Comparative studies of E-region ionospheric drifts and meteor winds

Ionospheric drifts using total reflections from the E-region have been compared with neutral winds measured by meteor radar. Close agreement was found when both measurements were made in a common volume of atmosphere. Even with a separation of 700 km between the measuring regions the results were very similar. It is concluded that the drift technique does measure the movement of the neutral atmosphere in the altitude range 95–120 km. The agreement between measurements from widely separated regions indicates the horizontal scale of the wind structure is at least 700 km.     

Geopotential harmonics of order 15 and odd degree from analysis of resonant orbits

We have analysed the variations of inclination in 13 satellite orbits as they pass slowly, under the action of air drag, through 15th-order resonance with the geopotential, when successive equatorial crossings are 24° apart and the ground track repeats after 15 rev. The size and form of the change in inclination are determined mainly by the values of the geopotential harmonics of 15th order and odd degree, $\text{C}\text{?}{}_{\mathrm{l,15}}$ and $\text{S}\text{?}{}_{\mathrm{l,15}}$ (with l = 15, 17, 19, …) in the usual notation. Our analysis gives values of these coefficients up to l = 33 as follows:

     

963.

A full-wave study of downward propagating ELF waves in the ionosphere: Ion cutoff whistlers and the low frequency cutoff of ELF noise     

C. Altman  H. Cory  S. Zorea  E. Fijalkow 《Planetary and Space Science》1975,23(8):1155-1168

The downward propagation of ELF waves (100–700 Hz) in the ionosphere is studied by means of a generalised multiple-reflection full-wave method. It is shown that for the production of an ion cutoff whistler the incident wave-normal must point inwards (equatorwards) with respect to the vertical, the ion cutoff whistler conversion coefficient R_RL being a maximum when the reflected wave normal lies close to the geomagnetic field direction at the crossover level.For a low frequency cutoff of ELF noise to exist, the incident wave-normals at the crossover level must lie outside a ‘cone of penetration’ of ~40° semi-vertical angle, whose axis coincides with the geomagnetic field line. For propagation in the magnetic meridian plane, total reflection of downgoing whistlers is obtained either for large outward (poleward) incident angles, with reflection heights generally above the crossover level and possibly even above the gyrofrequency level, or else for inward (equatorward) wave-normal directions, in which case the reflection process usually occurs below the crossover level, and involves an R to L mode conversion on the downgoing path.Analysis of a scatter plot of the lower cutoff frequencies of ELF noise as a function of altitude and latitude shows that widely varying abundances must be postulated at all latitudes in order to explain the observations.     

964.

Inductive electric field of a time-dependent ring current     

C.H. Murphy  C.S. Wang  J.S. Kim 《Planetary and Space Science》1975,23(8):1205-1209

The inductive electric field generated by a time-dependent symmetric ring current has been investigated. The symmetric ring current was modelled by a population of protons drifting in a magnetic dipole field. The interaction of these protons with ion-cyclotron waves was assumed to be the dominant energy loss process for the ring current protons, at least under certain conditions. The calculation, with spectral densities for the ion-cyclotron waves that are based on experimental data, showed that an azimuthal inductive electric field of as much as 0.25 mV/m can be produced by this mechanism. Furthermore there is evidence that if the spectral density of the waves is substantially larger than the one adopted here, the electric field might increase to the order of 1.0 mV/m or more.     

965.

THE ELLA ISLAND,GREENLAND, CHONDRITE     

J. H. Carman  G. R. McCormick 《Meteoritics & planetary science》1975,10(1):1-8

The Ella Island, Greenland, meteorite was found in August of 1971. Electron microprobe study of the meteorite revealed it to contain olivine, low-calcium pyroxene, high-calcium pyroxene, plagioclase, kamacite, taenite, chromian-hercynite and troilite. On the basis of fayalite and ferrosilite content, poorly-defined chondrules, absence of glass in chondrules, presence of well-developed feldspar in the matrix and chondrules, and degree of recrystallization of the matrix, the Ella Island meteorite is classified as an L-6 chondrite.     

966.

On the dynamic activity in sheared corridors of large delta spots     

F. Tang  H. Wang 《Solar physics》1993,143(1):107-118

In the extraordinarily flare-prolific region of March 1989, NOAA region No. 5395, unusual dynamic activity in the photosphere was observed for the first time inside the large delta spot (Wanget al., 1991). Analyses of two additional large delta spots with sheared penumbral fibrils revealed that what occurred in the March 1989 delta spot is not an isolated case; similar complex dynamic activity was observed in the August and October 1989 delta spots. Both are flare-prolific regions as well, each producing 5 X-class flares. As in the March 1989 case, registered and highly time-compressed white-light movies were made from digital data obtained at Big Bear Solar Observatory. The new evidence confirmed the unusual activity: (1) penumbral motions in the directions of sheared penumbral fibrils near the inversion line as well as elsewhere in the delta complex, and (2) new spots emerging in the midst of penumbral motions. The manner and place of emergence are different from those in ordinary emerging flux regions, and often the spots are without observable opposite polarity flux. It is easy to see how the emergence of new spots in the midst of strong fields as well as the shear motions near the inversion line further enhance the flare productivity of the large delta spot regions. But we have yet to understand the origin of the dynamic activity observed.     

967.

Wavelet imaging cleaning method for atmospheric Cherenkov telescopes     

R. W. Lessard  L. Cayn  G. H. Sembroski  J. A. Gaidos 《Astroparticle Physics》2002,17(4):427-440

We present a new method of image cleaning for imaging atmospheric Cherenkov telescopes. The method is based on the utilization of wavelets to identify noise pixels in images of gamma-ray and hadronic induced air showers. This method selects more signal pixels with Cherenkov photons than traditional image processing techniques. In addition, the method is equally efficient at rejecting pixels with noise alone. The inclusion of more signal pixels in an image of an air shower allows for a more accurate reconstruction, especially at lower gamma-ray energies that produce low levels of light. We present the results of Monte Carlo simulations of gamma-ray and hadronic air showers which show improved angular resolution using this cleaning procedure. Data from the Whipple Observatory's 10-m telescope are utilized to show the efficacy of the method for extracting a gamma-ray signal from the background of hadronic generated images.     

968.

Starbursts And Their Consequences: The Case Of NGC 1569     

S. Mühle  S. Hüttemeister  U. Klein  E.M. Wilcots 《Astrophysics and Space Science》2002,281(1-2):327-328

     

969.

A Study of the Abundance of Low-Z Elements in the Sun During its Whole Predicted Life     

M. H. Talafha  M. A. Al-Wardat  N. M. Ershaidat 《Astrophysical Bulletin》2018,73(2):235-240

The study of the chemical composition of stars and galaxies is a key topic for understanding their origin and evolution. In this study, we present the results of the calculation of solar abundances of the isotopes ¹H, ⁴He, ¹²C, ¹⁴N, ¹⁵O, ¹⁶O, ¹⁷O, and ¹⁸O during the four phases of the solar life: hydrogen burning, onset of rapid growth and red giant, helium burning and helium exhaustion. The open source package “NucNet Tools” from the Webnucleo Group in Clemson University, SC, USA was used for this purpose. The results for all isotopes are listed in tables for future use. Abundances found, globally, agree fairly well with those predicted in the literature. Results obtained for the last two phases have no equivalents elsewhere.     

970.

Observation and preliminary analysis of a recent Jovian satellite phenomenon     

Allen  W. H.  Budding  E. 《Earth, Moon, and Planets》1986,35(1):73-77

The occultation of Io by Ganymede as observed on 10 June 1985 is reported. The middle of the occultation minimum was found to occur at 14h 14m 5.7s UT. In the plane perpendicular to the line of sight the centres of the two satellite disks passed to within ~ 2530 km of each other, at a relative velocity, in this plane, of about 11 kms^–1. The values of these last two quantities, however, depend on what assumptions are made about the light distribution over io's disk.     

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l	109C?l,15	109S?l,15
15	?23.5 ± 0.8	?7.7 ± 0.8
17	6.3 ± 1.5	5.6 ± 1.5
19	?25.1 ± 2.5	?7.3 ± 2.3
21	27.8 ± 3.6	?0.7 ± 3.4
23	17.1 ± 4.1	13.9 ± 4.8
25	?1.1 ± 3.0	8.5 ± 4.2
27	10.0 ± 3.3	6.7 ± 2.7
29	?9.4 ± 3.5	0.1 ± 4.7
31	10.1 ± 5.4	3.8 ± 5.6
33	1.1 ± 5.7	3.1 ± 5.8

A full-wave study of downward propagating ELF waves in the ionosphere: Ion cutoff whistlers and the low frequency cutoff of ELF noise

The downward propagation of ELF waves (100–700 Hz) in the ionosphere is studied by means of a generalised multiple-reflection full-wave method. It is shown that for the production of an ion cutoff whistler the incident wave-normal must point inwards (equatorwards) with respect to the vertical, the ion cutoff whistler conversion coefficient R_RL being a maximum when the reflected wave normal lies close to the geomagnetic field direction at the crossover level.For a low frequency cutoff of ELF noise to exist, the incident wave-normals at the crossover level must lie outside a ‘cone of penetration’ of ~40° semi-vertical angle, whose axis coincides with the geomagnetic field line. For propagation in the magnetic meridian plane, total reflection of downgoing whistlers is obtained either for large outward (poleward) incident angles, with reflection heights generally above the crossover level and possibly even above the gyrofrequency level, or else for inward (equatorward) wave-normal directions, in which case the reflection process usually occurs below the crossover level, and involves an R to L mode conversion on the downgoing path.Analysis of a scatter plot of the lower cutoff frequencies of ELF noise as a function of altitude and latitude shows that widely varying abundances must be postulated at all latitudes in order to explain the observations.     

Inductive electric field of a time-dependent ring current

The inductive electric field generated by a time-dependent symmetric ring current has been investigated. The symmetric ring current was modelled by a population of protons drifting in a magnetic dipole field. The interaction of these protons with ion-cyclotron waves was assumed to be the dominant energy loss process for the ring current protons, at least under certain conditions. The calculation, with spectral densities for the ion-cyclotron waves that are based on experimental data, showed that an azimuthal inductive electric field of as much as 0.25 mV/m can be produced by this mechanism. Furthermore there is evidence that if the spectral density of the waves is substantially larger than the one adopted here, the electric field might increase to the order of 1.0 mV/m or more.     

THE ELLA ISLAND,GREENLAND, CHONDRITE

The Ella Island, Greenland, meteorite was found in August of 1971. Electron microprobe study of the meteorite revealed it to contain olivine, low-calcium pyroxene, high-calcium pyroxene, plagioclase, kamacite, taenite, chromian-hercynite and troilite. On the basis of fayalite and ferrosilite content, poorly-defined chondrules, absence of glass in chondrules, presence of well-developed feldspar in the matrix and chondrules, and degree of recrystallization of the matrix, the Ella Island meteorite is classified as an L-6 chondrite.     

On the dynamic activity in sheared corridors of large delta spots

In the extraordinarily flare-prolific region of March 1989, NOAA region No. 5395, unusual dynamic activity in the photosphere was observed for the first time inside the large delta spot (Wanget al., 1991). Analyses of two additional large delta spots with sheared penumbral fibrils revealed that what occurred in the March 1989 delta spot is not an isolated case; similar complex dynamic activity was observed in the August and October 1989 delta spots. Both are flare-prolific regions as well, each producing 5 X-class flares. As in the March 1989 case, registered and highly time-compressed white-light movies were made from digital data obtained at Big Bear Solar Observatory. The new evidence confirmed the unusual activity: (1) penumbral motions in the directions of sheared penumbral fibrils near the inversion line as well as elsewhere in the delta complex, and (2) new spots emerging in the midst of penumbral motions. The manner and place of emergence are different from those in ordinary emerging flux regions, and often the spots are without observable opposite polarity flux. It is easy to see how the emergence of new spots in the midst of strong fields as well as the shear motions near the inversion line further enhance the flare productivity of the large delta spot regions. But we have yet to understand the origin of the dynamic activity observed.     

Wavelet imaging cleaning method for atmospheric Cherenkov telescopes

We present a new method of image cleaning for imaging atmospheric Cherenkov telescopes. The method is based on the utilization of wavelets to identify noise pixels in images of gamma-ray and hadronic induced air showers. This method selects more signal pixels with Cherenkov photons than traditional image processing techniques. In addition, the method is equally efficient at rejecting pixels with noise alone. The inclusion of more signal pixels in an image of an air shower allows for a more accurate reconstruction, especially at lower gamma-ray energies that produce low levels of light. We present the results of Monte Carlo simulations of gamma-ray and hadronic air showers which show improved angular resolution using this cleaning procedure. Data from the Whipple Observatory's 10-m telescope are utilized to show the efficacy of the method for extracting a gamma-ray signal from the background of hadronic generated images.     

A Study of the Abundance of Low-Z Elements in the Sun During its Whole Predicted Life

The study of the chemical composition of stars and galaxies is a key topic for understanding their origin and evolution. In this study, we present the results of the calculation of solar abundances of the isotopes ¹H, ⁴He, ¹²C, ¹⁴N, ¹⁵O, ¹⁶O, ¹⁷O, and ¹⁸O during the four phases of the solar life: hydrogen burning, onset of rapid growth and red giant, helium burning and helium exhaustion. The open source package “NucNet Tools” from the Webnucleo Group in Clemson University, SC, USA was used for this purpose. The results for all isotopes are listed in tables for future use. Abundances found, globally, agree fairly well with those predicted in the literature. Results obtained for the last two phases have no equivalents elsewhere.     

Observation and preliminary analysis of a recent Jovian satellite phenomenon

The occultation of Io by Ganymede as observed on 10 June 1985 is reported. The middle of the occultation minimum was found to occur at 14h 14m 5.7s UT. In the plane perpendicular to the line of sight the centres of the two satellite disks passed to within ~ 2530 km of each other, at a relative velocity, in this plane, of about 11 kms^–1. The values of these last two quantities, however, depend on what assumptions are made about the light distribution over io's disk.