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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.

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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS2024

Preface to the Special Issue on Modeling and Data Analysis Methods for the SMILE mission

The SMILE (Solar wind Magnetosphere Ionosphere Link Explorer) project (http://www.nssc.cas.cn/smile/, https://www.cosmos.esa.int/web/smile/mission) is a joint spacecraft mission of the European Space Agency (ESA) and the Chinese Academy of Sciences (CAS) with an expected launch in 2025. SMILE aims to study the global interactions of solar wind–magnetosphere–ionosphere innovatively by imaging the Earth’s magnetosheath and cusps in soft X-rays and the northern auroral region in ultraviolet (UV) while simultaneously measuring plasma and magnetic field parameters in the solar wind and magnetosheath along a highly-elliptical and highly-inclined orbit. This special issue is composed of 22 articles, presenting recent progress in modeling and data analysis techniques developed for the SMILE mission. In this preface, we categorize the articles into the following seven topics and provide brief summaries: (1) instrument descriptions of the Soft X-ray Imager (SXI), (2) numerical modeling of the X-ray signals, (3) data processing of the X-ray images, (4) boundary tracing methods from the simulated images, (5) physical phenomena and a mission concept related to the scientific goals of SMILE-SXI, (6) studies of the aurora, and (7) ground-based support for SMILE.

SMILE↗
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 NTRS1978

Research on solar-wind and magnetospheric electric fields and plasmas

Attempts were made to determine the role of the interplanetary magnetic field in controlling: (1) particle acceleration processes in the earth's polar cap; (2) plasma convection patterns at high latitudes; and, (3) the topology of magnetic field lines in the earth's polar cusps. The primary result of the study on polar-cap particle acceleration regions was that they tend to occur in only one polar cap at a time, and that they occur in the hemisphere for which the magnetospheric tail-lobe field lines have solar-magnetospheric x components that are antiparallel to those of the interplanetary and tail-lobe magnetic field. Southward-directed interplanetary magnetic fields give rise to broad convection throats which cover several hours of local time across the dayside cleft. Under such conditions, solar-wind plasma is channeled efficiently through the polar cusps to populate the plasma mantle and dayside boundary layer. On the other hand, the appearance of strong northward components in the interplanetary magnetic field result in a very constricted throat, resulting in inefficient plasma entry at the cusps by diffusion processes.

Burch, J. L.↗
NASA NTRS1978

Effects of the solar wind on magnetospheric dynamics: Energetic electrons at the synchronous orbit

A correlation of the observations of energetic electron fluxes at the synchronous orbit with the interplanetary medium and the behavior of energetic trapped radiation at the synchronous altitude were analyzed. Data covering the 1967 to 1978 interval were obtained by the ATS 1, ATS 5, and ATS 6 spacecraft. Long term (year) and short term (days) electron flux averages are found to correlate positively with corresponding averages of the solar wind velocity.

Paulikas, G. A.↗
NASA NTRS1986

Quantitative model of magnetic coupling between solar wind and magnetosphere

Preliminary results are presented of a quantitative three-dimensional model of an open steady-state magnetosphere configuration incorporating a normal-component distribution corresponding to the subsolar merging-line hypothesis. The distribution of the normal magnetic-field component at the magnetopause is used as input and is used to calculate an interconnection magnetic field that links the internal and external fields. The interconnected field is then used to map the solar-wind electric field onto the polar cap. The resulting polar-cap flow patterns are found to be in agreement with observations.

Toffoletto, F. R.↗
NASA NTRS1987

Numerical simulation of solar wind and magnetospheric phenomena

The nature of the nonlinear evolution of Kelvin-Helmholtz instability in the presence of sheared magnetic fields was investigated via numerical simulation. Models of the magnetosheath-magnetopause boundary in earth's tail and stream interaction regions in the inner heliosphere were studied. The development of the instability is influenced strongly by the orientation and magnitude of the magnetic field. Large vortical structures that resemble observations in the earth's tail can form while other cases generate turbulent spectra that provide insight into the generation of Alfven turbulence in the solar wind.

Goldstein, Melvyn L.↗
NASA NTRS1986

Acceleration of charged particles in magnetic reconnection Solar flares, the magnetosphere, and solar wind

A possible source of free energy available for accelerating charged particles is conversion of magnetic energy to particle energy in reconnecting magnetic fields. Recent simulations using test particles suggests that reconnection may efficiently accelerate particles to the maximum energies that are observed in several astrophysical contexts. A simple analytic formula is used in conjunction with the simulation results to predict the maximum energy achievable in a particular plasma environment with the result that in solar flares reconnection is capable of accelerating particles to several GeV. In magnetospheric substorms the predicted maximum can reach several hundred keV, and near magnetic sector crossings in the solar wind the maximum energy can approach 100 keV.

Goldstein, M. L.↗
DOE OSTI2024

Estimating Interplanetary Magnetic Field Conditions at Mercury's Orbit From MESSENGER Magnetosheath Observations Using a Feedforward Neural Network

Abstract Mercury's small magnetosphere is embedded in the dynamic and intense solar wind environment characteristic of the inner heliosphere. Both the magnitude and orientation of the interplanetary magnetic field (IMF) significantly influence the solar wind‐magnetospheric interaction at Mercury, driving phenomena such as magnetic reconnection. The MErcury Surface, Space Environment, Geochemistry and Ranging (MESSENGER) spacecraft provided in‐situ magnetic field measurements of the solar wind, the magnetosheath, and the magnetosphere along each orbit. However, it is a challenge to directly assess the IMF's impact on Mercury's plasma environment due to the temporal separation between observations within the solar wind and the magnetosphere, especially in the absence of an upstream monitor. Here, we present a feedforward neural network (FNN) trained on a subset of magnetosheath observations to estimate the strength and orientation of the IMF upstream of the bow shock. Utilizing magnetosheath magnetic field, cylindrical spatial coordinates, and heliocentric distance measurements, the FNN predicts upstream IMF conditions with an score of 0.70 and mean averaged error of 5.3 nT, thereby greatly decreasing the temporal separation between IMF estimates and magnetospheric measurements throughout the MESSENGER mission. This approach yields IMF estimates for all magnetosheath data measured by MESSENGER, providing a useful tool for future investigations of the IMF impact on Mercury's magnetosphere. This method will be integrable with the dual‐spacecraft BepiColombo magnetosheath measurements, providing useful estimates of upstream IMF conditions particularly during the extended periods in which neither spacecraft sample the solar wind. Our results demonstrate the utility of machine learning techniques on advancing space science research.

Bowers, Charles F.↗
NASA NTRS1990

Solar wind dynamic pressure variations: Quantifying the statistical magnetospheric response

Solar wind dynamic pressure variations are common and have large amplitudes. Existing models for the transient magnetospheric and ionospheric response to the solar wind dynamic pressure variation are quantified. The variations drive large amplitude (approx 1 R sub E) magnetopause motion with velocities of approx. 60 km/s and transient dayside ionospheric flows of 2 km/s which are organized into double convection vortices. Ground magnetometer signatures are more pronounced under the auroral ionosphere, where they reach 60 to 300 nT, and under the equatorial electrojet. A statistical comparison of transient ground magnetometer events seen at a South Pole station and geosynchronous orbit indicates that all but the weakest ground events are associated with clear compressional signatures at the dayside geosynchronous orbit.

Sibeck, D. G.↗
NASA NTRS1965

Plasma and space physics

Continuum plasma dynamics, and properties of corona, solar wind, magnetosphere, and transition region

SOLAR WIND↗
NASA NTRS1981

Research on solar-wind and magnetospheric electric fields and plasmas

The phenomena of particle preciptation and ion convection at high latitudes and their response to variations in the interplanetary magnetic field. Data from the low energy electron experiment and the retarding potential analyzer drift meter on Atmosphere Explorers C and D were analyzed. Additional data from the spacecraft Imp-J were utilized.

Burch, J. L.↗
NASA NTRS1984

Anomalous transport by magnetohydrodynamic Kelvin-Helmholtz instabilities in the solar wind-magnetosphere interaction

The high latitude, or downstream flank, and dayside low latitude magnetospheric boundaries are modeled in an MHD simulation of Kelvin-Helmholtz instablities in a compressible plasma for parallel and transverse configurations. Detailed attention is given to the nonlinear consequences of the instabilities for several different Alfven and sound Mach numbers in both configurations. Emphasis is given to the anomalous transport of momentum and energy by the Kelvin-Helmholtz instabilities across the magnetospheric boundary, which is crucial in evaluating the instabilities' contribution to magnetospheric convection. It is concluded that the anomalous tangential stress at the magnetospheric boundary caused by the instability may be of the order of 1 percent of the magnetosheath flow momentum adjacent to the boundary, and gives a contribution to the convection potential drop over the polar cap of 10-30 kV.

Miura, A.↗