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Klumpar, D. M.

Publications and source records attributed to Klumpar, D. M..

At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Investigation of the effects of external current systems on the MAGSAT data utilizing grid cell modeling techniques

Progress made in reducing MAGSAT data and displaying magnetic field perturbations caused primarily by external currents is reported. A periodic and repeatable perturbation pattern is described that arises from external current effects but appears as unique signatures associated with upper middle latitudes on the Earth's surface. Initial testing of the modeling procedure that was developed to compute the magnetic fields at satellite orbit due to current distributions in the ionosphere and magnetosphere is also discussed. The modeling technique utilizes a linear current element representation of the large scale space current system.

Klumpar, D. M.↗
NASA NTRS1982

Investigation of the effects of external current systems on the MAGSAT data utilizing grid cell modeling techniques

Efforts in support of the development of a model of the magnetic fields due to ionospheric and magnetospheric electrical currents are discussed. Specifically, progress made in reading MAGSAT tapes and plotting the deviation of the measured magnetic field components with respect to a spherical harmonic model of the main geomagnetic field is reported. Initial tests of the modeling procedure developed to compute the ionosphere/magnetosphere-induced fields at satellite orbit are also described. The modeling technique utilizes a liner current element representation of the large scale current system.

Klumpar, D. M.↗
NASA NTRS1981

Investigation of the effects of external current systems on the MAGSAT data utilizing grid cell modeling techniques

Refinements to the modeling procedure developed to compute the magnetic fields at satellite orbit due to current distributions in the ionosphere and magnetosphere are described. The modeling technique utilizes a linear current element representation of the large scale space current system. A model polar current system is presented and magnetic field perturbations resulting from this system are computed along two hypothetical satellite orbits.

Klumpar, D. M.↗
NASA NTRS1981

Investigation of the effects of external current systems on the MAGSAT data utilizing grid cell modeling techniques

Efforts devoted to reading MAGSAT data tapes in preparation for further analysis of the MAGSAT data are discussed. A modeling procedure developed to compute the magnetic fields at satellite orbit due to hypothesized current distributions in the ionosphere and magnetosphere is described. This technique utilizes a linear current element representation of the large-scale space-current system. Several examples of the model field perturbations computed along hypothetical satellite orbits are shown.

Klumpar, D. M.↗
NASA NTRS1981

Transversely accelerated ions in auroral arcs

Ionospheric ions apparently accelerated transversely to the geomagnetic field in the topside ionosphere are regularly detected by the soft particle spectrometers on the ISIS satellites. Such gyro-accelerated ions are observed in association with precipitating auroral electrons. A detailed study of their relationship with such electrons and with field-aligned currents, together with simultaneous measurements of the local plasma composition and density, reveals the specific conditions present in the topside ionosphere during the generation of such transversely accelerated ions (TAI). A proposed mechanism for generation of TAI involving acceleration by electrostatic ion cyclotron waves is consistent with the present observations.

Klumpar, D. M.↗
NASA NTRS1981

ISIS observations of auroral particles and large-scale Birkeland currents

Simultaneous electron and positive ion observations made with single-component magnetic perturbations on the ISIS-2 satellite are used to compare and contrast the relationships between primary and secondary auroral particle distributions at 5 eV-15 keV, and the large-scale Birkeland currents, in the pre- and post-midnight local time sectors. No unique relation is found between the regions of the Birkeland current system and regions of auroral particle distribution, though repeatable systematics in the region of upward-directed current are observed, and little evidence exists in either local time sector for the direct detection of the downward current-associated current carriers.

Klumpar, D. M.↗
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 NTRS1980

The suprathermal electron contributions to high-latitude Birkeland currents

The paper extends the search for return current carriers to the thermal energy range for electrons, using simultaneous observations on Isis 2 by a magnetometer, retarding potential analyzer, and soft particle spectrometer. Each instrument is described along with data available. Simple magnetic models are used to illustrate how magnetic perturbations may be interpreted as currents remote from the satellite or local to it and that the choice of model cannot be uniquely established by magnetometer measurements alone.

Maier, E. J.↗
NASA NTRS1980

Investigation of the effects of external current systems on the MAGSAT data utilizing grid cell modeling techniques

The feasibility of modeling magnetic fields due to certain electrical currents flowing in the Earth's ionosphere and magnetosphere was studied. Initial efforts were devoted to reading MAGSAT data tapes in preparation for further analysis of the MAGSAT data. Further efforts concern a modeling procedure developed to compute the magnetic field at satellite orbit due to hypothesized current distributions in the ionosphere and magnetosphere. This technique utilizes a linear current element representation of the large scale space current system.

Klumpar, D. M.↗
NASA NTRS1980

An unusual SAR arc observed during ring current development, 4 August 1972

An unusual SAR arc observed during the growth phase of the ring current is described. Proton precipitation was observed, with electron temperature enhancements throughout the region, and an F-region trough present at the equatorward boundary; a high flux of low energy at the SAR arc location and a 'slot' in the ambient electron density are characteristic of this event. Comparisons are made with S3-A spacecraft observations made in the equatorial region at the same time and with Isis-II observations of a more normal SAR arc; the kinetic Alfven process described by Hasegawa and Mima (1978) appears to account for the acceleration of these low energy electrons, although an auroral-type acceleration process cannot be excluded.

Shepherd, G. G.↗
NASA NTRS1979

Transversely accelerated ions - An ionospheric source of hot magnetospheric ions

The paper considers observational data on transversely accelerated ion (TAI) events observed from the Isis 1 and 2 satellites. A source of hot magnetospheric ions was discovered in the auroral topside ionosphere, and a part of the cold ionospheric ion distribution is transversely accelerated within a source region as low as 1000 km. Subsequent to transverse acceleration, the ions are driven upward into the magnetosphere by the gradient B mirror force; they are observed by the soft particle spectrometers on the Isis 1 and 2 satellites, with sharply defined pitch angle distributions centered between 90 and 120 deg, and with energy distributions up to several hundred electron volts. Observations at 1400 km indicate that the transversely accelerated ion (TAI) events are predominantly a winter nightside auroral zone phenomenon, but in the summertime TAI events were observed at altitudes above 2750 km on the day-side within the cleft. Typical intensities exceeding 10 to the 8th power ions/sq cm s sr during TAI events suggest that they may be a significant source of hot ions for the magnetosphere.

Klumpar, D. M.↗
NASA NTRS1979

Heating of ions to superthermal energies in the topside ionosphere by electrostatic ion cyclotron waves

The soft particle spectrometer on the Isis 2 spacecraft occasionally observes fluxes of ions moving upward out of the ionosphere in the vicinity of the auroral oval. These ion fluxes are characterized by a sharp pitch angle distribution usually peaked at an angle somewhat greater than 90 deg, indicative of particles heated to a large transverse temperature in a narrow range below the spacecraft. The observations are interpreted in terms of electrostatic ion cyclotron waves, which heat the ions to superthermal energies transverse to the earth's magnetic field. When the transverse energy increases, the repulsive force of the earth's magnetic field, proportional to the particle magnetic moment, repels the particles away from the earth.

Ungstrup, E.↗
NASA NTRS1977

Numerical model of the convecting F2 ionosphere at high latitudes

In previous work Knudsen (1974) presented a model for the convection field of the high latitude F layer and evaluated the time-dependent behavior of a tube of F layer plasma carried around the polar regions by the field. The present paper describes the initial results of a more detailed numerical study of the behavior of the F layer tubes, where it is assumed that the tubes are subjected to time-dependent ionization rates from both solar photons and precipitating energetic electrons. The numerical results are presented in the form of a map view of N-m F2 contours, electron concentration in vertical section over the magnetic pole from noon to midnight, and several vertical profiles of electron concentration for both convecting and nonconvecting flux tubes. The proposed convection field produced a tongue of F layer plasma extending from the dayside of the cleft over the polar cap with concentrations consistent with those observed by Isis 2.

Knudsen, W. C.↗
NASA NTRS1976

Simultaneous observations of field-aligned currents and particle fluxes in the post-midnight sector

The paper presents several examples of simultaneous measurements of electrons and positive ions (5 eV to 15 eV) and of magnetic field perturbations due to field-aligned currents made on the polar-orbiting ISIS-2 satellite at 1400 km altitude in the early morning local time (MLT) sector. There is a good general correspondence between changes in the gradient of the E-W component of the magnetic field along the spacecraft orbit and changes in the character of the low-energy electron fluxes. The equatorward region of outward current flow in this post-midnight sector is spatially coincident with the isotropic precipitation associated with the low-altitude plasma sheet. In cases examined, electron current density always exceeds positive ion current density by a factor of 10 and usually by a factor of over 100.

Klumpar, D. M.↗
NASA NTRS1975

Rocket-borne particle, field, and plasma observations in the cleft region

Results are reported for comprehensive observations of magnetic and electric fields together with ambient and suprathermal plasmas above the dayside auroral oval with rocket-borne instrumentation which penetrated the cleft region. Measurements were also obtained equatorward and poleward of the cleft. Convection velocities as inferred from electric-field measurements were generally toward noon equatorward of the cleft and were antisunward over the polar cap. Observations of electron temperatures, electric fields, and low-frequency electrostatic noise provide strong evidence of a plasma instability (Farley-Buneman) in the E-layer associated with the appearance of the 'slant E condition' identified in ground-acquired ionograms. The positions of these measurements relative to that of the cleft were firmly established via the determination of the plasma environment with an electrostatic analyzer.

Ungstrup, E.↗