scholarly journals Enhancement of Lyman-.ALPHA. Emission for Detection of Diffracted Atomic Hydrogen Beams.

1996 ◽  
Vol 44 (4) ◽  
pp. 461-472 ◽  
Author(s):  
Kohichi KOTAKI ◽  
Tatsuo ARIKAWA
Keyword(s):  
Atomic Hydrogen ◽  
Lyman Alpha ◽  
Alpha Emission

scholarly journals A High-Velocity Component of Atomic Hydrogen in Comet Bennett (1970 II)

1976 ◽  
Vol 25 (Part1) ◽  
pp. 316-321
Author(s):  
H. U. Keller ◽  
Gary E. Thomas
Keyword(s):  
Radiation Pressure ◽  
Velocity Component ◽  
Atomic Hydrogen ◽  
Orbital Plane ◽  
Field Of View ◽  
Lyman Alpha ◽  
Hydrogen Density ◽  
University Of Colorado ◽  
Alpha Emission ◽  
The University

The Lyman alpha emission from Comet Bennett (1970II) was measured near perihelion (March 1970) by the University of Colorado ultraviolet photometer experiment on OGO-5 The spectrometer field of view of about 3° crossed the cometary hydrogen coma four times. The hydrogen coma was observed to extend more than 30 x 106 km in the antisolar direction.A model for the hydrogen density was developed which took the actual cometary motion and the gradients of the forces of gravitation and radiation pressure into account Exact trajectories of atoms in the orbital plane representing the column densities perpendicular to the plane were calculated. The variation of the hydrogen lifetime along the trajectory as well as the solar Lα profile were considered.

scholarly journals Solar Irradiance Variability Due to Solar Flares Observed in Lyman-Alpha Emission

Solar Physics ◽  
2021 ◽  
Vol 296 (3) ◽  
Author(s):  
Ryan O. Milligan
Keyword(s):  
Solar Flares ◽  
Solar Spectrum ◽  
Neutral Hydrogen ◽  
Solar Limb ◽  
High Background ◽  
Superposed Epoch Analysis ◽  
Lyman Alpha ◽  
Alpha Emission ◽  
Epoch Analysis ◽  
Very High

AbstractAs the Lyman-alpha (Ly$\upalpha $ α ) line of neutral hydrogen is the brightest emission line in the solar spectrum, detecting increases in irradiance due to solar flares at this wavelength can be challenging due to the very high background. Previous studies that have focused on the largest flares have shown that even these extreme cases generate enhancements in Ly$\upalpha $ α of only a few percent above the background. In this study, a superposed-epoch analysis was performed on ≈8500 flares greater than B1 class to determine the contribution that they make to changes in the solar EUV irradiance. Using the peak of the 1 – 8 Å X-ray emission as a fiducial time, the corresponding time series of 3123 B- and 4972 C-class flares observed in Ly$\upalpha $ α emission by the EUV Sensor on the Geostationary Operational Environmental Satellite 15 (GOES-15) were averaged to reduce background fluctuations and improve the flare signal. The summation of these weaker events showed that they produced a 0.1 – 0.3% enhancement to the solar Ly$\upalpha $ α irradiance on average. For comparison, the same technique was applied to 453 M- and 31 X-class flares, which resulted in a 1 – 4% increase in Ly$\upalpha $ α emission. Flares were also averaged with respect to their heliographic angle to investigate any potential center-to-limb variation. For each GOES class, the relative enhancement in Ly$\upalpha $ α at the flare peak was found to diminish for flares that occurred closer to the solar limb due to the opacity of the line and/or foreshortening of the footpoints. One modest event included in the study, a C6.6 flare, exhibited an unusually high increase in Ly$\upalpha $ α of 7% that may have been attributed to a failed filament eruption. Increases of this magnitude have hitherto only been associated with a small number of X-class flares.

H I Lyman alpha emission from Saturn (1980-1990)

1992 ◽  
Vol 97 (A9) ◽  
pp. 13691 ◽  
Author(s):  
Melissa A. McGrath ◽  
John T. Clarke
Keyword(s):  
Lyman Alpha ◽  
Alpha Emission

scholarly journals Unveiling the nature of the brightest z > 6 galaxies with ALMA and JWST

2019 ◽  
Vol 15 (S352) ◽  
pp. 20-20
Author(s):  
Rebecca Bowler
Keyword(s):  
Star Formation ◽  
Rest Frame ◽  
Small Samples ◽  
Star Forming ◽  
Lyman Alpha ◽  
Alpha Emission ◽  
Formation Conditions ◽  
Formation And Evolution ◽  
Insight Into

AbstractThe very brightest z > 6 galaxies are ideal laboratories for studying the physical properties of star-forming objects into the epoch of reionization. Selected from degree-scale, ground-based fields, these rare objects provide a key insight into early dust production and may harbour faint AGN. Targeted follow-up of small samples have unexpectedly shown both Lyman-alpha emission and other rest-frame UV lines (e.g CIV and HeII), suggesting unique star-formation conditions (or AGN) at early times. Furthermore, ALMA observations have revealed that 75% of the star-formation in these galaxies may be obscured. I will talk about HST/ALMA follow-up of bright z ∼ 7 LBGs in COSMOS and present new results from even brighter samples from z = 6 – 9 selected over ∼ 5 deg2. The power of both ALMA and JWST, coupled with the intrinsic luminosity of these sources, will provide a unique insight into the formation and evolution of vigorously star-forming galaxies in the first billion years.

Lyman-alpha emission from nonthermal proton beams

1976 ◽  
Vol 208 ◽  
pp. 618 ◽  
Author(s):  
F. Q. Orrall ◽  
J. B. Zirker
Keyword(s):  
Proton Beams ◽  
Lyman Alpha ◽  
Alpha Emission

The hydrogen Lyman-alpha emission of Capella

1993 ◽  
Vol 402 ◽  
pp. 710 ◽  
Author(s):  
Thomas R. Ayres ◽  
A. Brown ◽  
K. G. Gayley ◽  
Jeffrey L. Linsky
Keyword(s):  
Lyman Alpha ◽  
Alpha Emission
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