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NASA NTRS1986

Plasmaphere and plasmapause region characteristics as measured by DE-1

Thermal ion composition measurements by the retarding ion mass spectrometer (RIMS) on the Dynamics Explorer-1 have revealed new and intriguing features of the thermal ion distributions in the plasmasphere and plasmapause regions. Some of the interesting new findings include: the presence of intense fluxes of heated and equatorially-trapped light ions within the plasmapause region; the existence of a heavy ion 'torus' or 'shell' in the outer plasmasphere; and the relatively stable nature of the He(+)/(H+) concentration ratio within the plasmasphere. The relatively short orbital period of DE-1 has also allowed improved observations on the formation of the new outer plasmasphere during the recovery of geomagnetic storms. Statistical studies of the plasmaspheric density structure and boundaries are beginning to reveal a picture of their relation to other magnetospheric boundaries, such as the inner edge of the electron plasma sheet, and trends in the internal density structure of the plasmasphere.

Horwitz, J. L.↗

NASA NTRS1986

Global auroral responses to magnetospheric compressions by shocks in the solar wind - Two case studies

The global auroral responses to shocks in the solar wind at earth were studied. The z-component of the interplanetary magnetic field, Bz, is negative ahead and behind the first shock and positive for the second case. A sudden-commencement geomagnetic storm develops in each case, with maximum D sub st 190 nT. An immediate auroral response is detected at all longitudes around the auroral oval, in which auroral luminosities increase by a factor of 2 to 3 with the first samples after each sudden commencement. The time delay in obtaining the first sample varies with local time from approx. 1 to 19 mins. No other significant variations in the aurora are associated with the immediate response. Beginning approx. 30 mins after each sudden commencement, the aurora becomes active and displays significant variations in its luminosity and spatial distribution. For Bz 0 an intense substorm develops. A sun-aligned transpolar arc forms when Bz 0, appearing first at local midnight as a polar arc and then lengthening sunward from the auroral oval across the polar cap to noon at an average speed of approx. 1 km/sec.

Craven, J. D.↗

NASA NTRS1987

Effect of possible passage through Halley's magnetic tail on geomagnetic activity

It is found that there occurred a geomagnetic storm on May 18/19, 1910 that cannot be dismissed as a recurrent storm. The period of storminess is close to the period of time at which the magnetic and plasma tail of Halley should have passed over the earth. The signature is worldwide and of the form and magnitude expected if the solar wind were shielded from the earth by the comet. Comparison with computer simulations applicable closer to the comet suggests that this interpretation is feasible. If this interpretation is correct, the 'lobes' of the Halley tail have deeper lows at 24 x 10 to the 6th km than in the present model at 7 x 10 to the 6th km downstream and are at least twice as wide.

Russell, C. T.↗

NASA NTRS1988

The large-scale structure of flare-associated interplanetary shocks

The large-scale structure of flare-associated interplanetary shocks is investigated by examining the properties of 116 shocks which originated in solar flare events during a 18.7-year period commencing mid-May 1967. The best average representation of these shocks is an expansion which is uniform over about 100 deg. The highest compression ratio across the shock is about 15 deg west of the radial from the flare site. The loose coupling of shocks and their drivers is supported by the observation that drivers are generally only detected for shocks originating near central meridian. A comparison of the numbers of shocks per year with the numbers of sudden commencement geomagnetic storms indicates that the percentage of shocks at 1 AU which originate in flare events is less than 50 percent. Many shock-flare associations made in the past are probably in error.

Cane, H. V.↗

NASA NTRS1988

Plasma interactions monitoring system

The plasma environment around the space station is expected to be different from that environment which occurs naturally at these altitudes because of the unprecedented size of the space station, its orbital motion, and its high power distribution system. Although there are models which predict the environment around the station, they do not take into account changes in configuration, changes in the natural and induced environments, nor interactions between the different environments. There will be unique perturbations associated with the space station, which will vary as the space station is being developed. Even after the developed space station has been completed environmental conditions will change as the payloads are changed and as the station systems and materials undergo degradation and modification. Because the space station will be a point of many varied activities the environment will continually undergo perturbations from effluents resulting from operations of the reboost module, EVA, airlock operations, and vacuum venting. The use of the Mobile Service Center will cause disturbances which cannot, at this time, be predicted. Also, the natural environment will be affected by solar flares. In addition, the operations of attached payloads, (e.g., ASTROMAG) themselves will undoubtedly cause perturbations to the ambient environment. Finally, the natural environment will change as a result of natural perturbations such as solar flares and geomagnetic storms.

Roberts, William T.↗

NASA NTRS1988

Correlations between solar activity and operationally determined satellite drag variation parameters

Operational orbit determination of the Earth Radiation Budget Satellite (ERBS) and the Solar Maximum Mission (SMM) spacecraft using the Goddard Trajectory Determination System (GTDS) in the Flight Dynamics Facility (FDF) of the Goddard Space Flight Center (GSFC) has yielded an orbit solution data base of 3 years for ERBS and 8 years for SMM. One of the parameters in each data base is the drag variation parameter used in the GTDS atmospheric drag model; this parameter is solved routinely to accommodate the different atmospheric densities as they are encountered solution to solution. These two data bases of the drag variation parameter solutions are analyzed to evaluate correlations in the variations of the parameter with changes in the 10.7-cm wavelength solar flux, F10.7, and the geomagnetic index. The data for SMM span a wider range of solar flux values and show a stronger correlation. The data for ERBS, which is at a higher altitude and inclination than SMM, show a significant degree of scatter. For both satellites, the data indicate that changes in the drag variation parameter are more strongly correlated with the F10.7 solar flux than with the geomagnetic index. Correlations with the geomagnetic index are apparent only for severe geomagnetic storm conditions. Results from this analysis enhance the understanding of the drag model and the accommodation density variations in operational orbit determination support.

Smith, E. A.↗

NASA NTRS1988

Review of microscopic plasma processes of occurring during refilling of the plasmasphere

Refilling of the plasmashere after geomagnetic storms involves both macroscopic and microscopic plasma processes. The latter types of processes facilitate the refilling by trapping the plasma in the flux tube and by thermalizing the interhemispheric flow. A review of studies on microscopic processes is presented. The primary focus in this review is on the processes when the density is low and the plasma is collisionless. The discussion includes electrostatic shock formation, pitch angle scatterring extended ion heating and localized ion heating in the equatorial region.

Singh, N.↗

NASA NTRS1989

Some of the terrestrial effects of AR 5395

Active Region 5395 was extraordinary for both its flare production for a complete disk transit and for one of the largest geomagnetic storms on record. Some of the more dramatic terrestrial effects resulting from the flare activity are briefly discussed.

Speich, D.↗

NASA NTRS1989

Ionospheric effects of the extreme solar activity of February 1986

During February 1986, near the minimum of the 11 year Solar sunspot cycle, after a long period of totally quiet solar activity (R sub z = 0 on most days in January) a period of a suddenly enhanced solar activity occurred in the minimum between solar cycles 21 and 22. Two proton flares were observed during this period. A few other flares, various phenomena accompanying proton flares, an extremely severe geomagnetic storm and strong disturbances in the Earth's ionosphere were observed in this period of enhanced solar activity. Two active regions appeared on the solar disc. The flares in both active regions were associated with enhancement of solar high energy proton flux which started on 4 February of 0900 UT. Associated with the flares, the magnetic storm with sudden commencement had its onset on 6 February 1312 UT and attained its maximum on 8 February (Kp = 9). The sudden enhancement in solar activity in February 1986 was accompanied by strong disturbances in the Earth's ionosphere, SIDs and ionospheric storm. These events and their effects on the ionosphere are discussed.

Boska, J.↗

NASA NTRS1990

Modeling of a series of interplanetary disturbance events in September 1978

A series of three interplanetary disturbance events in September 1978 are modeled. Flares responsible for the three shock waves are tentatively identified. It is shown that the computed interplanetary scintillation (IPS) sky maps for flares on September 21 and 23 clearly show that the September 21 flare was responsible for the IPS event and the geomagnetic storms which were observed on September 24-25, although it has been generally believed that a flare on September 23 was their origin. Thus, this is a good example to show the usefulness of IPS observations to identify the responsible solar event and predict the arrival of the shock wave. It is also shown that the IPS event was not caused by a high speed stream from a coronal hole.

Akasofu, S.-I.↗

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 NTRS1991

Recent improvements in atmospheric environment models for Space Station applications

The capability of empirical models of the earth's thermosphere must continually be updated if they are to keep pace with their many applications in the aerospace industry. This paper briefly summarizes the progress of several such efforts in support of the Space Station Program. The efforts consists of the development of data bases, analytical studies of the data, and evaluation and intercomparison of thermosphere models. A geomagnetic storm model of Slowey does not compare as well to the MSIS-86 model as does the Marshall Engineering Thermosphere (MET). LDEF orbit decay data is used to evaluate the performance of the MET and MSIS-86 during a period of high solar activity; equal to or exceeding the highest levels that existed during the time of the original data sets upon which these models are based.

Anderson, B. Jeffrey↗

NASA NTRS1991

Numerical simulations of high-speed solar wind streams within 1 AU and their signatures at 1 AU

A parametric study of the evolution within, and signatures at, 1 AU of high-speed streams is performed with the use of a MHD two-and-a-half-dimensional time-dependent model. This study is an extension of an earlier one by Smith and Dryer (1990) who examined the ecliptic plane consequences of relatively short-duration, energetic solar disturbances. The present study examines both the erupting and corotating parts of long-duration, high-speed streams characteristic of coronal hole flows. By examining the variation of the simulated plasma velocity, density, temperature, and magnetic field at 1 AU, as well as the location of the solar coronal hole sources relative to the observer at 1 AU, it was possible to provide some insight into the identification of the solar sources of interplanetary disturbances. Two definitions for angle locating the solar source of interplanetary disturbances at 1 AU are presented and discussed. The results are applied to the suggestion by Hewish (1988) that low-latitude coronal holes are suitably positioned to be the sources of major geomagnetic storms when the holes are in the eastern half of the solar hemisphere at the time of the commencement of the storm. The results indicate that, for these cases, the streams emanating from within the hole must be very fast, greater than 1000 km/s, or very wide, greater than 60 deg, at the inner boundary of 18 solar radii.

Smith, Z.↗

NASA NTRS1991

Role of electromagnetic noise in the interhemispheric plasma exchange along closed field lines

Satellite observations have demonstrated that the equatorially trapped superthermal hydrogen ions are a common occurrence in the outer plasmaspheric flux tubes. Such ions occur in conjunction with broadband waves over a frequency spectrum from the proton-cyclotron frequency to the lower-hybrid frequency. Trapped ions are produced by the transverse heating of the ions by the waves. The effect of such ion heating on the interhemispheric plasma flow is studied here. The consequences of the trapped ion production on the plasmaspheric refilling after geomagnetic storms are examined.

Singh, Nagendra↗

NASA NTRS1991

Handbook of solar-terrestrial data systems, version 1

The interaction between the solar wind and the earth's magnetic field creates a large magnetic cavity which is termed the magnetosphere. Energy derived from the solar wind is ultimately dissipated by particle acceleration-precipitation and Joule heating in the magnetosphere-ionosphere. The rate of energy dissipation is highly variable, with peak levels during geomagnetic storms and substorms. The degree to which solar wind and magnetospheric conditions control the energy dissipation processes remains one of the major outstanding questions in magnetospheric physics. A conference on Solar Wind-Magnetospheric Coupling was convened to discuss these issues and this handbook is the result.

Source record↗

NASA NTRS1992

Changes of neutral composition in the thermosphere

An overview is given of the changes in neutral composition that occur in the upper thermosphere during geomagnetic storms. Emphasis is given to solar EUV radiation, upward propagating tides and gravity waves, and coupling between magnetosphere and the ionosphere/thermosphere as the sources of the compositional changes. Present understanding of the poststorm recovery is summarized.

Burns, A. G.↗

NASA NTRS1992

Ulysses plasma observations of coronal mass ejections near 2.5 AU

The Ulysses solar wind plasma experiment observed a series of interplanetary shocks and coronal mass ejections (CMEs), the latter evidenced by counterstreaming electrons and a variety of ion signatures, during March and April 1991. A striking sequence was observed near 2.5 AU from March 23 through April 2, with the second of two counterstreaming events lasting 6.4 days. The plasma observations for these features are summarized suggesting that the second counterstreaming period may be two juxtaposed CMEs. The relationship between the events observed at Ulysses, about 60 deg east of earth in ecliptic longitude, and those causing a geomagnetic storm on March 24, is unclear.

Phillips, J. L.↗

NASA NTRS1993

The effects on the ionosphere of inertia in the high latitude neutral thermosphere

High-latitude ionospheric currents, plasma temperatures, densities, and composition are all affected by the time-dependent response of the neutral thermosphere to ion drag and Joule heating through a variety of complex feedback processes. These processes can best be studied numerically using the appropriate nonlinear numerical modeling techniques in conjunction with experimental case studies. In particular, the basic physics of these processes can be understood using a model, and these concepts can then be applied to more complex realistic situations by developing the appropriate simulations of real events. Finally, these model results can be compared with satellite-derived data from the thermosphere. We used numerical simulations from the National Center of Atmospheric Research Thermosphere/Ionosphere General Circulation Model (NCAR TIGCM) and data from the Dynamic Explorer 2 (DE 2) satellite to study the time-dependent effects of the inertia of the neutral thermosphere on ionospheric currents, plasma temperatures, densities, and composition. One particular case of these inertial effects is the so-called 'fly-wheel effect'. This effect occurs when the neutral gas, that has been spun-up by the large ionospheric winds associated with a geomagnetic storm, moves faster than the ions in the period after the end of the main phase of the storm. In these circumstances, the neutral gas can drag the ions along with them. It is this last effect, which is described in the next section, that we have studied under this grant.

Burns, Alan↗