Search Publications
Magnetic Flux Cancelation as the Buildup and Trigger Mechanism for CME-producing Eruptions in Two Small Active Regions
Panesar, Navdeep K.; Moore, Ronald L.; Sterling, Alphonse C.
We follow two small, magnetically isolated coronal mass ejection (CME)-producing solar active regions (ARs) from the time of their emergence until several days later, when their core regions erupt to produce the CMEs. In both cases, magnetograms show: (a) following an initial period where the poles of the emerging regions separate from each other,…
A Very High Energy γ-Ray Survey toward the Cygnus Region of the Galaxy
Abeysekara, A. U.; Archer, A.; Aune, T. +67 more
We present results from deep observations toward the Cygnus region using 300 hr of very high energy (VHE) γ-ray data taken with the VERITAS Cerenkov telescope array and over 7 yr of high-energy γ-ray data taken with the Fermi satellite at an energy above 1 GeV. As the brightest region of diffuse γ-ray emission in the northern sky, the Cygnus regio…
Impact of Type II Spicules in the Corona: Simulations and Synthetic Observables
Martínez-Sykora, Juan; De Pontieu, Bart; Carlsson, Mats +2 more
The role of type II spicules in the corona has been a much debated topic in recent years. This paper aims to shed light on the impact of type II spicules in the corona using novel 2.5D radiative MHD simulations, including ion-neutral interaction effects with the Bifrost code. We find that the formation of simulated type II spicules, driven by the …
Pre-eruptive Magnetic Reconnection within a Multi-flux-rope System in the Solar Corona
Wang, Haimin; Wang, Yuming; Shen, Chenglong +2 more
The solar corona is frequently disrupted by coronal mass ejections (CMEs), whose core structure is believed to be a flux rope made of helical magnetic field. This has become a “standard” picture; though, it remains elusive how the flux rope forms and evolves toward eruption. While one-third of the ejecta passing through spacecraft demonstrate a fl…
A Subarcsecond ALMA Molecular Line Imaging Survey of the Circumbinary, Protoplanetary Disk Orbiting V4046 Sgr
Kastner, Joel H.; Forveille, T.; Hily-Blant, P. +6 more
We present a suite of Atacama Large Millimeter Array (ALMA) interferometric molecular line and continuum images that elucidate, on linear size scales of ∼30-40 au, the chemical structure of the nearby, evolved, protoplanetary disk orbiting the close binary system V4046 Sgr. The observations were undertaken in the 1.1-1.4 mm wavelength range (ALMA …
On the Factors Determining the Eruptive Character of Solar Flares
Veronig, Astrid M.; Thalmann, Julia K.; Baumgartner, Christian
We investigated how the magnetic field in solar active regions (ARs) controls flare activity, i.e., whether a confined or eruptive flare occurs. We analyzed 44 flares of GOES class M5.0 and larger that occurred during 2011-2015. We used 3D potential magnetic field models to study their location (using the flare distance from the flux-weighted AR c…
First Results from the Herschel and ALMA Spectroscopic Surveys of the SMC: The Relationship between [C II]-bright Gas and CO-bright Gas at Low Metallicity
Warren, Steven R.; Bolatto, Alberto D.; Meixner, Margaret +15 more
The Small Magellanic Cloud (SMC) provides the only laboratory to study the structure of molecular gas at high resolution and low metallicity. We present results from the Herschel Spectroscopic Survey of the SMC (HS3), which mapped the key far-IR cooling lines [C II], [O I], [N II], and [O III] in five star-forming regions, and new ALMA …
The COS CGM Compendium. I. Survey Design and Initial Results
Lehner, Nicolas; Howk, J. Christopher; O'Meara, John M. +3 more
We present a neutral hydrogen-selected absorption-line survey of gas with H I column densities 15< {log}{N}{{H}{{I}}}< 19 at z≲ 1 using the Cosmic Origins Spectrograph on the Hubble Space Telescope. Our main aim is to determine the metallicity distribution of these absorbers. Our sample consists of 224 absorbers selected on the ba…
Hierarchical Fragmentation in the Perseus Molecular Cloud: From the Cloud Scale to Protostellar Objects
Bourke, Tyler L.; Myers, Philip C.; Gutermuth, Robert A. +8 more
We present a study of hierarchical structure in the Perseus molecular cloud, from the scale of the entire cloud (≳ 10 pc) to smaller clumps (∼1 pc), cores (∼0.05-0.1 pc), envelopes (∼300-3000 au), and protostellar objects (∼15 au). We use new observations from the Submillimeter Array (SMA) large project “Mass Assembly of Stellar Systems and their …
An Analytical Diffusion-Expansion Model for Forbush Decreases Caused by Flux Ropes
Dumbović, Mateja; Temmer, Manuela; Vršnak, Bojan +2 more
We present an analytical diffusion-expansion Forbush decrease (FD) model ForbMod, which is based on the widely used approach of an initially empty, closed magnetic structure (i.e., flux rope) that fills up slowly with particles by perpendicular diffusion. The model is restricted to explaining only the depression caused by the magnetic structure of…