Laboratory simulation of the induced magnetospheres of comets and Venus     

I. M. Podgorny  E. M. Dubinin  P. L. Israelevich 《Earth, Moon, and Planets》1980,23(3):323-338

The comparison of data obtained in laboratory experiments on the solar wind interaction with a body endowed with a plasma shell, the observations of comet type I tails and the direct measurements near Venus show that an induced magnetosphere is formed with an extended magnetic tail. This magnetosphere appears due to currents associated with unipolar induction. The distribution of electrodynamical forces associated with the formation of the induced magnetosphere makes it possible to explain the acceleration of matter towards the tail as in the motion across the tail observed in comets and Venus. The analysis of the condensation motion in Halley's comet yields an estimate of tail magnetic field of 30 to 50. A three-dimensional model of the induced magnetospheres of Venus and comets is developed.  相似文献   

Regional and local magmatic anomalies and tectonics of rift zones between the Antarctic and South American plates     

N. M. Sushchevskaya  N. A. Migdisova  E. P. Dubinin  B. V. Belyatsky 《Geochemistry International》2016,54(6):494-508

The study provides new understanding of magmatism at extinct and modern spreading zones around the western margin of East Antarctica from Bransfield Strait to the Bouvet Triple Junction (BTJ) in the Atlantic Ocean and reveals causes of geochemical heterogeneity of mantle magmatism during the early opening of the Southern Ocean. The results indicate the involvement of an enriched source component in the generation of parental melts, which was formed in several tectonic stages. The enriched (metasomatized) mantle generated at rift zones has geochemical characteristics typical of the western Gondwana lithosphere (with isotopic compositions similar to those inferred for the enriched HIMU and EM-2 sources). This mantle source may have been produced by the thermal erosion of the continental mantle during the early stages of the Karoo–Maud–Ferrar superplume activity. This enriched mantle generated in the apical parts of the plume (sub-oceanic) began to melt during tectonic displacement and fragmentation of Gondwana. The Bouvet Triple Junction, located along modern spreading zones between the Antarctic and South American plate, is characterized by a greater depth of melting and a higher degree of enrichment of primary tholeiitic magmas. The highest enrichment of magmas in this region is controlled by a contribution from a pyroxenite-rich component, which was also identified in the extinct spreading center in Powell Basin.  相似文献   

Experimental modeling of structure-forming deformations in rift zones of mid-ocean ridges     

A. L. Grokholskii  E. P. Dubinin 《Geotectonics》2006,40(1):64-80

The modern methods of physical modeling of structure-forming deformations in extension zones of oceanic lithosphere are discussed; the methods differ in their experimental equipment, model material, and experimental techniques. The simulation performed with an elastic-ductile model has demonstrated that extension of a brittle lithospheric layer results in disruption of its continuity and in formation of a rift valley according to the mechanism of running fracture propagation. The modeling results provide insights into qualitative pattern of faulting and fracturing within a rift zone, specific features of rift segmentation, and development of various structural elements (axis bends, echelons of fractures, nontransform offsets, small and large overlaps, etc.) under various geodynamic conditions of spreading. The modeling has shown that origination and evolution of structures of various types depend on the lithosphere’s thickness beneath the rift axis; the width of the lithosphere’s heating zone; the spreading orientation; and, to a lesser degree, on the spreading rate. A relatively rectilinear rift broken into particular segments bounded by small-amplitude offsets with or without minor overlaps arises in the case of both a small width of the heating zone, closely related to the axial magma chamber, and a small thickness of the lithosphere (fast-spreading conditions). In the case of a wide heating zone caused by ascent of an asthenospheric wedge or a mantle plume, offsets of rift are more pronounced and deformations embrace a wider region. If, as a result, the thickness of the lithosphere increases, the rift will be less linear and the structural heterogeneity will become more contrasting. In addition to the thickness of the lithosphere, the angle between the rift zone and the extension axis also controls the rift configuration: the greater the angle, the more conspicuous the en echelon arrangement of fractures. For any spreading type, the propagating front of linear microfractures that disrupt the upper brittle layer of the lithosphere predates the origin of mesoscopic fractures and predetermines a general trend of the rift zone. This indicates that the fractures of various sizes propagate simultaneously.  相似文献   

Crustal Structure,Tectonic Subsidence,and Lithospheric Stretching of the Princess Elizabeth Trough Basin,East Antarctica     

Leitchenkov  G. L.  Galushkin  Yu. I.  Guseva  Yu. B.  Gandyukhin  V. V.  Dubinin  E. P. 《Geotectonics》2019,53(6):726-737

Geotectonics - This paper considers the crustal structure, seismic stratigraphy, thermal evolution, and lithospheric stretching of the deep-water basin located on the East Antarctic passive margin...  相似文献   

Physical modeling of the formation conditions of microcontinents and continental marginal plateaus     

E. P. Dubinin  A. L. Grokholsky  A. I. Makushkina 《Izvestiya Physics of the Solid Earth》2018,54(1):66-78

The geodynamical conditions allowing formation of microcontinents or blocks of continental crust that are not completely detached from the parent continent are considered. These blocks can be preserved in the form of islands emerging above sea level or exist as submerged plateaus located within the continental margins, depending on the thermomechanical conditions of continental rifting. Physical modeling has shown that formation of microcontinents or partially detached continental microblocks is constrained by the following key conditions: presence of rift segments that are offset relative to each other and are propagating toward each other; formation of oceanic crust along at least one or two rift segment; for a microcontinent, it is the presence of a hot spot, which weakens the lithospheric strength and thus facilitates the jump of the spreading axis from one rift segment to another due to which the continental microblock can become completely detached from the parent continental plate. During the evolution, microblocks undergo rotational deformations in both the horizontal and vertical planes also leading to the local jumps of the spreading axes and the formation of an asymmetric rift.  相似文献   

A comparison of global models for the solar wind interaction with Mars   总被引：1，自引：1，他引：0  

D. Brain  S. Barabash  S. Bougher  G. Chanteur  E. Dubinin  M. Fraenz  E. Harnett  E. Kallio  S. Ledvina  K. Liu  Y. Ma  A. Nagy  H. Nilsson  S. Simon 《Icarus》2010,206(1):139-151

We present initial results from the first community-wide effort to compare global plasma interaction model results for Mars. Seven modeling groups participated in this activity, using MHD, multi-fluid, and hybrid assumptions in their simulations. Moderate solar wind and solar EUV conditions were chosen, and the conditions were implemented in the models and run to steady state. Model output was compared in three ways to determine how pressure was partitioned and conserved in each model, the location and asymmetry of plasma boundaries and pathways for planetary ion escape, and the total escape flux of planetary oxygen ions. The two participating MHD models provided similar results, while the five sets of multi-fluid and hybrid results were different in many ways. All hybrid results, however, showed two main channels for oxygen ion escape (a pickup ion ‘plume’ in the hemisphere toward which the solar wind convection electric field is directed, and a channel in the opposite hemisphere of the central magnetotail), while the MHD models showed one (a roughly symmetric channel in the central magnetotail). Most models showed a transition from an upstream region dominated by plasma dynamic pressure to a magnetosheath region dominated by thermal pressure to a low altitude region dominated by magnetic pressure. However, calculated escape rates for a single ion species varied by roughly an order of magnitude for similar input conditions, suggesting that the uncertainties in both the current and integrated escape over martian history as determined by models are large. These uncertainties are in addition to those associated with the evolution of the Sun, the martian dynamo, and the early atmosphere, highlighting the challenges we face in constructing Mars’ past using models.  相似文献   

Interplanetary coronal mass ejection influence on high energy pick-up ions at Venus     

T.R. McEnulty  J.G. Luhmann  I. de Pater  D.A. Brain  A. Fedorov  T.L. Zhang  E. Dubinin 《Planetary and Space Science》2010,58(14-15):1784-1791

We have used the ion mass analyzer (IMA) and magnetometer (MAG) on Venus Express (VEX) to study escaping O⁺ during interplanetary coronal mass ejections (ICMEs). Data from 389 VEX orbits during 2006 and 2007 revealed 265 samples of high energy pick-up ion features in 197 separate orbits. Magnetometer data during the same time period showed 17 ICMEs. The interplanetary conditions associated with the ICMEs clearly accelerate the pick-up ions to higher energies at lower altitudes compared to undisturbed solar wind. However, there is no clear dependence of the pick-up ion flux on ICMEs which may be attributed to the fact that this study used data from a period of low solar activity, when ICMEs are slow and weak relative to solar maximum. Alternatively, atmospheric escape rates may not be significantly changed during ICME events.  相似文献   

Electric fields within the martian magnetosphere and ion extraction: ASPERA-3 observations     

E. Dubinin  R. Lundin  J. Woch  A. Fedorov  N. Krupp  M. Holmström  M. Yamauchi  J.-J. Thocaven  J. Sharber  A. Coates  K.S. Hsieh  H. Koskinen  P. Riihelä  T. Säles  J. Luhmann  R. Cerulli-Irelli  M. Maggi  D. Williams  P. Wurz  C. Dierker  M. Carter 《Icarus》2006,182(2):337-342

Observations made by the ASPERA-3 experiment onboard the Mars Express spacecraft found within the martian magnetosphere beams of planetary ions. In the energy (E/q)-time spectrograms these beams are often displayed as dispersive-like, ascending or descending (whether the spacecraft moves away or approach the planet) structures. A linear dependence between energy gained by the beam ions and the altitude from the planet suggests their acceleration in the electric field. The values of the electric field evaluated from ion energization occur close to the typical values of the interplanetary motional electric field. This suggests an effective penetration of the solar wind electric field deep into the martian magnetosphere or generation of large fields within the magnetosphere. Two different classes of events are found. At the nominal solar wind conditions, a ‘penetration’ occurs near the terminator. At the extreme solar wind conditions, the boundary of the induced magnetosphere moves to a more dense upper atmosphere that leads to a strong scavenging of planetary ions from the dayside regions.  相似文献   

Tectonics and types of riftogenic basins of the Scotia Sea,South Atlantic     

E. P. Dubinin  A. V. Kokhan  D. E. Teterin  A. L. Grokhol’sky  E. S. Kurbatova  N. M. Sushchevskaya 《Geotectonics》2016,50(1):35-53

Western, central, and eastern provinces are recognized in the Scotia Sea. They are distinguished by their bottom topography, geophysical characteristics, and crustal structure, which record their different origin and evolution. The western province is characterized by the oceanic crust that formed on the West Scotia Ridge, where active spreading may have ceased as a result of a collision between propagating rift and the structural barrier of the thick continental lithosphere of the Falkland Plateau. The central province is a series of blocks mainly composed of continental crust that subsided to various depths depending on the degree of extension in the course of rifting. These blocks are separated by local areas with oceanic crust formed due to the breakup of the continental crust and diffusive spreading. These areas are characterized by deep bottom and high values of Bouguer anomalies. The southern framework of the central province consists of subsided continental blocks and microcontinents divided by small spreading-type basins formed by lithospheric extension complicated by strike-slip faulting. The eastern province is composed of oceanic crust formed on the backarc spreading East Scotia Ridge. The results of density analysis, analog, and numerical simulations allowed us to explain some features of the structure and evolution of these provinces. The insight into tectonic structure of the provinces and their evolution allowed us to recognize several types of riftogenic basins differing in geodynamics, age, and geological and geophysical characteristics.  相似文献   

Structure formation in the rift zones and in the tranvers offset of the spreading axes: Results of physical modeling     

A. L. Grokholskii  E. P. Dubinin 《Izvestiya Physics of the Solid Earth》2010,46(5):412-418

The paper presents the results of experimental modeling of the specific features in the structure formation within the rift zones and also within lateral displacements of the spreading axes such as transform faults and nontransform displacements. The experiments were conducted on materials consisting of liquid and solid hydrocarbons; the similarity conditions were taken into account.  相似文献