[en] In the kinetic theory of waves in an E region plasma, collisions are usually represented by a relaxation model. The particular model used in previous work affords a realistic description of frictional effects, but is not well suited for the description of energy transfer and isotropization. The present paper gives an improved theory of electrostatic waves in an E region plasma by using a new relaxation model which describes realistically momentum transfer, energy transfer, and isotropization. Both kinetic and fluid results are derived, the latter by expansion of the kinetic results into the fluid regime. It is thereby assured that the kinetic and the fluid results are continuously connected with each other. The ion gas is treated in the weak magnetic field limit. Particular emphasis is placed on the polytropic exponent, and its transition from the one-dimensionally adiabatic limit to the isothermal limit, as the number of encounters increases, is discussed in detail. The electron gas is treated in the strong magnetic field limit. The general results are simplified in a sequence of approximations, pertinent to cases of practical interest, as, for instance, electrojet instabilities and incoherent scatter

No abstract available

[en] During an extended ionospheric heating experiment near Tromso, Norway on 20 September 1985, ELF waves of 1425 Hz were generated in the ionospheric D-region and the horizontal wave-field was recorded on the ground with high temporal resolution. A half hour interval near noon shows amplitude and phase oscillations of ∼ 3s period which are associated with a Pc 1 geomagnetic pulsation recorded simultaneously on the ground at several Scandinavian stations. We interpret these data as representing ionospheric electric field pulsations in a region ∼ 16 km diameter with amplitudes in the range ∼ 4-12 mV/m. The electric pulsation polarization ellipse was found to be predominantly left-hand polarized ranging from circular to linear with rare intervals of right-hand polarization. These observations show the potential of using heating-induced ELF waves for examining ionospheric electric fields from dc upto at least Pc 1 frequencies which cannot be readily measured by other ground-based techniques

[en] Ionospheric modification experiments have been performed in 1980-1982 at a heating facility which generates CW power of up to 1.5 MW in the 2.5-8 MHz frequency range. D region modification experiments were performed with a partial reflection experiment facility. Amplitude-modulated heating of the D region with ELF and VLF modulation frequencies gives rise to electron temperature modulation, and therefore no ionospheric conductivity modulation. At ULF frequencies, the effect of electron density modulation dominates over the effect of electron temperature modulation. Attention is also given to HF backscatter from F region striations, the anomalous absorption of HF waves, phase changes of a diagnostic HF wave, the plasma line associated with the parametric decay instability, airglow modification, and F region cross-modulation. 19 references

[en] An approximate evaluation is made of the ELF/VLF dipole moment of the polar electrojet antenna established by ionospheric heating via the use of powerful HF waves amplitude modulated with frequencies in the ELF/VLF range. The theory of reciprocity is used to determine the magnitude of the ELF/VLF waveguide excitation produced by such a dipole immersed in the ionosphere. Propagation under a series of ionospheres ranging from quiet auroral nighttime to disturbed auroral daytime is considered. 32 references

[en] Following a brief description of the Tromso heating facility, the expected F region modification effects are discussed. A short review is given of the theories explaining these effects, with emphasis on those dealing with instabilities excited by powerful electromagnetic waves and phenomena caused by these instabilities. (orig.)

[en] The essence of the Bernstein endash Landau paradox is that in a stable unmagnetized plasma electrostatic waves exhibit collisionless Landau damping, while in a magnetized plasma the Bernstein modes, perpendicular to the magnetic field, are exactly undamped, independent of the strength of the magnetic field. This problem is the subject of the present study. An analytical solution of the initial value problem for perturbations perpendicular to the magnetic field is given, which is a generalization of the well-known Landau work to magnetized plasmas. By introducing, according to Plemelj close-quote s prescription, plus- and minus-functions, having unique analytical properties, the character of the short-term and long-term plasma response is revealed, showing in the small magnetic field limit Landau damping in the first gyroperiod, followed by recurrence, and exhibiting irregular behavior with no damping at large times. The initial damping rate is seen to be close to the commonly used Landau damping rate for unmagnetized plasmas, however with a significant systematic deviation. A corrected expression for the Landau damping rate is found which yields a perfect description of the initial damping of oscillations perpendicular to a weak magnetic field. An alternative approach, expansion over Bernstein modes, is also employed. It is found that a zero-frequency (convective) mode, revealed earlier in particle simulations, is included in the complete linear treatment. copyright 1997 American Institute of Physics

[en] A uniform treatment of longitudinal waves or wave-like perturbations in neutral gases and plasmas is presented, using the method of kinetic transport theory in conjunction with a ten-moment collision model. The perturbations are considered to be generated by an oscillating boundary, and their spatial evolution for given frequency is investigated. Special emphasis is placed on the damping of the perturbations, as apparent from their spatial decay. The close intrinsic relation between longitudinal perturbations in plasmas and neutral gases is revealed by systematic variation of the collision to wave frequency ratio and of the charge number. The strong damping of neutral sound found in the small collision frequency limit is seen to be a continuous extension of Landau damping, either of ion-acoustic or Langmuir waves, when starting at the full charge number and reducing the latter to zero. Application of the present theory to experimental neutral sound data leads to almost quantitative agreement, from the near-collisionless to the collision-dominated limit. copyright 1995 American Institute of Physics

[en] Direct comparisons have been made of the ionospheric ELF radiation produced by the new (1 GW ERP) and old (250 MW ERP) antennas of the Tromsoe heater system, but no significant differences in the ELF signal strength have been detected. This initially surprising result is shown to require a value of unity for the index relating the received ELF signal strength to HF power input to the antenna. A series of experiments performed solely to derive more accurate values for this power index provided values ranging from 0.74 to 0.97, dependent on the ELF frequencies generated. It has been suggested that ELF radiation from the normal Tromsoe heater facility should be limited by saturation effects, even when operating well below the maximum HF power density (3mW/m² in the D-region). No evidence for such saturation effects has been found even at power densities greater than 10mW/m²

[en] An ionospheric modification experiment (Heating experiment) will be carried out by the Max-Planck-Institut fuer Aeronomie near Tromso, Norway, beginning 1979. The heating facility and the major modification effects are briefly described. The majority of the modification effects can be measured by ground based facilities, the most important of these being the EISCAT incoherent scatter facility. Some, however, require in situ methods. Therefore, rocket experiments will also be carried out to complement the ground based measurements. Among the quantities to be measured in situ are the electron energy distribution in the lower eV range and the electrostatic fluctuation spectrum in the electron plasma and ion acoustic frequency ranges and in the full angular range with respect to the magnetic field. (author)