Two populations of sunspots and secular variations of their characteristics     

Yu. A. Nagovitsyn  A. A. Pevtsov  A. A. Osipova  A. G. Tlatov  E. V. Miletskii  E. Yu. Nagovitsyna 《Astronomy Letters》2016,42(10):703-712

We investigate the magnetic fields and total areas of mid- and low-latitude sunspots based on observations at the Greenwich and Kislovodsk (sunspot areas) and Mount Wilson, Crimean, Pulkovo, Ural, IMIS, Ussuriysk, IZMIRAN, and Shemakha (magnetic fields) observatories. We show that the coefficients in the linear form of the dependence of the logarithm of the total sunspot area S on its maximum magnetic field H change with time. Two distinct populations of sunspots are identified using the twodimensional H–log S occurrence histogram: small and large, separated by the boundaries log S = 1.6 (S = 40 MSH) and H = 2050 G. Analysis of the sunspot magnetic flux also reveals the existence of two lognormally distributed populations with the mean boundary between them Φ = 10²¹ Mx. At the same time, the positions of the flux occurrence maxima for the populations change on a secular time scale: by factors of 4.5 and 1.15 for small and large sunspots, respectively. We have confirmed that the sunspots form two physically distinct populations and show that the properties of these populations change noticeably with time. This finding is consistent with the hypothesis about the existence of two magnetic field generation zones on the Sun within the framework of a spatially distributed dynamo.  相似文献   

Estimating Sensible and Latent Heat Fluxes over an Inland Water Body Using Optical and Microwave Scintillometers     

Pierre  Adrien  Isabelle  Pierre-Erik  Nadeau  Daniel F.  Thiboult  Antoine  Perelet  Alexei  Rousseau  Alain N.  Anctil  François  Deschamps  Jaril 《Boundary-Layer Meteorology》2022,185(2):277-308

Boundary-Layer Meteorology - Observations of turbulent heat fluxes over inland water bodies are scarce despite being critical to adequate lake parametrization for numerical weather forecast and...  相似文献   

Late Weichselian (Valdaian) and Holocene vegetation and environmental history of the northern Timan Ridge, European Arctic Russia     

Aage Paus  John Inge Svendsen  Alexei Matiouchkov 《Quaternary Science Reviews》2003,22(21-22):2285-2302

Lake and peat deposits from the Timan Ridge, Arctic Russia, were pollen analysed, reconstructing the vegetation history and paleoenvironment since the Last Glacial Maximum (LGM) 20–18,000 years ago. The sites studied are located inside the margins of a large paleolake of about 20 km², by us named Lake Timan. This lake developed in the Late Weichselian, more than 30,000 years after the deglaciation of this region, and was formed due to increased precipitation and warmer summers that accelerated the melting of stagnant ice within its catchment. The lake was drained during the early Holocene when the outlet rivers eroded the spillways. A new generation of much smaller lakes formed during the Holocene when the last remnants of buried glacier ice melted away causing the exposed floor of Lake Timan to subside. Since deglaciation, the following regional vegetation development has been recorded: (1) During the initial stage of Lake Timan, the dominant vegetation was discontinuous steppe/tundra, with patches of snow bed vegetation. (2) A dwarf-shrub tundra established during the Late Weichselian interstadial (Allerød), probably reflecting warmer and moister conditions. (3) The Younger Dryas cooling is recognised by a reversal to steppe/tundra and snowbeds on unstable mineral-soils, and higher palynological richness. (4) Soon after the transition into the Holocene, a birch-forest established on the Timan Ridge. (5) A cooling starting around 8200 cal.years BP initiated the deforestation of the exposed hills. In the most protected sites, birch trees persisted until later than 4000 years ago, reflecting a gradual development into the present treeless dwarf-shrub tundra.  相似文献   

Monitoring tidal currents with a towed ADCP system   总被引：1，自引：1，他引：0  

Alexei Sentchev  Max Yaremchuk 《Ocean Dynamics》2016,66(1):119-132

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Precursory groundwater level changes in the period of activation of the weak intraplate seismic activity on the NE margin of the Bohemian Massif (central Europe) in 2005     

Vladimír Stejskal  Ladislav Kašpárek  Galina N. Kopylova  Alexei A. Lyubushin  Lumír Skalský 《Studia Geophysica et Geodaetica》2009,53(2):215-238

tWe analyse continuous measurements of groundwater level in two deep wells VS-3 and V-28 at the experimental hydro-meteorological station situated on the NE margin of the Bohemian Massif, central Europe, characterized by the weak intraplate seismic activity. The aim of our study is to examine the relationships between changes in the groundwater level and earthquake occurrence. Based on the tidal and barometric response of the water level, we estimated selected elastic parameters of the observed aquifers: the shear modulus G, the Skempton ratio B, the drained matrix compressibility β and the undrained compressibility β_u. Using these parameters and assuming the homogeneous poroelastic material, we derived the sensitivity of the wells to the crustal volume strain. During the observation period from November 1998 to December 2005 we detected in the VS-3 well two pre-seismic steps, related to August 10, 2005 (M = 2.4) and October 25, 2005 (M = 3.3) earthquakes. Amplitudes of the recorded precursory changes (+6 cm and +15 cm) are several times higher than the values predicted from the theoretical precursory crustal strain and the strain sensitivity of the well. Therefore, we presume that the observed pre-seismic water level steps can be attributed to heterogeneity of poroelastic material. We consequently propose the hypothesis of the origin of precursory events based on the presumption of a sensitive site, at which the well is situated.  相似文献   

Long-term variations in the sunspot magnetic fields and bipole properties from 1918 to 2014     

K. A. Tlatova  V. V. Vasil’eva  A. A. Pevtsov 《Geomagnetism and Aeronomy》2015,55(7):896-901

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Studies of Solar Helicity Using Vector Magnetograms     

Hagyard  M.J.  Pevtsov  A.A. 《Solar physics》1999,189(1):25-43

Observations of photospheric magnetic fields made with vector magnetographs have been used recently to study helicity on the Sun. In this paper we indicate what can and cannot be derived from vector magnetograms, and point out some potential problems in these data that could affect the calculations of `helicity'. Among these problems are magnetic saturation, Faraday rotation, low spectral resolution, and the method of resolving the ambiguity in the azimuth.  相似文献   

Discriminating Fog and Rain at the Kilometre Scale Using the Extinction from Collocated Infrared and Microwave Scintillometers     

Perelet  Alexei O.  Gultepe  Ismail  Hoch  Sebastian W.  Pardyjak  Eric R. 《Boundary-Layer Meteorology》2021,181(2-3):295-315

Boundary-Layer Meteorology - We investigate the path-averaged visibility and discrimination of fog and rain events using a two-wavelength (near-infrared and microwave) scintillometer system. These...  相似文献   

Maser Action in Methanol Transitions     

Maxim Voronkov  Andrej Sobolev  Simon Ellingsen  Andrei Ostrovskii  Alexei Alakoz 《Astrophysics and Space Science》2005,295(1-2):217-223

We report the detection with the ATCA of 6.7 GHz methanol emission towards OMC-1. The source has a size between 40 and 90, is located to the south-east of Ori-KL and may coincide in position with the 25 GHz masers. The source may be an example of an interesting case recently predicted in theory where the transitions of traditionally different methanol maser classes show maser activity simultaneously. In addition, results of recent search for methanol masers from the 25 and 104.3 GHz transitions are reported.  相似文献   

Machine Learning Can Assign Geologic Basin to Produced Water Samples Using Major Ion Geochemistry     

Shelton  Jenna L.  Jubb  Aaron M.  Saxe  Samuel W.  Attanasi  Emil D.  Milkov  Alexei V.  Engle  Mark  Freeman  Philip A.  Shaffer  Christopher A.  Blondes  Madalyn S. 《Natural Resources Research》2021,30(6):4147-4163

Natural Resources Research - Understanding the geochemistry of waters produced during petroleum extraction is essential to informing the best treatment and reuse options, which can potentially be...  相似文献