To what extent is mass loading responsible for the Venus bowshock precursor?

Significant ion and electron flux enhancements immediately upstream of the Venus bow shock were observed by the Electron Temperature Probe on the Pioneer Venus Orbiter. It is shown that mass loading of the solar wind by oxygen ions accounts for only about 10 percent of the observed effect

The possibility of supersonic plasma flow in a collapsing post-sunset ionosphere

As a result of the rapidly decreasing pressure in the topside ionosphere during twilight hours, a rapid downward flow of hydrogen plasma from the protonosphere takes place. In the case of steady state, isothermal, frictionless flow the criterion for the existence of a critical point (transition to supersonic flow) above 1000 km is that the plasma temperature be lower than a certain limiting temperature Ti which is a function of the field line considered. In the latitude region between 40[deg] and 70[deg] this upper temperature limit varies from 963[deg]K to 1066[deg]K. Since these temperatures are considerably lower than the observed temperatures, it follows that in the case of steady state, isothermal flow the velocities will always remain subsonic. When the effect of the neglected terms is examined, the temperature gradient is shown to exert the strongest influence on the nature of the flow. For each latitude there is shown to exist a certain gradient ([part]T/[part]r)0 such that, if [part]T/[part]rT/[part]r)0 the criterion for a critical point to exist above 1000 km is again that the temperature at the critical point be less than some limiting temperature tl. If, however, [part]T/[part]r>([part]T/[part]r)O, then the criterion turns out to be that the temperature at the critical point be larger than Tl. The values of ([part]T/[part]r)0 are between 9 x 10-6[deg]K cm-1 and 6.75 x 10-6[deg]K cm-1 for latitudes between 40[deg] and 70[deg]. For values of the temperature gradient above about 4 x 10-6[deg]K cm-1 the criterion is satisfied for physically realistic temperatures (above 1500[deg]K), i.e. a critical point may exist above 1000 km. On this basis it is concluded that there is a definite possibility that supersonic downward flows in a post-sunset topside ionosphere may occur.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/34189/1/0000478.pd

Classification of auroral precipitation fluxes by characteristic parameters and their effects on the coupling of the precipitation to the ambient ionosphere

The spectral shapes of the precipitating auroral electron flux spectra are quantified by an automated fitting procedure which represents each flux spectrum as a superposition of Maxwellian and Gaussian partial fluxes. This makes it possible to represent each spectrum by a set of characteristic parameters which describe the shape of that spectrum. A set of inverted-V events observed by the Low-Energy Plasma Instrument on Dynamics Explorer 2 near the fall 1981 equinox, has been analyzed. The distribution of the peak inverted-V energies in magnetic local time and invariant latitude has been obtained, and it is shown that by far the highest peak energies occur in the range 65 < IL < 70 and 18 < MLT < 24 hours. It is also shown how the difference in spectral characteristics of the precipitation fluxes between the cusp and the nighttime auroral zone determines the thermal coupling of the precipitation to the ambient ionosphere.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28832/1/0000667.pd

Turbulent transport and heating in the auroral plasma of the topside ionosphere

Using plasma parameters from a typical stormtime ionospheric energy balance model, we have investigated the effects of plasma turbulence on the auroral magnetoplasma. The turbulence is assumed to be comprised of electrostatic ion cyclotron waves. These waves have been driven to a nonthermal level by a geomagnetic field-aligned, current-driven instability. The evolution of this instability is shown to proceed in two stages and indicates an anomalous increase in field-aligned electrical resistivity and cross-field ion thermal conductivity as well as a decrease in electron thermal conductivity along the geomagnetic field. In addition, this turbulence heats ions perpendicular to the geomagnetic field and hence leads to a significant ion temperature anisotropy.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/23640/1/0000604.pd

Comparison of theory and in situ observations for electron and ion distributions in the near wake of the explorer 31 and AE-C satellites

Measurements of electron density, plasma potential, and mean ion mass from the Explorer 31 satellite and measurements of ion current, plasma potential, and ion composition from the Atmosphere Explorer C (AE-C) satellite were used in a comparative study with theory regarding the charged particle distribution in the near wake of an ionospheric satellite. The theoretical wake model of Parker (1976) has been used in the study. It is shown that theory and experiment agree fairly well in the angle-of-attack range between 90 and 135[deg]. In that angular range even the neutral approximation (which treats ions as if they were neutral particles thus ignoring the influence of the electric field) gives fair agreement with the measurements. In the maximum rarefaction zone (145 < [theta] < 180[deg]), however, the theoretical model overestimates the measured ion depletion (AE-C measurements) by several orders of magnitude. A similar conclusion is drawn from the comparison between theory and the Explorer 31 electron measurements where the theory also significantly overestimates the electron depletion. The study indicates that the discrepancies are mainly due to the use of a steady-state theory and of a single ion equation (using a mean ion mass). It is recommended that improved agreement between theory and experiment be obtained by the use of the timedependent Vlasov-Poisson equations with separate equations for the various ion species.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24274/1/0000540.pd

Establishment of stability by collective interactions in a plasma with collisions

http://deepblue.lib.umich.edu/bitstream/2027.42/4931/5/bac2423.0001.001.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/4931/4/bac2423.0001.001.tx

Wave-Particle Interactions Due To Precipitating Particles

It is shown that under conditions typical of the high latitude upper ionosphere instabilities- caused by precipitating electrons are saturated by nonlinear wave-particle interactions. Consequently, a part of the energy stored in the oscillating field is randomized resulting in a temperature increase of the plasma. This heat input mechanism is considerably more effective than the heat input based on binary Coulomb collisions, since the major contribution to the latter comes from very low energy electrons (E \u3c kTe) , while the heating rate due to nonlinear interactions provides an efficient mechanism for direct energy transfer from the higher energy precipitating electrons to the ambient plasma. The heat input rate obtained in this way is of the same order as the rates of energy change due to conduction and convection. Therefore, the energy transfer ,from the precipitating electrons to the ambient electron gas through wave-particle interactions plays an important part in the thermal structure and the dynamics of the upper ionosphere

Theoretical investigation of plasma waves and space vehicle plasma sheaths : second semi-annual report

http://deepblue.lib.umich.edu/bitstream/2027.42/4932/5/bac2826.0001.001.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/4932/4/bac2826.0001.001.tx

A personal memoir of Kristallnacht.

Ernest Fontheim's account of November 10, 1938, the day after Kristallnacht, in Berlin; eyewitness account of Fasanenstrasse synagogue burning, and anti-Semitic violence at the scene of the fire. Includes short translation of article from Berliner Tageblatt, August 26, 1912, covering dedication of Fasanenstrasse synagogue in Berlin.Ernest Fontheim was a boy in 1938 when he experienced the pogrom of November 9/10, 1938 (Kristallnacht).Synopsis in fil

Theoretical investigation of Langmuir probe characteristics and of electron temperatures in the ionoshere and protonosphere and of airglow : semi-annual report

http://deepblue.lib.umich.edu/bitstream/2027.42/4936/5/bac2822.0001.001.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/4936/4/bac2822.0001.001.tx