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Analysis and visualization of global magnetospheric processes

Description: This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The purpose of this project is to develop new computational and visualization tools to analyze particle dynamics in the Earth`s magnetosphere. These tools allow the construction of a global picture of particle fluxes, which requires only a small number of in situ spacecraft measurements as input parameters. The methods developed in this project have led to a better understanding of particle dynamics in the Earth`s magnetotail in the presence of turbulent wave fields. They have also been used to demonstrate how large electromagnetic pulses in the solar wind can interact with the magnetosphere to increase the population of energetic particles and even form new radiation belts.
Date: December 31, 1998
Creator: Winske, D.; Mozer, F.S. & Roth, I.
Partner: UNT Libraries Government Documents Department

Observations of magnetospheric substorms occurring with no apparent solar wind/IMF trigger

Description: An outstanding topic in magnetospheric physics is whether substorms are always externally triggered by disturbances in either the interplanetary magnetic field or solar wind, or whether they can also occur solely as the result of an internal magnetospheric instability. Over the past decade, arguments have been made on both sides of this issue. Horwitz and McPherron have shown examples of substorm onsets which they claimed were not externally triggered. However, as pointed out by Lyons, there are several problems associated with these studies that make their results somewhat inconclusive. In particular, in the McPherron et al. study, fluctuations in the B{sub y} component were not considered as possible triggers. Furthermore, Lyons suggests that the sharp decreases in the AL index during intervals of steady IMF/solar wind, are not substorms at all but rather that they are just enhancements of the convection driven DP2 current system that are often observed to occur during steady magnetospheric convection events. In the present study, we utilize a much more comprehensive dataset (consisting of particle data from the Los Alamos energetic particle detectors at geosynchronous orbit, IMP 8 magnetometer and plasma data, Viking UV auroral imager data, mid-latitude Pi2 pulsation data, ground magnetometer data and ISEE1 magnetic field and energetic particle data) to show as unambiguously as possible that typical substorms can indeed occur in the absence of an identifiable trigger in the solar wind/IMF.
Date: March 1, 1996
Creator: Henderson, M.G.; Reeves, G.D.; Belian, R.D. & Murphree, J.S.
Partner: UNT Libraries Government Documents Department

Long term behavior of trapped relativistic electrons and their correlation with solar wind speed

Description: We examine Los Alamos energetic electron data from 1979 through the present to show long term trends in the trapped relativistic electron populations at geosynchronous Earth orbit. Such populations are thought to be associated with high-speed solar wind structures typically present near solar minimum. We will show that high-energy electron fluxes, E > 1.4 MeV, displayed a solar-like cycle of about 10.5 years, but that the behavior is out of phase with the sunspot cycle. We will also compare relativistic electrons during the cycle with solar wind speed from the MIT plasma analyzers on IMP-8. It will be shown that relativistic electrons correlate well with high solar winds only during limited, short periods of time. We will also confirm the observation that the higher-energy electrons occur with a longer delay after the establishment of the high-speed solar wind. Comparison of our data with previously published data indicate that the higher the solar wind speed, the sooner the relativistic electrons occur.
Date: December 1995
Creator: Belian, R. D.; Cayton, T. E.; Christensen, R. A.; Ingraham, J. C. & Reeves, G. D.
Partner: UNT Libraries Government Documents Department

Analysis of the bi-modal nature of solar wind-magnetosphere coupling

Description: It has been shown that the optimal linear prediction filter relating the solar wind electric field and the geomagnetic activity, as measured by the AL index, is both bi-modal and dependent on the level of activity in the magnetosphere. Further studies truncated the prediction filter to a five parameter model containing two low-pass filtered delta functions of arbitrary amplitude and delay time. The present study elaborates on the nature of the bi-modal response by using the five parameter model to quantify the effects of the level of geomagnetic activity on each of the modes of the filter individually. The authors find that at all levels of activity, the second mode, occurring at approximately one hour, is relatively unchanged. The first mode, however, has a one parameter dependence on the level of activity in the magnetosphere. The amplitude of the first mode is shown to have a significant increase with respect to activity.
Date: May 1, 1997
Creator: Smith, J. P. & Horton, W.
Partner: UNT Libraries Government Documents Department

Nonlinear whistler wave scattering in space plasmas

Description: In this paper the evolution of nonlinear scattering of whistler mode waves by kinetic Alfven waves (KAW) in time and two spatial dimensions is studied analytically. The authors suggest this nonlinear process as a mechanism of kinetic Alfven wave generation in space plasmas. This mechanism can explain the dependence of Alfven wave generation on whistler waves observed in magnetospheric and ionospheric plasmas. The observational data show a dependence for the generation of long periodic pulsations Pc5 on whistler wave excitation in the auroral and subauroral zone of the magnetosphere. This dependence was first observed by Ondoh T.I. For 79 cases of VLF wave excitation registered by Ondoh at College Observatory (L=64.6 N), 52 of them were followed by Pc5 geomagnetic pulsation generation. Similar results were obtained at the Loparskaia Observatory (L=64 N) for auroral and subauroral zone of the magnetosphere. Thus, in 95% of the cases when VLF wave excitation occurred the generation of long periodic geomagnetic pulsations Pc5 were observed. The observations also show that geomagnetic pulsations Pc5 are excited simultaneously or insignificantly later than VLF waves. In fact these two phenomena are associated genetically: the excitation of VLF waves leads to the generation of geomagnetic pulsations Pc5. The observations show intensive generation of geomagnetic pulsations during thunderstorms. Using an electromagnetic noise monitoring system covering the ULF range (0.01-10 Hz) A.S. Fraser-Smith observed intensive ULF electromagnetic wave during a large thunderstorm near the San-Francisco Bay area on September 23, 1990. According to this data the most significant amplification in ULF wave activity was observed for waves with a frequency of 0.01 Hz and it is entirely possible that stronger enhancements would have been measured at lower frequencies.
Date: April 1, 1997
Creator: Yukhimuk, V. & Roussel-Dupre, R.
Partner: UNT Libraries Government Documents Department

A quantitative test of different magnetic field models using conjunctions between DMSP and geosynchronous orbit

Description: We report here on a study which tests the magnetic field line mapping between geosynchronous orbit and the ionosphere. The mapping is determined both observationally and from five magnetospheric magnetic field models. The mapping is tested observationally by comparing electron energy spectra obtained by the Magnetospheric Plasma Analyzer (MPA) at geosynchronous orbit and by the DMSP spacecraft. Because the orbits are nearly perpendicular, in general, the spectra match well for only a few seconds providing a good determination of when DMSP crosses the geosynchronous drift shell. In this way the mapping between geosynchronous orbit and the ionosphere can be determined to better than one degree. We then compare the measured magnetic footpoints of geosynchronous orbit with the footpoints predicted by five magnetospheric field models: Tsyganenko-89, Tsyganenko-87, Tsyganenko-82, Oslen-Pfitzer, and Hilmer-Voigt. Based on a set of over 100 measured magnetic conjunctions we find that, in general, there are significant differences between the mappings predicted by various magnetic field models but that there is no clear ``winner`` in predicting the observed mapping. We find that the range of magnetic latitudes at which we measure conjunctions is much broader than the range of latitudes which the models can accommodate. This lack of range is common to all magnetic field models tested. Although there are certainly cases where the models are not sufficiently stretched, we find that on average all magnetic field models tested are too stretched. This technique provides an excellent opportunity for testing future magnetic field models and for determining the appropriate parameterizations for those models. 21 refs., 4 figs.
Date: March 1, 1996
Creator: Reeves, G.D.; Weiss, L.A.; Thomsen, M.F. & McComas, D.J.
Partner: UNT Libraries Government Documents Department

Two wide-angle imaging neutral-atom spectrometers

Description: The Two Wide-angle Imaging Neutral-atom Spectrometers (TWINS) mission provides a new capability for stereoscopically imaging the magnetosphere. By imaging the charge exchange neutral atoms over a broad energy range (1 < E , {approximately} 100 keV) using two identical instruments on two widely-spaced high-altitude, high-inclination spacecraft, TWINS will enable the 3-dimensional visualization and the resolution of large scale structures and dynamics within the magnetosphere for the first time. These observations will provide a leap ahead in the understanding of the global aspects of the terrestrial magnetosphere and directly address a number of critical issues in the ``Sun-Earth Connections`` science theme of the NASA Office of Space Science.
Date: December 31, 1997
Creator: McComas, D.J.
Partner: UNT Libraries Government Documents Department

Magnetic energy storage and the nightside magnetosphere-ionosphere coupling

Description: The change m in the magnetic energy stored m in the Earth`s magnetotail as a function of the solar wind, BIF conditions are investigated using an empirical magnetic field model. The results are used to calculate the two normal modes contained m in the low-dimensional global model called WINDMI for the solar wind driven magnetosphere-ionosphere system. The coupling of the magnetosphere-ionosphere (MI) through the nightside region 1 current loop transfers power to the ionosphere through two modes: a fast (period of minutes) oscillation and a slow (period of one hour) geotail cavity mode. The solar wind drives both modes m in the substorm dynamics.
Date: May 1, 1998
Creator: Horton, W.; Pekker, M. & Doxas, I.
Partner: UNT Libraries Government Documents Department

Experimental studies of auroral arc generators

Description: This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). An all-sky video camera system was deployed in Eagle, Alaska at the foot of the magnetic field line that threads geosynchronous satellite 1989-046 as part of a campaign to study correlations of ground-based auroral activity with satellite-based plasma and energetic particle measurements. The overall intent of the project was to study magnetosphere-ionosphere coupling as it relates to the aurora, and, in particular, to look for signatures that may help to identify various auroral generator mechanism(s). During this study, our efforts were primarily directed towards identifying the generator mechanism(s) for pulsating aurora. Our data, though not conclusive, are found to support theories that propose a cyclotron resonance mechanism for the generation of auroral pulsations.
Date: August 1, 1997
Creator: Suszcynsky, D.M.; Borovsky, J.E. & Thomsen, M.F.
Partner: UNT Libraries Government Documents Department

The magnetospheric trough

Description: The authors review the history of the concepts of the magnetospheric cold-ion trough and hot-electron trough and conclude that the two regions are actually essentially the same. The magnetospheric trough may be viewed as a temporal state in the evolution of convecting flux tubes. These flux tubes are in contact with the earth`s upper atmosphere which acts both as a sink for precipitating hot plasma sheet electrons and as a source for the cold ionospheric plasma leading to progressive depletion of the plasma sheet and refilling with cold plasma. Geosynchronous plasma observations show that the rate of loss of plasma-sheet electron energy density is commensurate with the precipitating electron flux at the low-latitude edge of the diffuse aurora. The rate at which geosynchronous flux tubes fill with cold ionospheric plasma is found to be consistent with previous estimates of early-time refilling. Geosynchronous observations further indicate that both Coulomb collisions and wave-particle effects probably play a role in trapping ionospheric material in the magnetosphere.
Date: March 4, 1997
Creator: Thomsen, M. F.; McComas, D. J.; Elphic, R. C. & Borovsky, J. E.
Partner: UNT Libraries Government Documents Department

Signatures of mode conversion and kinetic Alfven waves at the magnetopause

Description: It has been suggested that resonant mode conversion of compressional MHD waves into kinetic Alfven waves at the magnetopause can explain the abrupt transition in wave polarization from compressional to transverse commonly observed during magnetopause crossings. The authors analyze magnetic field data for magnetopause crossings as a function of magnetic shear angle (defined as the angle between the magnetic fields in the magnetosheath and magnetosphere) and compare with the theory of resonant mode conversion. The data suggest that amplification in the transverse magnetic field component at the magnetopause is not significant up to a threshold magnetic shear angle. Above the threshold angle significant amplification results, but with weak dependence on magnetic shear angle. Waves with higher frequency are less amplified and have a higher threshold angle. These observations are qualitatively consistent with theoretical results obtained from the kinetic-fluid wave equations.
Date: July 21, 2000
Creator: Johnson, Jay R. & Cheng, C. Z.
Partner: UNT Libraries Government Documents Department

Low energy neutral atom imaging: Remote observations of the magnetosphere

Description: Recent developments in detection of neutral atom imaging should enable imaging the global structure and dynamics of the terrestrial magnetosphere. The inherent technical challenge of imaging low energy neutral atoms (LENAs) with energy < 30 keV is their separation from the tremendous UV background, to which LENA detectors are sensitive, without loss of information of LENA trajectory and energy. Three instrument concepts for separating LENAs from the background UV are presented: LENA charge conversion via transmission through an ultrathin carbon foil and subsequent electrostatic deflection, EUV grating polarizers and attenuators, and high frequency shutters. Each of these concepts can be mated to a detector section that provides both LENA imaging capability and coincidence/time-of-flight.
Date: February 1, 1995
Creator: Funsten, H. O.; McComas, D. J.; Scime, E. E. & Moore, K. R.
Partner: UNT Libraries Government Documents Department

Random and periodic substorms and their origins in the solar wind

Description: Substorms occur (recur) in two fashions: periodically with time or randomly in time. A statistical analysis of the time intervals {Delta}t between subsequent substorm onsets clearly shows these two types of substorms. When substorms are recurring periodically, the period is 3.1 {plus_minus} 1.2 hours, and the distribution of periods is gaussian. When substorms are occurring randomly, the time intervals {Delta}t between successive substorm onsets are distributed according to the exponential distribution exp({minus}{delta}t//5 hours), with a 5-hour mean interval between random onsets. With the use of the Los Alamos geosynchronous energetic-particle dam and the OMNI solar-wind data, it is shown that periodic substorms are associated with time intervals when the average value of the IMF is southward for extended periods of time and it is shown that randomly occurring substorms are statistically correlated with randomly occurring northward-to-southward reversals of the 1-hour-averaged values of the IMF B{sub z}.
Date: May 1, 1994
Creator: Borovsky, J. E.; Belian, R. D.; Nemzek, R. J. & Smith, C. W.
Partner: UNT Libraries Government Documents Department

Substorm statistics: Occurrences and amplitudes

Description: The occurrences and amplitudes of substorms are statistically investigated with the use of three data sets: the AL index, the Los Alamos 3-satellite geosynchronous energetic-electron measurements, and the GOES-5 and -6 geosynchronous magnetic-field measurements. The investigation utilizes {approximately} 13,800 substorms in AL, {approximately} 1400 substorms in the energetic-electron flux, and {approximately} 100 substorms in the magnetic field. The rate of occurrence of substorms is determined as a function of the time of day, the time of year, the amount of magnetotail bending, the orientation of the geomagnetic dipole, the toward/away configuration of the IMF, and the parameters of the solar wind. The relative roles of dayside reconnection and viscous coupling in the production of substorms are assessed. Three amplitudes are defined for a substorms: the jump in the AL index, the peak of the >30-keV integral electron flux at geosynchronous orbit near midnight, and the angle of rotation of the geosynchronous magnetic field near midnight. The substorm amplitudes are statistically analyzed, the amplitude measurements are cross correlated with each other, and the substorm amplitudes are determined as functions of the solar-wind parameters. Periodically occurring and randomly occurring substorms are analyzed separately. The energetic-particle-flux amplitudes are consistent with unloading and the AL amplitudes are consistent with direct driving plus unloading.
Date: May 1, 1994
Creator: Borovsky, J. E. & Nemzek, R. J.
Partner: UNT Libraries Government Documents Department

Geosynchronous orbit magnetopause crossings

Description: In this study we extend the analysis of magnetopause crossings observed with Magnetospheric Plasma Analyzer measurements to examine a much larger statistical data set. This study examines 39 maiznetosheath/LLBL intervals from 79 spacecraft-months of observations: these observations were taken from a survey of data from the start of each spacecraft mission and extending through March 1993. In contrast to the previous findings, we find no evidence for a significant dawn/dusk asymmetry in geosynchronous magnetopause crossings.
Date: July 1, 1994
Creator: McComas, D. J.; Elphic, R. C.; Moldwin, M. B. & Thomsen, M. F.
Partner: UNT Libraries Government Documents Department

Observations of cold magnetospheric ions at geosynchronous orbit during times of high activity

Description: Flowing, cold magnetospheric ions have been observed in conjunction with geosynchronous orbit magnetopause crossings since the earliest ATS and OGO missions. The authors have reported on the occurrence and convection of low-energy (10-100 eV) ions seen by multiple satellites in association with geosynchronous orbit magnetopause and low-latitude boundary layer (LLBL) encounters. More generally, Los Alamos 3-D plasma instruments observe these ions following storm sudden commencements (SSCs), when activity levels are high. The ions appear to be convecting radially outward and usually westward at speeds of a few to several tens of kilometers per second. Often the energy spectra reveal peaks at energies appropriate for cold convecting H{sup +}, He{sup +} and O{sup +}. The occurrence frequency distribution of these dense cold ions is peaked near 1400 LT, with an overall range from 1000 to beyond 1800 LT. This local time distribution is greatly skewed from the overall plasmaspheric distribution, which peaks closer to 1800 LT. Multisatellite observations show that the ions are seen first at late afternoon local times and then at progressively earlier and earlier local times (though usually no earlier than 1000 LT). This apparent evolution in local time suggests that the late-afternoon plasmaspheric plasma moves out and dawnward during times of increased magnetospheric activity. The three-satellite observations also allow the authors to track cold plasma convection at multiple points in the magnetosphere, and potentially provide a glimpse of the large-scale convection pattern.
Date: October 1, 1994
Creator: Elphic, R. C.; Weiss, L. A.; Thomsen, M. F.; McComas, D. J. & Bame, S. J.
Partner: UNT Libraries Government Documents Department

An upper bound for the proton temperature anisotrophy

Description: This tutorial describes recent research concerning the upper bound on the hot proton temperature anisotropy imposed by wave-particle scattering due to enhanced fluctuations from the electromagnetic proton cyclotron anisotropy instability. This upper bound, which has been observed in both the magnetosheath and the outer magnetosphere, represents a limited closure relation for the equations of anisotropic magnetohydrodynamics. Such a closure relation has the potential to improve the predictive capability of large-scale anisotropic models of the magnetosphere.
Date: November 1, 1994
Creator: Gary, S. P.
Partner: UNT Libraries Government Documents Department

Measuring the magnetic connectivity of the geosynchronous region of the magnetosphere

Description: This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The purpose of this project was to determine the magnetic connectivity of the geosynchronous region of the magnetosphere to the auroral zone in the polar ionosphere in order to test and refine current magnetospheric magnetic field models. The authors used plasma data from LANL instruments on three geosynchronous satellites and from USAF instruments on three low-altitude, polar-orbiting, DMSP satellites. Magnetic connectivity is tested by comparing plasma energy spectra at DMSP and geosynchronous satellites when they are in near conjunction. The times of closest conjugacy are used to evaluate the field models. They developed the tools for each step of the process and applied them to the study of a one-week test set of conjunctions. They automated the analysis tools and applied them to four months of two-satellite observations. This produced a database of about 130 definitive magnetic conjunctions. They compared this database with the predictions of the widely-used Tsyganenko magnetic field model and showed that in most cases one of the various parameterizations of the model could reproduce the observed field line connection. Further, they explored various measurables (e.g., magnetospheric activity indices or the geosynchronous field orientation) that might point to the appropriate parameterization of the model for these conjunctions, and ultimately, for arbitrary times.
Date: March 1, 1996
Creator: Thomsen, M.; Hones, E.; McComas, D.; Reeves, G. & Weiss, L.
Partner: UNT Libraries Government Documents Department

Three-dimensional magnetospheric equilibrium with isotropic pressure

Description: In the absence of the toroidal flux, two coupled quasi two-dimensional elliptic equilibrium equations have been derived to describe self-consistent three-dimensional static magnetospheric equilibria with isotropic pressure in an optimal ({Psi},{alpha},{chi}) flux coordinate system, where {Psi} is the magnetic flux function, {chi} is a generalized poloidal angle, {alpha} is the toroidal angle, {alpha} = {phi} {minus} {delta}({Psi},{phi},{chi}) is the toroidal angle, {delta}({Psi},{phi},{chi}) is periodic in {phi}, and the magnetic field is represented as {rvec B} = {del}{Psi} {times} {del}{alpha}. A three-dimensional magnetospheric equilibrium code, the MAG-3D code, has been developed by employing an iterative metric method. The main difference between the three-dimensional and the two-dimensional axisymmetric solutions is that the field-aligned current and the toroidal magnetic field are finite for the three-dimensional case, but vanish for the two-dimensional axisymmetric case. With the same boundary flux surface shape, the two-dimensional axisymmetric results are similar to the three-dimensional magnetosphere at each local time cross section.
Date: May 1, 1995
Creator: Cheng, C.Z.
Partner: UNT Libraries Government Documents Department

Transport processes in space plasmas

Description: This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The project represents a comprehensive research effort to study plasma and field transport processes relevant for solar-terrestrial interaction, involving the solar wind and imbedded magnetic field and plasma structures, the bow shock of the Earth`s magnetosphere and associated waves, the Earth`s magnetopause with imbedded flux rope structures and their connection with the Earth, plasma flow in the Earth`s magnetotail, and ionospheric beam/wave interactions. The focus of the work was on the interaction between plasma and magnetic and electric fields in the regions where different plasma populations exist adjacent to or superposed on each other. These are the regions of particularly dynamic plasma behavior, important for plasma and energy transport and rapid energy releases. The research addressed questions about how this interaction takes place, what waves, instabilities, and particle/field interactions are involved, how the penetration of plasma and energy through characteristic boundaries takes place, and how the characteristic properties of the plasmas and fields of the different populations influence each other on different spatial and temporal scales. These topics were investigated through combining efforts in the analysis of plasma and field data obtained through space missions with theory and computer simulations of the plasma behavior.
Date: August 1, 1997
Creator: Birn, J.; Elphic, R.C. & Feldman, W.C.
Partner: UNT Libraries Government Documents Department

Multi-satellite characterization of the large energetic electron flux increase at L = 4-7, in the five-day period following the March 24, 1991, solar energetic particle event

Description: Following the giant magnetic storm that started on March 24, 1991, and the immediately-preceding solar energetic particle (SEP) event, a dramatic increase in the flux of energetic electrons was observed to occur on several satellites (using Los Alamos instruments aboard two geosynchronous satellites and two GPS satellites, plus energetic electron data from the CRRES satellite) sampling the L=4-7 region of the magnetosphere. We find that: this flux buildup at the larger L-values (L--6-7) first appears near the magnetic equator and subsequently spreads to higher magnetic latitudes; the flux buildup near the magnetic equator peaks first at the higher L before it peaks at the lower L; analysis of the angular distribution of energetic electrons at geosynchronous orbit shows that the flux buildup begins first with the buildup of energetic electrons (>300 keV) moving perpendicular to the magnetic field.
Date: December 31, 1994
Creator: Ingraham, J. C.; Cayton, T. E. & Belian, R. D.
Partner: UNT Libraries Government Documents Department

Proxy and in-situ studies of dayside magnetopause reconnection

Description: The functional dependence of magnetic reconnection on solar wind parameters is examined utilizing the am geomagnetic index and satellite observations at the magnetopause. Several parameters in the solar wind are found to control geomagnetic activity. Reconnection is found to be most efficient when the interplanetary magnetic field is southward, although some activity remains when the IMF is horizontal and slightly northward. The reconnection efficiency increases with the solar wind dynamic pressure but decreases when the Mach number is greater than 7.5. These results are compared with the functional dependencies found by correlating solar wind and magnetosheath measurements with observations of accelerated tows at the magnetopause. Accelerated tows are found to occur most often when the interplanetary magnetic field is directed southward. However, accelerated flows do occur when the IMF is horizontal and northward. Accelerated flows are also affected by the magnetosheath beta such that higher beta inhibits their occurrence. The location of accelerated tows indicates that reconnection occurs mainly at the subsolar point.
Date: December 1, 1992
Creator: Scurry, L.; Russell, C. T. & Gosling, J. T.
Partner: UNT Libraries Government Documents Department

Ballooning-mirror instability and internally driven Pc 4--5 wave events

Description: A kinetic-MHD field-aligned eigenmode stability analysis of low frequency ballooning-mirror instabilities has been performed for anisotropic pressure plasma sin the magnetosphere. The ballooning mode is mainly a transverse wave driven unstable by pressure gradient in the bad curvature region. The mirror mode with a dominant compressional magnetic field perturbation is excited when the product of plasma beta and pressure anisotropy (P{sub {perpendicular}}/P{sub {parallel}} > 1) is large. From the AMPTE/CCE particle and magnetic field data observed during Pc 4--5 wave events the authors compute the ballooning-mirror instability parameters and perform a correlation study with the theoretical instability threshold. They find that compressional Pc 5 waves approximately satisfy the ballooning-mirror instability condition, and transverse Pc 4--5 waves are probably related to resonant ballooning instabilities with small pressure anisotropy.
Date: March 1, 1994
Creator: Cheng, C.Z.; Qian, Q.; Takahashi, K. & Lui, A.T.Y.
Partner: UNT Libraries Government Documents Department