Observations of naturally occurring vlf and man-made hf plasma waves in auroral regions of the ionosphere
Polar ionosphere auroral oval position detection by satellite observations of naturally occurring VLF and man-made HF plasma waves
Bell, F. T.↗
SEARCH · Search NASA
Results for “HF”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Energetics of HCl and HF in volcanic emanations
Fugacities of hCl and HF compared with abundance in volcanic fumarolic emanations, indicating magma undersaturation
Mueller, R. F.↗
HCl, HF, and DF partially inverted CW chemical lasers
CW chemical lasers operation from partially inverted transitions of HCl, HF and DF molecules in subsonic flow
Cool, T. A.↗
VLF phase disturbances, HF absorption, and solar protons in the PCA events of 1967
VLF phase disturbances, HF absorption and solar protons in 1967 PCA events, using ionization model
Haave, C. R.↗
HF sounder study Final report, 16 Oct. - 18 Dec. 1970
Developing communications equipment for HF Lunar Sounder
Source record↗
On electron-cyclotron wave resonance in inductively coupled HF discharges
Electron-cyclotron wave resonance in inductively coupled HF ring discharges
Szuszczewicz, E. P.↗
Observation of intense superradiant emission in the high-gain infrared transitions of HF and DF molecules
Intense superradiant emission in HF and DF molecules high gain IR transitions, examining spectral distributions with pneumatically tuned Fabry-Perot interferometer
Goldhar, J.↗
Line shifts in the first overtone of DF broadened by HF
Line shifts in first overtone band of DF perturbed by HF, studying pressure induced transitions and partial pressures
Desai, U. G.↗
Magnetoionic mode coupling of hf radio waves
Magnetoionic mode coupling of HF radio waves, considering Faraday rotation of satellite signals
Titheridge, J. E.↗
Mode coupling of hf waves in the ionosphere
Ionospheric HF wave ordinary /O/ and extraordinary /E/ modes coupling effect on satellite signal Faraday rotation
Titheridge, J. E.↗
Luna 16 - Some Li, K, Rb, Sr, Ba, rare-earth, Zr, and Hf concentrations.
Concentrations of Li, K, Rb, Sr, Na, rare-earths, Zr and Hf have been determined for some Luna 16 core materials by mass-spectrometric isotope-dilution. Two regolith fines samples from different depths in the core, and four rock-chips, including both igneous rocks and breccias, have similar trace-element concentrations. The Luna 16 materials have general lunar trace-element characteristics but differ from other returned lunar samples in a manner that suggests the presence of excess feldspar. Unless the Luna 16 igneous rocks are fused soils, they appear to represent either partial plagioclase cumulates or the least differentiated igneous material yet returned from the moon. The similarity in trace-element concentrations of the igneous rocks and the fines would then suggest largely local derivation of the Luna 16 regolith.
Philpotts, J. A.↗
Stress-rupture strength and microstructural stability of W-HF-C wire reinforced superalloy composites
W-Hf-C/superalloy composites were found to be potentially useful for turbine blade applications on the basis of stress-rupture strength. The 100-and 1000-hour rupture strengths obtained for 70 volume percent fiber composites tested at 1090 C were 420 and 280 MN/sq m (61,000 and 41,000 psi). The investigation indicated that with better quality fibers, composites having 100- and 1000-hour rupture strengths of 570 and 370 MN/sq m (82,000 and 54,000 psi) may be obtained. Metallographic studies indicated sufficient fiber-matrix compatibility for long time applications at 1090 C for 1000 hours or more.
Petrasek, D. W.↗
Stress-rupture strength and microstructural stability of W-HF-C wire-reinforced superalloy composites
W-Hf-C superalloy composites were found to be potentially useful for turbine-blade applications on the basis of stress-rupture strength. The 100- and 1000-hour rupture strengths obtained for 70 volume percent fiber composites tested at 1090 C were 420 and 280 MN/sq m. The investigation indicated that with better quality fibers, composites having 100- and 1000-hour rupture strengths of 570 and 370 MN/sq m may be obtained. Metallographic studies indicated sufficient fiber-matrix compatibility for long-term applications at 1090 C for 1000 hours or more.
Petrasek, D. W.↗
The temporal structure of HF and VHF radiations during Florida lightning return strokes
Measurements have been made of the HF and VHF radiation at 3, 30, 139, and 295 MHz produced during lightning return strokes, in correlation with wideband electric field measurements covering from about 300 Hz to 2 MHz. Intense pulses of RF are observed during the first return stroke in a discharge to ground, but with a 10-30 µsec time delay between the beginning of the stroke and the occurrence of significant RF radiation. The delay occurs at all frequencies and is short enough to suggest that the main channel and/or branches are the main initial sources of RF during the first stroke. During a subsequent return stroke, the RF starts an average of 265 µsec prior to the onset of the stroke. At 139 and 295 MHz, the subsequent stroke RF lasts only about 115 µsec; however, at 3 MHz, the radiation frequently persists up to and during the stroke.
David M Le Vine↗
Stratospheric HF and HCl observations /15 June 1981/
Balloon measurements of the stratospheric HF/HCl ratio are reported. Seven far-infrared rotational lines of HF and HCl were observed at elevation angles of 25, 18 and 8 deg by a far-infrared Fourier-transform spectrometer on board a balloon platform at 28.5 km. Analysis of line intensities yields an average HF/HCl ratio of 0.18 + or - 0.02 at an effective altitude of 33 km, with a water vapor mixing ratio of about 4 ppmv. Results are noted to be in reasonable agreement with the calculated profile of Sze and Ko (1981) with 4.5 ppmv H2O.
Traub, W. A.↗
Measured spectral amplitude of lightning sferics in the HF, VHF, and UHF bands
An experimental study was carried out to measure the spectral amplitude of lightning sferics at 22.5 MHz, 225 MHz, and 2.25 GHz. This effort included the detection, storage, and analysis of RF emission data to accurately determine the relative electric field strength produced by the lightning associated with a typical local thunderstorm. These measured spectral amplitudes are normalized and plotted relative to similar data from other investigators. These data support a 1/F to the 2nd to 1/F to the 3rd slope for sferics at frequencies above the HF range.
Shumpert, T. H.↗
Pb, Sr, Nd and Hf isotopic evidence of multiple sources for Oahu, Hawaii basalts
Pb, Sr, Nd and Hf isotopic compositions of Oahu volcanics indicate that the three principal volcanic series on Oahu Koolau, Honolulu and Waianae - were derived from isotopically distinct sources. Honolulu and Waianae basalts plot on the Nd-Pb-Sr 'mantle plane' whereas Koolau data plot distinctly below the plane.
Stille, P.↗
Hf chronometer for the early solar system
It is now widely believed that Al-26 (half-life, 7.2 x 10 to the 5th yr) and Pd-107 (half-life, 6.5 x 10 to the 6th yr) were present in the early solar system. The nucleosynthetic event responsible for the production of these nuclei must therefore have occurred no more than a few million years before the formation of solid bodies. It is possible that this event also gave a rise to the I-129 believed to be present in the early solar system. The last event to contribute Pu-244 to the solar system, however, occurred approximately 10 to the 8th yr before the time of solidification. It is noted that this latter time scale is also consistent with the lack of evidence for a Cm-247 chronometer. It is proposed that Hf-182 (half-life, 9 x 10 to the 6th yr) can resolve the question whether heavy-element nonactinide nucleosynthesis occurred during the (Al-26)-producing event. It is believed that an answer to this question will help to clarify the chronology of the formation of the solar system and will help to determine the astrophysical sites of heavy-element nucleosynthesis.
Norman, E. B.↗