Meridian-scanning photometer, coherent HF radar, and magnetometer observations of the cusp: a case study   总被引：2，自引：0，他引：2  

S. E. Milan  M. Lester  S. W. H. Cowley  J. Moen  P. E. Sandholt  C. J. Owen 《Annales Geophysicae》1999,17(2):159-172

The dynamics of the cusp region and post-noon sector for an interval of predominantly IMF B_y, B_z < 0 nT are studied with the CUTLASS Finland coherent HF radar, a meridian-scanning photometer located at Ny Ålesund, Svalbard, and a meridional network of magnetometers. The scanning mode of the radar is such that one beam is sampled every 14 s, and a 30° azimuthal sweep is completed every 2 minutes, all at 15 km range resolution. Both the radar backscatter and red line (630 nm) optical observations are closely co-located, especially at their equatorward boundary. The optical and radar aurora reveal three different behaviours which can interchange on the scale of minutes, and which are believed to be related to the dynamic nature of energy and momentum transfer from the solar wind to the magnetosphere through transient dayside reconnection. Two interpretations of the observations are presented, based upon the assumed location of the open/closed field line boundary (OCFLB). In the first, the OCFLB is co-located with equatorward boundary of the optical and radar aurora, placing most of the observations on open field lines. In the second, the observed aurora are interpreted as the ionospheric footprint of the region 1 current system, and the OCFLB is placed near the poleward edge of the radar backscatter and visible aurora; in this interpretation, most of the observations are placed on closed field lines, though transient brightenings of the optical aurora occur on open field lines. The observations reveal several transient features, including poleward and equatorward steps in the observed boundaries, braiding of the backscatter power, and 2 minute quasi-periodic enhancements of the plasma drift and optical intensity, predominantly on closed field lines.  相似文献   

Long-Term Stability Of Geoidal Geopotential FromTopex/Poseidon Satellite Altimetry 1993–1999     

Burša  Milan  Kenyon  Steve  Kouba  Jan  Müller  Achim  Raděj  Karel  Vatrt  Viliam  Vojtíšková  Marie  Vítek  Vojtěch 《Earth, Moon, and Planets》1999,84(3):163-176

The TOPEX/POSEIDON (T/P) satellite altimeter data from January 1, 1993to October 24, 1999 (cycles 11–261) was used for investigating thelong-term variations in the geoidal geopotential W₀ and/orin the geopotential scale factor R₀ = GM/W₀ (GM is theadopted geocentric gravitational constant). The mean valuesdetermined for the whole period covered are: W₀ =(62 636 856.161 ± 0.002) m² s^-2, R₀ =(6 363 672.5448 ± 0.0002) m. The actual accuracy is limited bythe altimeter calibration error (2–3 cm) and it isestimated to be about ± 0.5 m² s^-2 (± 5 cm).The yearly variations of the above mean values are at the formalerror level. No long-term trend in W₀, representing the oceanvolume change, was found for the seven years period 1993–9 on thebasis of T/P altimeter (AVISO) data. No sea surface topography modelwas used in the solution. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Geoidal curvature radii from satellite data for different degrees of smoothing     

Milan Burša  Reviewer Jan Picha 《Studia Geophysica et Geodaetica》1973,17(3):193-198

Summary Radii of curvature and their anomalies of a smoothed geoidal surface are computed using Stokes's constants J _n ^(k) , S _n ^(k) of the Earth's body, obtained from satellite orbit dynamics[2]. Different degrees n of smoothing are used (n = 8, 12, 21). The notations are the same as in[4, 5].  相似文献   

The telluric field in a halfspace with a spherical inhomogeneity     

Milan Hvoždara  Reviewer V. Petr 《Studia Geophysica et Geodaetica》1973,17(2):131-143

Summary An exact solution of the distribution of the intensity of the telluric field in a halfspace with a spherical inhomogeneity has been obtained by solving the Laplace equation in bipolar coordinates. This exact solution is compared with the presently known approximate solution, obtained by the method of images, and the region of their coincidence has been determined. For the image solution theoretical relations have been derived for computing the anomaly of the magnetic field. Craphs depict many of the properties of the telluric and magnetic fields on the surface of the considered halfspace for various parameters of the given problem.Dedicated to 90th Birthday of Professor Frantiek Fiala  相似文献   

Equations of motion of the moon retaining higher harmonics in the force function     

Milan Burša  Reviewer J. Pícha 《Studia Geophysica et Geodaetica》1976,20(4):313-328

u u u u uu smu um ¶rt;um ¶rt; a, s¶rt;a ¶rt;a ¶rt;u suu (n — mn, k — n¶rt;): saumauo n u: n=2, k=0; n=2, k=2; n=3, k=0, 1, 2, 3; n=4, k=0; n=4, k=3; saumau n : n=2, k=0; n=2, k=2; saumau n a: n=2, k=0.

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Dedicated to Prof. RNDr. Emil Buchar, DrSc., Corresponding Member of the Czechoslovak Academy of Sciences, on the Occasion of His 75^th Birthday  相似文献   

Expansion of a function given over an equipotential surface into spherical harmonics     

Milan Burša  Reviewer K. Pěč 《Studia Geophysica et Geodaetica》1977,21(3-4):217-227

¶rt;m ¶rt; uuauu uum auu uu, a¶rt;a a nmunmuaa, ¶rt; n uu u. aa, m u u ¶rt;um nmu, uu n¶rt; m nm, u aaaa u aa m nmua.  相似文献   

КРИТИКА     

Milan Burša  Jan Bednář 《Studia Geophysica et Geodaetica》1983,27(4):417-418

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Distribution of radioactive elements in three progressively metamorphosed pelite series of the Bohemian Massif     

Jiří Fiala  Věra Vaňková  Milan Krešl  Werner Franke  Reviewer M. Chlupáčová  J. Losert 《Studia Geophysica et Geodaetica》1980,24(1):65-87

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Variations in the Earth's rotation and crustal deformations     

Milan Burša  Reviewer O. Novotný 《Studia Geophysica et Geodaetica》1982,26(3):215-230

a mmuu ¶rt; ¶rt;au nm u , a auauu ma mu au u. aamuam m¶rt; a, ma u mua mu ¶rt;au u ¶rt;aa u uma a; m a mu ¶rt;auu m ¶rt;muam 10% m ¶rt;au, a u nuuau m .  相似文献   

Theoretical organic geochemistry. I. The thermodynamic stability of several cholestane isomers calculated by molecular mechanics     

Ger van Graas  Jan M.A. Baas  B. van de Graaf  J.W. de Leeuw 《Geochimica et cosmochimica acta》1982,46(11):2399-2402

The thermodynamic stabilities of thirteen cholestane isomers have been computed using molecular mechanics. The calculated composition of a mixture of these isomers at thermodynamic equilibrium is in agreement with the composition of a cholestane isomerate. From the calculated stabilities the extent to which isomerisation reactions can proceed during maturation can be predicted. The GLC retention order on non-polar phases of 20R/S isomeric pairs has been estimated from the preferred geometries of the molecules which are also obtained by molecular mechanics.  相似文献