Search Publications
Interpreting Mars ionospheric anomalies over crustal magnetic field regions using a 2-D ionospheric model
Withers, Paul; Mendillo, Michael; Matta, Majd +1 more
spatially inhomogeneous, small-scale crustal magnetic fields of Mars influence the escape of planetary atmospheric species and the interaction of the solar wind with the ionosphere. Understanding the plasma response to crustal magnetic field regions can therefore provide insight to ionospheric structure and dynamics. To date, several localized spa…
Thermal evolution of Venus with argon degassing
O'Rourke, Joseph G.; Korenaga, Jun
Decades-old measurements of atmospheric and elemental surface composition constrain the history of Venus. In this study, we search for a model featuring continuous evolution in the stagnant-lid regime that predicts the present-day atmospheric mass of radiogenic argon and satisfies the other available constraints. For comparison, we also consider t…
Light Bridge in a Developing Active Region. II. Numerical Simulation of Flux Emergence and Light Bridge Formation
Toriumi, Shin; Cheung, Mark C. M.; Katsukawa, Yukio
Light bridges, the bright structure dividing umbrae in sunspot regions, show various activity events. In Paper I, we reported on an analysis of multi-wavelength observations of a light bridge in a developing active region (AR) and concluded that the activity events are caused by magnetic reconnection driven by magnetconvective evolution. The aim o…
Feedback from Mass Outflows in Nearby Active Galactic Nuclei. II. Outflows in the Narrow-line Region of NGC 4151
Fischer, Travis C.; Crenshaw, D. Michael; Schmitt, Henrique R. +1 more
We present a detailed study of active galactic nucleus feedback in the narrow-line region (NLR) of the Seyfert 1 galaxy NGC 4151. We illustrate the data and techniques needed to determine the mass outflow rate (\dot{M}out) and kinetic luminosity (L KE) of the outflowing ionized gas as a function of position in the NLR. We fin…
Star formation rates from young-star counts and the structure of the ISM across the NGC 346/N66 complex in the SMC
Bernard, J. -P.; Lebouteiller, V.; Madden, S. C. +21 more
The rate at which interstellar gas is converted into stars, and its dependence on environment, is one of the pillars on which our understanding of the visible Universe is build. We present a comparison of the surface density of young stars (Σ⋆) and dust surface density (Σdust) across NGC 346 (N66) in 115 independent pixels of…
Proper Motions and Trajectories for 16 Extreme Runaway and Hypervelocity Stars
Anderson, Jay; Bond, Howard E.; Geller, Margaret J. +3 more
We measure proper motions with the Hubble Space Telescope for 16 extreme radial velocity stars, mostly unbound B stars in the Milky Way halo. Twelve of these stars have proper motions statistically consistent with zero, and thus have radial trajectories statistically consistent with a Galactic center “hypervelocity star” origin. The trajectory of …
Galactic cold cores. V. Dust opacity
Bernard, J. -P.; Juvela, M.; Marshall, D. J. +13 more
Context. The project Galactic Cold Cores has carried out Herschel photometric observations of interstellar clouds where the Planck satellite survey has located cold and compact clumps. The sources represent different stages of cloud evolution from starless clumps to protostellar cores and are located in different Galactic environments.
Aims: …
Propagation of the 7 January 2014 CME and Resulting Geomagnetic Non-event
Thompson, B. J.; Möstl, C.; Jian, L. K. +9 more
On 2014 January 7 an X1.2 flare and coronal mass ejection (CME) with a radial speed ≈2500 km s-1 was observed from near an active region close to disk center. This led many forecasters to estimate a rapid arrival at Earth (≈36 hr) and predict a strong geomagnetic storm. However, only a glancing CME arrival was observed at Earth with a t…
Predicting the Arrival Time of Coronal Mass Ejections with the Graduated Cylindrical Shell and Drag Force Model
Zhang, Jie; Ding, Mingde; Cheng, Xin +3 more
Accurately predicting the arrival of coronal mass ejections (CMEs) to the Earth based on remote images is of critical significance for the study of space weather. In this paper, we make a statistical study of 21 Earth-directed CMEs, specifically exploring the relationship between CME initial speeds and transit times. The initial speed of a CME is …
Revealing the X-ray variability of AGN with principal component analysis
Fabian, A. C.; Brenneman, L.; Matt, G. +7 more
We analyse a sample of 26 active galactic nuclei (AGN) with deep XMM-Newton observations, using principal component analysis (PCA) to find model-independent spectra of the different variable components. In total, we identify at least 12 qualitatively different patterns of spectral variability, involving several different mechanisms, including five…