Speed-Resonant Terminator Wave Generation In The Earth Troposphere

Main features of high-frequency wave disturbances (periods ≤5 min), generated by the solar terminator passing through the Earth atmosphere in a speed-resonance mode, are theoretically investigated. With the troposphere model, formulated in this paper, and the solar terminator, considered as a wave source, the wave spectral density parameters have been computed. Both the terminator local speed, relating to the background, and the space-time lag of atmospheric heating are shown to essentially influence these features. Some possible methods for identification of high-frequency speed-resonant atmospheric waves are also discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Deflection of Hazardous Near-Earth Objects by High Concentrated Sunlight and Adequate Design of Optical Collector

Some detailed astronomical and applied aspects deflection of hazardous near-Earth objects (NEO) by direct high concentrated sunlight, causing intensive local ablation of their surfaces, are considered. The major requirements to solar concentrating optics within a single collector (a large mirror) approach, along with the asteroid properties being most substantial in achieving the predetermined effect for the period less than a year (mid-thrust action), are discussed. Such a hastened strategy may become topical in the case of late detection of potential danger, and also, if required, in providing the possibility for some additional action. It is also more acceptable in the public perception and keeping the peace for mankind rather than a long-run expectation of the incorrigible deflection resulting shortly ahead of the predicted hazard. The conventional concave reflectors have been graved to be practically inapplicable within the high concentrating geometry. This is primarily because of the dramatic spread of their focal spots at needful inclinations of optical axis from the direction toward the Sun, as well as of problematic use of the secondary optics. An alternative design of a mirrored ring-array collector is presented (as a tested and approved point-focus version of innovative reflective lenses for sunlight concentration within this approach), and comparative analysis was made. The assessment argues in favor of such a type of high-aperture optics having more capabilities than conventional devices. Mainly, this is because of the underside position (as respects the entrance aperture) of its focal area that allows avoidance of target shadowing the reflecting surfaces and minimizes their coating by the ejected debris. By using the modern asteroids database, some key estimations have been obtained. The surface irradiance around 4–5 MW/m² (average across the focal spot concentration level ~5 × 10³) for the ring-array collector size ~0.5 of asteroid diameter might suffice to deflect a 0.5-km-diameter NEO during several months. For the larger diameter NEOs, to 1.3–2.2 km, the required collector sizes are about the asteroid diameters, and they are even greater for more massive objects.