Changes in the structure and function of biological communities in the Aral Sea, with particular reference to the northern part (Small Aral Sea), 1985--1994: A review     

N.V. Aladin  A.A. Filippov  I.S. Plotnikov  M.I. Orlova  W.D. Williams 《International Journal of Salt Lake Research》1998,7(4):301-343

The construction of a dam between the Small and Large Aral Sea in 1993 has had an effect on biological communities. From field and laboratory investigations and analysis of the literature, the structure and function of the main plant and animal communities in the northern (Small) Aral Sea are described and discussed, first, for the period before 1985, and, second, between 1985 and 1994. A prognosis for future changes is provided.  相似文献   

Three‐dimensional terrain modeling with multiple‐source illumination     

I. V. Florinsky  S. V. Filippov 《Transactions in GIS》2019,23(5):937-959

Three‐dimensional (3D) terrain modeling based on digital elevation models (DEMs) with the use of orthographic and perspective projections is a standard procedure implemented in many commercial and open‐source geoinformation systems. However, standard tools may be insufficient for 3D scientific visualization. In particular, single‐source illumination of 3D models may be deficient for topographically complex terrains. We present an approach for 3D terrain modeling with multiple‐source illumination in the virtual environment of the Blender free and open‐source software. The approach includes the following key stages: (1) automatic creation of a polygonal object; (2) selecting an algorithm to model the 3D geometry; (3) selecting a vertical exaggeration scale; (4) selecting types, parameters, a number, and positions of light sources; (5) selecting methods for generating shadows; (6) selecting a shading method for the 3D model; (7) selecting a material for the 3D model surface; (8) overlaying a texture on the 3D model; (9) setting a virtual camera; and (10) rendering the 3D model. To illustrate the approach, we processed a test DEM extracted from the International Bathymetric Chart of the Arctic Ocean version 3.0 (IBCAO 3.0). The approach is currently being used to develop a system for geomorphometric modeling of the Arctic Ocean floor.  相似文献   

Selenium minerals in gold-bearing veins of the North Urals     

Kuznetsov  S. K.  Sokerina  N. V.  Filippov  V. N.  Sokerin  M. Yu.  Zharkov  V. A. 《Doklady Earth Sciences》2012,442(1):148-151

The gold-bearing veins of the North Urals contain rare mineral selenium phases such as kawazulite, clausthalite, bohdanowiczite, volynskite, soucekite, naumannite, and eucairite, new for this region. They are largely observed as the finest inclusions in copper sulfides and closely associate with bismuth and tellurium minerals. Selenides were formed at the final oregenesis stages. Selenium was likely taken from the host rocks in the course of hydrothermal metasomatic processes initiated by granite intrusions.  相似文献   

Multiwavelength Observations of a Failed Flux Rope in the Eruption and Associated M-Class Flare from NOAA AR 11045     

Pankaj Kumar  Ablishek K. Srivastava  B. Filippov  R. Erdélyi  Wahab Uddin 《Solar physics》2011,272(2):301-317

We present the multiwavelength observations of a flux rope that was trying to erupt from NOAA AR 11045 and the associated M-class solar flare on 12 February 2010 using space-based and ground-based observations from TRACE, STEREO, SOHO/MDI, Hinode/XRT, and BBSO. While the flux rope was rising from the active region, an M1.1/2F class flare was triggered near one of its footpoints. We suggest that the flare triggering was due to the reconnection of a rising flux rope with the surrounding low-lying magnetic loops. The flux rope reached a projected height of ≈0.15R _⊙ with a speed of ≈90 km s⁻¹ while the soft X-ray flux enhanced gradually during its rise. The flux rope was suppressed by an overlying field, and the filled plasma moved towards the negative polarity field to the west of its activation site. We found the first observational evidence of the initial suppression of a flux rope due to a remnant filament visible both at chromospheric and coronal temperatures that evolved a couple of days earlier at the same location in the active region. SOHO/MDI magnetograms show the emergence of a bipole ≈12 h prior to the flare initiation. The emerged negative polarity moved towards the flux rope activation site, and flare triggering near the photospheric polarity inversion line (PIL) took place. The motion of the negative polarity region towards the PIL helped in the build-up of magnetic energy at the flare and flux rope activation site. This study provides unique observational evidence of a rising flux rope that failed to erupt due to a remnant filament and overlying magnetic field, as well as associated triggering of an M-class flare.  相似文献   

A Challenging Solar Eruptive Event of 18 November 2003 and the Causes of the 20 November Geomagnetic Superstorm. I. Unusual History of an Eruptive Filament     

V. V. Grechnev  A. M. Uralov  V. A. Slemzin  I. M. Chertok  B. P. Filippov  G. V. Rudenko  M. Temmer 《Solar physics》2014,289(1):289-318

This is the first of four companion papers, which comprehensively analyze a complex eruptive event of 18 November 2003 in active region (AR) 10501 and the causes of the largest Solar Cycle 23 geomagnetic storm on 20 November 2003. Analysis of a complete data set, not considered before, reveals a chain of eruptions to which hard X-ray and microwave bursts responded. A filament in AR 10501 was not a passive part of a larger flux rope, as usually considered. The filament erupted and gave origin to a coronal mass ejection (CME). The chain of events was as follows: i) a presumable eruption at 07:29 UT accompanied by a not reported M1.2 class flare probably associated with the onset of a first southeastern CME (CME1), which most likely is not responsible for the superstorm; ii) a confined eruption (without a CME) at 07:41 UT (M3.2 flare) that destabilized the large filament; iii) the filament acceleration around 07:56 UT; iv) the bifurcation of the eruptive filament that transformed into a large “cloud”; v) an M3.9 flare in AR 10501 associated to this transformation. The transformation of the filament could be due to the interaction of the eruptive filament with the magnetic field in the neighborhood of a null point, located at a height of about 100 Mm above the complex formed by ARs 10501, 10503, and their environment. The CORONAS-F/SPIRIT telescope observed the cloud in 304 Å as a large Y-shaped darkening, which moved from the bifurcation region across the solar disk to the limb. The masses and kinematics of the cloud and the filament were similar. Remnants of the filament were not clearly observed in the second southwestern CME (CME2), previously regarded as a source of the 20 November geomagnetic storm. These facts do not support a simple scenario, in which the interplanetary magnetic cloud is considered as a flux rope formed from a structure initially associated with the pre-eruption filament in AR 10501. Observations suggest a possible additional eruption above the bifurcation region close to solar disk center between 08:07 and 08:17 UT, which could be the source of the 20 November superstorm.  相似文献   

Coronal mass ejections: Some possibilities for prediction     

B. P. Filippov  A. M. Zagnetko  A. Ajabshirizadeh  O. G. Den 《Solar System Research》2006,40(4):319-325

The onset stage of coronal mass ejections (CMEs) is difficult to observe and is poorly studied. In spite of their practical importance, methods for CME predictions with sufficient lead times are only in the nascent stages of development. The most probable CME mechanism is a catastrophic loss of equilibrium of a large-scale current system in the corona (a flux rope). A twisted magnetic rope is maintained by the tension of field lines of photospheric sources until parameters of the system reach critical values and the equilibrium is lost. Unfortunately, there is low-density plasma (coronal cavity) in most of the rope volume; thus, it is difficult to observe a rope. However, the lower parts of the helical field lines of a rope are fine traps for the dense cold plasma of prominences. Thus, prominences are the best tracers of flux ropes in the corona. The maximal height up to which the rope is in stable equilibrium can be found by analyzing the distribution of the magnetic field generated by photospheric sources in the corona. Comparing this critical height with the actually observed prominence height, one can estimate the probability of the loss of equilibrium by a magnetic rope with a following eruption of prominences and coronal mass ejections.  相似文献   

Formation of a White-Light Jet Within a Quadrupolar Magnetic Configuration     

Boris Filippov  Serge Koutchmy  Ehsan Tavabi 《Solar physics》2013,283(1):143-156

The cadence and resolution of solar images have been increasing dramatically with the launch of new spacecraft such as STEREO and SDO. This increase in data volume provides new opportunities for solar researchers, but the efficient processing and analysis of these data create new challenges. We introduce a fuzzy-based solar feature-detection system in this article. The proposed system processes SDO/AIA images using fuzzy rules to detect coronal holes and active regions. This system is fast and it can handle different size images. It is tested on six months of solar data (1 October 2010 to 31 March 2011) to generate filling factors (ratio of area of solar feature to area of rest of the solar disc) for active regions and coronal holes. These filling factors are then compared to SDO/EVE/ESP irradiance measurements. The correlation between active-region filling factors and irradiance measurements is found to be very high, which has encouraged us to design a time-series prediction system using Radial Basis Function Networks to predict ESP irradiance measurements from our generated filling factors.  相似文献   

Longitudinal statistics of plasma bubbles observed as He+ density depletions at altitudes of the topside ionosphere     

L. N. Sidorova  S. V. Filippov 《Geomagnetism and Aeronomy》2013,53(1):60-72

This work presents a new examination of the hypothesis regarding the equatorial origin of low He⁺ density plasma depletions (or subtroughs). For this purpose, we have conducted a detailed comparative analysis of longitudinal variations in the occurrence probabilities of subtroughs in both hemispheres and variations in the occurrence probabilities of equatorial F-region irregularities (EFIs), equatorial spread F (RFS and ESF), and equatorial plasma bubbles (EPBs). Taking into consideration the seasonal dependence and some peculiarities of magnetic field variations in different hemispheres, a conclusion has been reached regarding the similarity between longitudinal statistical occurrences of subtroughs and equatorial ionospheric F-region irregularities. In addition, another piece of evidence in favor of the similarity of the nature of the above-mentioned phenomena has been obtained. We have got a confirmation once again that low He⁺ density depletions (or subtroughs) can be rightfully considered as equatorial plasma “bubbles,” which can be observed at altitudes of the topside ionosphere as depletions in the He⁺ density.  相似文献   

Possible Use of Satellite Geomagnetic Observations in Geological and Tectonic Studies of Lithosphere Structure     

Abramova  D. Yu.  Filippov  S. V.  Abramova  L. M. 《Izvestiya Atmospheric and Oceanic Physics》2020,56(12):1695-1704

Izvestiya, Atmospheric and Oceanic Physics - Features that reflect parameters of the geological and tectonic structure in lithospheric magnetic anomalies obtained using measurements by the CHAMP...  相似文献   

Method for the determination of the height of a solar filament     

B. P. Filippov 《Geomagnetism and Aeronomy》2016,56(1):1-7

A comparison of the actual filament height above the solar photosphere with the limiting height calculated by magnetic data provides information about the filament stability margin and its readiness for eruption. A method is proposed for the determination of the height of solar filaments by a comparison of the position of the upper edge of the filament (spine) with the position of the polarity-inversion line of the potential magnetic field calculated for different heights. The line closest to the filament spine corresponds to its height. Observations of the Solar Terrestrial Relations Observatory (STEREO) spacecraft were used to verify the proposed method when they were at an angular distance of ~90° from the Earth and provided a side view of the filaments near the central meridian in observations from the Earth and near-Earth orbits. The proposed method can be useful in the estimation of the possible geoeffectiveness of filaments on the solar disk.  相似文献