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Results for “MAGNETIC FIELD DISTURBANCE”

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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

The magnetosphere of Mercury

Data on Mercury's magnetosphere and on the plasma, planetomagnetic, and energetic particle environment of the planet obtained in three encounters (Mariner 10 flybys) are compared, and tasks for future research are outlined. The Mercury bow shock and magnetopause are much closer to the planet than the earth counterparts are to the earth. The magnetotail with embedded plasma sheet-field reversal region, global deflection of the solar wind by an intrinsic dipolar magnetic field, variations in solar wind momentum flux, and absence of such features as ionosphere, plasmasphere, and radiation belts, are described. Energetic electrons are accelerated in the magnetotail, however, and the interplanetary magnetic field variations distort Mercury's magnetosphere to produce a southward field associated with substorm-like disturbances.

Ness, N. F.↗
NASA NTRS1997

CO and the Temperature Structure of the Solar Atmosphere

The surface layers of the Sun provide a crucial boundary condition for many of the processes that occur in the deep interior. The stratification of the outer solar atmosphere once was thought to be well understood. However, studies of thermally sensitive molecular absorptions in the infrared revealed puzzling anomalies. Strong lines of the CO fundamental vibration-rotation bands near 5 microns showed very cool temperatures at the extreme limb, and remarkable off-limb emissions extending well into the supposedly hot chromosphere. The conflicting pictures of the photosphere/chromosphere interface, from the widely separated wavelength regimes, has raised suspicions that those "layers" of the atmosphere are much more inhomogeneous than previously suspected. One proposal is that the low chromosphere is dominated by cool gas--the "COmosphere," if you will--which is threaded by a network of persistent small-scale hot magnetic filaments and occasionally disrupted by localized acoustic disturbances. The COmosphere is capped by the merged fields of the network elements in the chromospheric "canopy." I will describe the evidence in favor of that model, including recent work at the NSO McMath-Pierce telescope (including use of the new "Phoenix" spectrometer) and translimb far-UV spectroscopy by SOHO/SUMER.

Ayres, Thomas R.↗
DOE OSTI2025

Magnetohydrodynamic simulations preliminarily predict the habitability and radio emission of TRAPPIST-1e

TRAPPIST-1e, an Earth-sized exoplanet in the habitable zone of the nearby M dwarf TRAPPIST-1, may experience magnetospheric responses that vary with stellar space weather, which could potentially influence both its habitability and radio emissions. Our objective is to investigate how different Earth-like magnetospheric configurations of TRAPPIST-1e – specifically variations in dipolar magnetic field strength and axial tilt – respond to diverse stellar space weather conditions, including events analogous to coronal mass ejections (CMEs), and to assess their implications for potential habitability and expected radio emissions. We conducted 3D magnetohydrodynamic simulations of the TRAPPIST-1e system using the PLUTO code in spherical coordinates. The planetary magnetic field was modelled as dipolar, with equatorial strengths from Earth-like to several times stronger. The dipole axis spans a representative range of axial tilts. We investigate four stellar wind environments, from sub-Alfvénic flow to CME-like disturbances. Planetary shielding was quantified based on the magnetopause standoff distance, and radio powers were estimated via empirical scaling laws. Our simulations show that both shielding and radio power depend strongly on the magnetic configuration. Stronger fields increase protection, while larger tilts reduce it. Radio power increases with both field strength and tilt across all wind regimes. An Earth-like magnetic field can provide effective shielding even under intense CMEs, whereas high tilts require stronger fields. Predicted radio powers reach ~10 20 erg s −1 during CMEs, making bursts from close-in, magnetised planets more detectable. However, for TRAPPIST-1e, the maximum cyclotron frequency lies below the Earth’s ionospheric cutoff (~10 MHz), making ground-based detection currently infeasible.

Sun: magnetic fields↗
NASA NTRS1980

Rocket observations at the northern edge of the eastward electrojet

The paper discusses a Nike-Tomahawk rocket launched north over quiet, late evening auroral arcs in March 1975. A northward magnetic disturbance was observed on the ground under the rocket trajectory; south of the arcs the northward electric field was 60 mV/m, indicating strong westward plasma flow. An eastward electrojet current layer was penetrated in the upward flight, and precipitating electrons were observed over each arc. Using the observed electron flux and a model of the ionosphere, the Hall and Pedersen conductivities were calculated which were used to compute the eastward and northward components of the horizontal ionospheric currents. The joule power decreased abruptly in the auroral arcs, as the precipitating electron power increased; the total dissipated power was the same inside the arcs, between them and southward. North of the aurora the electric field and dissipated power remained low; field-aligned currents carried by the observed electrons were about a factor of 3 lower than those inferred from the magnetic field measurements.

Cahill, L. J., Jr.↗
NASA NTRS1989

Fast Fermi acceleration in the plasma sheet boundary layer

A longstanding question in the field of magnetospheric physics is the source of the energetic particles which are commonly observed along the plasma-sheet boundary layer (PSBL). Several models have been suggested for the acceleration of these particles. Here, a means is suggested by which the fast Fermi acceleration mechanism (Wu, 1984) can accelerate electrons at the plasma sheet and perhaps account for some of the observations. In this scheme, a localized hydromagnetic disturbance propagating through the tail lobe region impinges upon the PSBL, deforming it and displacing it in toward the central plasma sheet. The boundary layer can then act like a moving magnetic mirror. If the disturbance is propagating nearly perpendicular to the layer, then its velocity projected parallel to the layer (and the magnetic field) can be very large, resulting in significant acceleration of reflected particles.

Wu, C. S.↗
NASA NTRS2022

The Imprint of Intermittent Interchange Reconnection on the Solar Wind

The solar wind is known to be highly structured in space and time. Observations from Parker Solar Probe have revealed an abundance of so-called magnetic switchbacks within the near-Sun solar wind. In this Letter, we use a high-resolution, adaptive-mesh, magnetohydrodynamics simulation to explore the disturbances launched into the solar wind by intermittent/bursty interchange reconnection and how they may be related to magnetic switchbacks. We find that repeated ejection of plasmoid flux ropes into the solar wind produces a curtain of propagating and interacting torsional Alfvénic waves. We demonstrate that this curtain forms when plasmoid flux ropes dynamically realign with the radial field as they are ejected from the current layer and that this is a robust effect of the 3D geometry of the interchange reconnection region. Simulated flythroughs of this curtain in the low corona reveal an Alfvénic patch that closely resembles observations of switchback patches, but with relatively small magnetic field deflections. Therefore, we suggest that switchbacks could be the solar wind imprint of intermittent interchange reconnection in the corona, provided an in situ process subsequently amplifies the disturbances to generate the large deflections or reversals of radial field that are typically observed. That is to say, our results indicate that a combination of low-coronal and inner-heliospheric mechanisms may be required to explain switchback observations.

corona↗
NASA NTRS1976

The triggering and subsequent development of a solar flare

A solar flare which occurred on Sept. 5, 1973, is discussed on the basis of high temporal and spatial resolution pictures taken with the Skylab S-056 X-ray telescope. The temporal evolution of the flare is outlined, and magnetic-field data for the active region are compared with the soft X-ray observations. A close similarity between calculated magnetic-field lines and the overall structure of the X-ray core is shown to suggest that the flare occurred in an entire arcade of loops rather than in a single loop. Sequential brightening of different X-ray features is taken as an indication that some triggering disturbance moved from one side to the other in the flare core at velocities of 180 to 280 km/s. The two most intense X-ray features were found in places where the magnetic field composing the arcade had a small radius of curvature with horizontal field gradients higher than the surrounding area and where the axis of the arcade changed direction. It is suggested that a magetosonic wave triggered the energy releases as it propagated down the arcade and steepened the field gradients

Vorpahl, J. A.↗
NASA NTRS1989

On the relation between the electron content of the ionospheric D-region, variations of the riometer absorption, and the H-component of the geomagnetic field

The correlation between lower ionosphere disturbances, geomagnetic variations and radiowave absorption is an important geophysical problem. The correlation is investigated between the electron density profile structure and riometer absorption, and between the absorption and the H-component magnetic field, in order to determine the relation between the (e)-profile parameters and the geomagnetic field variations.

Zelenkova, L. V.↗
NASA NTRS1978

A magnetohydrodynamic theory for the lunar response to time variations in a spatially uniform ambient magnetic field

An analytic theory based on principles of magnetohydrodynamics is derived for interpreting the lunar magnetic response to magnetic field fluctuations in the lobes of the geomagnetic tail. Only the case of magnetic perturbations parallel to a spatially uniform ambient magnetic field is treated. The theoretical frequency-dependent MHD transfer function depends on both the lunar electrical conductivity profile and the Alfven speed of the tail lobe plasma. For circular frequencies much less than the Alfven speed/lunar radius, the MHD transfer function reduces to the vacuum transfer function, while at higher frequencies the finite propagation speed of magnetic disturbances affects the response. These characteristics of the MHD transfer function are in qualitative agreement with observation. A carefully selected set of magnetic field transient events could be used together with this theory to infer lunar electrical conductivity profiles and the tail lobe plasma density (via its dependence on the Alfven speed).

Hood, L. L.↗
NASA NTRS1963

ROTATION OF THE MAGNETOSPHERE

Two topological geomagnetic field models of rotating magnetosphere interactions, with the solar wind and its effects on magnetic and auroral disturbances

GEOMAGNETIC STORM↗
NASA NTRS1972

Electric field variations during substorms: OGO-6 measurements

The OGO-6 electric field measurements make it clear that the general pattern of high latitude electric fields in magnetic time-invariant latitude coordinates is not highly variable and that when unusual variations, or field distributions, occur they are relatively isolated in time and spatial extent. Thus, electric field changes on a global scale cannot, in general, be evoked as a direct cause of substorms. Polar traverses along the 18(h) to 6(h) magnetic time meridian show that the sum of potential drops across the evening auroral belt and morning auroral belt approximately equals the potential drop across the polar cap. The integrated polar cap potential drop ranges from 20 to 100 keV and values in the center of this range are most common under conditions of moderate magnetic disturbance. Roughly near 18(h) magnetic local time, a latitudinally narrow strip at the transition between auroral belt and polar cap fields exhibits unusually large field fluctuations immediately following the sudden onset of a negative bay at later magnetic local times. It appears likely that this spatially isolated correlation is related to an effect rather than a cause of substorm enhancement.

Heppner, J. P.↗
NASA NTRS1980

Uncertainty in ring current parameters due to the quiet magnetic field variability at mid-latitudes

At midlatitudes the presence of Sq variation is a problem, as variability of Sq currents may produce magnetic perturbations comparable to the magnetic effects of the partial ring current on comparable time scales. The paper reports the results of an empirical determination of the quiet magnetic field, which includes the Sq variation and secular variation at 27 midlatitude magnetic observatories for the 1967-1968 period. The main concern is with the consequences of the quiet field uncertainty in terms of using midlatitude magnetic data to quantify the size and location of the magnetic disturbances caused by substorms and the ring current. Attention is given to investigating the error associated with the empirical model used. It is shown how the uncertainty can be reduced by examining the changes occurring in some interval of time.

Clauer, C. R.↗
NASA NTRS1987

Simulation of January 1-7, 1978 events

The solar wind disturbances of January 1 to 7, 1978 are reconstructed by a modeling method. First, the interplanetary magnetic field (IMF) background pattern, including a corotating shock, is reproduced using the Stanford source surface map. Then, two solar flares with their onset times on January 1, 0717 UT at S17 deg E10 deg and 2147 UT S17 deg E32 deg, respectively, are selected to generate two interplanetary transient shocks. It is shown that these two shocks interacted with the corotating shock, resulting in a series of interplanetary events observed by four spacecraft, Helios 1 and 2, IMP-8 (Interplanetary Monitoring Platform 8), and Voyager 2. Results show that these three shock waves interact and coalesce in interplanetary space such that Helios 2 and Voyager 2 observed only one shock and Helios 1 and IMP-8 observed two shocks. All shocks observed by the four spacecraft, except the corotating shock at Helios 1, are either a transient shock or a shock which is formed from coalescing of the transient shocks with the corotating shock. The method is useful in reconstructing a very complicated chain of interplanetary events observed by a number of spacecraft.

Chao, J. K.↗
NASA NTRS1987

Simulation of January 1-7, 1978 events

The solar wind disturbances of January 1 to 7, 1978 are reconstructed by a modeling method. First, the interplanetary magnetic field (IMF) background pattern, including a corotating shock, is reproduced using the Stanford source surface map. Then, two solar flares with their onset times on January 1, 0717 UT at S17 deg E10 deg and 2147 UT S17 deg E32 deg, respectively, are selected to generate two interplanetary transient shocks. It is shown that these two shocks interacted with the corotating shock, resulting in a series of interplanetary events observed by four spacecraft, Helios 1 and 2, IMP-8 (Interplanetary Monitoring Platform 8), and Voyager 2. Results show that these three shock wave interact and coalesce in interplanetary space such that Helios 2 and Voyager 2 observed only one shock and Helios 1 and IMP-8 observed two shocks. All shocks observed by the four spacecraft, except the corotating shock at Helios 1, are either a transient shock or a shock which is formed from coalescing of the transient shocks with the corotating shock. The method is useful in reconstructing a very complicated chain of interplanetary events observed by a number of spacecraft.

Chao, J. K.↗
NASA NTRS1989

Investigation of active regions at high resolution by balloon flights of the Solar Optical Universal Polarimeter (SOUP)

SOUP is a versatile, visible-light solar observatory, built for space or balloon flight. It is designed to study magnetic and velocity fields in the solar atmosphere with high spatial resolution and temporal uniformity, which cannot be achieved from the surface of the earth. The SOUP investigation is carried out by the Lockheed Palo Alto Research Laboratory, under contract to NASA's Marshall Space Flight Center. Co-investigators include staff members at a dozen observatories and universities in the U.S. and Europe. The primary objectives of the SOUP experiment are: to measure vector magnetic and velocity fields in the solar atmosphere with much better spatial resolution than can be achieved from the ground; to study the physical processes that store magnetic energy in active regions and the conditions that trigger its release; and to understand how magnetic flux emerges, evolves, combines, and disappears on spatial scales of 400 to 100,000 km. SOUP is designed to study intensity, magnetic, and velocity fields in the photosphere and low chromosphere with 0.5 arcsec resolution, free of atmospheric disturbances. The instrument includes: a 30 cm Cassegrain telescope; an active mirror for image stabilization; broadband film and TV cameras; a birefringent filter, tunable over 5100 to 6600 A with 0.05 A bandpass; a 35 mm film camera and a digital CCD camera behind the filter; and a high-speed digital image processor.

Tarbell, T.↗
NASA NTRS1991

Shuffling foot points and magnetohydrodynamic discontinuities in the solar wind

ISEE three-field and plasma data are used to investigate the frequency of occurrence of isolated, large-amplitude rotational (RD) and tangential (TD) discontinuities in different types of solar wind flow. It is found that there are relatively more TDs in solar wind that originates in closed field regions and is ejected into interplanetary space by coronal transients than in the solar wind that originates in open field regions. The speed of the wind from open field regions is approximately linearly related to the number of RDs per hour; such a relation does not exist for the wind associated with coronal mass ejections. These results are consistent with the hypothesis that the convection-driven shuffling of magnetic foot points at the solar surface leads to TDs, magnetic reconnection, and heating of the corona on closed field lines, while in the open field regions the disturbances created by the shuffling are carried off by waves which contribute to the acceleration of the solar wind.

Neugebauer, M.↗