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Results for “INTERPLANETARY MAGNETIC FIELD”

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 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Origin of interplanetary southward magnetic fields responsible for major magnetic storms near solar maximum (1978-1979)

Simultaneous ISEE-3 field and plasma data were used to examine interplanetary phenomena associated with 10 major magnetic storms detected from August 16, 1978, to December 28, 1979, in a study of Gonzalez and Tsurutani (1987), and, in particular to determine the origins of the southward magnetic fields which caused the storms. In nine of the 10 cases, the responsible interplanetary events were found, as expected, to be associated with the high magnetic fields in the stream-stream interaction regions (sheaths) or driver gases, with the events following the interplanetary shocks. The tenth event was found to be associated not with a high-speed stream, but with a noncompressional density-enhancement event. The results of this study indicate the equal importance of both the sheath fields or draped fields and the driver gas fields for the generation of major geomagnetic storms.

Tsurutani, Bruce T.↗
NASA NTRS1984

Magnetic field draping against the dayside magnetopause

Interplanetary magnetic fields observed upstream of Earth's magnetosphere at ISEE 3 form input for a gasdynamic model of magnetic field draping in the dayside magnetosheath. Model results near the magnetopause are compared with appropriately lagged observations at ISEE 1. In 16 to 24 cases, the angle between the transverse component of the model and observed fields is less than 20 deg. The agreement is surprisingly good in view of the uncertainty introduced by the large distances between ISEE 1 and ISEE 3. The results indicate that magnetohydrodynamic and energy transfer processes at the magnetopause do not cause large distortions of the magnetosheath magnetic field. In addition, a comparison between observed and model field magnitudes indicates that immediately outside the magnetopause the observed field behaves like the model field at a distance of approx. 0.5 R sub E from the magnetopause, outside the region where magnetohydrodynamic effects make the gasdynamic model inapplicable. Patterns of model magnetic field orientation at the magnetopause are presented for practical application.

Crooker, N. U.↗
NASA NTRS1985

Magnetic field draping against the dayside magnetopause

Interplanetary magnetic fields observed upstream of earth's magnetosphere at ISEE 3 form input for a gasdynamic model of magnetic field draping in the dayside magnetosheath. Model results near the magnetopause are compared with appropriately lagged observations at ISEE 1. In 16 to 24 cases, the angle between the transverse component of the model and observed fields is less than 20 deg. The agreement is surprisingly good in view of the uncertainty introduced by the large distances between ISEE 1 and ISEE 3. The results indicate that magnetohydrodynamic and energy transfer processes at the magnetopause do not cause large distortions of the magnetosheath magnetic field. In addition, a comparison between observed and model field magnitudes indicates that immediately outside the magnetopause the observed field behaves like the model field at a distance of approx. 0.5 R sub E from the magnetopause, outside the region where magnetohydrodynamic effects make the gasdynamic model inapplicable. Patterns of model magnetic field orientation at the magnetopause are presented for practical application.

Crooker, N. U.↗
NASA NTRS1998

CIIs During the May 98 CMEs

The Thermal Ion Dynamics Experiment (TIDE) instrument on the ISTP/Polar spacecraft observed intense Cusp Ion Injections (CIIs) during the May 1998 series of Coronal Mass Ejections (CMEs). The energy signatures of the CIIs can be used to determine the magnetic field topology of the geomagnetic field and the Interplanetary Magnetic Field (IMF) at the reconnection site. Particle tracing using model magnetic fields and the TIDE on observations are used to locate the point of magnetopause crossing.

Chandler, Michael O.↗
NASA NTRS1981

An electrodynamic model of electric currents and magnetic fields in the dayside ionosphere of Venus

The electric current configuration induced in the ionosphere of Venus by the interaction of the solar wind has been calculated in previous papers (Cloutier and Daniell, 1973; Daniell and Cloutier, 1977; Cloutier and Daniell, 1979) for average steady-state solar wind conditions and interplanetary magnetic field. This model is generalized to include the effects of (1) plasma depletion and magnetic field enhancement near the ionopause, (2) velocity-shear-induced MHD instabilities of the Kelvin-Helmholtz type within the ionosphere, and (3) variations in solar wind parameters and interplanetary magnetic field. It is shown that the magnetic field configuration resulting from the model varies in response to changes in solar wind and interplanetary field conditions, and that these variations produce magnetic field profiles in excellent agreement with those seen by the Pioneer-Venus Orbiter. The formation of flux-ropes by the Kelving-Helmholtz instability is shown to be a natural consequence of the model, with the spatial distribution and size of the flux-ropes determined by the magnetic Reynolds number.

Cloutier, P. A.↗
NASA NTRS2023

Estimating the Subsolar Magnetopause Position from Soft X-Ray Images Using a Low-Pass Image Filter

The Lunar Environment heliospheric X-ray Imager (LEXI) and Solar wind Magnetosphere Ionosphere Link Explorer (SMILE) missions will image the Earth’s dayside magnetopause and cusps in soft X-rays after their respective launches in the near future, to specify global magnetic reconnection modes for varying solar wind conditions. To support the success of these scientific missions, it is critical to develop techniques that extract the magnetopause locations from the observed soft X-ray images. In this research, we introduce a new geometric equation that calculates the subsolar magnetopause position ( R s ) from a satellite position, the look direction of the instrument, and the angle at which the X-ray emission is maximized. Two assumptions are used in this method: (1) The look direction where soft X-ray emissions are maximized lies tangent to the magnetopause, and (2) the magnetopause surface near the subsolar point is almost spherical and thus R s is nearly equal to the radius of the magnetopause curvature. We create synthetic soft X-ray images by using the Open Geospace General Circulation Model (OpenGGCM) global magnetohydrodynamic model, the galactic background, the instrument point spread function, and Poisson noise. We then apply the fast Fourier transform and Gaussian low-pass filters to the synthetic images to remove noise and obtain accurate look angles for the soft X-ray peaks. From the filtered images, we calculate R 2 and its accuracy for different LEXI locations, look directions, and solar wind densities by using the OpenGGCM subsolar magnetopause location as ground truth. Our method estimates R s with an accuracy of <0.3 R E when the solar wind density exceeds >10 cm -3 . The accuracy improves for greater solar wind densities and during southward interplanetary magnetic fields. The method captures the magnetopause motion during southward interplanetary magnetic field turnings. Consequently, the technique will enable quantitative analysis of the magnetopause motion and help reveal the dayside reconnection modes for dynamic solar wind conditions. This technique will support the LEXI and SMILE missions in achieving their scientific objectives.

Hyangpyo Kim↗
NASA NTRS1973

Observations of interactions between interplanetary and geomagnetic fields

Magnetospheric effects associated with variations of the north-south component of the interplanetary magnetic field are examined in light of recent recent experimental and theoretical results. Although the occurrence of magnetospheric substorms is statistically related to periods of southward interplanetary magnetic field, the details of the interaction are not understood. In particular, attempts to separate effects resulting directly from the interaction between the interplanetary and geomagnetic fields from those associated with substorms have produced conflicting results. The transfer of magnetic flux from the dayside to the nightside magnetosphere is evidenced by equatorward motion of the polar cusp and increases of the magnetic energy density in the lobes of the geomagnetic tail. The formation of a macroscopic X-type neutral line at tail distances less than 35 R sub E appears to be a substorm phenomenon.

Burch, J. L.↗
NASA NTRS1966

The Ames magnetometer.

Flux gate magnetometer for interplanetary magnetic field measurements

INTERPLANETARY MAGNETIC FIELD↗
NASA NTRS1974

Eleven-years inversion of the green corona emission

Study of the correlation between the green coronal emission and the polarity pattern of the interplanetary magnetic field for the years 1947-1970. Polarity data of the interplanetary magnetic field inferred from high latitude geomagnetic observations and synoptic tables of the intensity of the green corona emission line (5303 A) are used in the analysis. The analysis results indicate that the coronal features are organized in a constant pattern with respect to the 4-sector structure through the solar cycle. A sudden inversion of the coronal pattern with respect to the sector structure takes place at the solar minima.

Antonucci, E.↗
NASA NTRS1978

The interplanetary modulation and transport of Jovian electrons

Based on simultaneous measurements by Pioneer 11 of the 3-6 MeV Jovian electron flux, interplanetary magnetic field magnitude, and solar wind speed, the interplanetary transport of energetic particles is studied. It is found that corotating interaction regions (CIR's) greatly inhibit electron transport across the average field direction. Cross-field transport is also influenced by the degree of compression of the solar wind since CIR's are areas of compressed solar wind plasma. The propagation of Jovian electrons is studied by a model that includes the effects of CIR's. The model tests whether or not the three-dimensional convection-diffusion theory adequately describes the cross-field transport of electrons. The model is also valid for Jovian electron observations from earth-orbiting satellites. The model may be further applied to 1 AU from the sun where it is found that the cross-field diffusion of electrons explains why Jovian electrons are detected at the earth even during periods when the interplanetary magnetic field does not connect the earth directly to Jupiter.

Conlon, T. F.↗
NASA NTRS1987

Magnetic helicity of the Parker field

The topological properties of the interplanetary magnetic field are discussed based on a calculation of the magnetic helicity of the Parker field. The most striking feature of the helicity is that it is negative north of the heliospheric current sheet and positive south of the current sheet, regardless of the sign of the solar poloidal magnetic field. Informal arguments based on MHD turbulence theory suggest that the magnetic helicity of turbulence in the interplanetary medium may be related to the large-scale Parker helicity. Because charged particle scattering in certain types of magnetic turbulence (such as slab turbulence) depends strongly upon helicity, the existence of such a relationship could have important implications to cosmic-ray transport in the heliosphere.

Bieber, J. W.↗
NASA NTRS1974

Evidence of a primordial solar wind

A model is reviewed which requires a T Tauri 'wind' and at the same time encompasses certain early-object stellar features. The theory rests on electromagnetic induction driven by the 'wind'. Plasma confinement of the induced field prohibits a scattered field, and all energy loss is via ohmic heating in the scatterer (i.e., planetary objects). Two modes, one caused by the interplanetary electric field (transverse magnetic) and the other by time variations in the interplanetary magnetic field (transverse electric) are present. Parent body melting, lunar surface melting, and a primordial magnetic field are components of the proposed model.

Sonett, C. P.↗
NASA NTRS2020

Formation and Topology of Foreshock Bubbles

We use global and local hybrid (kinetic ions and fluid electrons) simulations to investigate the conditions under which foreshock bubbles (FBs) form and how their topology changes with solar wind conditions. FBs form as a result of the interaction between solar wind discontinuities and backstreaming ion beams in the foreshock. They consist of an outer shock and its associated sheath plasma and a low density high temperature core with low magnetic field strength. The structure of FBs is determined by the angle between the interplanetary magnetic field and the normal to the solar wind discontinuity. We show that interaction of rotational discontinuities with the foreshock during small angles between the interplanetary magnetic field and discontinuity normal results in the formation of a nearly spherical bubble with a radius that scales with the width of the foreshock. As this angle increases, FBs become more elongated and eventually become nearly planar structures with dimensions that scale with the length of the foreshock. Despite this transformation, the signatures of FBs in spacecraft time series data remain the same in agreement with the observations. Global simulation results show that FBs form when the solar wind flow speed corresponds to high or intermediate Alfvén Mach numbers (approximately >7 MA). In general, this is tied to the relative speed between the solar wind and ion beams and drop in density of the back streaming ions.

Nick Omidi↗
NASA NTRS1984

K-coronameter observations and potential field model comparison in 1976 and 1977

Results of determining the shape and location of the heliospheric current sheet from a potential field model and from K-coronameter observations are compared. Interplanetary magnetic field polarities as observed by IMP 8, Helios 1 and 2, and Voyager 2 spacecraft were used to test the two methods over the period May 1976 to August 1977 throughout 18 Carrington rotations. The computed heliospheric current sheets from both methods had a quasi-stationary four-sector structure and very similar shapes. Agreement between interplanetary magnetic field polarity and the results from the potential field model was found on 79 percent of the days, while agreement between the interplanetary field polarity and the polarities derived from the K-coronameter data was found on 87 percent of the days.

Bruno, R.↗
NASA NTRS1971

Magnetic field anomalies in the lunar wake

The interplanetary magnetic field is only slightly perturbed by the presence of the moon in the solar wind flow. A statistical study of umbral increases and of penumbral variations was conducted with respect to variation in the solar wind plasma value beta, the distance from the moon, and the selenographic longitude of the limb regions of the lunar surface in the solar wind flow. All lunar wake anomalies show a strong positive correlation with the plasma value beta, while only penumbral increases show a marked variation with distance from the moon. There is no clear correlation of penumbral anomaly occurrence with selenographic longitude of the exposed lunar limb in the solar wind flow.

Whang, Y. C.↗