The average magnetic field configuration of the outer magnetosphere
Magnetic field configuration in outer magnetosphere from data obtained by Interplanetary Monitoring Platform /IMP/
Fairfield, D. H.↗
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Magnetic field configuration in galactic spiral arms.
Spiral arm magnetic field configuration model simplifies star formation theory, discussing theoretical and observational evidence
COSMOLOGY↗
A model of the heliospheric magnetic field configuration
A three-dimensional model of the magnetic field configuration in the heliosphere is constructed by assuming that the interplanetary magnetic field consists of four components, (1) the solar dipole, (2) a large number of small spherical dipoles located along an equatorial circle just inside the sun (representing the magnetic field line arcade), (3) the field of the poloidal current system generated by the solar unipolar induction, and (4) the field of an extensive current disc around the sun lying in the ecliptic plane. The magnetic field intensity at a distance of 1 AU (about 20 solar radii above the ecliptic plane) is normalized to fit the observed spiral configuration.
Akasofu, S.-I.↗
Magnetic field configuration of the heliosphere in interstellar space
An improved model of the heliospheric magnetic field configuration is presented by including a uniform interstellar magnetic field and by adopting different values for a few magnetic field parameters. All the basic expressions for the magnetic field components remain the same as in Akasofu et al. (1980). In the magnetic arcade field, the magnetic field of the spherical dipoles is changed from 500 to 50 G. In the field of an extensive current disk around the sun lying in the ecliptic plane, the solar current disk extends from a distance of 1.5 solar radii instead of 10 solar radii. A uniform and southward directed interstellar magnetic field of 0.22 gamma is included. The total magnetic field configuration is constructed for the northward and southward orientation of the solar dipole field.
Akasofu, S.-L.↗
Average magnetic field configuration of the outer magnetosphere.
Outer magnetosphere average magnetic field configuration between 5 and 18 earth radii, noting various maps in equatorial plane
Fairfield, D. H.↗
The filament eruption in the 3B flare of July 29, 1973 - Onset and magnetic field configuration
The filament eruption in the large expanding two-ribbon solar flare which occurred July 29, 1973 is discussed. Observational evidence is presented for the preflare magnetic field configuration, the nature of the filament destabilization and triggering of the flare, and the magnetic field configuration after the filament eruption. The observations show that the filament is under an arcade of closed magnetic field lines prior to the eruption. The eruption of the filament and the onset of the two-ribbon H-alpha flare are preceded by precursor activity in the form of small H-alpha brightenings and mass motion along the neutral line and well below the bottom edge of the filament. The precursor H-alpha brightenings and the first brightenings in the flare ribbons are in the vicinity of the steepest magnetic field gradient in the flare region.
Moore, R. L.↗
Magnetic field configuration associated with solar gamma ray flares in June, 1991
The vector magnetic field configuration of the solar active region AR 6659 that produced very high levels of flare activity in Jun. 1991 is described. The morphology and evolution of the photospheric fields are described for the period 7-10 Jun., and the flares taking place around these dates and their locations relative to the photospheric fields are indicated. By comparing the observed vector field with the potential field calculated from the observed line-of-sight flux, we identify the nonpotential characteristics of the fields along the magnetic neutral lines where the flares were observed. These results are compared with those from the earlier study of gamma-ray flares.
Hagyard, M. J.↗
Superposed epoch analysis of pressure and magnetic field configuration changes in the plasma sheet
Using data from 41 substorm events in the near-Earth magnetotail, we have combined plasma, energetic ion, and magnetic field data from the AMPTE/IRM spacecraft to perform a superposed epoch analysis of changes in the total pressure and in the magnetic field configuration as a function of time relative to substorm onset. Unloading is evident in the total pressure profile; the pressure decreases by about 20 percent. Pressure changes during the growth phase are not as uniform for the different substorms as the pressure changes during the expansion phase. To study changes in the magnetic field configuration, we have determined the development of the plasma pressure profiles in z for an average of data from 15 to 19 R(E). At substorm onset, the field line dipolarization begins on the innermost field lines and then progresses to the outer field lines. The field lines map the closest to the Earth about 45 min after substorm onset, and then begin to stretch out again during the recovery phase of the substorm.
Kistler, L. M.↗
Steady state magnetic field configurations for the earth's magnetotail
A two-dimensional, force-balance magnetic field model is presented. The theoretical existence of a steady state magnetic field configuration that is force-balanced and consistent with slow, lossless, adiabatic, earthward convection within the limit of the ideal MHD is demonstrated. A numerical solution is obtained for a two-dimensional magnetosphere with a rectangular magnetopause and nonflaring tail. The results are consistent with the convection time sequences reported by Erickson (1985).
Hau, L.-N.↗
Magnetic field configuration in the magnetotail near 60 earth radii
The magnetic field line configuration in the geomagnetic tail near 60 earth radii is examined on the basis of nearly 3 years of magnetometer data from the lunar-orbiting Explorer 35 satellite. The magnetotail field line characteristics inside the plasma sheet and in the high-latitude tail, i.e., outside the plasma sheet, are separately examined. In the high-latitude tail the magnetic field lines systematically diverge in both longitudinal (east-west) and latitudinal (north-south) directions; the divergence angle between field lines near the dusk flank and those near the dawn flank is about 14 deg, but the divergence along the Z direction is only about 8 deg. The degree of divergence is found to be greater in the evening side than in the morning side and greater in the northern tail than in the southern tail. Inside the plasma sheet the field lines deviate by about 19 deg from the sun-earth line, and the spatial distribution of the field line deviation does not have any systematic tendency.
Meng, C.-I.↗
Numerical simulation of mass injection for the formation of prominence magnetic field configurations. II - Symmetric injection
A two-dimensional MHD model simulating the formation of Kippenhahn-Schluter (1957) quiescent prominence (QP) magnetic field configurations is used to explore symmetric mass injection into a dipole magnetic field. An optimum magnetic field strength for QP formation by mass injection is obtained. It is found that a weaker magnetic field strength is more favorable for the condensation of the injected plasma but that a stronger field is more favorable for supporting the condensed plasma against gravity.
An, C.-H.↗
A classification of magnetic field configurations associated with solar flares.
On the assumption that solar flares are due to instabilities which occur in current sheets in the sun's atmosphere, one may classify magnetic-field configurations associated with flares into two types. One is characterized by 'closed' current sheets, magnetic-field lines adjacent to these sheets beginning and ending at the sun's surface. The other is characterized by 'open' current sheets, magnetic-field lines adjacent to these sheets beginning at the sun's surface but extending out into interplanetary space. Flares associated with open current sheets can produce Type III radio bursts and high-energy-particle events, but flares associated with closed current sheets cannot. The flare of July 6, 1966 apparently consisted of one flare of each type.
Sturrock, P. A.↗
Magnetic field configuration of the theta aurora
A magnetic configuration of the open magnetosphere is described which is conducive to the formation of the theta aurora when the IMF has a significant northward component. A magnetic field topology and polar cap configuration, derived from a quantitative model of the open magnetosphere that incorporates Crooker's antiparallel merging hypothesis, are presented. Under this hypothesis, when the IMF has a northward component, the dayside merging line bifurcates, leaving a large fraction of the subsolar magnetopause untouched by the merging process. The polar cap, defined by tracing magnetic field lines that connect from the solar wind to the earth, is similarly bifurcated, leaving a sun-aligned stagnation region that is not magnetically connected to the solar wind and may plausibly be associated with the sun-aligned 'bar' of the theta aurora. The model provides testable predictions with regard to the position of this 'convection gap' in both Northern and Southern Hemispheres as functions of IMF direction.
Toffoletto, F. R.↗
Magnetic Field Configuration of Active Region NOAA 6555 at the Time of a Long Duration Flare on 23 March 1991: An Exception to Standard Flare Reconnection Model
The high-resolution H(sub alpha) images observed during the decay phase of a long duration flare on 23 March 1991 are used to study the three-dimensional magnetic field configuration of the active region NOAA 6555. Whereas, all the large flares in NOAA 6555 occurred at the location of high magnetic shear and flux emergence, this long duration flare was observed in the region of low magnetic shear at the photosphere. The H(sub alpha) loop activity started soon after the maximum phase of the flare. There were few long loop at the initial phase of the activity. Some of these were sheared in the chromosphere at an angle of about 45 deg with the east-west axis. Gradually, increasing number of shorter loops, oriented along the east-west axis, started appearing. The chromospheric Dopplergrams show blue-shifts at the end points of the loops. By using different magnetic field models, we have extrapolated the photospheric magnetograms to the chromospheric heights. The magnetic field lines computed by using the potential field model correspond to most of the observed H(sub alpha) loops. The height of the H(sub alpha) loops were derived by comparing them with the computed field lines. From the temporal evolution of the H(sub alpha) loop activity, we derive the negative rate of appearance of H(sub alpha) features as a function of height. It is found that the field lines oriented along one of the neutral lines was sheared and low lying. The higher field lines were mostly potential. The paper also outlines a possible scenario for describing the post-flare stage of the observed long duration flare.
Choudhary, Debi Prasad↗
Analysis of the magnetic field configuration of a filament-associated flare from X-ray, UV, and optical observations
X-ray and ultraviolet observations from SMM of a filament-associated event on November 22, 1980 are examined in conjunction with ground-based optical observations, in order to determine the magnetic field configuration involved in the flaring process. Evidence that the flare was produced by gradual energy release in a large sheared magnetic loop which interacted with another smaller loop is found. Nonthermal processes, as indicated by hard X-ray emission and impulsive UV kernels, were produced in the interaction of the two loops. Although this flare shared some of the characteristics of Long Duration (class II) Events, no indication of a helmet-type configuration, as generally envisaged for class II events, was found. On the contrary, the magnetic configuration of the November 22, 1980 event was more similar to that of a compact (class I) flare, although on a much larger spatial scale and longer time scale.
Cheng, C.-C.↗
Formation of active region and quiescent prominence magnetic field configurations
To investigate the formation of prominences, researchers studied chromospheric mass injection into an overlying coronal dipole magnetic field using a 2-D ideal magnetohydrodynamic (MHD) numerical model. Researchers propose that active region prominences are formed by chromospheric plasmas injected directly into the overlying coronal magnetic field and that quiescent prominences are formed by plasmas evaporated at the interface between spicules and corona. Hence, for the simulation of an active region prominence magnetic field we inject the mass from one side, but use a symmetric mass injection to form a quiescent prominence field configuration. Researchers try to find optimum conditions for the formation of Kippenhahn-Schuluter(K-S)type field configuration for stable support of the injection plasmas. They find that the formation of K-S type field configuration by mass injection requires a delicate balance between injection velocity, density, and overlying magnetic fields. These results may explain why a prominence does not form on every neutral line.
An, C.-H.↗
Plasma-dominated magnetic field configurations for the magnetosphere of Uranus
There is significant indirect evidence that the planet Uranus possesses a magnetic field. This evidence is based on the observation of hydrogen Lyman alpha emission from Uranus with the aid of the International Ultraviolet Explorer (IUE) spacecraft. The detection of water ice on the Uranian moons led Cheng (1984) to suggest that charged particle sputtering of the icy satellites could provide a significant internal source of oxygen ions and protons to the Uranian magnetosphere. Cheng concluded that this mechanism would predict aurorae around both magnetic poles of Uranus. Cheng's idea of the presence of a continuous internal plasma supply to the Uranian magnetosphere is further pursued in the present investigation. Questions are considered regarding the evolution of Uranus' magnetosphere from a vacuum configuration toward a plasma pressure dominated equilibrium configuration, taking into account the amount of the thermal plasma pressure as a free parameter.
Ip, A. K.↗
Analysis and Modeling of Coronal Holes Observed by CORONAS-1: Morphology and Magnetic Field Configuration - 1
Two low-latitude coronal holes observed by CORONAS-1 in April and June 1994 are analyzed together with magnetic field measurements obtained from Wilcox and Kitt Peak Solar Observatories. To estimate the comparable temperature of these two coronal holes, the YOHKOH observations are also utilized. Using this information, we have constructed three-dimensional magnetic field lines to illustrate the geometrical configuration of these coronal holes. The calculated synoptic maps are used to determine the existence of closed and open field regions of the hole. Finally, we have correlated the characteristics of two coronal holes with observed solar wind speed. We found that the brighter coronal hole has high speed solar wind, and the dimmer coronal hole has low speed solar wind.
Obridko, Vladmir↗