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This grant supported the analysis of a ROSAT observation of a field in the Orion OB1A star forming region. The data were obtained without problem, and a number of sources were detected. The data have been analyzed. We have obtained the optical and near-IR photometry, and some of the optical spectroscopy (the latter in November 1999) we need to fully analyzed and understand the data.
The magnetic field measurements made in the polar cusp region down to altitudes of about 4 earth radii are discussed. Measurements were made by the IMP 5 satellite. Measurements are characterized by unusually low magnitudes and large fluctuations. It was suggested that the low magnitudes are caused by currents of the magnetopause and the diamagnetic effect of the plasma. The transition between the magnetosheath and the cusp portion of the magnetosphere is not characterized by a well defined magnetopause as at low latitudes.
In order to infer the interplanetary sector polarity from polar geomagnetic field diurnal variations, measurements were carried out at Godhavn and Thule (Denmark) Geomagnetic Observatories. The inferred interplanetary sector polarity was compared with the polarity observed at the same time by Explorer 33 and 35 magnetometers. It is shown that the polarity (toward or away from the sun) of the interplanetary magnetic field can be reliably inferred from observations of the polar cap geomagnetic fields.
Interplanetary magnetic sector polarity effects on polar geomagnetic field diurnal variation
The Ulysses magnetic field measurements confirmed the general structure of the dayside magnetosphere and showed that the importance of the current sheet dynamics extends well into the middle and outer magnetosphere. On the dusk side, the magnetic field was found to be swept back significantly toward the magnetotail. It is pointed out that the external current densities need to be modified with respect to previous observations on the inbound pass which shows that Jovian magnetic and magnetospheric models are highly sensitive to both the intensity and the structure assumed for the current sheet. Data obtained revealed that all boundaries and boundary layers in the magnetosphere have a very complex microstructure.
With the use of a prediction technique it is shown that the polarity (toward or away from the sun) of the interplanetary magnetic field can be reliably inferred from observations of the polar geomagnetic field.
The particle detector and electric field data collected by the Dynamo Explorer 1 on the Pc 5 wave event encounter on July 14, 1982 are presented, yielding a nearly complete picture of the event. The overall structure of the Pc 5 seems to order the event into two distinct halves, suggesting a temporal or spatial variation of the micropulsation. Thermal plasma measurements showed that the dominant ion throughout both lobes was H(+). Significant quantities of He(+), O(+), N(+), and O(2+) were also observed to be present and rotating together in a plane normal to the magnetic field direction, due to the Pc5 E x B drift. The plasma parameters determined for the two lobes were used in theoretical calculations to predict the period of the observed resonance.
A series of electric field measurements is reported which was obtained from the Injun 5 satellite along with a simultaneous magnetic disturbance observed in the interplanetary medium and on the ground during a magnetic substorm. The substorm analyzed took place on February 24, 1970. Prior to the onset of the substorm a greatly enhanced anti-sunward plasma flow was observed over the polar cap. The enhanced plasma flow occurred about 30 minutes after a switch in the direction of the interplanetary magnetic field from northward to southward. The electric fields across the polar cap immediately before and during the substorm were essentially unchanged indicating that an enhancement in the ionospheric conductivity rather than the electric field must be responsible for the large increase in the auroral electrojet current during the substorm.
The NASA-GSFC magnetic field experiment on Mariner 10 is the first flight of a dual magnetometer system conceived to permit accurate measurements of weak magnetic fields in space in the presence of a significant and variable spacecraft magnetic field. Results from a preliminary analysis of a limited data set are summarized in this report, which is restricted primarily to Venus encounter. A detached bow shock wave that develops as the super Alfvenic solar wind interacts with the Venusian atmosphere has been observed. However, the unique coincidence of trajectory position and interplanetary field orientation at the time of bow shock crossing led to a very disturbed shock profile with considerably enhanced upstream magnetic fluctuations. At present it is not possible to ascertain the nature and characteristics of the obstacle responsible for deflecting the solar wind flow. Far downstream disturbances associated with the solar wind wake have been observed.
The region upstream from a planetary bow shock is a natural plasma laboratory containing a variety of wave particle phenomena. The study of foreshocks other than the Earth's is important for extending our understanding of collisionless shocks and foreshock physics since the bow shock strength varies with heliocentric distance from the Sun, and the sizes of the bow shocks are different at different planets. The Mercury's bow shock is unique in our solar system as it is produced by low Mach number solar wind blowing over a small magnetized body with a predominately radial interplanetary magnetic field. Previous observations of Mercury upstream ultra-low frequency (ULF) waves came exclusively from two Mercury flybys of Mariner 10. The MESSENGER orbiter data enable us to study of upstream waves in the Mercury's foreshock in depth. This paper reports an overview of upstream ULF waves in the Mercury's foreshock using high-time resolution magnetic field data, 20 samples per second, from the MESSENGER spacecraft. The most common foreshock waves have frequencies near 2 Hz, with properties similar to the I-Hz waves in the Earth's foreshock. They are present in both the flyby data and in every orbit of the orbital data we have surveyed. The most common wave phenomenon in the Earth's foreshock is the large-amplitude 30-s waves, but similar waves at Mercury have frequencies at near 0.1 Hz and occur only sporadically with short durations (a few wave cycles). Superposed on the "30-s" waves, there are spectral peaks at near 0.6 Hz, not reported previously in Mariner 10 data. We will discuss wave properties and their occurrence characteristics in this paper.
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Analysis of Voyager 2 low-energy charged particle and magnetic field data in the Uranian magnetotail show that this system has many features similar to those seen at earth. Isotropization of core magnetosphere 28-43 keV ions has been observed at the trapping boundary upon entry into the magnetotail near L = 17, an effect seen in ion populations at earth and attributed to neutral sheet scattering. An extensive and persistent plasma sheet boundary layer is found to contain field-aligned ion streams with a variety of angular and energetically dispersive effects. Streaming distributions in the magnetotail horn region map to the auroral emission region observed by the Voyager ultraviolet spectrometer. A quiet-time near-tail region is distinguished from a distant disturbed region, where evidence of a substorm is observed. There is evidence suggesting that the distant plasma sheet is not corotating with the planet.
Description of a series of electric field measurements obtained from the Injun 5 satellite and simultaneous magnetic disturbances observed in the interplanetary medium and on the ground during a magnetic substorm. The substorm analyzed took place on Feb. 24, 1970. Prior to the onset of the substorm, a greatly enhanced antisunward plasma flow was observed over the polar cap. The enhanced plasma flow occurred about 30 minutes after a switch in the direction of the interplanetary magnetic field from northward to southward. The electric fields across the polar cap immediately before and during the substorm were essentially unchanged, and it is thus indicated that an enhancement in the ionospheric conductivity rather than the electric field must be responsible for the large increase in the auroral electrojet current during the substorm.
Satellite data used for simultaneous trapped electron and geomagnetic tail field studies
Magnetic field data from OGO-2 spacecraft and surface magnetic observatories, noting magnetic storm occurrence and magnetosphere inflation and detection of polar ionospheric currents
Correlations between interplanetary magnetic fields (IMFs) at 0.72 AU and 1.0 AU have been examined using data sets obtained from the Pioneer Venus orbiter and Earth-orbiting spacecraft. While the two-sector structures are evident in long-term variations at these two heliocentric distances, the corresponding auto-correlation coefficients are consistently smaller at 1.0 AU than at 0.72 AU. This suggests that the IMF structures become less persistent at 1.0 AU due to the effects of changing solar wind dynamics between the Venus and Earth orbits. Short-term variations exhibit generally poor correlations between IMFs near Venus and those near Earth, though good correlations are sometimes obtained for well-defined structures when the Sun, Venus, and Earth are closely aligned. The rather poor correlations in the background streams indicate that the IMFs are still changing between the Venus and Earth orbits under the strong influence of solar wind dynamics.
Fitting of a Mach 2 shock surface to the ICE magnetic field data obtained near Comet Giacobini-Zinner has provided subsolar bow wave distances that infer neutral gas outflow rates comparable to previous measurements, and orientations of the bow wave symmetry axis that are consistent with the plasma measurements and motion of the comet relative to the solar wind. Mach values of 1.5-2 and transition thicknesses of the order of 10,000 km are inferred when the field magnitude and variance data are compared. Cross spectra of the transverse field components in and near the bow wave exhibit a peak near 0.01 Hz, or near the cyclotron frequency of ions from the water group. However, the level of turbulence is not consistent with that observed for similar configurations at planetary bow shocks.
The paper reports both dc and ac measurements of equatorial electric fields from the San Marco D satellite. These measurements were performed with double floating probe sensors and have yielded a surprising number of new phenomena and effects in regions of equatorial spread-F. Among the phenomena observed are unexpected large-amplitude Rayleigh-Taylor updrafting velocities in equatorial bubbles.