ULF waves at very high latitudes

Author(s):  
M. J. Engebretson ◽  
J. L. Posch ◽  
V. A. Pilipenko ◽  
O. M. Chugunova
Keyword(s):  
2016 ◽  
Vol 36 (2) ◽  
pp. 141-160 ◽  
Author(s):  
Sofwan Noerwidi

In 2014 there was found two "enigmatic" specimens of mandible, which named as Semedo 3417 and 3418. Both mandibles are morphologically similar but twice bigger than common primate’s jaw. In this research, we use morphology and morphometric analysis to determine the species identity and taxonomic position of those specimens. For comparison study we use some samples from Homo erectus (Java and China), Gigantopithecus (blacki and bilaspurensis), Australopithecines (robust and gracile). Based on morphology and morphometric characters on the mandible and teeth, it is concluded that Semedo specimen tends to be close to Gigantopithecus blacki. The discoveries of Gigantopithecus fossil in Java has implication on some research problem, especially regarding the adaptation pattern of this species which known only found at high latitudes environment. Furthermore this discovery has reinforced the perspective that tropical environment has a very high biodiversity, particularly on primate fossils.


1998 ◽  
pp. 327-342 ◽  
Author(s):  
C. G. Maclennan ◽  
L. J. Lanzerotti ◽  
D. J. Thomson
Keyword(s):  

1986 ◽  
Vol 91 (A1) ◽  
pp. 375 ◽  
Author(s):  
L. J. Lanzerotti ◽  
C. G. Maclennan ◽  
L. V. Medford ◽  
D. L. Carpenter
Keyword(s):  

1973 ◽  
Vol 21 (2) ◽  
pp. 201 ◽  
Author(s):  
W Hartley

Maps are presented showing the world distributions of the subfamily Festucoideae and the tribe Festuceae, based on data on relative specific frequency derived from about 500 widely-distributed floras and floristic lists. The maps show many points of similarity and, especially in N. America, there is a very high correlation between the numbers of species of the subfamily and tribe in regional floras. Both the Festucoideae and the Festuceae attain their highest relative specific frequency in high latitudes or at high altitudes. There is a strong negative correlation between high specific frequency and midsummer temperature in the flora of the United States, and evidence of a similar, though less marked, relationship in other regions. The effect of rainfall is not apparent in the distribution maps. Regions of high relative specific frequency of the tribes Agrostideae, Aveneae, Stipeae, and Triticeae are mapped, and discussed in relation to climate. In their geographical relationships, the tribes studied fall into two groups, viz. (1) Agrostideae, Aveneae, and Festuceae; (2) Stipeae and Triticeae. The significance of the distribution patterns is discussed in relation to the evolutionary development of the subfamily Festucoideae and its constituent tribes. The phytogeographical evidence supports the view that each tribe is monophyletic, with the exception of the Aveneae (sensu str.), which is well developed in regions of diverse climate. A strongly developed enclave of high relative specific frequency of Festuceae in part of south-eastern Europe, which shows no obvious relationship to climate, is interpreted as evidence for the occurrence of a cycle of secondary evolution of the tribe in this region.


2009 ◽  
Vol 27 (7) ◽  
pp. 2623-2631 ◽  
Author(s):  
D. M. Wright ◽  
R. S. Dhillon ◽  
T. K. Yeoman ◽  
T. R. Robinson ◽  
E. C. Thomas ◽  
...  

Abstract. On 10 October 2006 the SPEAR high power radar facility was operated in a power-stepping mode where both CUTLASS radars were detecting backscatter from the SPEAR-induced field-aligned irregularities (FAIs). The effective radiated power of SPEAR was varied from 1–10 MW. The aim of the experiment was to investigate the power thresholds for excitation (Pt) and collapse (Pc) of artificially-induced FAIs in the ionosphere over Svalbard. It was demonstrated that FAI could be excited by a SPEAR ERP of only 1 MW, representing only 1/30th of SPEAR's total capability, and that once created the irregularities could be maintained for even lower powers. The experiment also demonstrated that the very high latitude ionosphere exhibits hysteresis, where the down-going part of the power cycle provided a higher density of irregularities than for the equivalent part of the up-going cycle. Although this second result is similar to that observed previously by CUTLASS in conjunction with the Tromsø heater, the same is not true for the equivalent incoherent scatter measurements. The EISCAT Svalbard Radar (ESR) failed to detect any hysteresis in the plasma parameters over Svalbard in stark contract with the measurements made using the Tromsø UHF.


2005 ◽  
Vol 23 (11) ◽  
pp. 3457-3471 ◽  
Author(s):  
M. D. Sciffer ◽  
C. L. Waters ◽  
F. W. Menk

Abstract. A one dimensional, computational model for the propagation of ultra low frequency (ULF; 1-100 mHz) wave fields from the Earth's magnetosphere through the ionosphere, atmosphere and into the ground is presented. The model is formulated to include solutions for high latitudes where the Earth's magnetic field, (B0), is near vertical and for oblique magnetic fields applicable at lower latitudes. The model is used to investigate the wave polarisation azimuth in the magnetosphere compared with the ground wave fields, as a function of the dip angle of B0. We find that for typical ULF wave scale sizes, a 90° rotation of the wave polarisation azimuth from the magnetosphere to the ground occurs at high latitudes. However, this effect does not necessarily occur at lower latitudes in all cases. We show that the degree to which the wave polarisation azimuth rotates critically depends on the properties of the compressional ULF wave mode.


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