P. M. Banks

Spindle cell neoplasms of lymph nodes of probable reticulum cell lineage. True reticulum cell sarcoma

Primary spindle cell neoplasms involving hemalolymphoid organs are extremely rare. We present four cases of Spindle cell neoplasms of unusual phenotype arising within lymph nodes. Two of the four cases showed morphologic and immunophenotypic features suggestive of interdigitating reticulum cell lineage; these cases expressed several macrophage antigens and S-100 protein but not CDI. The other two cases showed evidence suggestive of dendritic reticulum cell lineage. Both cases expressed HLA-DR, several macrophage antigens, complement receptors C3b and C3d. one case expressed R4/23; both showed the presence of desmosomes on ultrastructoral examintion. A germline configuration for the immunoglobulin heavy chain and β-T-cell receptor genes was detected in all four cases. Of the two patients in the first group, one had local recurrence of tumor: the other died of widespread metastases. Of the two patients in the second group, both are alive and well at 12 and 27 months follow-up, respectively.

Recent results from studies of electron beam phenomena in space plasmas

Abstract Experiments involving the ejection of beams of electrons from spacecraft have been performed for more than 2 decades in order to study fundamental plasma physical processes as well as for a range of diagnostic- and application-oriented purposes. This paper reviews some of the key issues that have been pursued in the past 10 years. These include questions regarding spacecraft charging and beam dynamics, the interaction of beams with neutral gas and plasmas, and the electromagnetic radiation generated by continuous and pulsed electron beams. It is shown how our understanding of these phenomena has matured, thereby providing a solid foundation for future experiments involving the use of electron beams.

The interplanetary electric field, cleft currents and plasma convection in the polar caps

Abstract This report investigates the suggestion that the pattern of plasma convection in the polar cleft region is directly determined by the interplanetary electric field (IEF). Owing to the geometrical properties of the magnetosphere, the East-West component of the IEF will drive field-aligned currents which connect to the ionosphere at points lying on either side of noon, while currents associated with the North-South component of the IEF will connect the two polar caps as sheet currents centered at noon. The effects of the hypothesized IEF driven cleft current systems on polar cap ionospheric plasma convection are investigated through a series of numerical simulations. The simulations demonstrate that this simple electrodynamic model can account for the narrow “throats” of strong dayside antisunward convection observed during periods of southward interplanetary magnetic field (IMF) as well as the sunward convection observed during periods of strongly northward IMF. Thedawn-dusk shift of polar cap convection which is related to the By component of the IMF is also accounted for by the model.

Interactions between the orbiting space shuttle and the ionosphere

This paper presents an analysis of interactions between the space shuttle Orbiter and the ionosphere based on thermal plasma data obtained from a Spherical Retarding Potential Analyzer (SRPA) and a Langmuir Probe (LP) flown on the third Space Shuttle flight (STS-3) in March 1982. While previous work on spacecraft-plasma interactions has dealt with wake effects, the present work deals with effects that are seen in ram conditions that have not been previously discussed. One observation is a higher degree of plasma turbulence than has been reported from unmanned spacecraft measurements that manifests itself as a frequency component at 2.2 kHz in the SRPA signal. We also see unusually high number densities of what appear to be ions with a mass of at least 30 or 32 amu and a temperature in the range 2000–3000 K. Coincident with the enhanced molecular ion species we see the temperature of the thermal electrons elevated to above 5000 K. It is hypothesized that these measurements are evidence for a plasma instability resulting from the motion of the outgassing Orbiter through the ionosphere.

Measurements of the thermal plasma environment of the space shuttle

Abstract The paper presents some initial results on measurements of the thermal plasma environment obtained by a spherical retarding potential analyzer and a Langmuir probe flown on the third space shuttle flight (STS-3) as part of the NASA Office of Space Science-1 (OSS-1) payload in March 1982. One of the major effects observed is a higher degree of turbulence in the ambient plasma compared to what is observed from similar instruments flown on unmanned satellites. In addition we see the temperature of the thermal electrons elevated to values of 4000–5000 K. Associated with elevated electron temperatures are regions of enhanced plasma density resulting from the appearance of high densities of molecular ions. The thermal plasma data also show clear effects of an induced V × B · L potential at the location of the probes which matches that produced by an L vector linking the probes to the engine nozzles; thereby establishing the prime return current location on the Orbiter. The final observations discussed are the pronounced and complex wake effects resulting both from the main structure of the Orbiter and from the complex shapes of appendages attached to the Orbiter.

Results from the vehicle charging and potential experiment on STS-3

The Vehicle Charging and Potential Experiment formed part of the scientific experiments comprising the NASA Office of Space Sciences-1 pallet flown at an altitude of 250 km and an orbital inclination of 40 deg on the third flight of the Space Shuttle Orbiter in March 1982. Details of the objectives, the instrumentation of the experiment, and some preliminary results from the individual instruments are presented. The experiment studied passive vehicle charging using thermal plasma probes, and it is concluded that apart from moderate v x B (L)-induced electrical potential resulting from the large size and restricted plasma contact area, the Space Shuttle Orbiter behaved similarly to smaller spacecraft orbiting in the same ionospheric region. However, an unexpected passive orbital result was the detection of enhanced plasma density in the vicinity of the Orbiter under restricted orbital conditions, apparently composed of contaminant molecular species and with an electron component having a temperature considerably higher than the ambient ionosphere electrons. The active vehicle charging experiments were performed by using a 100 mA/1 keV electron beam emitted out of the payload bay. Charging measurements made during short electron beam pulse emissions provide an upper limit of about 1 mF for the Orbiter capacitance. Steady-state charging measurements showed that for the vehicle attitudes covered by the mission, the induced electrical potential was normally only a few volts, except during some nighttime conditions when it rose above 40 V.

Vehicle charging effects during electron beam emission from the CHARGE-2 experiment

The CHARGE-2 sounding rocket payload was designed to measure the transient and steady-state electrical charging of a space vehicle at low Earth orbit altitudes during the emission of a low-power electron beam from the vehicle. In addition to the electron gun, the payload contained several diagnostics to monitor plasma and waves resulting from the beam/space/vehicle interaction. The payload was configured as a mother-daughter arrangement with the two parts connected by an insulated conducting wire tether that extended to a maximum length of 426 m during the flight. In the paper we discuss the configuration of the payload, a description of the science instruments, and the flight operation plan. We then present some initial results from the flight, addressing the prime objective of the mission to study vehicle charging. The results show that the 1-keV electron beam was generated at beam currents of 1-48 mA emerging from the exit aperture of the electron gun. The beam emission always resulted in positive charging of the vehicle, which occurred as a two-step process; a transient charging took place about 10 its after beam turn-on, followed by a slower rise to a steady-state potential in a period of the order of milliseconds. The maximum steady-state potential we measured was 560 V for a 17-mA beam emission current. The highest transient potential we measured was 290 V for a 31-mA beam current. Studies of the distribution of currents and voltages in the complete tethered system show that the return currents are supplied from the space charge limited sheath currents above 240 km. Below 240 km the return current to the mother appears to be enhanced by the effects of beam plasma interactions. Detectable effects of the electron beam in vehicle potential and photon emission from the beam are seen for beam currents as low as 1 mA.

The Shuttle Electrodynamic Tether System (SETS) on TSS-1

SummaryThe Shuttle Electrodynamic Tether System (SETS) experiment formed part of the scientific experiments comprising the first flight of the NASA/ASI Tethered-Satellite System flown at an altitude of 300 km and an orbital inclination of 28.5 degrees in July–August 1992. The SETS experiment was designed to study electrodynamic behavior of the Orbiter-Tether-Satellite system as well as provide background measurements of the ionospheric environment near the Orbiter. The SETS experiment was able to operate continuously during the mission providing a large data set. Details of the SETS objectives, its instrumentation, and initial results from the mission highlighting voltage, current, and charging measurements are presented here.

Thermal proton flow in the plasmasphere - The morning sector

Abstract Vertical profiles of electron density obtained in the vicinity of the plasmapause using the Alouette-II topside sounder have been analyzed to assess the presence of H+ flow in the topside ionosphere. The observations in the midnight sector show clearly the presence of the plasmapause; i.e. there is a sharp boundary separating the poleward regions of polar wind H+ flow and the more gentle conditions of the plasmasphere where light ions are present in abundance. In contrast, in the sunlit morning sector upwards H+ flow is deduced to be present to invariant latitudes as low as 48° (L = 2·2) in the regions normally known to be well inside the plasmasphere. The upwards H+ flux is sufficiently large (3 × 108 ions cm−2 sec−1) that the plasmapause cannot be seen in the latitudinal electron density contours of the topside ionosphere. The cause for this flow remains unknown but it may be a result of a diurnal refilling process.

Review of electrodynamic tethers for space plasma science

This paper presents a review and analysis of possible uses of orbiting electrodynamic tether systems. The concept involves the electrical and mechanical connection of orbiting bodies. One particularly interesting configuration has the two bodies radially oriented with respect to the Earth with an electrically insulated wire maintaining both a mechanical constraint upon the bodies and, at the same time, providing electrical connectivity. In application, electrodynamic tethers offer a new way of probing different natural and artificial processes in space plasmas. In particular, the combination of orbital emf and the fact that electrical currents can pass through the tether, a variety of novel charge and current injection experiments can be undertaken. The basic modes of interaction are reasonably well-understood from various rocket experiments and theory and, based upon this information, it is possible to project a variety of important scientific uses. A simple division of these is into applications supported by high-impedance tether systems and those relying upon the existence of low impedance. However, because the electrodynamic tether systems can operate at high voltages, there is considerable uncertainty about the precise way they will interact with the ambient plasma of low Earth orbit, and this also provides an area of new technical investigation.