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Homogeneous positive plasma column perturbation analysis in axial magnetic field, deriving model for ionization waves dispersion characteristics
Split Langmuir probes have been used to study the near wake of small Langmuir probes on sounding rockets. Experiments have been performed on two rocket flights using planar disk and cylindrical geometries, and the results are presented. Significant wake perturbations in plasma density and temperature were found due to the probe body itself, even though the probes were of the order of or smaller than the Debye length. The largest effects of the wake are seen in the electron collection characteristics of the probe. The wake of small probes show apparent magnetic field aligned structure, even though the probes were much smaller than the ion gyroradius. On one flight, a space charge potential large enough to substantially alter photoemission, -3.5 volts, was observed.
Adriamycin was coupled to polyglutaraldehyde microspheres having an average diameter of 4500 A. The coupled microspheres remained stable during incubation with cells. Full cytostatic activity was observed when the coupled adriamycin was tested with murine or human leukemia and murine sarcoma cell lines. A 10-fold increase in sensitivity was obtained with drug-resistant human leukemia cell lines. Repeated use of the coupled microspheres in the cytostatic assays did not decrease their activity, indicating that these complexes can be recycled. The results suggest that coupled adriamycin sufficiently perturbs the plasma membrane to lead to cytostatic activity. It is proposed that this mode of drug delivery provides multiple and repetitious sites for drug-cell interactions. In addition, the drug-polymer complexes may overcome those forms of resistance that are the result of decreased drug binding at the cell surface.
We describe plasma flow perturbations in the outer magnetosphere during the passage of magnetopause boundary waves and cylindrically shaped flux transfer events (FTEs). Spacecraft which remain within the magnetosphere observe bipolar flows normal to the nominal magnetopause accompanied by flows nearly opposite to the direction of boundary wave and/or FTE motion. Flows are generally discontinuous across FTE and magnetopause boundaries, with reversals in the component of flow tangential to the nominal magnetopause expected during all magnetopause crossings and some entries into FTEs. No bipolar flows normal to the nominal magnetopause occur within FTEs unless they rotate and none occur in the magnetosheath unless the boundary waves propagate relative to the magnetosheath flow. IRM satellite observations on October 28, 1984 may be interpreted either in terms of FTEs or boundary waves.
The regulation of Ca(2+)-pumps is important for controlling [Ca(2+)] in the cytosol and organelles of all eukaryotes. Here, we report a genetic strategy to identify residues that function in autoinhibition of a novel calmodulin-activated Ca(2+)-pump with an N-terminal regulatory domain (isoform ACA2 from Arabidopsis). Mutant pumps with constitutive activity were identified by complementation of a yeast (K616) deficient in two Ca(2+)-pumps. Fifteen mutations were found that disrupted a segment of the N-terminal autoinhibitor located between Lys(23) and Arg(54). Three mutations (E167K, D219N, and E341K) were found associated with the stalk that connects the ATPase catalytic domain (head) and with the transmembrane domain. Enzyme assays indicated that the stalk mutations resulted in calmodulin-independent activity, with V(max), K(mATP), and K(mCa(2+)) similar to that of a pump in which the N-terminal autoinhibitor had been deleted. A highly conservative substitution at Asp(219) (D219E) still produced a deregulated pump, indicating that the autoinhibitory structure in the stalk is highly sensitive to perturbation. In plasma membrane H(+)-ATPases from yeast and plants, similarly positioned mutations resulted in hyperactive pumps. Together, these results suggest that a structural feature of the stalk is of general importance in regulating diverse P-type ATPases.
Collisionless plasma theory modification to include effects of finite Larmor radius of ion and electron on perturbation flow mixing
Small amplitude perturbations in interstellar medium, discussing order of magnitude estimates of properties of cosmic rays, thermal gas, dust and magnetic field
The radiation at the first and second harmonics of the electron plasma frequency from localized Langmuir oscillations is computed for a field-free plasma. The localized perturbations are assumed to have cylindrical symmetry about the direction of propagation of the localized perturbation. It is shown that when the wavelengths of the excited modes are much greater than the scale lengths of the Langmuir perturbation, a quadrupole radiation pattern is recovered for emission at twice the electron plasma frequency. An application to type III solar radio bursts is discussed briefly.
Local ionospheric disturbances which would be created by a planetary entry probe are investigated. Competing theories of spacecraft-ambient plasma interactions are used to estimate computationally the perturbations of the plasma, particularly the structure of the near wake behind planetary entry vehicles. The results have bearing on the location and operation of plasma diagnostic instrumentation aboard planetary entry vehicles. Recent estimates of Mars ionospheric properties plus vehicle dimensions and speeds similar to those of the Viking Mars Lander are used to define the parameters essential to the theory. Smaller entry bodies are also considered. Comparisons are made of the results based on the different theories for a given assumed planetary atmosphere, and also with the perturbations a similar vehicle would generate in the earth's ionosphere.
A 16-cm diameter plasma source operated on argon is described that is capable of producing a plasma environment that closely simulates the low Earth orbit (LEO) conditions experienced by satellites in the altitude range between 300 to 500 km. The plasma source uses a transverse-field magnetic filter, and has been successful in producing low electron temperature plasmas that contain streaming ion populations. Both of these characteristics are important because the plasma in LEO is relatively cold (e.g., Te approx. 0.1 eV) and the ram energy of the ions due to the motion of the satellite relative to the LEO plasma is high (e.g., 7,800 m/s which corresponds to approx. 5 eV for O+ ions). Plasma source operational conditions of flow rate and discharge power are presented that allow the electron temperature to be adjusted over a range from 0.14 to 0.4 eV. The expanding plasma flow field downstream of the source contains both low-energy, charge-exchange ions and streaming ions with energies that are adjustable over a range from 4 eV to 6 eV. At low flow rates and low facility pressures, the streaming ion component of the ion population comprises over 90% of the total plasma density. In the work described herein, a large area retarding potential analyzer was used to measure both electron and ion energy distribution functions in the low density, expanding plasma produced downstream of the plasma source. The benefits of using this type of plasma diagnostic tool in easily perturbed, low-density plasma are identified, and techniques are also discussed that can be used to perform real-time measurements of electron temperature. Finally, recommendations are made that may enable lower electron temperatures to be produced while simultaneously decreasing the plasma source flow rate below 1 to 2 sccm.
Two-dimensional unsteady flow in traveling wave plasma accelerator studied using small perturbation theory
During the magnetic storm of November 1, 1968, the Ogo 5 spacecraft encountered the polar cusp region at low magnetic latitudes. We show that the region just outside the last closed field lines contained a warm magnetosheath plasma, magnetic field perturbations interpretable as field-aligned current layers, and electrostatic waves possibly due to plasma instabilities driven by these currents. Estimates of anomalous resistivity extrapolated along the field lines due to these electrostatic waves lead to estimates of field-aligned potential drops between Ogo 5 and the ionosphere on the order of 2 kV.
The plasma and field perturbations of magnetospheres that would surround magnetized Galilean satellites embedded in the corotating Jovian plasma differ from those produced by interaction with an unmagnetized conductor. If the intrinsic satellite dipole is antiparallel to that of Jupiter, the magnetosphere will be open. It is predicted that Io has an internal magnetic field with a dipole moment of 6.5 x 10 to the 22nd gauss-cubic centimeters antiparallel to Jupiter's, and Io's special properties can be interpreted on the basis of a reconnecting magnetosphere.
The problem of the solar-wind structure resulting from long-lived inhomogeneities in the solar corona has been extended within the framework of a linearized hydrodynamic approach to allow for arbitrary perturbations in the plasma parameters, namely, velocity, density, and temperature. By using a Parker model for the zero-order flow speed, solutions are given for perturbations imposed at the zero-order critical point. Using the restriction that the solutions must be regular at the critical point, it is possible to express all situations as a linear sum of the solutions for pure velocity, density, and temperature perturbations at the critical point. The results of the integrations for three inner-boundary conditions can be used as the elements of matrices that map arbitrary perturbations at one heliocentric distance to any other distance. One interesting feature of the solutions is that the amplitudes at earth for the pure initial temperature situation are larger than for the other two situations.
An expansion making use of the eikonal is shown to yield a solution to the equations of a general weak turbulent plasma which is weakly dependent on space and time. The method is used to derive a quasi-particle conservation equation for quasi-static perturbations of Vlasov plasmas with general equilibrium field configurations.
A shuttle flight experiment, the purpose of which is to obtain space data on the interaction of a high voltage solar array with the ambient space plasma is addressed. This flight experiment is a reflight of the solar array flight experiment, SAFE, except that three active solar array panels, electron release devices and plasma diagnostics are added. This experiment, SAFE 2, evaluates power loss due to parasitic current collected by the solar array, arcing on the solar array and perturbations to the plasma which may increase power loss and disturb plasma and charged particle science acquisition.
In order to support the development of comprehensive performance and life models for future deep space missions that will utilize ion thrusters, we have undertaken a study of the plasma structure in hollow cathodes using an new pneumatic scanning probe diagnostic. This device is designed to insert a miniature probe directly into the hollow cathode orifice from either the upstream insert region in the interior of the hollow cathode, or from the downstream keeper-plasma region at the exit of the hollow cathode, to provide complete axial profiles of the discharge plasma parameters. Previous attempts to diagnose this region with probes was Limited by the melting of small probes in the intense discharge near the orifice, or caused significant perturbation of the plasma by probes large enough to survive. Our new probe is extremely compact, and when configured as a single Langmuir probe, the ceramic tube insulator is only 0.5mm in diameter and the current collecting conductor has a total area of 0.002 cm2. A series of current-voltage characteristics are obtained by applying a rapid sawtooth voltage waveform to the probe as it is scanned by the pneumatic actuator into and out of the plasma region, The bellow-sealed pneumatic drive scans the probe 4 cm in the cathode insert region and 10 cm in the anode/keeper plasmas region at average speeds of about 1 mm/msec, and the residence time at the end of the insertion stroke in the densest part of the plasma near the orifice is measured to be only 10 msec. Since the voltage sweep time is fast compared to the motion of the probe, axial profiles of the plasma density, temperature and potential with reasonable spatial resolution are obtained. Measurements of the internal cathode pressures and the axial plasma-parameter profiles for a hollow cathode operating at discharge currents of up to 35 A in xenon will be presented.
The validity of the orbital-motion theory for cylindrical Langmuir probes immersed in flowing- afterglow plasmas is investigated experimentally. It is found that the probe currents scale linearly with probe area only for electron-collecting but not for ion-collecting probes. In general, no agreement is found between the ion and electron densities derived from the probe currents. Measurements in recombining plasmas support the conclusion that only the electron densities derived from probe measurements can be trusted to be of acceptable accuracy. This paper also includes a brief derivation of the orbital-motion theory, a discussion of perturbations of the plasma by the probe current, and the interpretation of plasma velocities obtained from probe measurements.