Search NASA⌕ Search

SEARCH · Search NASA

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Determination of inverted-V stability from Dynamics Explorer satellite data

The longevity of a number of inverted-V electron precipitation events was measured by comparing electron distributions acquired from the two Dynamics Explorer spacecraft during close proximity passes through the southern auroral zone. Common events were identified in the two data sets for time separations up to 18 min. The maximum energy attained within an inverted-V sometimes varied between observations indicating growth or decay of the event. The number of events increasing in energy was roughly equal to those exhibiting decreasing energy, suggesting similar time scales for growth and decay. Observations closely spaced in time (minutes) had some events not in common, implying either a sudden cessation of the event or a limited spatial extent precluding observation by one of the two spacecraft due to its orbital displacement. A statistical study of 28 close proximity passes showed that the number of matched inverted-V events exceeded those which were unmatched. This was not true for comparisons of random pairs of electron distribution plots for the two spacecraft. This implies that the close proximity events observed by both spacecraft were not just random coincidences.

Thieman, J. R.↗
NASA NTRS1972

High energy electron spikes at high latitudes

Over 750 spikes of precipitating electrons with E or = 425 KeV were observed aboard the low altitude polar orbiter OGO-D between 30 July 1967 and 31 December 1967. The spikes may be divided into three distinct populations, depending on whether they occur at latitudes below, at, or above the local limit of trapping.

Brown, J. W.↗
NASA NTRS2011

Observation of Relativistic Electron Microbursts in Conjunction with Intense Radiation Belt Whistler-Mode Waves

We present multi-satellite observations of large amplitude radiation belt whistler-mode waves and relativistic electron precipitation. On separate occasions during the Wind petal orbits and STEREO phasing orbits, Wind and STEREO recorded intense whistler-mode waves in the outer nightside equatorial radiation belt with peak-to-peak amplitudes exceeding 300 mV/m. During these intervals of intense wave activity, SAMPEX recorded relativistic electron microbursts in near magnetic conjunction with Wind and STEREO. This evidence of microburst precipitation occurring at the same time and at nearly the same magnetic local time and L-shell with a bursty temporal structure similar to that of the observed large amplitude wave packets suggests a causal connection between the two phenomena. Simulation studies corroborate this idea, showing that nonlinear wave.particle interactions may result in rapid energization and scattering on timescales comparable to those of the impulsive relativistic electron precipitation.

Kersten, K.↗
NASA NTRS2022

Electron Heat Fluxes Generated by Intense Whistler Waves at the Upper Ionospheric Altitudes

Magnetospheric whistler waves, chorus and hiss, can't provide the resonance heating of the core electron plasma population. However, these whistler-mode branches, can implicitly participate in the heating processes of the core plasma thermal electron population by triggering the electron precipitation over a broad energy range from the magnetosphere and subsequent atmospheric ionization processes leading to the production of superthermal electron population. These superthermal electrons play a large role in the magnetosphere-ionosphere-atmosphere energy interplay with participation of both magnetically conjugate hemispheres, and their Coulomb interaction with background magnetospheric thermal electrons. Using strong hiss and chorus wave events measured by the Van Allen Probes and SuperThermal Electron Transport code, we evaluate the formation of electron heat fluxes at the upper ionospheric altitudes and discuss their consequences on the formation of electron temperature. It is found that chorus and hiss waves that initiate the precipitation of magnetospheric electrons with energies below 30 keV and the follow-up production of secondary electrons play an important role in the energy balance of ionosphere-magnetosphere system.

Magnetospheric whistler waves as an implicit sourc↗
NASA NTRS1995

AMPAS - A new active experiment mission

A new concept for an active experiments mission is presented: The Active Magnetospheric Particle Acceleration Satellite (AMPAS). It is proposed to fly a dual-payload tethered satellite to study three important areas of magnetopsheric physics: (1) electric and magnetic field structures of the Earth's magnetosphere, (2) electron beam-plasma interactions, and (3) far ultraviolet (FUV) signatures of energetic electron precipitation. The tethered system is to be flown in a gravity-gradient stabilized configuration with a 70 deg circular orbit at altitudes in the range 300-800 km. The upper payload will carry two electron beam accelerators (1-10 keV, 1 A) and a plasma contractor to electrically neutralize the payload, while the lower will carry a complement of optical imaging and plasma diagonstics instrumentation. Upward directed beams are injected to 'sound' electric and magnetic field structures, including parallel electric fields in the auroral region, while simultaneous optical instruments aimed downwards measure characteristics of reflected beam pulses precipitating into the upper atmosphere below the satellite. Downward directed beams, and simultaneous plasma wave, particle and optical measurements, are used for the investigation of beam-plasma interactions and electron precipitation studies. The payloads are to be connected by a 1-6 km long tether to be deployed in stages. The configuration of the beam source and the plasma and optical diagnostics on separate, tethered payloads allows the diagnostics to be performed outside of the disturbed region around the source payload, and plasma wave and particle observations of beam-plasma interactions to be performed at well-defined locations relative to the source.

Neubert, T.↗
NASA NTRS1989

Relativistic magnetospheric electrons: Lower ionospheric conductivity and long-term atmospheric variability

Long term observations of relativistic electrons in the earth's outer magnetosphere show a strong solar cycle dependence with a prominent intensity maximum during the approach to solar minimum. This population therefore closely corresponds to the presence of high speed solar wind streams emanating from solar coronal holes. Using a numerical code, the precipitating electron energy deposition in the earth's upper and middle atmosphere were calculated. Observed events (typically persisting several days) would have maximum effect in the 40 to 60 km altitude range with peak energy depositions greater than 110 keV/cu cm-s. It is suggested that this electron population could play an important long term role in modulating lower D region ionization and middle atmospheric ozone chemistry. Methods are described of observing middle atmospheric and lower ionospheric effects of the electrons including balloon, riometer, and space-based ozone sensor systems. A particularly promising approach may involve the monitoring of global Schumann resonance modes which are sensitive to global changes in the properties of the earth-ionosphere cavity. Present work indicates that Schumann resonance properties are moderately correlated with the flux of precipitating relativistic electrons thus offering the possibility of continuously monitoring this aspect of magnetosphere-atmosphere coupling.

Baker, D. N.↗
NASA NTRS1972

Precipitation of low energy electrons at high latitudes: Effects of substorms, interplanetary magnetic field and dipole tilt angle

Data from the auroral particles experiment on OGO-4 were used to study effects of substorm activity, interplanetary magnetic field latitutde, and dipole tilt angle on high-latitude precipitation of 700 eV electrons. It was found that: (1) The high-latitude zone of 700 eV electron precipitation in late evening and early morning hours moves equatorward by 5 to 10 deg during substorms. (2) The low-latitude boundary of polar cusp electron precipitation at 9 to 15 hours MLT also moves equatorward by several degrees during substorms and, in the absence of significant substorm activity, after a period of southward interplanetary magnetic field. (3) With times containing substorm activity or a southward interplanetary magnetic field eliminated, the low-latitude boundary of polar cusp electron precipitation is found to move by approximately 4 deg over the total yearly range of tilt angles. At maximum winter and summer conditions the invariant latitude of the boundary is shown to shift by approximately -3 deg and +1 deg respectively from its equinox location.

Burch, J. L.↗
NASA NTRS1974

Soft X-ray bremsstrahlung and fluorescent line production in the atmosphere by low energy electrons

The effect of low energy quasi-trapped or precipitating electrons which impact on the counter windows of soft X-ray detectors are discussed. The errors caused by X-rays produced in the residual atmosphere above a rocket-borne detector because of the resemblance to X-rays of cosmic origin are examined. The design and development of counter windows which make it possible to identify the atmospherically produced X-rays are described. Curves are presented to show the following: (1) preliminary low energy electron data from Atmospheric Explorer C, (2) X-ray flux in electron-excited nitrogen and oxygen, (3) typical proportional counter response to low energy cosmic rays, and (4) proportional counter response to X-radiation produced by electrons incident upon a gas of oxygen to nitrogen number of 0.4.

Kraushaar, W. L.↗
NASA NTRS1980

Simultaneous wave and particle observations in the auroral kilometric radiation source region

Simultaneous observations from the topside sounder and the soft particle spectrometer onboard the ISIS 1 satellite reveal that very specific conditions on the local electron density and the energetic electron distributions must both occur in the auroral kilometric radiation (AKR) source region. Such regions are associated with inverted V electron precipitation and with depletions in the local electron density. The electron velocity distribution functions obtained near the inverted V peak were found to increase near several keV energy with increasing velocity as required for plasma instability. The electron density observed near the inverted V peak was too high to support AKR for three events investigated, however, and the AKR source was identified with the edge of the inverted V where the density was low (less than or equal to 30/cu cm) in each case. Whereas this density depletion can extend deep into the ionosphere (approximately 1500 km altitude), the severe depletion associated with the AKR density cavity is restricted to higher altitudes (greater than 2750 km for an event studied in detail).

Benson, R. F.↗
NASA NTRS1972

High-energy electron spikes at high latitudes.

Observation of over 750 spikes of precipitating electrons with E greater than or equal to 425 keV aboard the low-altitude polar orbiter Ogo 4 between July 30 and Dec. 31, 1967. The spikes may be divided into three distinct populations, depending on whether they occur at latitudes below, at, or above the local limit of trapping. These spikes are designated type 1, 2, and 3, respectively. Type 3 spikes occur in a narrow latitude band about 3 deg wide, centered at invariant latitude Lambda approximately equal to 78 deg at 1000 MLT (magnetic local time) and 68 deg at 2000 MLT. Type 3 spikes appear to be associated with spikes observed near the magnetopause and the neutral sheet. Type 2 spikes also occur in a latitude band about 3 deg wide, centered at about 71 deg at 1000 MLT and 67 deg at 2200 MLG. Type 2 spikes appear to be related to island fluxes in the neutral sheet, although they occur on closed field lines and may persist for many hours. Type 1 spikes occur in a wider band of latitudes, from about 62 deg to 68 deg near midnight and 66 deg to 68 deg near noon. Although they are observed on closed field lines, type 1 spikes do not persist for periods longer than about 1 hour, and it is concluded that they are produced by strong pitch-angle scattering from the stably trapped population.

Brown, J. W.↗
NASA NTRS2003

Polar Cap Disturbances: Mesosphere and Thermosphere-Ionosphere Response to Solar-Terrestrial Interactions

The Polar Cap is the Upper-Atmosphere cum Mag-netosphere region which is enclosed by the poleward boundary of the Auroral Oval and is threaded by open geomagnetic tield lines. In this region, there is normally a steady precipition (Polar "drizzle") of low energy (w 300eV) electrons that excite optical emissions from the ionosphere. At times, enhanced ionization patches are formed near the Dayside Cusp regions that drift across the Polar Cap towards the Night Sector of the Auroral Oval. Discrete auroral arcs and auroras formed during Solar Magnetic Cloud (SMC)/Coronal Mass Ejection (CME) events are also observed in the Polar Cap. Spectrophotometric observations of all these Polar Cap phenomena provide a measure of the average energy as well a energy flux of the electrons precipitating in the Polar Cap region during these disturbances. Such measurements also point to modulations of the Polar Cap Mesosphere-Lower Thermosphere (MLT) air density and temperature by zonally symmetric tides whose Hough functions peak in the Polar region. MLT cooling during Stratospheric Warming events and their relation to Polar Vortex and associated Gravity wave activities are also observed at the Polar Cap sites.

Sivjee, G.↗
NASA NTRS1991

A case study of the cusp electrodynamics by the Aureol-3 satellite - Evidence for FTE signatures?

Particle and field data from a pass of the Aureol-3 satellite through the polar cusp, several minutes after the southward turning of the IMF, are analyzed in detail. Superposed on the classical cusp, characterized by the typical ion and electron precipitations, several very narrow arcs are detected where large fluxes of electrons and ions, accelerated to 2-4 keV, precipitate simultaneously. These localized arcs correspond to the upward current sheets of a succession in latitude of narrow, alternatively upward and downward field-aligned current sheets. The data suggest that the satellite has crossed the ionospheric footprints of 2 adjacent flux transfer events separated by 100-150 km in latitude. Electric spikes and electromagnetic turbulence are typically associated with the region of downward currents.

Bosqued, Jean M.↗
NASA NTRS1975

Rocket-borne measurements of auroral electrons

Rocket measurements of the pitch-angle and energy distributions of precipitated electrons in the 1- to 20-keV range show a consistent and relatively simple pattern. Features such as 'monoenergetic peaks' and pitch-angle distributions showing intense field-aligned components, rather than being anomalous, are characteristic of bright well-defined auroral forms. Presently available observations do not allow the identification of specific acceleration mechanisms, although they are consistent with several possibilities.

Boyd, J. S.↗