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Temperature dependence of emission measure in solar X-ray plasmas. 1: Non-flaring active regions
X-ray and ultraviolet line emission from hot, optically thin material forming coronal active regions on the sun may be described in terms of an emission measure distribution function, Phi (T). A relationship is developed between line flux and Phi (T), a theory which assumes that the electron density is a single-valued function of temperature. The sources of error involved in deriving Phi (T) from a set of line fluxes are examined in some detail. These include errors in atomic data (collisional excitation rates, assessment of other mechanisms for populating excited states of transitions, element abundances, ion concentrations, oscillator strengths) and errors in observed line fluxes arising from poorly - known instrumental responses. Two previous analyses are discussed in which Phi (T) for a non-flaring active region is derived. A least squares method of Batstone uses X-ray data of low statistical significance, a fact which appears to influence the results considerably. Two methods for finding Phi (T) ab initio are developed. The coefficients are evaluated by least squares. These two methods should have application not only to active-region plasmas, but also to hot, flare-produced plasmas.
Suprathermal particles
Recent observations of suprathermal particles in the interplanetary medium in the energy range from solar wind (above about 1 keV) to low energy solar cosmic rays (about 1 MeV) are reviewed. A crude classification of the types of observed fluxes is given, and the sources of the suprathermal particle populations and energy contained in them are discussed. Among the possible interactions of these particles with the solar wind plasma, the particular interaction which generates type III solar radio bursts is analyzed.
Correlation of bow shock plasma wave turbulence with solar wind parameters
The r.m.s. field strengths of electrostatic and electromagnetic turbulence in the earth's bow shock, measured in the frequency range 20 Hz to 200 kHz with IMP-6 satellite, are found to correlate with specific solar wind parameters measured upstream of the bow shock.
Effect of parasitic plasma currents on solar-array power output
Solar-array voltage-current curves are calculated by assuming the existence of parasitic loads that consist of local currents of charged particles collected by the array. Three cases of interest are calculated to demonstrate how the distribution and magnitude of parasitic currents affect output. Solar array performance degradation became significant when the total parasitic current plus the load current exceeded the short-circuit current. Approximate graphical methods were useful for many applications. Power loss, which was calculated by summing the product of parasitic current and the local potential, underestimated the loss in maximum power.
The importance of spectroscopy in the 80-800 A region for plasma diagnostics in the solar atmosphere
The importance of the spectral range from about 80 to 800 A for determining physical conditions in different regions of the solar atmosphere is discussed. Examples are given of line ratios that may be used to determine electron densities in quiet-sun regions, active regions, and flares. The possibility of determining electron temperatures from line ratios in the EUV is considered. It is shown that profiles, as well as intensities, of spectral lines must be obtained for a proper interpretation of the spectra. Approximate parameters are provided for a solar grazing-incidence spectrograph suitable for the study of the 80-800-A wavelength region.
Electrodynamic Interactions
It is apparent that the electrodynamic tether offers new potential for unique scientific experiments which should enhance the understanding of space plasma physics and in particular certain classes of solar system plasma phenomena, and that these science studies will also address a number of key engineering concerns which may open up new power and thrust generation technology that could be a significant factor in future space operations.
Spacelab 1 - Scientific objectives, life sciences, space plasma physics, astronomy and solar physics
A general overview of the accomplishments of the Spacelab 1 complement to the Shuttle mission of Nov. 28, 1983, is presented. Consideration is given to scientific results in the fields of life sciences, materials sciences, atmospheric physics, and earth observations. A table is given which lists the scientific objectives and the percentage of objectives accomplished in each field.
Current collection from the space plasma through defects in solar array insulation
Operating high-voltage solar arrays in the space environment can result in anomalously large currents being collected through small insulation defects. Tests simulating the electron collection have shown that there are two major collection modes. The first involves current enhancement by means of a surface phenomenon involving secondary electron emission from the surrounding insulator. In the second mode, the current collection is enhanced by vaporization and ionization of the insulator material, in addition to the surface enhancement of the first mode. The electron collection due to surface enhancement (first mode) has been modeled. Using this model, simple calculations yield realistic predictions.
Ulysses near-ecliptic observations of differential flow between protons and alphas in the solar wind
The evolution of differential streaming between protons and alpha particles in the solar wind was observed with the solar wind plasma experiment on the Ulysses spacecraft over the solar range of 1.15 to 5.40 AU between November 18, 1990, and May 5, 1992. The correlation of the difference in ion speeds, Delta V = the absolute value of V(sub alpha) - the absolute value of V(sub p), with the proton speed V(sub p) observed by other spacecraft at solar distances less than or equal to 1 AU disappeared at approximately 2 AU. At solar distances greater than or equal to 2.85 AU, the largest values of both V(sub alpha p) = the absolute value of V(sub alpha p) = the absolute value of V(sub alpha) - V(sub p) and the absolute value of Delta V were found in the interaction regions on the leading edges of high-speed streams. The differential streaming was typically enhanced just downstream of strong forward and reverse shocks, and large negative values of Delta V were frequently encountered in the interaction regions. A correlation between V(sub alpha p) and the ratio tau(sub zero)/tau(sub e) of Coulomb collision time to expansion time was observed at all distances, but it is suggested that at the larger values of tau(sub zero)/tau(sub e) observed correlation may arise from enhanced production of differential streaming by processes that also increase the entropy of the solar wind protons.
On Determination of 3D Morphology and Plasma Properties of the Solar Corona
An earlier analysis preformed and published will be revisited and applied to SECCHI's observations. Using coronal models and imaging-rendering techniques we will investigate several important facts regarding the solar stereographic mission. A synthesized image will be presented formed from integrating the emission from the volume elements along the line-of-sight path through a three-dimensional volume. We used analysis of pairs of these synthesized images with various angular perspectives to investigate the effect of angular separation on mission objectives. The resulting images and analysis provide guidelines for developing a stereographic mission analysis program.
NIAC Phase I Final Report: On-Orbit, Collision-Free Mapping of Small Orbital Debris
Sub-centimeter orbital debris is currently undetectable using ground-based radar and optical methods. However, the pits in Space Shuttle windows produced by paint chips (e.g. the 3.8mm diameter pit produced by a 0.2mm paint chip on STS-7) demonstrate that small debris can cause serious damage to spacecraft. Recent analytical, computational and experimental work has shown that charged objects moving quickly through a plasma will cause the formation of solitons in the plasma density. Due to their exposure to the solar wind plasma environment, even the smallest space debris will be charged. Depending on the debris size, charge and velocity, the plasma signature of the solitons may be detected by simple instrumentation on spacecraft. We will describe the amplitude and velocity of solitons that may be produced by mm-cm scale orbital debris in LEO. We will discuss the feasibility of mapping sub-cm orbital debris using a fleet of CubeSats equipped with Langmuir probes. The time and fleet size required to map the debris will also be described. Plasma soliton detection would be the first collision-free method of mapping the small debris population.
Ulysses Near-Ecliptic Observations of Differential Flow Between Protons and Alphas in the Solar Wind
Describes the solar wind plasma experiment on the Ulysses spacecraft over the solar range of 1.15 to 5.40 AU between Nov. 18, 1990 and May 5, 1992.
Solar Coronal Mass Ejections Plasma Diagnostics Expressed as Potential Stellar CME Signatures
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Solar cycle variation of plasma mass density in the outer magnetosphere: Magnetoseismic analysis of toroidal standing Alfvén waves detected by Geotail
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Magnetic fields, plasmas, and coronal holes: The inner solar system
In situ magnetic field and plasma observations within 1 AU which describe MDH stream flows and Alfvenic fluctuations, the latest theories of those phenomena are discussed. Understanding of streams and fluctuations was enhanced by the acquisition of nearly complete sets of high resolution plasma and magnetic data simultaneously at two or more points by IMPs 6, 7, and 8, Mariner-Venus-Mercury, HELIOS 1, and HELIOS 2. Observations demonstrate that streams can have very thin boundaries in latitude and longitude near the sun. This has necessitated a revision of earlier views of stream dynamics, for it is now clear that magnetic pressure is a major factor in the dynamics of stream in the inner solar system and that nonlinear phenomena are significant much closer to the sun than previously believed. Simultaneous IMP 6, 7, and 8 observations of Alfvenic fluctuations indicate that they are probably not simply transverse Alfven waves and suggest that Alfvenic fluctuations are better described as nonplanar, large-amplitude, general Alfven waves moving through an inhomogeneous and discontinuous medium, and coupled to a compressive mode.
Effects of solar wind composition on the threshold for plasma instability in the tran- sition region
Effect of solar wind composition on plasma instability threshold in transition region
Minor constituents in the solar wind originating from plasma-dust interactions
Atoms, molecules, and atomic and molecular ions generated by solar wind interactions with dust grains of the zodiacal cloud are discussed. The main processes leading to the generation of these particles are described and relevant methods of observation are examined.