scholarly journals Neutral hydrogen density profiles derived from geocoronal imaging

2003 ◽  
Vol 108 (A7) ◽  
Author(s):  
N. Østgaard
Keyword(s):  
Neutral Hydrogen ◽  
Density Profiles ◽  
Hydrogen Density

Variation of the amount of hydrogen along the galactic ridge

1967 ◽  
Vol 31 ◽  
pp. 171-172
Author(s):  
Th. Schmidt-Kaler
Keyword(s):  
Surface Brightness ◽  
Milky Way ◽  
Neutral Hydrogen ◽  
Line Of Sight ◽  
Optical Surface ◽  
Hydrogen Density ◽  
Continuous Radiation ◽  
Galactic Longitude

The integralNHof neutral-hydrogen density along the line of sight is determined from the Kootwijk and Sydney surveys. The run ofNHwith galactic longitude agrees well with that of thermal continuous radiation and that of the optical surface brightness of the Milky Way.

scholarly journals Observations of interstellar Lyman-α absorption

1970 ◽  
Vol 36 ◽  
pp. 281-301 ◽  
Author(s):  
Edward B. Jenkins
Keyword(s):  
Neutral Hydrogen ◽  
Local Region ◽  
Line Of Sight ◽  
Small Scale ◽  
Line Broadening ◽  
Interstellar Gas ◽  
B Stars ◽  
Hydrogen Density ◽  
The Galaxy ◽  
To Come

Absorption at the Lyman-α transition from interstellar neutral hydrogen has been observed in the ultraviolet spectra of 18 nearby O and B stars. Radiation damping is the dominant cause of line broadening, which makes the derived line-of-sight column densities proportional to the square of the observed equivalent widths. An average hydrogen density on the order of 0.1 atom cm−3 has been found for most of the stars observed so far. This is in contrast to the findings from surveys of 21-cm radio emission, which suggest 0.7 atom cm−3 exists in the local region of the Galaxy. Several effects which might introduce uncertainties into the Lyman-α measurements are considered, but none seems to be able to produce enough error to explain the disagreement with the 21-cm data. The possibility that small-scale irregularities in the interstellar gas could give significantly lower values at Lyman-α is explored. However, a quantitative treatment of the factor of ten discrepancy in Orion indicates the only reasonable explanation requires the 21-cm flux to come primarily from small, dense, hot clouds which are well separated from each other. The existence of such clouds, however, poses serious theoretical difficulties.

Generation of coherent lyman-alpha radiation with an alexandrite laser for diagnostis of neutral hydrogen density

1984 ◽  
Vol 128-129 ◽  
pp. 974-976 ◽  
Author(s):  
S. Himeno ◽  
E. Noda ◽  
Q.Q. Lü ◽  
S. Kogoshi ◽  
Y. Iida ◽  
...  
Keyword(s):  
Neutral Hydrogen ◽  
Alexandrite Laser ◽  
Alpha Radiation ◽  
Lyman Alpha ◽  
Hydrogen Density

scholarly journals Plasma transport modelling in the inner magnetosphere: effects of magnetic field, electric field and exospheric models

2011 ◽  
Vol 29 (2) ◽  
pp. 427-442 ◽  
Author(s):  
A. Woelfflé ◽  
D. Boscher ◽  
I. Dandouras
Keyword(s):  
Electric Field ◽  
Particle Trajectory ◽  
Neutral Hydrogen ◽  
Plasma Source ◽  
Particle Dynamics ◽  
Plasma Transport ◽  
Loss Assessment ◽  
Transport Modelling ◽  
Inner Magnetosphere ◽  
Hydrogen Density

Abstract. A qualitative study is performed on plasma transport modelling in the inner magnetosphere, revealing the significance of a model use choice and its parameterization. First, we examine particle transport using comparative analysis of both magnetic and electric field models. This work reveals that the electric field plays an important role in understanding particle dynamics and the models lead to various results in terms of plasma source, energy and particle trajectory. We then concentrate particularly on proton loss assessment considering the charge exchange phenomenon. For that, models are needed to provide a neutral hydrogen density estimation. So, exospheric models were tested in light of the Dynamics Explorer 1 measurements analysed by Rairden.

Observation of Dust Generated Hydrogen in the Solar Vicinity

1980 ◽  
Vol 91 ◽  
pp. 155-158
Author(s):  
H. J. Fahr ◽  
H. W. Ripken ◽  
G. Lay
Keyword(s):  
Solar Wind ◽  
Neutral Hydrogen ◽  
Interplanetary Dust ◽  
Proton Flux ◽  
Zodiacal Light ◽  
Solar Wind Proton ◽  
Density Profiles ◽  
Spectral Separation ◽  
Spectral Profiles ◽  
Dust Distribution

Solar wind protons impinging on interplanetary dust grains are trapped, deionized, and subsequently desorbed. The steady state distribution of desorbed neutral hydrogen inside of 0.4 AU can be deduced by observation of resonantly scattered solar 121.6 nm radiation. Calculated integral intensities and spectral profiles are given, showing the clear spectral separation of the different radiation components. Given a specific solar wind proton flux, the interplanetary dust distribution can be determined. Conversely, dust density profiles from zodiacal light measurements can be used to deduce solar wind proton fluxes at heliocentric distances of 0.4 to 0.15 AU. Observations of latitudinal and short-term temporal proton flux variations seem feasible.

scholarly journals The Neutral Hydrogen Distribution in Spiral and Irregular Galaxies

1972 ◽  
Vol 44 ◽  
pp. 67-73
Author(s):  
R. D. Davies
Keyword(s):  
Neutral Hydrogen ◽  
Hii Regions ◽  
Morphological Type ◽  
Central Hole ◽  
Hydrogen Distribution ◽  
Irregular Galaxy ◽  
Hydrogen Density ◽  
Irregular Galaxies ◽  
Ngc 6822

An investigation of several nearby and irregular galaxies shows significant changes in the neutral hydrogen distribution with morphological type. M31, an Sb, has a central hole while M33, an Sc, has relatively a much smaller hole or no hole at all and NGC 6822, an irregular galaxy, is centrally concentrated. The Hii regions in all these morphological types are found in the regions of highest neutral hydrogen density.

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