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Results for “ELECTRON PRECIPITATION”

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.

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At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Perturbations of subionospheric LF and MF signals due to whistler-induced electron precipitation bursts

Increasing attention is now being devoted to the problem of the pitch angle scattering and resulting precipitation of magnetospheric energetic electrons by coherent waves. The present investigation has the objective to report the first evidence of a correlation between whistlers and amplitude perturbations on low-frequency (LF) signals at 37.2 kHz and medium-frequency (MF) signals at 780 kHz. Whistler-correlated amplitude perturbations were observed on a 780-kHz MF signal propagating on an approximately 1800 km path from South America to Palmer. The observed MF perturbations were of order 50 percent in amplitude and developed much more quickly than other changes of comparable magnitude on the signal.

Carpenter, D. L.↗
NASA NTRS1977

VLF transmission induced slot electron precipitation

A study is made of electrons in the drift and bounce loss cones of the magnetospheric slot region. It is observed that discrete events account for the arrival of most electrons in the 100-400 keV range into the drift loss cone. Most such events originate from a high power level VLF transmitter. Calculations of the loss rate caused by the events indicate that the electron flux in the slot region may decrease by as much as 50% per day. It is likely that wave-particle interaction occurs low on the field line due to the particular particle energies and wave frequencies. In order to transport particles to the lower interaction region, additional near-equator scattering, via power-line harmonic emissions or ELF hiss, may be required.

Vampola, A. L.↗
NASA NTRS1976

Electron precipitation in the postmidnight sector of the auroral zones

Measurements of the angular distributions and energy spectra of electron intensities within the energy range 50 eV to 15 keV with electrostatic analyzer arrays on board the low-altitude satellite Injun 5 are reported for the postmidnight sector of the auroral zones during the high-intensity events accompanying magnetic substorms. Precipitation features on closed terrestrial field lines well equatorward of the trapping boundary for electrons with energies greater than 45 keV are examined. Precipitation of low-energy electron intensities was characterized by isotropy for all pitch angles outside the atmospheric backscatter cone. The region of electron precipitation observed is associated with the diffuse aurora and with pulsating aurora in the postmidnight sector. Similar variations of the energetic electron intensities with energies above 45 keV were observed in the regions of fluctuating energy fluxes of low-energy electrons associated with auroral luminosity. The increases of energetic electron intensities were not coincident with those of the principal energy fluxes into the atmosphere, except when the average electron energy for the energy fluxes was unusually high, i.e., in the 10-keV range. Precipitation of electron intensities within these energy ranges is consistent with strong pitch angle diffusion of electron intensities near or at the magnetic equator by high-frequency wave turbulence, the effectiveness of which is modulated by perturbations attributable to micropulsations.

Frank, L. A.↗
NASA NTRS1987

A possible energy source to power stable auroral red arcs - Precipitating electrons

Results of coincident measurements by ground-based photometers and the low-altitude plasma instrument on board the Dynamics Explorer 2 satellite are presented that demonstrate the association of precipitating low-energy electrons with stable auroral red (SAR) arcs. A search of available data has yielded 23 instances of DE 2 overflights during the presence of SAR arcs being monitored by the photometers. For each case, downward fluxes of electrons are found to be enhanced along field lines penetrating the arcs in relation to regions both north and south of the features. Modeling of the atmospheric response to these influxes indicates that these electrons can represent a major source of the energy required to establish temperature profiles within the ionospheric electron gas that are sufficient to produce the recorded 6300-A emission rates. The sensitivity of these results to uncertainties of the assumed spacecraft potential and thermospheric composition has been investigated and found to be important, but does not alter the conclusion that precipitating electrons are a fundamental link in the production of SAR arcs.

Slater, D. W.↗
NASA NTRS1989

Comment on 'Observations of Low-Latitude Electron Precipitation' by R. Lieu, J. Watermann, K. Wilhelm, J. J. Quenby, and W. I. Axford

Observations made by an electron spectrometer aboard Spacelab 1 and presented by Lieu et al. (1988) are examined critically. The precipitation of electrons in the energy range of 0.1-12.5 keV was measured on December 6 and 7, 1983. Data for 16 passes near 240 km altitude, between + and - 30 deg geographic latitude, outside the South Atlantic Anomaly were included. It is argued that there is no geophysical confirmation of the large electron fluxes reported by Lieu et al. In their response, Lieu et al. discuss the sampling bias in the Spacelab 1 data and the magnetic shielding deficiencies of the calibration facility below about 500 eV.

Rassoul, H. K.↗
NASA NTRSDate not supplied

The Electron Heat Fluxes Associated with Electron Precipitation in the Region of Diffuse Aurora

Electron heat flux that comes from the magnetosphere to the upper ionospheric altitudes controls the value of electron temperature in the core plasma, and, as a result, the total electron density content that is required for different kinds of space weather applications. Knowing the thermal electron heat flux at the upper ionospheric boundaries is the Achilles' heel of all ionospheric models. Such a thermal heat flux setting is especially difficult to justify in the region of the diffuse aurora that is connected to a large energy reservoir of electrons with energies of a few kiloelectron volts, the Earth's plasma sheet, where magnetosphere-ionosphere coupling processes are strongly interconnected. We use the simulated heat flux provided by SuperThermal Electron Transport (STET) code to estimate electron temperatures at the upper ionospheric altitudes and compare these results with corresponding observations from the Defense Meteorological Satellite Program satellite during Saint Patrick's Days 2013 and 2015 Geomagnetic Storms.

George V. Khazanov↗
NASA NTRS2000

Global Remote Sensing of Precipitating Electron Energies: A Comparison of Substorms and Pressure Pulse Related Intensifications

The Polar Ultraviolet Imager (UVI) observes aurora responses to incident solar wind pressure pulses and interplanetary shocks such its those associated with coronal mass ejections. Previous observations have demonstrated that the arrival of it pressure pulse at the front of the magnetosphere results in highly disturbed geomagnetic conditions and a substantial increase in both dayside and nightside aurora precipitations. Our observations show it simultaneous brightening over bread areas of the dayside and nightside auroral in response to a pressure pulse, indicating that more magnetospheric regions participate as sources for auroral precipitation than during isolate substorm. We estimate the characteristic energies of incident auroral electrons using Polar UVI images and compare the precipitation energies during pressure pulse associated event to those during isolated substorms. We estimate the characteristic energies of incident auroral electrons using Polar UVI images and compare the precipitation energies during pressure pulse associated events to those during isolated auroral substorms. Electron precipitation during substorms has characteristic energies greater than 10 KeV and is structured both in local time and in magnetic latitude. For auroral intensifications following the arrival of'a pressure pulse or interplanetary shock. Electron precipitation is less spatially structured and has greater flux of lower characteristic energy electrons (Echar less than 7 KeV) than during isolated substorm onsets. These observations quantify the differences between global and local auroral precipitation processes and will provide a valuable experimental check for models of sudden storm commencements and magnetospheric response to perturbations in the solar wind.

Chua, D.↗
NASA NTRS1983

Electron precipitation and related aeronomy of the Jovian thermosphere and ionosphere

A comprehensive theoretical model of both the auroral and nonauroral atmosphere and ionosphere of Jupiter is presented and used to study particle precipitation effects in the Jovian upper atmosphere, both at middle and high latitudes. The sources of energy in the model include extreme ultraviolet radiation and energetic electrons. The precipitation of monoenergetic beams of both one and ten keV electrons at high Jovian latitudes are treated in detail, and the effects of higher energy electrons and soft electrons at middle and low latitudes are considered. The effects of this precipitation, such as airglow excitation, ionization, dissociation, and heating are examined. Calculations of the densities of hydrogen, hydrocarbons, and the important ions as well as the temperatures of the neutral, electron, and ion species are included.

Waite, J. H., Jr.↗
NASA NTRS1982

Precipitating electron energy flux and auroral zone conductances - An empirical model

Data from the low energy electron (LEE) experiments on the Atmosphere Explorer C and D satellites have been used to determine the average global distribution of the energy flux of precipitating auroral electrons and their average energy for different levels of geomagnetic activity. Measurements from the Atmosphere Explorer unified abstract file (15-s resolution) have been binned according to invariant latitude (in the range 50-90 deg), magnetic local time, and geomagnetic activity as measured by the Kp and auroral electrojet (AE) indices, separately. Bin-averaged values of precipitating energy flux and average energy have been calculated, and a smoothing algorithm used to reduce stochastic variations in the raw data. The results indicate that, for the parameters studied, the AE inces does a superior job of ordering the data with regard to geomagnetic activity. The global distribution of the auroral enhancement porition of the Pedersen and Hall conductances were inferred from the data by means of an empirical fit to detailed energy deposition calculations.

Spiro, R. W.↗
NASA NTRS1985

Precipitating electron interaction with the atmosphere. II - The dayside cusp region

Interaction of precipitating low-energy magnetosheath electrons with the atmosphere in the dayside cusp region has been studied. Both pitch angle and energy distributions of the fluxes as well as excitation functions for selected N2 and O UV emissions were obtained by numerically solving the multiangle equations of electron transport. There is some possibility that atmospheric emissions may be used for remote measurements of incident soft energy flux, because the ratios of molecular to atomic emission line intensities in the low-energy region are quite different from those in the high-energy region.

Prasad, S. S.↗
NASA NTRS1986

Field-aligned electron precipitation at the edge of an arc

Measurements of field-aligned electrons at the edge of an arc are presented from a sounding rocket flight through a quiet afternoon auroral arc. High time resolution measurements show the evolution of the electron distribution function over the 2.3-km width of field-aligned precipitation. A nearly constant 1.2-eV perpendicular temperature was found for these field-aligned fluxes over a broad range of parallel energies (100 - 900 eV). The small perpendicular temperature indicates that the acceleration region is located at a low altitude. Two models of cold plasma convection into the edge of a V-shaped potential structure are examined and found to be consistent with both the observed fluxes and spatial width of the edge precipitation. Both models predict an average source plasma density less than 130/cu cm to account for the observed field-aligned fluxes and thus an acceleration region well above 1000 km.

Mcfadden, J. P.↗
NASA NTRS1995

A BATSE investigation of radiation belt electrons precipitated by VLF waves

The Compton Observatory commonly encounters fluxes of energetic electrons which have been scattered from the inner radiation belt to the path of the satellite by resonant interactions with VLF waves from powerful man-made transmitters. The present investigation was motivated by the fact that in the Fall of 1993, the Gamma Ray Observatory was boosted from a 650 km altitude circular orbit to a 750 km altitude circular orbit. This was an opportunity, for the first time, to make observations at two different altitudes using the same instrument. We have examined DISCLA data from the Burst & Transient Source Experiment (BATSE) experiment from 1 Sep. 1993 to 29 Jan. 1994. During the period of study we identified 48 instances of the satellite encountering a cloud of energetic electrons which had been scattered by VLF transmitters. We find that boosting the altitude of the circular orbit from 650 km to 750 km increased the intensity of cyclotron resonance scattered electrons by a factor of two. To search for long term changes in the cyclotron resonance precipitation, we have compared the approx. 750 km altitude data from 106 days at the end of 1993 with data at the same altitudes and time of year in 1991. The cyclotron resonance events in 1991 were three times more frequent and 25% of those cases were more intense than any seen in the 1993 data. We attribute this difference to increased level of geomagnetic activity in 1991 near the Solar Maximum.

Datlowe, Dayton W.↗
NASA NTRS1995

A BATSE investigation of radiation belt electrons precipitated by VLF waves

The Compton Observatory commonly encounters fluxes of energetic electrons which have been scattered from the inner radiation belt to the path of the satellite by resonant interactions with VLF waves from powerful man-made transmitters. The present investigation was motivated by the fact that in the Fall of 1993, the Gamma Ray Observatory was boosted from a 650 km altitude circular orbit to a 750 km altitude circular orbit. This was an opportunity, for the first time, to make observations at two different altitudes using the same instrument. We have examined DISCLA data from the Burst & Transient Source Experiment (BATSE) experiment from 1 Sep. 1993 to 29 Jan. 1994. During the period of study we identified 48 instances of the satellite encountering a cloud of energetic electrons which had been scattered by VLF transmitters. We find that boosting the altitude of the circular orbit from 650 km to 750 km increased the intensity of cyclotron resonance scattered electrons by a factor of two. To search for long term changes in the cyclotron resonance precipitation, we have compared the approx. 750 km altitude data from 106 days at the end of 1993 with data at the same altitudes and time of year in 1991. The cyclotron resonance events in 1991 were three times more frequent and 25% of those cases were more intense than any seen in the 1993 data. We attribute this difference to increased level of geomagnetic activity in 1991 near the Solar Maximum.

Datlowe, Dayton W.↗
NASA NTRS1975

Electron precipitation in the post midnight sector of the auroral zones

Comprehensive measurements of the angular distributions and energy spectra of electron intensities with electrostatic analyzer arrays on board the low-altitude satellite Injun 5 are reported. These are for the post-midnight sector of the auroral zones during the high-intensity events accompanying magnetic substorms. Precipitation features on closed terrestrial field lines well equatorward of the trapping boundary for energetic electrons with E greater than 45 keV were examined. No evidences of maxima in the differential energy spectra or of strongly field-aligned currents which are indicative of quasi-static electric fields aligned parallel to the geomagnetic field were found. Precipitation of low-energy electron intensities fluctuated on time scales greater than 2 seconds as viewed at the satellite position. This precipitation was characterized by isotropy for all pitch angles outside the atmospheric backscatter cone.

Frank, L. A.↗
NASA NTRS1973

Relations between ionospheric electric fields and energetic trapped and precipitating electrons.

Balloon-borne electric field and X ray detectors have been flown from Fort Churchill and from near the foot of the magnetic field line on which the ATS 5 satellite is located in order to obtain satellite and balloon measurements of trapped and precipitating particles and to compare them with balloon measurements of the ionospheric electric field. The approximately 80 hours of coordinated data show that nighttime precipitation events (1) are preceded by enhancements of the westward component of ionospheric electric field about 70% of the time, (2) cause the westward electric field strength to decrease about 70% of the time, (3) are unrelated to variations of the southward component of the ionospheric electric field. The westward electric field enhancement before many precipitation events occurs when the trapped electron flux is at or near the stable trapping limit.

Mozer, F. S.↗
NASA NTRS1989

Ionization from soft electron precipitation in the auroral F region

Rocket-borne instrumentation, launched into the morning sector auroral zone from Sondre Stromfjord, Greenland, detects electron density enhancements correlated with enhancements in the flux of soft (less than 1 keV) downgoing electrons. These electron density enhancements seem most likely to have been generated by direct production of ionization at F region altitudes. Model calculations of the electron impact ionization rate, based on the measured electron spectrum, lend support to this hypothesis.

Labelle, J.↗