Search Publications
Plasma Density and Magnetic Field Fluctuations in the Ion Gyro-Frequency Range Near the Diamagnetic Cavity of Comet 67P
Nilsson, H.; André, M.; Vaivads, A. +8 more
We report the detection of large-amplitude, quasi-harmonic density fluctuations with associated magnetic field oscillations in the region surrounding the diamagnetic cavity of comet 67P. Typical frequencies are ∼0.1 Hz, corresponding to ∼10 times the water and ≲ 0.5 times the proton gyro-frequencies, respectively. Magnetic field oscillations are n…
HiFLEx—A Highly Flexible Package to Reduce Cross-dispersed Echelle Spectra
Anglada-Escudé, Guillem; Sithajan, Sirinrat; Feng, Fabo +8 more
We describe a flexible data reduction package for high resolution cross-dispersed echelle data. This open-source package is developed in Python and includes optional GUIs for most of the steps. It does not require any pre-knowledge about the form or position of the echelle-orders. It has been tested on cross-dispersed echelle spectrographs between…
A multi-diagnostic spectral analysis of penumbral microjets
Rouppe van der Voort, Luc; Drews, Ainar
Context. Penumbral microjets (PMJs) are short-lived, jet-like objects found in the penumbra of sunspots. They were first discovered in chromospheric lines and have later also been shown to exhibit signals in transition region (TR) lines. Their origin and manner of evolution is not yet settled.
Aims: We perform a comprehensive analysis of PMJs…
On extreme space weather events: Solar eruptions, energetic protons and geomagnetic storms
Miteva, Rositsa
The purpose of this study is to identify the extreme space weather events in the available satellite and ground-based databases and to relate them to other associated or accompanied solar activity events. Solar flares, coronal mass ejections, energetic protons and geomagnetic storms are selected among all manifestations/consequences of solar activ…
Diverse Polygonal Patterned Grounds in the Northern Eridania Basin, Mars: Possible Origins and Implications
Xiao, Long; Xu, Yi; Zhao, Jiannan +4 more
Diverse polygonal patterned grounds are found to occur in the Eridania basin system (a set of connecting irregular-shaped depressions interpreted as a paleolake basin system) located in the martian highland region between Terra Cimmeria and Sirenum. We here use multiple sets of imagery to document diverse polygonal patterned grounds in the fluvio-…
H-He collision-induced satellite in the Lyman α profile of DBA white dwarf stars
Xu, Siyi; Hubeny, Ivan; Kielkopf, John F. +6 more
The spectra of helium-dominated white dwarf stars with hydrogen in their atmosphere present a distinctive broad feature centred around 1160 Å in the blue wing of the Lyman α line. It is extremely apparent in WD 1425+540 recently observed with Hubble Space Telescope(HST) Cosmic Origins Spectrograph (COS). With new theoretical line profiles based on…
Closed depressions in Kotido crater, Arabia Terra, Mars. Possible evidence of evaporite dissolution-induced subsidence
García-Arnay, Ángel; Gutiérrez, Francisco; Baioni, Davide +3 more
The identification of karst sinkholes in Mars may provide evidence of dissolution processes caused by liquid water and information on paleoclimatic and paleohydrological conditions. This work presents a comprehensive cartographic inventory of 513 closed depressions developed on evaporite-bearing Equatorial Layered Deposits (ELDs) within Kotido cra…
Two Substructures in the nearby Stellar Halo Found in Gaia and RAVE
Shi, Jianrong; Ma, Jun; Du, Cuihua +4 more
We use the second Gaia data release (Gaia DR2), combined with Radial Velocity Experiment spectroscopic surveys, to identify the substructures in the nearby stellar halo. We select 3845 halo stars kinematically and chemically and determine their density distribution in energy and angular momentum space. To select the substructures from overdensitie…
Early High-contrast Imaging Results with Keck/NIRC2-PWFS: The SR 21 Disk
Baranec, Christoph; Jensen-Clem, Rebecca; Uyama, Taichi +22 more
High-contrast imaging of exoplanets and protoplanetary disks depends on wave front sensing and correction made by adaptive optics instruments. Classically, wave front sensing has been conducted at optical wavelengths, which made high-contrast imaging of red targets such as M-type stars or extincted T Tauri stars challenging. Keck/NIRC2 has combine…
Axial Asymmetry Studies in Gaia Data Release 2 Yield the Pattern Speed of the Galactic Bar
Yanny, Brian; Gardner, Susan; Hinkel, Austin
Our recent studies of axial-symmetry breaking in the nearby (d < 3 kpc) star counts are sensitive to the distortions of stellar orbits perpendicular and parallel to the orientation of the bar just within and beyond the outer Lindblad resonance (OLR) radius. Using the location of the sign flip in the left-right asymmetry in stars counts about th…