A5041027651- Astro and Planetary Science
- Planetary Science and Exploration
- Solar and Space Plasma Dynamics
- Ionosphere and magnetosphere dynamics
- Geomagnetism and Paleomagnetism Studies
- Space Exploration and Technology
- Atmospheric Ozone and Climate
- Scientific Research and Discoveries
- Space Science and Extraterrestrial Life
- Earthquake Detection and Analysis
- Geophysics and Gravity Measurements
- Radio Astronomy Observations and Technology
- Climate variability and models
- Geology and Paleoclimatology Research
- Radio Wave Propagation Studies
- Antenna Design and Optimization
- Pharmaceutical and Antibiotic Environmental Impacts
- Atmospheric chemistry and aerosols
- GNSS positioning and interference
- History and Developments in Astronomy
- Chemistry and Chemical Engineering
- Spaceflight effects on biology
- Mass Spectrometry Techniques and Applications
- Lightning and Electromagnetic Phenomena
- Space exploration and regulation
National Radio Astronomy Observatory
2016
Goddard Space Flight Center
1976-1987
The first in situ measurements of the details global composition and dynamics ionosphere Venus have been obtained from Bennett ion mass spectrometer on Pioneer orbiter during period December 1978 through August 1979. These results include observations three related plasma regimes, including (1) bowshock‐ionosheath region, (2) thermal ionosphere, (3) a superthermal flowing layer interfacing with at ionopause extending outward to variable heights above planet. During quiet periods an abundant...
First results from the Ogo-A positive ion spectrometer experiment are presented for period September 23 through December 10, 1964. Thermal hydrogen and helium distributions extend lowest observations at 1500 km to an altitude of 30,000 km. The density obtained H+ 2000 is order 103 ions cm−3, He+ concentration 1% over most range. Whereas distribution observed lower altitudes in general agreement with theoretical models, upper profiles show significant departure predictions based on diffusive...
Direct measurements of the thermal positive ions hydrogen and helium have been obtained from ion mass spectrometers aboard Orbiting Geophysical Observatories 1 3. Observations made during 1965 1966 show distributions H+ He+ extending to altitudes as great 40,000 kilometers, corresponding a magnetospheric coordinate L = 8. The outer boundary plasmasphere is characterized by an abrupt decrease in concentration. This or plasmapause, defined reduction concentration 5 × 10° ions/cm³ less, often...
The Pioneer Venus Orbiter measurements of the plasma and magnetic environment near tail show that ionosphere becomes increasingly filamentary with increasing altitude, apparently forming cometlike rays extend several thousand kilometers behind planet. We call this region ionotail Venus. are envisioned as plumes high‐beta ionospheric origin surrounded by regions low‐density, low‐beta plasma. appears to be in quasi‐equilibrium, pressure approximately balanced surrounding rays. field is...
Comprehensive model calculations of the dayside ion density distributions were carried out and compared with results from Pioneer Venus mass spectrometer. The coupled continuity momentum equations solved for O 2 + , CO C N He H densities altitudes well away ionopause, where horizontal transport terms are negligible. Chemical equilibrium solutions, describing conditions below about 200 km, also obtained NO . agreement between measurements is good some species, such as rather poor others,...
The concentration of atomic hydrogen in the Venus thermosphere near 165km altitude and ∼18° north latitude has been derived from Pioneer situ measurements n(H + ), n(O n(O), n(CO 2 under assumption chemical equilibrium. Altitude profiles n(H) suggest that equilibrium prevails to an at least 200km on dayside 165 km nightside. Measurements below these limits were made by ion neutral mass spectrometers orbiter spacecraft between December 1978 July 1979, while periapsis traversed a complete...
Pioneer Venus observations are used in conducting a study of the location and structure bow shock. The trace shock solar wind aberrated terminator plane is nearly circular at an altitude 1.38 R V independent interplanetary magnetic field orientation with extrapolated subsolar height 0.38 . Gas dynamic relations scaling terrestrial analogue to determine effective impenetrable obstacle from mean surface conclusion that it lies beneath observed ionopause. short‐term variability position similar...
Plasmapause irregular structure and position indicated by measured distributions of hydrogen helium thermal positive ions in duskside magnetosphere
In situ measurements of neutral thermospheric composition derived from orbiter mass spectrometer (ONMS) and ion (OIMS) experiments on Pioneer Venus are interpreted. Observed day to night density variations with asymmetries between dawn dusk contain pronounced signatures various transport processes due winds, exospheric flow, vertical diffusion. The relative magnitudes these depend significantly the rotation rate thermosphere its turbulent properties. On basis a theoretical three‐dimensional...
Plasmapause position measurements by ion mass spectrometers and broadband VLF receivers on OGO 1 3 recordings at Antarctica
Measurement of ion concentration and total density in exosphere using mass spectrometer electrostatic probe
The Hydrogen Epoch of Reionization Array (HERA) is a radio interferometer aiming to detect the power spectrum 21 cm fluctuations from neutral hydrogen (EOR). Drawing on lessons Murchison Widefield (MWA) and Precision for Probing (PAPER), HERA hexagonal array large (14 m diameter) dishes with suspended dipole feeds. Not only does dish determine overall sensitivity, it affects observed frequency structure foregrounds in interferometer. This first series four papers characterizing angular...
The positive ion mass spectrometer on the Geoprobe (NASA 8.25) rocket measured concentrations of O+, N+, H+, He+, NO+, O2+ and N2+ between 200 km peak altitude, 630 km, at 1300 EST March 2, 1966, above Wallops Island, Virginia. dominant throughout altitude range was with a maximum concentration 5 × 105 ions/cm³ 260 km. first detection H+ occurred 230 its increasing to 7 10³ altitude. H+/He+ ratio never lower than 6.0, value 420 molecular ions NO+ were important constituents each being 104...
Ion depletion in high latitude exosphere, considering OGO 2 simultaneous observations of positive ion concentration, VLF signal propagation and whistlers
This is a preliminary report of atmospheric ion composition data obtained over Wallops Island, Virginia, from two successful Aerobee Hi rocket flights, serial numbers NASA 4.09 and 4.14. These rockets were instrumented primarily to determine the composition, pressure, temperature, density neutral particle atmosphere above 100 km. An experiment, identical for launchings, was also included as part payload. Continuous ionosonde monitoring provided by CRPL, Fort Belvoir, NATC, Patuxent Hiver,...
ABSTRACT We use time-domain electromagnetic simulations to determine the spectral characteristics of Hydrogen Epoch Reionization Arrays (HERA) antenna. These are part a multi-faceted campaign effectiveness dish’s design for obtaining detection redshifted 21 cm emission from epoch reionization. Our show existence reflections between HERA’s suspended feed and its parabolic dish reflector that fall below −40 dB at 150 ns and, reasonable impedance matches, have negligible impact on ability...
Magnetic field structures are analyzed for both the ionospheric hole region and magnetosheath‐ionosphere interaction of nightside Venus, in search possible coupling between these two regimes. A magnetic coordinate system based on directions solar wind interplanetary (IMF) is found to order data reasonably well, allowing consistent superposition observational from individual passes Pioneer Venus orbiter. The main findings (1) holes form a zone ±45° latitude covering possibly entire width wake...
The dominant mass 2 ion in the ionosphere of Venus is identified as D + through analysis height variation [mass ion]/[H ] measured chemical equilibrium region by spectrometer on Pioneer Orbiter. This result leads to [D]/[H] = (2.2 ± 0.6) × 10 −2 at turbopause, which agrees with ratio lower atmosphere large probe spectrometer. 100‐fold deuterium enrichment supports previous suggestions that has lost least 0.3 percent a terrestrial ocean.