Search Publications
Megaflood Erosion on Mars—How Lava-Filled Craters Became Mesas (With Insights From Lava Physics, Stream Power, and Rock Mechanics)
Coleman, Neil M.
Round mesas up to 500 m high occur in Martian outflow channels. Mesas in Ravi and Elaver Valles occur in deepest parts of the channels where the most intense megaflood erosion occurred. I theorize that Noachian basalts poured into craters which acted as lava traps, similar to Kilauean lava lakes. Subsequent flood basalts buried the infilled crater…
The Dustiest Galactic S Stars: Mid-infrared Spectra from SOFIA/FORCAST
Sloan, G. C.; Kraemer, Kathleen E.; Ramirez, Ramses M.
We present spectra of 12 of the reddest, and hence dustiest, S stars in the Milky Way, observed with the FORCAST grisms on SOFIA. S stars are asymptotic giant branch (AGB) stars with C/O ∼ 1, so their molecular and dust chemistries are dominated by neither O nor C, often leading to atypical spectral features from their molecules and dust grains. A…
Characterisation of the stellar wind in Cyg X-1 via modelling of colour-colour diagrams
Sala, G.; Wilms, J.; Bachetti, M. +11 more
Context. Cygnus X-1 (Cyg X-1) is a high-mass X-ray binary where accretion onto the black hole (BH) is mediated by the stellar wind from the blue supergiant companion star HDE 226868. Due to its inclination, the system is a perfect laboratory to study the not yet well-understood stellar wind structure. In fact, depending on the position of the BH a…
Towards understanding time variations of proton to helium ratios in the heliosphere: Implication for the time dependence of the elements of the diffusion tensor
Potgieter, M. S.; Aslam, O. P. M.; Ngobeni, M. D.
A comprehensive three-dimensional numerical model for the modulation of cosmic rays in the heliosphere is applied to investigate the relative roles of the time dependence of the elements of the diffusion tensor on the proton to total Helium (p/He) and Helium-3 to Helium-4 (3He2/4He2) ratios at rigidities…
Limb Observations of Global Solar Coronal Extreme-ultraviolet Wavefronts: The Inclination, Kinematics, Coupling with the Expanding Coronal Mass Ejections, and Connection with the Coronal Mass Ejection Driven Shocks
Wang, Rui; Liu, Ying D.; Hu, Huidong +3 more
We select and investigate six global solar extreme-ultraviolet (EUV) wave events using data from the Solar Dynamics Observatory and the Solar and Heliospheric Observatory. These eruptions are all on the limb but recorded as halo coronal mass ejections (CMEs) because the CME-driven shocks have expanded laterally to the opposite side. With the limb …
Calculation of the Non-Gravitational A2 Parameter Using Ground-Based Observations of the Apparent Close Approaches between Near-Earth Asteroids and Gaia Stars
Gorshanov, D. L.; Khovrichev, M. Yu.; Bikulova, D. A.
The Yarkovsky effect is one of the noticeable factors in the orbital evolution of near-Earth asteroids (NEAs). The A2 non-gravitational parameter describes the corresponding acceleration in the NEA motion model. This parameter can be derived from astrometric observations of the NEA. We present the results of astrometric observations of …
A Geometric Distortion Solution Specifically for Historical Observations and its Implementation
Lin, F. R.; Peng, Q. Y.; Zheng, Z. J. +1 more
Geometric distortion (GD) critically constrains the precision of astrometry. Using well-established methods to correct GD requires calibration observations, which can only be obtained using a special dithering strategy during the observation period. Unfortunately, this special observation mode is not often used, especially for historical observati…
Resolution Enhancement of SOHO/MDI Magnetograms
Qin, Ying; Yu, Xiao-Guang; Ji, Kai-Fan +1 more
Research on the solar magnetic field and its effects on solar dynamo mechanisms and space weather events has benefited from the continual improvements in instrument resolution and measurement frequency. The augmentation and assimilation of historical observational data timelines also play a significant role in understanding the patterns of solar m…
Estimating the Total Energy Content in Escaping Accelerated Solar Electron Beams
Reid, Hamish A. S.; James, Alexander W.
Quantifying the energy content of accelerated electron beams during solar eruptive events is a key outstanding objective that must be constrained to refine particle acceleration models and understand the electron component of space weather. Previous estimations have used in situ measurements near the Earth, and consequently suffer from electron-be…
Population of excited levels of Fe+, Ni+, and Cr+ in exocomets' gaseous tails
Lecavelier des Etangs, A.; Vrignaud, T.
The star β Pictoris is widely known for harbouring a large population of exocomets, which create variable absorption signatures in the stellar spectrum as they transit the star. Although the physical and chemical properties of these objects have long been elusive, the recently developed exocomet curve of growth technique has, for the first time, e…