Satellite Model of $\boldsymbol{fo}\mathbf{F}2$ in the High-Latitude Winter Ionosphere of the Northern and Southern Hemispheres

Author(s):  
A.T. Karpachev ◽  
M.V. Klimenko
1962 ◽  
Vol 40 (6) ◽  
pp. 706-718 ◽  
Author(s):  
Doris H. Jelly ◽  
C. Collins

The phenomenon known as polar-cap absorption (PCA) has been studied by several different radio techniques and some of the characteristics of the absorbing regions are now fairly well known. In the present study the deviations of minimum frequencies (Δƒmin), recorded by ionosondes at high-latitude Arctic and Antarctic stations, have been used synoptically to investigate the simultaneous occurrence of the absorbing regions in the northern and southern hemispheres. Detailed examination of these ionosonde data has revealed the occurrence of periods of weak absorption which have the characteristics of the large PCA events. Several of the PCA features such as starting times and durations are discussed and the morphology of one of the weak events is considered in some detail.


2020 ◽  
pp. SP512-2020-97
Author(s):  
Stanislav Opluštil ◽  
Christopher J. Cleal ◽  
Jun Wang ◽  
Mingli Wan

AbstractIn the Carboniferous, terrestrial vegetation became widespread, diverse and abundant. The resulting fossil record has proved to be an effective biostratigraphic tool for intra- and interbasinal correlations. Besides palaeogeographic configurations, Carboniferous plant biostratigraphy is affected by a transition from greenhouse conditions during most of the Mississippian to an icehouse climate in the Pennsylvanian. The greenhouse Mississippian climate resulted in weak provincialism, with a cosmopolitan flora ranging from the tropics to middle latitudes. The global cooling around the Mississippian - Pennsylvanian boundary enhanced development of a latitudinal climatic zonation and related floral provincialism. These changes are expressed in the recognition of distinct realms or kingdoms, where the tropical Amerosinian Realm (or Euramerican and Cathaysian realms) is surrounded by the Angaran and Gondwanan realms occupying middle to high latitude of the northern and southern hemispheres, respectively. Floristic endemism in the Pennsylvanian precludes development of a global macrofloral biostratigraphy. Instead, each realm or area has its own biostratigraphic scheme. Poorer and less diverse floras of the Gondwanan and Angaran realms resulted in the establishment of relatively low-resolution macrofloral biostratigraphic schemes. Higher resolution macrofloral zonations exist only in the tropical Amerosinian Realm due to diverse and abundant floras dominated by free-sporing and early seed plants occupying extensive wetlands.


2006 ◽  
Vol 12 (1) ◽  
pp. 80-84
Author(s):  
S.N. Samsonov ◽  
◽  
I.Ya. Plotnikov ◽  
D.Y. Sibeck ◽  
Yu. Watermann ◽  
...  

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