.5 {M}⊙ at z ∼ 1.7-2 from th…
The Green Bank Ammonia Survey: Observations of Hierarchical Dense Gas Structures in Cepheus-L1251
Caselli, Paola; Di Francesco, James; Rosolowsky, Erik +20 more
We use Green Bank Ammonia Survey observations of NH3 (1, 1) and (2, 2) emission with 32″ FWHM resolution from a ∼10 pc2 portion of the Cepheus-L1251 molecular cloud to identify hierarchical dense gas structures. Our dendrogram analysis of the NH3 data results in 22 top-level structures, which reside within 13 lower…
Sagittarius A* High-energy X-Ray Flare Properties during NuSTAR Monitoring of the Galactic Center from 2012 to 2015
Hailey, Charles J.; Mori, Kaya; Zhang, Shuo +17 more
Understanding the origin of the flaring activity from the Galactic center supermassive black hole Sagittarius A* is a major scientific goal of the NuSTAR Galactic plane survey campaign. We report on the data obtained between 2012 July and 2015 April, including 27 observations on Sgr A*, with a total exposure of ≃ 1 Ms. We found a total of 10 X-ray…
Neutral ISM, Lyα, and Lyman-continuum in the Nearby Starburst Haro11
Hayes, Matthew; Östlin, Göran; Rivera-Thorsen, T. Emil +1 more
Star-forming galaxies are believed to be a major source of Lyman continuum (LyC) radiation responsible for reionizing the early universe. Direct observations of escaping ionizing radiation have however been sparse and with low escape fractions. In the local universe, only 10 emitters have been observed, with typical escape fractions of a few perce…
Mirror Instability in the Turbulent Solar Wind
Franci, Luca; Landi, Simone; Hellinger, Petr +2 more
The relationship between a decaying strong turbulence and the mirror instability in a slowly expanding plasma is investigated using two-dimensional hybrid expanding box simulations. We impose an initial ambient magnetic field perpendicular to the simulation box, and we start with a spectrum of large-scale, linearly polarized, random-phase Alfvénic…
Rotating Magnetic Structures Associated with a Quasi-circular Ribbon Flare
Yang, Bo; Yang, Jiayan; Bi, Yi +4 more
We present the detection of a small eruption and the associated quasi-circular ribbon flare during the emergence of a bipole occurring on 2015 February 3. Under a fan dome, a sigmoid was rooted in a single magnetic bipole, which was encircled by negative polarity. The nonlinear force-free field extrapolation shows the presence of twisted field lin…
The Frequency-dependent Damping of Slow Magnetoacoustic Waves in a Sunspot Umbral Atmosphere
Erdélyi, R.; Christian, D. J.; Krishna Prasad, S. +5 more
High spatial and temporal resolution images of a sunspot, obtained simultaneously in multiple optical and UV wavelengths, are employed to study the propagation and damping characteristics of slow magnetoacoustic waves up to transition region heights. Power spectra are generated from intensity oscillations in sunspot umbra, across multiple atmosphe…
Study on Precursor Activity of the X1.6 Flare in the Great AR 12192 with SDO, IRIS, and Hinode
Lee, Kyoung-Sun; Kusano, Kanya; Bamba, Yumi +1 more
The physical properties and their contribution to the onset of a solar flare are still uncleare even though chromospheric brightening is considered a precursor phenomenon of a flare. Many studies suggested that photospheric magnetic field changes cause destabilization of large-scale coronal structure. We aim to understand how a small photospheric …