Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “MAGNETOSPHERE”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Recent advancements and remaining challenges associated with inner magnetosphere cross-energy/population interactions (IMCEPI)

The geospace inner magnetosphere, within about ten Earth radii, contains various plasma populations with energy from a few eV to MeV and plays important roles in regulating the energy density of the magnetosphere, the magnetic field configuration, and wave dynamics. As an integrated part of the magnetosphere, the inner magnetosphere region also ties to other regions and can change the global geospace circulation. Therefore understanding both internal and external cross–energy/population interactions can help further our knowledge of the inner magnetosphere dynamics and non–linear feedback processes. In view of this, in the past five years (2014–2018), the GEM Focus Group (FG) “Inner magnetosphere cross–energy/population interactions (IMCEPI)” has gathered and boosted community–wide interactions among observation, simulation and modeling studies. As a result, this commentary reports some major accomplishments of the interactive inner magnetosphere community that were advanced by the IMCEPI FG discussions and layouts remaining challenges that need to be carried on.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
NASA NTRS2022

The Transmission of ULF Waves From the Solar Wind to the Magnetosphere: An Analysis of Some Critical Aspects

Several critical aspects may influence the analysis of the relationship between the solar wind (SW) and magnetospheric fluctuations, for example, the characteristics and frequency of SW fluctuations that are expected to impinge the magnetosphere may not be the same when they are observed by spacecraft located at different places in front of the magnetosphere; similarly, the choice of analytical methods adopted for the spectral analysis might influence the frequency estimate (as well as the wave identification itself) both in the SW and magnetosphere. Focusing our attention on these aspects, we present an analysis of SW compressional fluctuations (f ≈ 1–5 mHz), following two interplanetary shocks observed by two interplanetary spacecraft, regarded as two different situations in terms of spacecraft separation and distance from the magnetosphere. Our results show that some differences in the characteristics of SW fluctuations emerge when the same stream is observed at different places and confirm the critical role of analytical methods in determining fluctuation characteristics. We compared aspects of SW fluctuations with those of magnetospheric fluctuations following the sudden impulses due to the impact of interplanetary shocks. For this scope, we examined observations by two satellites at geostationary orbit and at several ground-based stations. We found that the magnetospheric fluctuations were related to compressional SW fluctuations approximately at the same frequencies, with no evidence for wave activity of internal origin or directly driven by the shock impact.

ULF waves↗
NASA NTRS1971

Convective motion and the structure of the Jupiter magnetosphere

The convective motion and its relation to the electric field in the magnetosphere of Jupiter are investigated. It is shown that the electric field is induced in the Jovian ionosphere due to the corotating action of the ionospheric gases and further is communicated into the magnetosphere along the magnetic lines of force which connect between the ionosphere and the magnetosphere. This electric field drives the plasma to corotate with the planet in the magnetosphere. The distribution of the electric field and its effect on the plasma motion is estimated in the magnetosphere. The shape of the magnetosphere is then estimated considering the equilibrium condition. Discussion is given on the equilibrium plasma distribution in the magnetosphere and on the condition for the excitation of wave-particle interaction at the Io orbit.

Sakurai, K.↗
NASA NTRS1974

The aurora and the magnetosphere - The Chapman Memorial Lecture

Review of recent progress in magnetospheric physics, in particular, in understanding the magnetospheric substorm. It is shown that a number of magnetospheric phenomena can now be understood by viewing the solar wind-magnetosphere interaction as an MHD dynamo; auroral phenomena are powered by the dynamo. Also, magnetospheric responses to variations of the north-south and east-west components of the interplanetary magnetic field have been identified. The magnetospheric substorm is entirely different from the responses of the magnetosphere to the southward component of the interplanetary magnetic field. It may be associated with the formation of a neutral line within the plasma sheet and with an enhanced reconnection along the line. A number of substorm-associated phenomena can be understood by noting that the new neutral line formation is caused by a short-circuiting of a part of the magnetotail current.

Akasofu, S.-I.↗
NASA NTRS1974

The solar wind and magnetospheric dynamics

The dynamic processes involved in the interaction between the solar wind and the earth's magnetosphere are reviewed. The evolution of models of the magnetosphere is first surveyed. The existence of the auroral substorm and the cyclical polar magnetic substorm is evidence that the magnetosphere is a dynamic system. The dynamic changes occurring in the magnetosphere, including erosion of the magnetopause, changes in the size of the polar cap, variations in the flaring angle of the tail, neutral point formation, plasma sheet motions, and the inward collapse of the midnight magnetosphere, are discussed. The cyclical variations of geomagnetic activity are explained in terms of the control of the solar wind-magnetosphere interaction by the north-south component of the interplanetary magnetic field. Present phenomenological models allow prediction of geomagnetic activity from interplanetary measurements, but modeling of detailed magnetospheric processes is still in its infancy.

Russell, C. T.↗
NASA NTRS1976

Jupiter's magnetic field and magnetosphere

The Jovian magnetosphere is described on the basis of observations made by vector helium magnetometers aboard Pioneers 10 and 11. The results obtained from the two encounters are combined without emphasizing details peculiar to either of them. It is shown that near the planet, Jupiter's field is that of an eccentric tilted dipole with some admixture of higher-order terms; in this respect, it is similar to the earth's field, although it is 10 times as strong and has the opposite polarity. The magnetic field measurements reveal the existence of 3 distinct regions within the magnetosphere: outer magnetosphere, inner magnetosphere, and middle magnetosphere. The properties of these three regions are discussed, with observations being explained in terms of plausible physical causes. The observations are compared with several large-scale models of the entire magnetosphere. These observations do not favor models based on the continual outflow or convection of plasma from the Jovian magnetosphere in the vicinity of the equator.

Smith, E. J.↗
NASA NTRS1977

Global problems in magnetospheric plasma physics and prospects for their solution

Selected problems in magnetospheric plasma physics are critically reviewed. The discussion is restricted to questions that are 'global' in nature (i.e., involve the magnetosphere as a whole) and that are beyond the stage of systematic survey or isolated study requirements. Only low-energy particle aspects are discussed. The article focuses on the following subjects: (1) the effect of the interplanetary magnetic field on the topography, topology, and stability of the magnetospheric boundary; (2) solar-wind plasma entry into the magnetosphere; (3) plasma storage and release mechanisms in the magnetospheric tail; and (4) magnetic-field-aligned currents and magnetosphere-ionosphere interactions. A brief discussion of the prospects for the solution of these problems during and after the International Magnetospheric Study is given.

Roederer, J. G.↗
NASA NTRS1979

The electric field and global electrodynamics of the magnetosphere

The conception of the electrodynamics of the quiet-time magnetosphere obtained during the last four years of magnetospheric study is presented. Current understandings of the open magnetosphere, convective plasma flows in the plasma sheet, the shielding of the inner magnetosphere from the convective magnetospheric electric field, the space charge produced when injected electrons drift towards dawn and injected ions drift towards dusk, the disruption of the flow of the Birkeland current by plasma instabilities and the shielding of the convective electric field by the dayside magnetopause are discussed. Attention is also given to changes of magnetic field line topology magnetic storms and substorms. Unresolved questions and new tools which may play a role in the further understanding of magnetospheric electrodynamics and the role of the magnetospheric electric field are presented.

Stern, D. P.↗
NASA NTRS1981

Energy coupling between the solar wind and the magnetosphere

A description is given of the path leading to the first approximation expression for the solar wind-magnetosphere energy coupling function (epsilon), which correlates well with the total energy consumption rate (U sub T) of the magnetosphere. It is shown that epsilon is the primary factor controlling the time development of magnetospheric substorms and storms. The finding of this particular expression epsilon indicates how the solar wind couples its energy to the magnetosphere; the solar wind and the magnetosphere make up a dynamo. In fact, the power generated by the dynamo can be identified as epsilon through the use of a dimensional analysis. In addition, the finding of epsilon suggests that the magnetosphere is closer to a directly driven system than to an unloading system which stores the generated energy before converting it to substorm and storm energies. The finding of epsilon and its implications is considered to have significantly advanced and improved the understanding of magnetospheric processes.

Akasofu, S.-I.↗
NASA NTRS1982

Planetary magnetospheres - The in situ astrophysical laboratories

Descriptions of the behavior, mechanisms, and effects of the magnetospheres of the inner six planets of the solar system are presented. The components of the earth's magnetosphere are detailed, including mention of the field-aligned current connecting the ionosphere of the earth to the magnetosphere, which is a situation in which a current travels along a magnetic field line. Similarities and differences are noted for known aspects of the magnetospheres of Venus, Mars, and Mercury, with the solar wind-planet interactions being modeled by gas dynamic calculations. Particular attention is given to the Jupiter magnetosphere as analog for the magnetospheres of astrophysical objects. Voyager 1 and 2 data are cited for evidence of upstream ion increases originating from the Jovian magnetosphere. Finally, the mechanisms of the Io plasma torus are examined.

Krimigis, S. M.↗
NASA NTRS1983

The magnetosphere of Saturn

Characterizations of the Saturn magnetospheric activities that have been made possible through data gathered by means of the Pioneer 11 and Voyagers 1 and 2 flybys are reviewed. The spacecraft data confirmed the presence of a Saturn magnetosphere, which features inward diffusion and energization of trapped energetic particles as well as cosmic ray albedo neutron decay as a source of inner belt protons. A dense plasma was identified in the region covering the outer magnetosphere to the magnetopause, which extends outward 17.3-23.6 Saturn radii on the sunward side and from 30.3-70 radii on the far side, according to the satellite measurements. Characteristics of the particle populations and behaviors of the outer magnetosphere, the slot region, the inner magnetosphere, and the ring region are reviewed, as are those of the magnetic field, the solar wind-magnetospheric interaction, and the Titan-magnetospheric interaction are described. Further investigation of the longitudinal asymmetry of decimetric radio emissions from Saturn is recommended.

Schardt, A. W.↗
NASA NTRS1983

Modeling planetary magnetospheres

Recent advances in the development of models of the macroscopic properties of the terrestrial and planetary magnetospheres are reviewed. Particular attention is given to work on semiempirical models of magnetic and electric fields in the earth's magnetosphere, the modeling of magnetospheric storms and substorms in the inner magnetosphere, and the self-consistent modeling of processes in the magnetotail, including reconnection. Magnetohydrodynamic models of the dayside magnetosphere and the magnetotail which are based on calculations of the interaction of the solar wind with the magnetosphere are also considered. Finally, work on the modeling of the magnetospheres of Mercury, Venus, Jupiter, Saturn and Uranus is presented.

Walker, R. J.↗
NASA NTRS1984

Active experiments in the distant magnetosphere - The AMPTE program

The Active Magnetospheric Particle Tracer Explorers (AMPTE) program consists of three spacecraft that will be launched to inject tracer ions (lithium and barium) inside and outside the earth's magnetosphere and to detect and monitor these ions as they convect and diffuse through the inner magnetosphere. The principal objectives of the program are: (1) to investigate the transfer of mass from the solar wind to the magnetosphere and its further transport and energization within the magnetosphere; (2) to study the interaction between artificially injected and cosmical plasmas; (3) to establish the elemental and charge composition and dynamics of the charged particle population in the magnetosphere over a broad energy range; and (4) to explore further the structure and dynamics of ambient plasmas in the magnetosphere. The implementation of the above objectives is discussed, with emphasis placed on the tracer aspect of the program.

Krimigis, S. M.↗
NASA NTRS1984

Boundary layers of the earth's outer magnetosphere

The magnetospheric boundary layer and the plasma-sheet boundary layer are the primary boundary layers of the earth's outer magnetosphere. Recent satellite observations indicate that they provide for more than 50 percent of the plasma and energy transport in the outer magnetosphere although they constitute less than 5 percent by volume. Relative to the energy density in the source regions, plasma in the magnetospheric boundary layer is predominantly deenergized whereas plasma in the plasma-sheet boundary layer has been accelerated. The reconnection hypothesis continues to provide a useful framework for comparing data sampled in the highly dynamic magnetospheric environment. Observations of 'flux transfer events' and other detailed features near the boundaries have been recently interpreted in terms of nonsteady-state reconnection. Alternative hypotheses are also being investigated. More work needs to be done, both in theory and observation, to determine whether reconnection actually occurs in the magnetosphere and, if so, whether it is important for overall magnetospheric dynamics.

Eastman, T. E.↗
NASA NTRS1991

Report of the magnetospheric physics panel

Magnetospheric research is a relatively new area in the study of the Earth's environment. The present report attempts to overview past and future research on this topic. The goals of magnetospheric research are numerous, and include: understanding large scale magnetospheres of the Earth and other planets; understanding the plasma physical processes operating within the various magnetospheres; to understand how mass, energy and momentum are transmitted from the solar wind; to understand quantitatively the coupling between magnetospheres and their ionospheres; and to understand the magnetospheric mechanisms which accelerate particles to high energies, as well as the ultimate fate of these particles. The report continues on to summarize a number of proposed space missions aimed at data acquisition. Finally, there is a brief discussion of the theory and modeling of magnetospheres.

Burch, James L.↗
NASA NTRS1993

Modeling of the coupled magnetospheric and neutral wind dynamos

The solar wind interaction with the earth's magnetosphere generates electric fields and currents that flow from the magnetosphere to the ionosphere at high latitudes. Consequently, the neutral atmosphere is subject to the dissipation and conversion of this electrical energy to thermal and mechanical energy through Joule heating and Lorentz forcing. As a result of the mechanical energy stored within the neutral wind (caused in part by Lorentz--and pressure gradient--forces set up by the magnetospheric flux of electrical energy), electric currents and fields can be generated in the ionosphere through the neutral wind dynamo mechanism. At high latitudes this source of electrical energy has been largely ignored in past studies, owing to the assumed dominance of the solar wind/magnetospheric dynamo as an electrical energy source to the ionosphere. However, other researchers have demonstrated that the available electrical energy provided by the neutral wind is significant at high latitudes, particularly in the midnight sector of the polar cap and in the region of the magnetospheric convection reversal. As a result, the conclusions of a number of broad ranging high-latitude investigations may be modified if the neutral-wind contribution to high-latitude electrodynamics is properly accounted for. These include the following: studies assessing solar wind-magnetospheric coupling by comparing the cross polar cap potential with solar wind parameters; research based on the alignment of particle precipitation with convection or field aligned current boundaries; and synoptic investigations attributing seasonal variations in the observed electric field and current patterns to external sources. These research topics have been initiated by satellite and ground-based observations and have been attributed to magnetospheric causes. However, the contribution of the neutral wind to the high-latitude electric field and current systems and their seasonal and local time dependence has yet to be quantitatively evaluated. In this program, we are evaluating the coupled magnetospheric and neutral wind dynamos at high latitudes under various conditions. In addition to examining the impact of seasonal variations, we are investigating the consequences of the separate dynamos having pure current-source or voltage-source behaviors.

Thayer, Jeff P.↗
NASA NTRS2008

MESSENGER: Exploring Mercury's Magnetosphere

The MESSENGER mission to Mercury offers our first opportunity to explore this planet's miniature magnetosphere since Mariner 10's brief fly-bys in 1974-5. Mercury's magnetosphere is unique in many respects. The magnetosphere of Mercury is the smallest in the solar system with its magnetic field typically standing off the solar wind only - 1000 to 2000 km above the surface. For this reason there are no closed dri-fi paths for energetic particles and, hence, no radiation belts; the characteristic time scales for wave propagation and convective transport are short possibly coupling kinetic and fluid modes; magnetic reconnection at the dayside magnetopause may erode the subsolar magnetosphere allowing solar wind ions to directly impact the dayside regolith; inductive currents in Mercury's interior should act to modify the solar In addition, Mercury's magnetosphere is the only one with its defining magnetic flux tubes rooted in a planetary regolith as opposed to an atmosphere with a conductive ionosphere. This lack of an ionosphere is thought to be the underlying reason for the brevity of the very intense, but short lived, approx. 1-2 min, substorm-like energetic particle events observed by Mariner 10 in Mercury's magnetic tail. In this seminar, we review what we think we know about Mercury's magnetosphere and describe the MESSENGER science team's strategy for obtaining answers to the outstanding science questions surrounding the interaction of the solar wind with Mercury and its small, but dynamic magnetosphere.

Slavin, James A.↗
NASA NTRS2009

MESSENGER Observations of Mercury's Dynamic Magnetosphere

MESSENGER's 14 January and 6 October 2008 encounters with Mercury have provided new measurements dynamic variations in the coupled atmosphere magnetosphere system. The two flybys took place under very different interplanetary magnetic field (IMF) conditions. The northward IMF during the first encounter produced a very quiet, stable magnetosphere. Neutral sodium atoms and photo-ions were observed to high altitudes ; > 2000 km, even in the subsolar region demonstrating the important role played by more energetic neutral atom production processes such as sputtering. Consistent with predictions of magnetospheric models for northward IMF, the neutral atmosphere was observed to have its strongest sources in the high latitude northern hemisphere for the first flyby. The southward IMF for the second encounter revealed a highly dynamic magnetosphere. Reconnection between the interplanetary and planetary magnetic fields is known to control the rate of energy transfer from the solar wind and to drive magnetospheric convection. The MESSENGER magnetic field measurements revealed that the rate at which interplanetary magnetic fields were reconnecting to planetary fields was a factor of 10 greater than is usually observed at Earth. This extremely high reconnection results in a large magnetic field component normal to the magnetopause and the formation of flux transfer events that are much larger relative to the size of the forward magnetosphere than is observed at Earth. The resulting magnetospheric configuration allows the solar wind access to much of the dayside surface of the Mercury. This widespread impingement of the solar wind on Mercury's surface is a likely source of the less structured sodium exosphere imaged during the second flyby and quite possibly the high degree of exospheric temporal variability observed by ground-based telescopes.

Slavin, James A.↗