Stability analysis of the martian obliquity during the Noachian era

We performed numerical simulations of the obliquity evolution of Mars during the Noachian era, at which time the giant planets were on drastically different orbits than today. For the preferred primordial configuration of the planets we find that there are two large zones where the martian obliquity is stable and oscillates with an amplitude lower than 20°. These zones occur at obliquities below 30° and above 60°; intermediate values show either resonant or chaotic behaviour depending on the primordial orbits of the terrestrial planets.     

From the Sun to the Earth: The 13 May 2005 Coronal Mass Ejection

We report the results of a multi-instrument, multi-technique, coordinated study of the solar eruptive event of 13 May 2005. We discuss the resultant Earth-directed (halo) coronal mass ejection (CME), and the effects on the terrestrial space environment and upper Earth atmosphere. The interplanetary CME (ICME) impacted the Earth’s magnetosphere and caused the most-intense geomagnetic storm of 2005 with a Disturbed Storm Time (Dst) index reaching ?263 nT at its peak. The terrestrial environment responded to the storm on a global scale. We have combined observations and measurements from coronal and interplanetary remote-sensing instruments, interplanetary and near-Earth in-situ measurements, remote-sensing observations and in-situ measurements of the terrestrial magnetosphere and ionosphere, along with coronal and heliospheric modelling. These analyses are used to trace the origin, development, propagation, terrestrial impact, and subsequent consequences of this event to obtain the most comprehensive view of a geo-effective solar eruption to date. This particular event is also part of a NASA-sponsored Living With a Star (LWS) study and an on-going US NSF-sponsored Solar, Heliospheric, and INterplanetary Environment (SHINE) community investigation.     

A late Holocene paleoenvironmental reconstruction from Agua Caliente,southern Belize,linked to regional climate variability and cultural change at the Maya polity of Uxbenká

We report high-resolution macroscopic charcoal, pollen and sedimentological data for Agua Caliente, a freshwater lagoon located in southern Belize, and infer a late Holocene record of human land-use/climate interactions for the nearby prehistoric Maya center of Uxbenká. Land-use activities spanning the initial clearance of forests for agriculture through the drought-linked Maya collapse and continuing into the historic recolonization of the region are all reflected in the record. Human land alteration in association with swidden agriculture is evident early in the record during the Middle Preclassic starting ca. 2600 cal yr BP. Fire slowly tapered off during the Late and Terminal Classic, consistent with the gradual political demise and depopulation of the Uxbenká polity sometime between ca. 1150 and 950 cal yr BP, during a period of multiple droughts evident in a nearby speleothem record. Fire activity was at its lowest during the Maya Postclassic ca. 950–430 cal yr BP, but rose consistent with increasing recolonization of the region between ca. 430 cal yr BP and present. These data suggest that this environmental record provides both a proxy for 2800 years of cultural change, including colonization, growth, decline, and reorganization of regional populations, and an independent confirmation of recent paleoclimate reconstructions from the same region.     

A classification of the available astrophysical data of particular Hii regions — IX NGC 2264

A classification of the observational data on NGC 2264 is presented. Optical, infrared and radio data for the Hii region are tabulated, and maps of the molecular cloud structure are shown. The observations of the NGC 2264 star cluster are also summarized. The role of star formation in this young region is briefly assessed.     

Detection of transient signals in multipath environments

This research examines methods for detecting unknown transient waveforms that are contaminated by noise. The sensitivity of the performance levels of the energy detector and the lack of knowledge about the structure of the transient waveform motivate the examination of other moment- or spectra-based detection techniques. We examine the performance of a bispectral energy detector and show that its performance will degrade if the bispectra is smoothed and that signals with no bispectral content can be detected if the bispectra is not smoothed. Further, it is shown that the performance levels of the bispectral detector are slightly better, and slightly less sensitive, than those of the energy detector for the multipath linear frequency modulated signal. Finally, the performance levels of narrowband implementations of the energy and bispectral energy detectors are compared. It is shown that for a large enough sample, the performance levels of the bispectral detector are nearly as good as those of the optimal energy detector for the single narrowband signal case. However, when the received waveform contains multiple narrowband components, the narrowband bispectral detector performs slightly better than the energy detector     

Target detection and tracking with a high frequency ground waveradar

Northern Radar's Cape Race Ground Wave Radar (GWR) system became operational in the fall of 1990. The radar facility has the potential to provide surveillance of over 160000 square kilometres of the Grand Banks off Newfoundland, from a coastal station. GWR is a multipurpose sensor capable of detecting ships, monitoring icebergs and sea-ice, and measuring surface currents and sea state. The radar system employs a frequency modulated interrupted continuous wave (FMICW) as the transmit waveform. This waveform uses a pulse compression technique that combines good range resolution and high maximum range with a relatively high duty cycle. In this paper, we describe the implementation of the FMICW waveform in a practical real time radar system. We also show some examples of vessel, iceberg, acid aircraft detection and tracking using the Cape Race facility. These examples demonstrate that the Cape Race GWR may be used as an effective tool to assist in the management, surveillance, and enforcement of Canadian interests in the Exclusive Economic Zone     

Vertical Stacking Statistics of Multi-facies Object-Based Models

Mathematical Geosciences - Equations describing facies proportions and amalgamation ratios are derived for randomly placed objects belonging to two or three foreground facies embedded in a...     

The OSIRIS‐REx target asteroid (101955) Bennu: Constraints on its physical,geological, and dynamical nature from astronomical observations

We review the results of an extensive campaign to determine the physical, geological, and dynamical properties of asteroid (101955) Bennu. This investigation provides information on the orbit, shape, mass, rotation state, radar response, photometric, spectroscopic, thermal, regolith, and environmental properties of Bennu. We combine these data with cosmochemical and dynamical models to develop a hypothetical timeline for Bennu's formation and evolution. We infer that Bennu is an ancient object that has witnessed over 4.5 Gyr of solar system history. Its chemistry and mineralogy were established within the first 10 Myr of the solar system. It likely originated as a discrete asteroid in the inner Main Belt approximately 0.7–2 Gyr ago as a fragment from the catastrophic disruption of a large (approximately 100‐km), carbonaceous asteroid. It was delivered to near‐Earth space via a combination of Yarkovsky‐induced drift and interaction with giant‐planet resonances. During its journey, YORP processes and planetary close encounters modified Bennu's spin state, potentially reshaping and resurfacing the asteroid. We also review work on Bennu's future dynamical evolution and constrain its ultimate fate. It is one of the most Potentially Hazardous Asteroids with an approximately 1‐in‐2700 chance of impacting the Earth in the late 22nd century. It will most likely end its dynamical life by falling into the Sun. The highest probability for a planetary impact is with Venus, followed by the Earth. There is a chance that Bennu will be ejected from the inner solar system after a close encounter with Jupiter. OSIRIS‐REx will return samples from the surface of this intriguing asteroid in September 2023.     

The High-Resolution Coronal Imager (Hi-C)

The High-Resolution Coronal Imager (Hi-C) was flown on a NASA sounding rocket on 11 July 2012. The goal of the Hi-C mission was to obtain high-resolution (≈?0.3?–?0.4′′), high-cadence (≈?5 seconds) images of a solar active region to investigate the dynamics of solar coronal structures at small spatial scales. The instrument consists of a normal-incidence telescope with the optics coated with multilayers to reflect a narrow wavelength range around 19.3 nm (including the Fe xii 19.5-nm spectral line) and a 4096×4096 camera with a plate scale of 0.1′′?pixel^?1. The target of the Hi-C rocket flight was Active Region 11520. Hi-C obtained 37 full-frame images and 86 partial-frame images during the rocket flight. Analysis of the Hi-C data indicates the corona is structured on scales smaller than currently resolved by existing satellite missions.