Engineering topics

Ipavich, F. M.

Publications and source records attributed to Ipavich, F. M..

At least 37 records · Page 2

NASA NTRS1992

Variable carbon and oxygen abundances in the solar wind as observed in earth's magnetosheath by AMPTE/CCE

A comprehensive list is presented of the solar wind oxygen and carbon charge states and abundances measured in all magnetosheath periods during the lifetime of the AMPTE/CCE satellite, 1984-1988. A surprisingly variable C/O ratio is found. The variations seem to be strongly correlated to the source temperature in the corona where the solar wind responsible for the particular flow originated.

Von Steiger, R.↗

NASA NTRS1992

Focused transport of energetic particles along magnetic field lines draped around a coronal mass ejection

Evidence is presented for focused transport of energetic particles along magnetic field lines draped around a coronal mass ejection. This evidence was obtained with the University of Maryland/Max-Planck-Institute experiment on the ISEE-3 spacecraft during the decay phase of the June 6, 1979, solar particle event. During the early portion of the decay phase of this event, interplanetary magnetic field lines were apparently draped around a coronal mass ejection, leading to a small focusing length on the western flank where ISEE 3 was located. A period of very slow decrease of particle intensity was observed, along with large sunward anisotropy in the solar wind frame, which is inconsistent with predictions of the standard Fokker-Planck equation models for diffusive transport. It was found possible to fit the observations, assuming that focused transport dominates and that the particle pitch angle scattering is isotropic.

Tan, L. C.↗

NASA NTRS1992

Silicon and oxygen charge state distributions and relative abundances in the solar wind measured by SWICS on Ulysses

We report an initial survey of solar wind silicon and oxygen using data obtained with the Ulysses Solar Wind Ion Composition Spectrometer. In this study, the O(+7)/O(+6) ratio is used to group silicon counts accumulated over a two month period. Results on Si charge state distributions, relative Si/O abundances, and associated proton kinetic temperature and speed distributions are presented.

Galvin, A. B.↗

NASA NTRS1992

Solar wind iron and oxygen charge states and relative abundances measured by SWICS on Ulysses

We present the results of a survey of iron and oxygen charge state distributions as detected by the Solar Wind Ion Composition Spectrometer on the Ulysses spacecraft. The results are categorized in terms of the ionization temperature determined every approximately 13 minute instrument cycle from the O(+7) to O(+6) ratio. Our preliminary Fe/O abundance ratio is 0.12 averaged over this 3 month survey. The Fe charge state distributions accumulated during times of high oxygen ionization temperatures are clearly nonisothermal.

Ipavich, F. M.↗

NASA NTRS1990

Spatial variations in the suprathermal ion distributions during substorms in the plasma sheet

The preinjection and postinjection suprathermal energy spectra of the ion species H(+), O(+), He(+), and He(++) in two events in which substorm-associated particle injections were observed in both the near-earth plasma sheet and farther down the tail were determined using data obtained by the Suprathermal Energetic Ion Charge Analyzer on AMPTE IRM and the Charge Energy Mass Spectrometer on AMPTE CCE. Similar spectral changes were observed in both locations. In both cases, the spectra became harder with injection. Postinjection, the flux decreased exponentially with radial distance. The gradients observed for all ion species were very similar.

Kistler, L. M.↗

NASA NTRS1990

New high-resolution electrostatic ion mass analyzer using time of flight

The design of a high-resolution ion-mass analyzer is described, which is based on an accurate measurement of the time of flight (TOF) of ions within a region configured to produce a harmonic potential. In this device, the TOF, which is independent of ion energy, is determined from a start pulse from secondary electrons produced when the ion passes through a thin carbon foil at the entrance of the TOF region and at a stop pulse from the ion striking a microchannel plate upon exciting the region. A laboratory prototype instrument called 'VMASS' was built and was tested at the Goddard Space Flight Center electrostatic accelerator, showing a good mass resolution of the instrument. Sensors of the VMASS type will form part of the WIND Solar Wind and Suprathermal Ion experiment, the Soho mission, and the Advanced Composition Explorer.

Hamilton, D. C.↗

NASA NTRS1990

The Joint NASA/Goddard-University of Maryland Research Program in Charged Particle and High Energy Photon Detector Technology

The Univ. of Maryland portion investigated the following areas. The Space Physics Group performed studies of data from the AMPTE/CCE spacecraft CHEM experiment and found that the ratio of solar wind to photospheric abundances decreased rather smoothly with the first ionization potential (FIP) of the ion with the low FIP ion being about a factor of two overabundant. Carbon and hydrogen fit this trend particularly well. Several occurrences were analyzed of field aligned beams observed when CCE was upstream of the Earth's bow shock. Also using CHEM data, ring current intensity and composition changes during the main and recovery phases of the great geomagnetic storm that occurred in February 1986 was examined in detail. Still using CHEM data, ring current characteristics were examined in a survey of 20 magnetic storms ranging in size from -50 nT to -312 nT. A study was done of energetic ion anisotropy characteristics in the Earth's magnetosheath region using data from the UMD/MPE experiment on ISEE-1. The properties were analyzed of approx. 30 to 130 keV/e protons and alpha particles upstream of six quasi-parallel interplanetary shocks that passed by the ISEE-3 spacecraft during 1978 to 1979. Work from NASA-Goddard include studies from the High Energy Cosmic Ray Group, Low Energy Cosmic Ray Group, Low Energy Gamma Ray Group, High Energy Astrophysics Theory Group, and the X ray Astronomy Group.

Ipavich, F. M.↗

NASA NTRS1989

Multispacecraft observations of energetic ions upstream and downstream of the bow shock

Simultaneous measurements of energetic protons and alpha particles were obtained inside and outside of the magnetopause and upstream and downstream of the bow shock. In the magnetosheath, no gradient or streaming is found in the upstream direction. The present results are consistent with first-order Fermi acceleration at the bow shock and subsequent downstream convection, and exclude the possibility of a magnetospheric source for these particles.

Scholer, M.↗

NASA NTRS1989

Energetic particle diffusion coefficients upstream of quasi-parallel interplanetary shocks

The properties of about 30 to 130-keV/e protons and alpha particles upstream of six quasi-parallel interplanetary shocks that passed by the ISEE 3 spacecraft during 1978-1979 were analyzed, and the values for the upstream energegic particle diffusion coefficient, kappa, in these six events were deduced for a number of energies and upstream positions. These observations were compared with predictions of Lee's (1983) theory of shock acceleration. It was found that the observations verified the prediction of the A/Q dependence (where A and Q are the particle atomic mass and ionization state, respectively) of kappa for alpha and proton particles upstream of the quasi-parallel shocks.

Tan, L. C.↗

NASA NTRS1989

Energy spectra of the major ion species in the ring current during geomagnetic storms

Nearly equatorial storm time energy spectra of the four major magnetospheric ions, H(+), O(+), He(+), and He(2+), obtained for the August 1984-November 1985 period by the charge-energy-mass spectrometer aboard the AMPTE/CCE spacecraft during the main and early recovery phases of all geomagnetic storms with minimum Dst of less than -50 nT were examined. It was found that, in the dawn-to-noon sector, there was a dip in the a spectra of all ions at 5-20 keV/e, while in the noon-to-dusk sector, the proton phase space density dropped off sharply below 5 keV. These spectra were compared with those predicted by a model of ion drift and loss in the magnetosphere. It was found that the spectra are most consistent with a Volland-Stern electric field with gamma = 2 and with a rotation of the nominal dawn-to-dusk electric field eastward by 2 hrs local time.

Kistler, L. M.↗

NASA NTRS1989

The ion energy spectra in the ring current during the geomagnetic storm of February 1986

The largest geomagnetic storm in several decades occurred in February 1986, with a minimum Dst of -312 nT. In this experiment, the CHEM instrument on the AMPTE/CCE spacecraft has been used to study the development of this storm in more detail. By comparing measurements of phase space density (f) vs magnetic moment (mu) for four ion species H(+), O(+), He (+), and He(++) during consecutive passes through the ring current region, a distinction can be made between flux increases that require the injection of a new population and those that are consistent with the adiabatic acceleration of a pre-existing population. It is shown that the smaller flux observed during the outbound pass compared to the preceding inbound pass at the time of minimum Dst is due to the difference in local times of the two measurements. This local time difference is consistent with a greatly enhanced convection electric field, which brings a new population from the magnetotail to the post-noon, but not to pre-noon local time sector.

Kistler, L. M.↗

NASA NTRS1988

Ring current development during the great geomagnetic storm of February 1986

The variations of the ring current energy density and composition during the great magnetic storm of February 1986 were investigated using particle measurements obtained by the charge-energy-mass instrument on the AMPTE Charge Composition Explorer spacecraft. The ring current composition of this storm, which had a complicated main phase and a minimum Dst of -312 nT on February 9, was followed for five days from the prestorm quiet time to the early recovery phase. Results suggested that the very rapid initial Dst recovery (tau of about 9.3 hrs) in this storm resulted largely from the rapid loss of 75- to 100-keV O(+) via charge exchange in the inner portion of the ring current. It is proposed that a major O(+) + N(+) ring current component generally exists near the maximum phase of great storms.

Hamilton, D. C.↗

NASA NTRS1988

Protons and alpha particles in field-aligned beams upstream of the bow shock

Measurements of H(+) and He(2+) ions in field-aligned beams (about 10 keV/nuc) made with the AMPTE-CCE spacecraft are reported. The proton beam population has a density of less than about 1 percent of the solar wind density and a significant thermal anisotropy, in agreement with previous observations. The observed beam velocities are in reasonable agreement with the 'direct reflection' model, in which a portion of the solar wind is reflected and energized at the earth's bow shock, but are consistently larger than expected from magnetosheath leakage models. The He(2+) ions in the beams have approximately the same velocity as the H(+) ions, but the He(2+) to H(+) density ratio is dramatically smaller than that measured simultaneously in the solar wind. The present beam observations were obtained during several of the time intervals previously analyzed by other workers, using data from the same spacecraft, who attributed the streaming upstream ions to magnetospheric rather than bow shock origin.

Ipavich, F. M.↗

NASA NTRS1988

Downstream energetic proton and alpha particles during quasi-parallel interplanetary shock events

This paper considers the energetic particle populations in the downstream region of three quasi-parallel interplanetary shock events, which was explored using the ISEE 3 Ultra Low Energy Charge Analyzer sensor, which unambiguously identifies protons and alpha particles using the electrostatic deflection versus residual energy technique. The downstream particles were found to exhibit anisotropies due largely to convection in the solar wind. The spectral indices of the proton and the alpha-particle distribution functions were found to be remarkably constant during the downstream period, being generally insensitive to changes in particle flux levels, magnetic field direction, and solar wind densities. In two of the three events, the proton and the alpha spectra were the same throughout the entire downstream period, supporting the prediction of diffusive shock acceleration theory.

Tan, L. C.↗

NASA NTRS1987

Solar wind iron charge states preceding a driver plasma

Iron and silicon/sulfur charge state and velocity measurements and iron density measurements in the shocked solar wind which preceded the flare-related driver plasma observed on September 29, 1978 by ISEE 3 are reported. Given the assumption that the driver plasma is magnetically isolated from the ambient solar wind, the contact surface separating these two plasma regimes is expected to form an distinct boundary in the charge state composition. Instead, an apparent transition in the ionization state of the shocked solar wind from ambient solar wind values to those typical of the driver plasma is observed. This result may reflect X-ray ionization of the solar wind plasma near the flare site.

Galvin, A. B.↗

NASA NTRS1987

Reduction and scientific analysis of data from the charge-energy-mass (CHEM) spectrometer on the AMPTE/CCE spacecraft

The Charge-Energy-Mass (CHEM) spectrometer instrument on the AMPTE/Charge Composition Explorer (CCE) spacecraft is designed to measure the mass and charge-state abundance of magnetospheric and magnetosheath ions between 0.3 and 315 keV/e, an energy range that includes the bulk of the ring current and the dynamically important portion of the plasma sheet population. Continuing research is being conducted using the AMPTE mission data set, and in particular, that of the CHEM spectrometer which has operated flawlessly since launch and still provides excellent quality data. The requirted routine data processing and reduction, and software develpment continues to be performed. Scientific analysis of composition data in a number of magnetospheric regions including the ring current region, near-earth plasma sheet and subsolar magnetosheath continues to be undertaken. Correlative studies using data from the sister instrument SULEICA, which determines the mass and charge states of ions in the energy range of approximately 10 to 250 keV/e on the IRM, as well as other data from the CCE and IRM spacecraft, particularly in the upstream region and plasma sheet have also been undertaken.

Gloeckler, G.↗

NASA NTRS1987

Nuclear and ionic charge distribution experiment on ISEE-1 and ISEE-3

The experimental work carried out under this contract is a continuation of that originally performed under Contracts NAS5-20062 and NAS5-26739. The data analyzed are from the Max-Planck Institut/Univ. of Maryland experiment on ISEE-1 and ISEE-3. Each spacecraft experiment consists of a nearly identical set of three sensors (designated the ULECA, ULEWAT, and ULEZEQ sensors) designed to measure the energy spectra and composition of suprathermal and energetic ions over a broad energy range (less than 3 keV/e to more than 20 MeV/nucleon). Since the launch of ISEE's 2 and 3, the MPI/Univ. of Maryland experiments have generally performed as expected except for a partial failure of the ULEWAT sensor on ISEE-1 in August 1978. A number of scientific studies have either been completed, initiated or are at various stages of completion. A brief summary of Primary Results is given, followed by a more detailed summary of the major accomplishments at the Univ. of Maryland.

Gloeckler, G.↗

NASA NTRS1987

Energetic ion and electron beams at the plasma-sheet boundary in the distant tail

Several energetic particle bursts observed by ISEE 3 in the distant tail are analyzed. The energetic particle data are supplemented by the electron plasma and magnetic field measurements. These bursts are characterized by large velocity-dispersion effects, with energetic electrons observed first, followed by ions with continuously lower velocities. Both ions and electrons stream in the tailward direction. Protons and alpha particles of the same energy per nucleon are observed at the same time. The dispersion effects are observed in reverse order when the spacecraft leaves from the boundary layer into the lobe. No obvious signature indicating the passage of a plasmoid has been observed in the particle or magnetic field data during or immediately following these bursts. It is concluded that these beams at the plasma-sheet boundary originate at a steady source, presumably close to a neutral line, and not at a time varying source. The velocity filter effect in a dawn-dusk electric field arranges particles with progressively lower velocity further inside the wedge-shaped region of reconnected field lines. The plasma electron distribution exhibits a tailward directed heat flux within this layer.

Scholer, M.↗