SEARCH · Search NASA

Results for “GEOMAGNETIC EFFECT”

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.

SourceResearch connectionFrom yearThrough year

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

At least 595 records · Page 33

All sources NASA NTRS DOE OSTI

NASA NTRS1987

A model of ionospheric image structure underneath a braking, cross-field plasma jet

A plasma jetting across the geomagnetic field above the ionosphere tends to brake by ohmic dissipation of Pedersen currents. The braking can affect the ionosphere underneath if the associated Pedersen drifts are intense and prolonged enough to cause cumulative image structuring. Here, such image structuring is studied for the parameter regime of forthcoming releases from the Combined Release and Radiation Effects Satellite, involving photoionization of kilograms of barium vapor moving at orbital velocity. The resultant structuring in the upper E-region offers possible diagnostic telltales of the braking process.

Jacobson, Abram R.↗

NASA NTRS1975

Some early results from the ATS-6 radio beacon experiment

The multifrequency satellite radio beacon enables the measurement of the columnar electron content of the ionosphere and plasmasphere along the ray path and its spatial and temporal structure. Measurements include modulation phase, Faraday rotation, and amplitude. The characteristics of the beacon transmitter and its design are presented together with the design of the Boulder receiver and antennas and the calibration procedures. A shape factor F is defined which depends on the electron density and geomagnetic field distributions. It is found that F varies by about 30% from day to night. It is shown that the ratio of the plasmaspheric content to total content varies from about 0.08 during the day to about 0.35 at night. Other examples which are presented to illustrate the uses of the radio beacon include sunrise effects, solar flare enhancements of total content, and the ionospheric storms of early July 1974.

Davies, K.↗

NASA NTRS1977

Explorer 45 and Imp 6 observations in the magnetosphere of injected waves from the Siple Station VLF transmitter

Results are reported for an experiment in which VLF waves from a transmitter in Antarctica were injected into the magnetosphere along geomagnetic field lines and detected near the magnetic equatorial plane by high-altitude spacecraft. The purpose of this experiment was to conduct a controlled in situ study of VLF wave-particle interactions and to determine the propagation characteristics of the injected waves in the magnetosphere, the regions where VLF emissions are produced, and the effective volume of the magnetosphere illuminated by the transmitter. The results indicate that: (1) the bulk of the satellite receptions occurred during periods of quieting following magnetic disturbances, (2) receptions generally occurred inside the plasmapause, (3) the spacecraft detected predominantly unducted waves, (4) the injected signals could illuminate a large volume of the magnetosphere, and (5) VLF emissions were triggered by nonducted transmitter pulses.

Inan, U. S.↗

NASA NTRS1985

Enhanced growth of whistlers due to bunching of untrapped electrons

Man-made signals propagating in the whistler mode in the magnetoshere have been observed to be amplified and to trigger other VLF emissions in the absence of other detectable magnetospheric signals in ground-based recordings. The absence of other magnetospheric signals implies that the growth rate of the triggered wave is enhanced over background noise. It is shown that, for at least low amplitude triggering waves, the phase bunching of untrapped electrons can account for the observed enhanced growth. The phase bunching is initially produced by perturbations in the electron trajectories due to their interactions with the front of the wave. Due to the inhomogeneity of the geomagnetic field, the phase-bunched electrons are able to gyroresonantly interact with a later portion of the triggering wave. Because the electrons are phase bunched, the electrons can lose energy to the wave faster than phase-random electrons and are thereby able to produce enhanced growth. Plasma conditions for which this phase bunching is effective in producing enhanced growth are derived.

Winglee, R. M.↗

NASA NTRS2006

Time Serial Analysis of the Induced LEO Environment within the ISS 6A

Anisotropies in the low Earth orbit (LEO) radiation environment were found to influence the thermoluminescence detectors (TLD) dose within the (International Space Station) ISS 7A Service Module. Subsequently, anisotropic environmental models with improved dynamic time extrapolation have been developed including westward and northern drifts using AP8 Min & Max as estimates of the historic spatial distribution of trapped protons in the 1965 and 1970 era, respectively. In addition, a directional dependent geomagnetic cutoff model was derived for geomagnetic field configurations from the 1945 to 2020 time frame. A dynamic neutron albedo model based on our atmospheric radiation studies has likewise been required to explain LEO neutron measurements. The simultaneous measurements of dose and dose rate using four Liulin instruments at various locations in the US LAB and Node 1 has experimentally demonstrated anisotropic effects in ISS 6A and are used herein to evaluate the adequacy of these revised environmental models.

Wilson, John W.↗

NASA NTRS2011

The Sun, Its Extended Corona, the Interplanetary Space, the Earth's Magnetosphere, Ionosphere, Middle and Low Atmosphere, are All Parts of a Complex System - the Heliosphere

Various manifestations of solar activity cause disturbances known as space weather effects in the interplanetary space, near-Earth environment, and all the Earth's "spheres. Longterm variations in the frequency, intensity and relative importance of the manifestations of solar activity are due to the slow changes in the output of the solar dynamo, and they define space climate. Space climate governs long-term variations in geomagnetic activity and is the primary natural driver of terrestrial climate. To understand how the variable solar activity affects the Earth's environment, geomagnetic activity and climate on both short and long time scales, we need to understand the origins of solar activity itself and its different manifestations, as well as the sequence of coupling processes linking various parts of the system. This session provides a forum to discuss the chain of processes and relations from the Sun to the Earth's surface: the origin and long-term and short-term evolution of solar activity, initiation and temporal variations in solar flares, CMEs, coronal holes, the solar wind and its interaction with the terrestrial magnetosphere, the ionosphere and its connection to the neutral dominated regions below and the plasma dominated regions above, the stratosphere, its variations due to the changing solar activity and its interactions with the underlying troposphere, and the mechanisms of solar influences on the lower atmosphere on different time-scales. Particularly welcome are papers highlighting the coupling processes between the different domains in this complex system.

Gopalswamy, Natchimuthuk↗

NASA NTRS2012

What Properties of CMEs are Most Important for Space Weather?

Severe space weather is characterized by intense particle radiation from the Sun and major geomagnetic storm caused by magnetized solar plasmas arriving at Earth. Coronal mass ejections (CMEs) are key players in both these aspects. CMEs traveling at super-Alfv nic speeds drive fast-mode MHD shocks that create the high levels of particle radiation. When a CME arrives at Earth, the CME-associated magnetic fields reconnect with Earth s magnetopause fields resulting in solar plasma entry into the magnetosphere and a geomagnetic storm depending on the magnetic structure of the CME. Particle radiation starts affecting geospace as soon as the CMEs leave the Sun and the geospace may be immersed in the radiation for several days. On the other hand, the geomagnetic storm happens only upon CME arrival at Earth. The requirements for the production of particles and magnetic storms by CMEs are different in a number of respects: solar source location, CME magnetic structure, conditions in the ambient solar wind, and shock-driving ability of CMEs. Intense shocks arriving at Earth have additional space weather effects such as sudden impulse that shrinks the magnetosphere often exposing satellites in geosynchronous orbit to the solar wind and energetic storm particle events. This paper highlights these space weather effects using CME observations space and ground based instruments during of solar cycles 23 and 24.

Gopalswamy, Nat↗

DOE OSTI2026

Satellite Reentry Predictions During Sudden Stratospheric Warmings

Prediction of uncontrolled satellite reentry time and trajectory are essential to avoid damages to human being and properties over land. Reentry time and trajectory are largely controlled by aerodynamic drag and mass neutral density below 200 km. In this paper, using a numerical model of the whole atmosphere, WACCM‐X, and a Precision Orbital Determination software, we demonstrate the major sudden stratospheric warming (SSW) in January 2009, during the deep solar minimum of 2009, may cause 0.2–0.3 day of variation in reentry time. The SSW can alter the mass density and composition mixing ratio in the lower thermosphere below 200 km through changed wave forcing and general circulation in the lower thermosphere. This is comparable to the effect of a 2‐SFU (Solar Flux Unit) solar radiance variation on the neutral density. 0.1 day of reentry time uncertainty corresponds to a global shift in impact location, that is, thousands of kilometers distance. For comparison, a major SSW during solar maximum contributes little to reentry time variation, which is predominantly controlled by the solar and geomagnetic forcing. We suggest a few proxies such as O/N 2 in the lower thermosphere or mean meridional wind to account for the lower atmosphere impacts in an operational model. This needs to be investigated in rigorous future work.

54 ENVIRONMENTAL SCIENCES↗

NASA NTRS1981

Electrical coupling between the lower atmosphere and the ionosphere

The evidence for interactions between the ionosphere and troposphere is reviewed as a first step in establishing the role of electrical coupling between two regions. Upward processes appear to include the transfer of energy through gravity waves, or through the transmittance of VLF radio waves induced by lightning. In each case, the excitation of the upper atmosphere by tropospheric sources can stimulate feedback processes returning to the troposphere. Downward coupling involves changes in the global and local electrical structure of the atmosphere, and is often induced by solar activity. These effects are more direct and may possibly bypass the stratosphere. The responses in the atmospheric circuit to local changes are nearly instantaneous, and therefore are looked on with promise for possible influences on weather systems. Emerging experimental evidence indicates that atmospheric electric fields, especially at high latitudes and in the upper atmosphere, are responsive to solar and geomagnetic phenomena. Corpuscular radiations are known to strongly enhance the local atmospheric electrical conductivity and ionizations at stratospheric and mesospheric altitudes. Theories postulate that the electric field perturbations regulated by solar activity may be responsibile for the observed statistical correlations between solar activity and thunderstorms.

Goldberg, R. A.↗

NASA NTRS1991

Kinetic friction attributed to enhanced radiation by cyclotron maser instability

Along the auroral field lines, a fraction of the energetic electrons injected from the magnetotail is reflected by the earth's convergent geomagnetic field. The reflected loss-cone electrons are unstable with respect to the cyclotron maser instability, resulting in the auroral kilometric radiation. This paper investigates the kinetic friction force exerted on the energetic electrons by the enhanced radiation field. It is found that the enhanced radiation results in a deceleration of reflected electrons, thereby providing an effective resistivity. In addition, the rate of decrease (increase) of effective perpendicular (parallel) kinetic temperatures is also evaluated. The analysis is carried out over various physical parameters such as the degree of loss cone, average particle energy, and the ratio of plasma frequency to cyclotron frequency.

Yoon, Peter H.↗

NASA NTRS1995

Plasma turbulence enhanced current collection: Results from the plasma motor generator electrodynamic tether flight

The plasma motor generator (PMG) experiment, launched June 26, 1993, was a tethered system of two identical plasma contactors connected via a 500-m conducting tether. The experiment was designed to demonstrate the ability of plasma contactors to provide a low-impedance connection between a spacecraft and the ionosphere for both the electron emission and collection. The flight data indicate that plasma contactors enhance electron collection and emission by both neutralizing the electron space charge and scattering electrons across the geomagnetic field lines. Up to a 0.3 A steady current flowed along the tether in a curcuit completed through the ionosphere. An analytical model for plasma contactor interaction with a background plasma which incorporates electron scattering by plasma waves is compared with the flight data. Good agreement between the model and the data is achieved for an effective scattering frequency equal to one twentieth of the local plasma contactor plasma frequency.

Katz, I.↗

NASA NTRS1995

Large Enhancements in the O/N2 Ratio in the Evening Sector of the Winter Hemisphere During Geomagnetic Storms

In this paper, we have looked for enhancements of the O/N2 ratio in data measured by the Dynamics Explorer 2 (DE 2) satellite in the middle latitudes of the winter hemisphere, based on a prediction that was made by the National Center for Atmospheric Research thermosphere/tonosphere general circulation model (NCAR-TIGCM) that such increases occur. The NCAR-TIGCM predicts that these enhancements should be seen throughout the low latitude region and in many middle latitude locations, but that the enhancements in O/N2 are particularly strong in the middle-latitude, evening-to-midnight sector of the winter hemisphere. When this prediction was used to look for these effects in DE 2 NACS (neutral atmosphere composition spectrometer) data, large enhancements in the O/N2 ratio (approx. 50 to 90%) were seen. These enhancements were observed during the main phase of a storm that occurred on November 24, 1982, and were seen in the same region of the winter hemisphere predicted by the NCAR-TIGCM. They are partially the result of the depletion of N2 and, as electron loss is dependent on dissociative recombination at F(sub 2) altitudes, they have implications for electron densities in this area. Parcel trajectories, which have been followed through the NCAR-TIGCM history file for this event, show that large O/N2 enhancements occur in this limited region in the winter hemisphere for two reasons. First, these parcels of air are decelerated by the antisunward edge of the ion convection pattern; individual parcels converge and subsidence occurs. Thus molecular-nitrogen-poor air is brought from higher to lower heights. Because neutral parcels that are found a little poleward of the equatorial edge of the eveningside convection pattern are swept inward toward the center of the auroral oval, the enhancements occur only in a very limited range of latitudes. Second, nitrogen-poor air is transported from regions close to the magnetic pole in the winter hemisphere. During geomagnetic storms, enhanced meridional winds are driven by the increased pressure-gradient force that is associated with intensified Joule heating in the auroral oval. These pressure-driven winds decrease rapidly on the dayside beyond the auroral oval where the parcels originate, limiting the region into which the parcels can be transported. Thus these two processes drive values of O/N2 in a limited region of the winter hemisphere, and reinforce only in the evening sector, causing large changes in this region.

Burns, A. G.↗

NASA NTRS1975

The width of electron-photon cascades in air

Results of a Monte-Carlo simulation of electron-photon cascades are presented with particular emphasis on cascade lateral spread. The effects of single and multiple Coulomb scattering are represented by giving the particles suitable displacements in position and angle at each interaction point. Some of the more oblique particle tracks are first divided into a number of steps between interaction points and the scattering procedure is applied to each step separately. To represent the particle defections due the geomagnetic field, a field of 0.3 gauss is supposed present and the appropriate helical path is imposed on each particle between interaction points. The results are in good agreement with the calculations of Nordheim et al., with simulations using the Berger-Seltzer electron photon transport program and with experimental measurements in water.

Allan, H. R.↗

NASA NTRS1985

Magnetization of lower crust and interpretation of regional magnetic anomalies - Example from Lofoten and Vesteralen, Norway

During the last 20 years, studies have been conducted regarding the regional, or long-wavelength, geomagnetic anomalies of the lower crust of the earth. The present paper is mainly concerned with the petrologic and geophysical interpretation of the observed features. Attention is given to magnetic mineralogy and magnetic properties of high-grade rocks from Lofoten and Vesteralen, regional geology and geophysics, field measurements and sampling, magnetic mineralogy of the lower crust, the effects of metamorphism upon magnetic mineralogy and magnetic properties of high-grade rocks, susceptibility-temperature relations and the Hopkinson effect, and petrologic sources of regional crustal magnetic anomalies.

Schlinger, C. M.↗

NASA NTRS1987

Geomagnetic equatorial anomaly in zonal plasma flow

The observation of a geomagnetic signature in the zonal eastward plasma flow, which is a striking feature of the equatorial ionosphere in the evening quadrant is reported. These observations were derived fronm (E x B)/B-squared measurements made with the cylindrical double-floating-probe experiment carried on the Dynamics Explorer 2 satellite. The signature consists of a crest-trough-crest effect in the latitude dependence of the eastward plasma flow with the crests at + or - 8 dip latitude and the trough nearly centered at the dip equator at all geographic longitudes. This phenomenon can be readily interpreted in terms of the altitude dependence of the F region dynamo electric field, and it is related to dip equator signatures in the plasma density and the magnetic declination which have been reported earlier.

Aggson, T. L.↗

NASA NTRS1998

The Ionosphere and Upper Atmosphere

Because our society is becoming increasingly dependent on technological systems that can be affected by ionospheric phenomena during geomagnetic storms, the ionosphere, its electrodynamics, and its coupling with the neutral atmosphere and the magnetosphere are being studied as part of a coordinated program of "space weather" research. This research seeks to characterize the variability of ionospheric density and electric currents during magnetic storms, and to determine to what extent valid predictions of those phenomena and their effects can be made.

Richmond, A. D.↗

NASA NTRS2017

Geomagnetically Induced Currents: Science, Engineering, and Applications Readiness

This paper is the primary deliverable of the very first NASA Living With a Star Institute Working Group, Geomagnetically Induced Currents (GIC) Working Group. The paper provides a broad overview of the current status and future challenges pertaining to the science, engineering, and applications of the GIC problem. Science is understood here as the basic space and Earth sciences research that allows improved understanding and physics-based modeling of the physical processes behind GIC. Engineering, in turn, is understood here as the ''impact'' aspect of GIC. Applications are understood as the models, tools, and activities that can provide actionable information to entities such as power systems operators for mitigating the effects of GIC and government agencies for managing any potential consequences from GIC impact to critical infrastructure. Applications can be considered the ultimate goal of our GIC work. In assessing the status of the field, we quantify the readiness of various applications in the mitigation context. We use the Applications Readiness Level (ARL) concept to carry out the quantification.

Geomagnetically induced currents↗

NASA NTRS1980

Comparison of NASCAP modelling results with lumped circuit analysis

Engineering design tools that can be used to predict the development of absolute and differential potentials by realistic spacecraft under geomagnetic substorm conditions are described. Two types of analyses are in use: (1) the NASCAP code, which computes quasistatic charging of geometrically complex objects with multiple surface materials in three dimensions; (2) lumped element equivalent circuit models that are used for analyses of particular spacecraft. The equivalent circuit models require very little computation time, however, they cannot account for effects, such as the formation of potential barriers, that are inherently multidimensional. Steady state potentials of structure and insulation are compared with those resulting from the equivalent circuit model.

Stang, D. B.↗