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NASA NTRS1992

Method of separation of celestial gamma-ray bursts from solar flares

We recently discovered 217 'new' celestial gamma-ray burst candidates from the 'new' burst search of the PVO real time data base. The burst search covered the time period from September 1978 to July 1988. Sixty were confirmed by at least one other spacecraft, e.g., ISEE-3, V-II, V-12, etc. None triggered the PVO high time resolution memory. In this paper we describe a new algorithm based on the relationship between time width T(w) and hardness ratio HR, to distinguish cosmic gamma-ray bursts from solar flares without knowing the directions of the events. The algorithm was tested with 83 triggered and 60 nontriggered confirmed gamma-ray bursts and 30 confirmed solar flares from PVO.

Chuang, K. W.↗

NASA NTRS1993

Structure and properties of the subsolar magnetopause for northward interplanetary magnetic field - Multiple-instrument particle observations

The paper examines the structure and properties of the subsolar magnetopause for northward IMF on the basis of measurements from 10 different instrument for three ISEE crossings. It is shown that the overall structure and properties are similar for the three crossings, indicating that the magnetopause is relatively well determined in the subsolar region for strongly northward IMF. The combined data set suggests that the magnetopause region is best organized by defining a sheath transition layer and steplike boundary layers. The electron flux enhancements in the lowest energies in the boundary layers and magnetosphere are found to be ionospheric electrons and not photoelectrons from the spacecraft. For northward IMF, they are photoelectrons, but for southward IMF they may be secondary electrons. The density measurements from differential and integral techniques are similar, leaving no room for a significant 'invisible' population.

Song, P.↗

NASA NTRS1993

The distribution of flare parameters and implications for coronal heating

Assuming that solar hard X-ray flares are caused by bremsstrahlung from a distribution of accelerated electrons impinging on a thick target, we determine the relationship between the total flare energy released in the corona and observable flare parameters. It is shown that for the more numerous smaller flares to be energetically more important than larger ones, there must be an anticorrelation between observed flux and one or more of the photon spectral index, the total flare duration, the ratio of the total energy that goes into heating the corona to the energy that goes into acceleration of electrons, and the reciprocal of the low-energy cutoff of the accelerated electron spectrum. Using a new statistical test which properly takes account of data truncation due to observational selection effects, we find that neither spectral index nor duration show an anticorrelation with flux in ISEE 3/ICE hard X-ray data. Using a nonparametric method, we obtain single distributions of peak flux, spectral index, duration, and fluence, corrected for selection biases. The functional forms of these distributions do not support coronal heating by numerous small flares without very specific behavior by yet unobserved parameters.

Lee, Theodore T.↗

NASA NTRS1993

Solar flares and avalanches in driven dissipative systems

The contention of Lu and Hamilton (1991) that the energy release process in solar flares can be understood as avalanches of many small reconnection events is further developed. The dynamics of the complex magnetized plasma of solar active regions is modeled with a simple driven dissipative system, consisting of a vector field with local instabilities that cause rapid diffusion of the field. It is argued that the avalanches in this model are analogous to solar flares. The distributions of avalanches in this model are compared with the solar flare frequency distributions obtained from ISEE 3/ICE satellite observations. Quantitative agreement is found with the energy, peak luminosity, and duration distributions over four orders of magnitude in flare energy, from the largest flares down to the completeness limit of the observations. It is predicted that the power-law solar flare frequency distributions will be found to continue downward with the same logarithmic slopes to an energy of about 3 x 10 exp 25 ergs and duration of about 0.3 s, with deviations from power-law behavior below these values.

Lu, Edward T.↗

NASA NTRS1993

Characteristics of ion flow in the quiet state of the inner plasma sheet

We use AMPTE/IRM and ISEE 2 data to study the properties of the high beta plasma sheet, the inner plasma sheet (IPS). Bursty bulk flows (BBFs) are excised from the two databases, and the average flow pattern in the non-BBF (quiet) IPS is constructed. At local midnight this ensemble-average flow is predominantly duskward; closer to the flanks it is mostly earthward. The flow pattern agrees qualitatively with calculations based on the Tsyganenko (1987) model (T87), where the earthward flow is due to the ensemble-average cross tail electric field and the duskward flow is the diamagnetic drift due to an inward pressure gradient. The IPS is on the average in pressure equilibrium with the lobes. Because of its large variance the average flow does not represent the instantaneous flow field. Case studies also show that the non-BBF flow is highly irregular and inherently unsteady, a reason why earthward convection can avoid a pressure balance inconsistency with the lobes. The ensemble distribution of velocities is a fundamental observable of the quiet plasma sheet flow field.

Angelopoulos, V.↗

NASA NTRS1993

Space and Earth Sciences, Computer Systems, and Scientific Data Analysis Support, Volume 1

This Final Progress Report covers the specific technical activities of Hughes STX Corporation for the last contract triannual period of 1 June through 30 Sep. 1993, in support of assigned task activities at Goddard Space Flight Center (GSFC). It also provides a brief summary of work throughout the contract period of performance on each active task. Technical activity is presented in Volume 1, while financial and level-of-effort data is presented in Volume 2. Technical support was provided to all Division and Laboratories of Goddard's Space Sciences and Earth Sciences Directorates. Types of support include: scientific programming, systems programming, computer management, mission planning, scientific investigation, data analysis, data processing, data base creation and maintenance, instrumentation development, and management services. Mission and instruments supported include: ROSAT, Astro-D, BBXRT, XTE, AXAF, GRO, COBE, WIND, UIT, SMM, STIS, HEIDI, DE, URAP, CRRES, Voyagers, ISEE, San Marco, LAGEOS, TOPEX/Poseidon, Pioneer-Venus, Galileo, Cassini, Nimbus-7/TOMS, Meteor-3/TOMS, FIFE, BOREAS, TRMM, AVHRR, and Landsat. Accomplishments include: development of computing programs for mission science and data analysis, supercomputer applications support, computer network support, computational upgrades for data archival and analysis centers, end-to-end management for mission data flow, scientific modeling and results in the fields of space and Earth physics, planning and design of GSFC VO DAAC and VO IMS, fabrication, assembly, and testing of mission instrumentation, and design of mission operations center.

Estes, Ronald H.↗

NASA NTRS1992

Kinetic plasma processes occurring in the outer plasmasphere

One area of data analysis work that was begun under this contract is the fitting of the perpendicular velocity distributions of equatorially trapped ions with a Kappa function. This type of characterization of the trapped ions will be very useful for comparison with velocity distributions produced by the model. A second area of data analysis is to study data from consecutive passes when DE 1's apogee was near the magnetic equator and the spacecraft was often skimming along nearly the same L shell. In 1982 three such periods occurred in May, June, and July. For these consecutive events we have Kp histories, density measurements from a number of sources (Whistler data, DE SFR, ISEE SFR) and consecutive samples of ion pitch angle distributions along field lines. It is clear from this data how the pitch angle distributions evolve during a flux tube refilling event. Our modeling of the flow of plasma along closed field lines is following two basic tracks. The first is a study of the basic refilling process without the effect of wave-particle heating near the equator or the effect of large or abrupt field-aligned electric potential drops. This model includes the effects of Coulomb self-collisions and collisions with the O+ ions in the topside ionosphere. The second track is a study of the effects of wave produced pitch-angle scattering and perpendicular heating occurring near the magnetic equator, in connection with the development of large potential drops that result from electron heating and the development of density gradients.

Wilson, Gordon R.↗

NASA NTRS1994

A study of the formation and dynamics of the Earth's plasma sheet using ion composition data

Over two years of data from the Lockheed Plasma Composition Experiment on the ISEE 1 spacecraft, covering ion energies between 100 eV/e and about 16 keV/e, have been analyzed in an attempt to extract new information about three geophysical issues: (1) solar wind penetration of the Earth's magnetic tail; (2) relationship between plasma sheet and tail lobe ion composition; and (3) possible effects of heavy terrestrial ions on plasma sheet stability.

Lennartsson, O. W.↗

NASA NTRS1994

Tail lobe ion composition at energies of 0.1 to 16 keV/e: Evidence for mass-dependent density gradients

A large set of energetic (0.1 to 16 keV/e) ion composition data from the central magnetotail, obtained by the ISEE 1 spacecraft between 10 and 23R(sub E) from Earth, is sorted according to measured total ion beta value, in order to investigate whether bulk properties of different ions vary in different ways between plasma sheets and lobes, as suggested by a comparison of certain experimental and theoretical results in the literature. Despite inevitable difficulties with extracting statistically valid data at very low beta (10(exp -2) or lower), the results seem to support a recent theoretical model suggesting that lighter ions have a steeper density gradient than heavier ions, especially when comparing H(+) ions with O(+) ions. The results also indicate that ion velocity distributions are fairly isotropic even at low beta, at least those of H(+) ions, although field-aligned flows are common. The results are evaluated in the context of plasma transport and are found to lend some support to the notion that tail lobe convection may be directed inward from the dawn and dusk flanks.

Lennartsson, O. W.↗

NASA NTRS1994

Flank solar wind interaction

In this report we will summarize the results of the work performed under the 'Flank Solar Wind Interaction' investigation in support of NASA's Space Physics Guest Investigator Program. While this investigation was focused on the interaction of the Earth's magnetosphere with the solar wind as observed by instruments on the International Sun-Earth Explorer (ISEE) 3 spacecraft, it also represents the culmination of decades of research performed by scientists at TRW on the rich phenomenology of collisionless shocks in space.

Moses, Stewart L.↗

NASA NTRS1993

Magnetic structure of the low beta, quasi-perpendicular shock

The structure of the low-beta quasi-perpendicular shock is examined in view of ISEE 1 and 2 magnetic field measurements. An analysis of shock overshoots indicates that the strength of the overshoots of low-beta, quasi-perpendicular shocks increases as the ratio of the Mach number to the first critical Mach number increases. Wave analysis indicates that the power of the downstream waves also increases as a function of this ratio of criticality. The thickness of the shock is a factor of 1-2 times greater than a precursor wavelength, countering the conjecture that the shock is the last amplified cycle of the precursor wave.

Farris, M. H.↗

NASA NTRS1993

Signatures of shock drivers in the solar wind and their dependence on the solar source location

Solar wind and energetic ion observations following 40 interplanetary shocks with well-established solar source locations have been examined in order to determine whether signatures characteristic of the coronal material forming the shock driver are present. The signatures considered include magnetic-field-aligned bidirectional ion flows observed by the ISEE 3 and IMP 8 spacecraft; bidirectional solar wind electron heat fluxes; solar wind plasma proton and electron temperature depressions; low-beta plasma; enhanced, low-variance magnetic fields; and energetic ion depressions. Several shock driver signatures are commonly observed following shocks originating from within about 50 deg of central meridian, and are generally absent for other events. We conclude that shock drivers generally extend up to about 100 deg in longitude, centered on the solar source longitude. Since shocks from central meridian events are not usually associated with all the shock driver signatures examined, the absence of a driver cannot be confirmed from consideration of one of these signatures alone. We also find evidence that a few bidirectional energetic ion and solar wind electron heat flux events following shocks (in particular from far eastern sources) may occur on open field lines outside of shock drivers.

Richardson, I. G.↗

NASA NTRS1993

Observational test of hot flow anomaly formation by the interaction of a magnetic discontinuity with the bow shock

The formation of a hot flow anomaly (HFA) observed near the Earth's bow shock appears to be due to the interaction between the bow shock and an impinging discontinuity in the upstream plasma. Recent single-particle and 2D hybrid numerical studies have suggested that such an interaction will produce an HFA only if the motional electric field in the ambient plasma points toward the discontinuity, thereby focusing shock-reflected ions into it. We perform a test of this electric field orientation for a set of nine HFA events observed by the ISEE spacecraft and described previously in the literature. Under the assumption that the discontinuities were tangential, the predicted electric field orientation is found on at least one side of all nine observed HFAs (on the trailing edge of seven and the leading edge of five, and on both sides of three events). Further, there is evidence that asymmetries in the observed magnetic field signatures are related to the orientation of the motional electric field. The events in which the electric field points toward the discontinuity on both sides tend to be those with fairly symmetric flanking magnetic field enhancements.

Thomsen, M. F.↗

NASA NTRS1993

Polytropic relationship in interplanetary magnetic clouds

High time-resolution data from the ISEE 3 and IMP 8 spacecraft are presented for the magnetic field and the proton and electron populations of a number of magnetic clouds, in order to investigate such clouds' thermodynamics and the relationship between their magnetic and thermodynamic structures. It is judged on the basis of these data that while the magnetic flield of the cloud expands, the ions are cooled. Hot electrons are trapped by the magnetic field in the magnetic cloud's core. These conditions are favorable for the generation of ion-acoustic waves.

Osherovich, V. A.↗

NASA NTRS1993

Simultaneous observations of solar MeV particles in a magnetic cloud and in the earth's northern tail lobe - Implications for the global field line topology of magnetic clouds and for the entry of solar particles into the magnetosphere during cloud passage

Simultaneous ISEE 3 and IMP 8 spacecraft observations of magnetic fields and flow anisotropies of solar energetic protons and electrons during the passage of an interplanetary magnetic cloud show various particle signature differences at the two spacecraft. These differences are interpretable in terms of the magnetic line topology of the cloud, the connectivity of the cloud field lines to the solar surface, and the interconnection between the magnetic fields of the magnetic clouds and of the earth. These observations are consistent with a magnetic cloud model in which these mesoscale configurations are curved magnetic flux ropes attached at both ends to the sun's surface, extending out to 1 AU.

Farrugia, C. J.↗

NASA NTRS1994

Applications of squeezed states: Bogoliubov transformations and wavelets to the statistical mechanics of water and its bubbles

The squeezed states or Bogoliubov transformations and wavelets are applied to two problems in nonrelativistic statistical mechanics: the dielectric response of liquid water, epsilon(q-vector,w), and the bubble formation in water during insonnification. The wavelets are special phase-space windows which cover the domain and range of L(exp 1) intersection of L(exp 2) of classical causal, finite energy solutions. The multiresolution of discrete wavelets in phase space gives a decomposition into regions of time and scales of frequency thereby allowing the renormalization group to be applied to new systems in addition to the tired 'usual suspects' of the Ising models and lattice gasses. The Bogoliubov transformation: squeeze transformation is applied to the dipolaron collective mode in water and to the gas produced by the explosive cavitation process in bubble formation.

Defacio, Brian↗

NASA NTRS1992

Global and local current sheet thickness estimates during the late growth phase

The thinning and intensification of the cross tail current sheet during the substorm growth phase are analyzed during the CDAW 6 substorm (22 Mar. 1979) using two complementary methods. The magnetic field and current sheet development are determined using data from two spacecraft and a global magnetic field model with several free parameters. These results are compared with the local calculation of the current sheet location and structure previously done by McPherron et al. Both methods lead to the conclusion that an extremely thin current sheet existed prior to the substorm onset, and the thicknesses estimated by the two methods at substorm onset agree relatively well. The plasma data from the ISEE 1 spacecraft at 13 R(sub E) show an anisotropy in the low energy electrons during the growth phase which disappears just before the substorm onset. The global magnetic model results suggest that the field is sufficiently stretched to scatter such low energy electrons. The strong stretching may improve the conditions for the growth of the ion tearing instability in the near Earth tail at substorm onset.

Pulkkinen, T. I.↗

NASA NTRS1992

Energetic Ion Events Associated with Travelling Compression Regions

Preliminary results from the first extended study of energetic ion enhancements associated with the signatures of Traveling Compression Regions (TCR's) in the deep tail, using data from the ISEE 3 satellite, are presented. It is found that 46% of TCR signatures can be associated with an ion enhancement, indicating that the spacecraft entered the plasma sheet boundary layer as a result of a plasmoid passage down the tail. Events with ion enhancements are found to be on average a factor of approximately 2 larger in amplitude than those without, but there is no clear difference in the event duration. Almost all ion associated TCR's tailward of 100 Re show strong tailward streaming, indicating that the plasmoids are completely disconnected from the Earth. Most events Earthward of -80 Re show Earthward streaming, or no clear anisotropy, suggesting that the plasmoids may not be completely disconnected at the distances. A curious aspect of the data set, that a significant number of TCR's are associated with a turning off, or on, of the ion enhancement, is reported.

Owen, Chris J.↗