Search Publications
Solar Hα features with hot onsets. II. A contrail fibril
Rouppe van der Voort, L. H. M.; Rutten, R. J.
The solar chromosphere observed in Hα consists mostly of narrow fibrils. The longest typically originate in network or plage and arch far over adjacent internetwork. We use data from multiple telescopes to analyze one well-observed example in a quiet area. It resulted from the earlier passage of an accelerating disturbance in which the gas was hea…
Extreme relativistic electron fluxes in the Earth's outer radiation belt: Analysis of INTEGRAL IREM data
Meredith, Nigel P.; Horne, Richard B.; Sandberg, Ingmar +2 more
Relativistic electrons (E > 500 keV) cause internal charging and are an important space weather hazard. To assess the vulnerability of the satellite fleet to these so-called "killer" electrons, it is essential to estimate reasonable worst cases, and, in particular, to estimate the flux levels that may be reached once in 10 and once in 100 years…
NuSTAR and XMM-Newton observations of the Arches cluster in 2015: fading hard X-ray emission from the molecular cloud
Mori, Kaya; Tomsick, John; Poutanen, Juri +6 more
We present results of long Nuclear Spectroscopic Telescope Array (NuSTAR; 200 ks) and XMM-Newton (100 ks) observations of the Arches stellar cluster, a source of bright thermal (kT ∼ 2 keV) X-rays with prominent Fe xxv Kα 6.7 keV line emission and a nearby molecular cloud, characterized by an extended non-thermal hard X-ray continuum and fluoresce…
Planetary Nebulae and H II Regions in the Starburst Irregular Galaxy NGC 4449 from LBT MODS Data
Tosi, M.; Cusano, F.; Mignoli, M. +7 more
We present deep 3500-10000 Å spectra of H II regions and planetary nebulae (PNe) in the starburst irregular galaxy NGC 4449, acquired with the Multi Object Double Spectrograph at the Large Binocular Telescope. Using the “direct” method, we derived the abundance of He, N, O, Ne, Ar, and S in six H II regions and in four PNe in NGC 4449. This is the…
Evolution of Alfvénic Fluctuations inside an Interplanetary Coronal Mass Ejection and Their Contribution to Local Plasma Heating: Joint Observations from 1.0 to 5.4 au
Li, Hui; Wang, Chi; Richardson, John D. +1 more
Tracking an interplanetary coronal mass ejection (ICME) by widely separated spacecraft could provide us with a good opportunity to study the evolution of embedded Alfvénic fluctuations (AFs) and their possible contribution to local plasma heating directly. In this study, an ICME observed by Wind at 1.0 au on 1998 March 4-6 is tracked to the locati…
The Shock Dynamics of Heterogeneous YSO Jets: 3D Simulations Meet Multi-epoch Observations
Hansen, E. C.; Hartigan, P.; Frank, A. +1 more
High-resolution observations of young stellar object (YSO) jets show them to be composed of many small-scale knots or clumps. In this paper, we report results of 3D numerical simulations designed to study how such clumps interact and create morphologies and kinematic patterns seen in emission line observations. Our simulations focus on clump scale…
A statistical study on hot flow anomaly current sheets
Zhao, L. L.; Zhang, H.; Zong, Q. -G.
Hot flow anomalies (HFAs) are phenomena frequently observed near Earth's bow shock and form when the interplanetary discontinuities interact with Earth's bow shock. We perform a statistical study to determine what kind of discontinuities are more efficient to generate HFAs. We use strict criteria to identify classic HFAs, excluding similar foresho…
Production of Sulfur Allotropes in Electron Irradiated Jupiter Trojans Ice Analogs
Ehlmann, Bethany L.; Brown, Michael E.; Choukroun, Mathieu +7 more
In this paper, we investigate sulfur chemistry in laboratory analogs of Jupiter Trojans and Kuiper Belt Objects (KBOs). Electron irradiation experiments of CH3OH-NH3-H2O and H2S-CH3OH-NH3-H2O ices were conducted to better understand the chemical differences between primor…
Disturbed galaxy clusters are more abundant in an X-ray volume-limited sample
Böhringer, Hans; Chon, Gayoung
X-ray observations of clusters of galaxies have been used to study the large-scale structure of our Universe and to test cosmological models. In such studies it is critical to understand the unique survey selection function correctly. In comparison to the cluster detection by the Sunyaev-Zel'dovich effect (SZE), it has been shown that X-ray observ…
An Interactive Multi-instrument Database of Solar Flares
Kosovichev, Alexander G.; Nita, Gelu M.; Sadykov, Viacheslav M. +1 more
Solar flares are complicated physical phenomena that are observable in a broad range of the electromagnetic spectrum, from radio waves to γ-rays. For a more comprehensive understanding of flares, it is necessary to perform a combined multi-wavelength analysis using observations from many satellites and ground-based observatories. For an efficient …