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It was predicted (Carlson, 1987; 1993) that once HF radio waves achieved ionospheric energy densities comparable to that from the solar EUV, they could produce their own ionosphere. That work estimated a GW ERP of rf energy would produce an ionosphere half that from an overhead sun, assuming 15 efficiency conversion of rf energy to accelerated electron energy. [Until 2009 only one experimental estimate existed, 15 from Carlson, 1982.] The production mechanism proposed was impact ionization, by HF-accelerated electrons, to energies exceeding thermospheric ionization potentials. Solar EUV, aurora, and high-power HF radio-waves produce suprathermal electrons in the 15-100 eV energy range, yielding long-lived ionization in the ionosphere. Once suprathermal electrons are produced, the Aeronomy of production, transport, and recombination are in common. The key to understanding artificial ionization thus reduces to conversion efficiency of HF energy to ionization. By 2008 technology reached GW ERP. The prediction was tested, and confirmed [Pedersen et al, 2009, Blagoveschenskaya et al, 2009] at high latitudes.

We develop a theory of the magnetic-zenith effect (MZE) observed upon the ionosphere modification by powerful radio waves. The dependences of MZE on main parameters, such as the magnetic-field inclination angle, pump-wave frequency and power, and angular width of HF beam are obtained. The optimal elevation angle of pump-wave beam is predicted.

A kinetic theory is developed for strong Langmuir turbulence in the region of the reflection of a high-power ordinary radiowave in ionospheric plasma. The structure and quantity of the cavitons that form in the stage of well-developed turbulence are determined. The acceleration of electrons is investigated, and it is found that the electron distribution function acquires a significant tail with an effective temperature T{sub eff} of 50 to 100 times the plasma temperature. The region occupied by fast electrons is hundreds of times thicker than the layer of Langmuir turbulence. The theoretical results are shown to correlate well with the observational data on the electron acceleration and plasma emission in ionospheric experiments.

Observations of the ionospheric electron density modified by a powerful wave of the Sura HF heating facility were carried out in Russia at middle latitudes in August 2002. Amplitude scintillations and variations of the phase of VHF signals from Russian orbiting satellites passing over the heated region along the chain of three satellite receivers have been recorded. The experimental data were converted to electron density maps using a stochastic inversion. Tomographic measurements conducted during a low magnetic activity revealed that HF powerful waves can produce significant electron density disturbances up to heights significantly exceeding altitudes of the F layer peak. Both large-scale plasma enhancements and small-scale density irregularities can be generated by the HF radiation. Wavy density structures were also observed within a sector which is much wider than the area covered by the main lobe of the heating antenna. Small-scale density irregularities are mostly field-aligned although large-scale structures can be detected within a much larger area. A distinctive peculiarity of electron density changes occurred during heating is producing a zone of low density inside the area illuminated by the antenna beam. The results indicate that satellite radio tomography and scintillation measurements are effective diagnostic techniques giving a valuable information to studies of effects induced by HF modification. The complete system of plasma density disturbances describing by the theory of “the magnetic zenith effect” has been for the first time studied in this Letter. A good agreement between the theory and experimental data has been obtained.

The theory of ionospheric modification for the beam of powerful radio emission directed along magnetic field lines is developed. Nonlinear process of beam self-focusing on striations is shown to determine strong amplification of heating and acceleration of plasma electrons. It results in a dramatic enhancement of optic emission from the magnetic zenith region in ionospheric F-layer. An excellent agreement between the theory and recent fundamental observations at HAARP facility (Alaska) [T. Pedersen et al., Geophys. Res. Lett. (2002), in press] is demonstrated.

The first EISCAT Svalbard Radar (ESR) and ground optical campaign was carried out in January 1998 to cover a variety of dayside auroral activities in the 1000–1400 magnetic local time sector. The current paper focuses on 1 hour of combined radar, meridian scanning photometer, and ground magnetometer observations near the cusp convection throat on January 23, 1998. The radar was pointing north, at a fixed elevation of 45°, in the scan plane of the photometer. Several plasma dynamical features were revealed by this simplest possible convection mode of the ESR, such as spontaneous movement of the cusp inflow region and cusp-related ionization blobs pushing through the ambient incompressible plasma. Multiple morning discrete arcs were found to be aligned with convection streamlines equatorward of the flow reversal, while plasma in the polar cap inflow region streamed perpendicularly across the optical cusp boundary, as earlier anticipated.

This paper presents the first observations of simultaneous polar cap patches and polar cap arcs in a single common 1000-km field of view, and identifies a model that explains the interplanetary magnetic field (IMF) dependencies of the observed phenomenology. To study the characteristics of the polar cap optical emissions in the 630.0 nm line during transitions of the IMF Bz, we have scanned images taken at Qaanaaq, Greeland, between 1989 and 1994. We found that on a few occasions, when Bz changed from a south to a north orientation, a particular pattern of polar cap patches and Sun-aligned arcs coexisted. No similar pattern of coexisting arcs and patches was found during north-to-south IMF transitions. The detailed analyses of three of these events are presented here in which patches and polar cap arcs are clearly identified to reside simultaneously within the Qaanaaq imager field of view. The digisonde located also at Qaanaaq is used to confirm that the optical patches correspond to enhancements in the number density and a simultaneous decrease of the hmF2 value. These two factors increase the capability of the imager to differentiate between patches and the background airglow. Data collected by the DMSP F8 satellite during one of the events reaffirm the appearance of polar cap precipitation during the Bz positive period. The J4 sensor on board DMSP F8 detected typical electron fluxes commonly associated with polar cap arcs. The coexistence of patches and arcs is due to a slower response of the patches in exiting the polar cap, and then the relatively sudden appearance of polar cap arcs presumably driven by dayside reconnection between the IMF and open flux drawn initially equatorward toward the cusp. This model, of dayside reconnection switching from equatorward of the cusp for Bz south to poleward of the cusp for Bz north, likewise explains why arcs and patches are seen by the imager to coexist for rapid Bz reversals only from south to north and not from north to south.

Some implications are considered of recent theoretical work concerning the excitation of dayside ionospheric convection by magnetic reconnection at the dayside magnetopause. In particular, transient bursts of such reconnection (‘flux transfer events’) are considered as a cause of polar cap ‘patches’ of enhanced plasma density. Examples of such patches, as observed at European longitudes by the EISCAT radar, are presented and used to discuss the implications of the proposed mechanism.

The height distribution of the dayside cusp aurora and the relation between optical emissions and net downward electron energy flux are discussed. These two important characteristics of day-side cusp aurora are still unknown. It is instructive to compare particle flux and optical luminosity because these two quantities should be proportional if the cusp aurora is caused by electron impact, as has been found for nighttime aurora in the oval. Furthermore, there should then be a direct relation between auroral altitudes and particle energy. Based on coordinated auroral observations at Svalbard and Greenland, together with simultaneous, overhead F-9 satellite measurements, these quantities have been evaluated. >

Under current solar minimum conditions at Arecibo, Puerto Rico, large (∼1000–2000 K) enhancements in electron temperature are observed in the winter, nighttime ionosphere when high-power 3-MHz radio waves reflect near the F region peak. Computational modeling has been performed to determine the cause of the unusually large temperature enhancements. The results indicate that low collisional cooling rates combined with strong thermal conduction along geomagnetic field lines play a key role in elevating F region temperatures and spreading the electron temperature enhancements far outside of the region where radio wave energy is deposited. Thus, the dramatically large temperature enhancements are attributable primarily to expected low cooling rates of the electron gas, rather than unexpectedly high heating rates.

Spectral analysis of the midnight temperature anomaly observed on Atmosphere Explorer-E indicates that the phenomenon can be adequately represented with wave numbers between 1 and 5. Results from a multiconstituent circulation model suggest that this feature and associated variations in composition are the result of a complex interaction between the semidiurnal tide generated in the lower atmosphere and ion-neutral momentum coupling associated with the diurnal variation of the ion density which, in turn, also generates higher order tidal models.

Enhancements of various features of the incoherent scatter spectrum are observed when the ionosphere is illuminated with powerful, high frequency radio waves. The radio waves excite plasma instabilities producing lines or more complex spectral features near the local plasma frequency, at the local ion acoustic frequency, near the local gyrofrequency, and near twice the gyrofrequency. The enhancements occur in a thin slab as observed by the incoherent scatter radar and at both upshifted and downshifted frequencies with respect to the probing radar frequency. The enhancements are observed to vary with time when the excitation is held constant and is turned on or off. The high power radio waves are produced by a 160 kw transmitter feeding a log-periodic pair of curtains mounted at the focus of the 1000-ft reflector and covering the frequency range from 5 to 12 MHz. The effects are observed with the incoherent scatter radar using the same reflector and with ionosondes and photometers. The frequencies of the enhanced plasma line and the ion line and their relation to the pump (high frequency radio wave) frequency are predictable from available parametric instability theory. Other spectral features are being explained as the theory develops with the help of the observations. There remain some discrepancies, in particular the asymmetries in intensity, width, and fluctuations of the upshifted compared to the downshifted plasma lines.

A case study of coordinated observations of low-energy ( 10 radians for fluctuation frequencies >0.0067 Hz) were found to be well correlated with intense fluxes (>109 particles (cm2 s sr)−1) of precipitated low-energy electrons. Total electron content and magnetometer measurements indicate that the onset of the precipitation event was about 10 min prior to the DMSP pass. Within this time scale, the ionization generated in the F region could reach the topside so that the thermal sensor on board the DMSP satellite was able to measure a factor of 2–3 density enhancement at 840 km. The latitudinal width of these density structures is consistent with that of F region blobs observed at Chatanika. The gradient scale length measured in the topside was only 30 km, which was probably responsible for the fast growth rate of the scintillation-producing irregularities. The phase to amplitude scintillation ratio changed rather drastically compared to quiet magnetic times, however, implying that increased convection velocities during these magnetic disturbances were partially responsible for the enhanced phase scintillation.

It has now become technologically feasible to construct ground-based HF radar systems which can deliver RF energy to the ionospheric plasma, with power densities sufficient to alter the ionospheric electron thermal budget and plasma characteristics. Effects produced by a ground-based transmitter of a power aperture of the order of 10,000 Mw sq m in the frequency range from 4 to 12 MHz are shown in a graph. Another graph presents a profile of electron gas temperature enhancement due to energy deposition by a high power HF transmitter. The conduction of high-power HF ionospheric plasma experiments is discussed. Attention is given to plasma instabilities, wave-particle acceleration effects, spacial and time scales, parametric instabilities, spread-F, and the possibility of placing high power-aperture radars on an orbiting space platform.

Plasma line data gathered at the Arecibo Observatory are used to examine relative variations in topside F region differential photoelectron fluxes in the 5- to 20-eV range. A spectral feature not found in present theoretically calculated spectra is noted near 15 eV. A new approach to the interpretation of the measured spectra is taken, which allows a qualitative estimate of the relative importance of different energy loss mechanisms. The altitude variation of the observed photoelectron flux energy spectra at the higher altitudes (above 350 km) and the lower energies (less than 10 eV) agrees quantitatively with the expected variation of the spectrum.

An outbreak of reticuloendotheliosis occurred in a flock of Japanese quail. The most striking and consistent lesion observed was a marked thickening and nodular formations along the digestive tract. Other organs were involved with varying degrees of frequency, with tumour masses being observed in the lungs, liver, spleen, heart, pancreas, caeca! tonsils, ovary, kidney, airsacs, thyroid glands, testes and sciatic nerves. The histological changes were characterized by proliferation of an extremely anaplastic mononuclear type cell in the affected tissues. The cells bore all the characteristics of neoplastic growth, with large bizarre nuclei, numerous mitotic figures, misshapen nucleoli, and prominent pleomorphic cytoplasm.

Regular observations of incoherent backscatter spectrums of the ionosphere at the Arecibo Ionospheric Observatory in Puerto Rico since June 1964 establish presunrise and postsunset ionospheric heating above the Fmax to be present during the winter, though less evident toward either equinox, and absent during the summer. The observed heating is interpreted in terms of a streaming of photoelectrons from the sunlit magnetic conjugate ionosphere. The detailed timing of the onset of the heating supports this, and a semiquantitative model for the heating mechanism explains further details of the observations. Photoelectrons streaming from the magnetic conjugate ionosphere are concluded to produce significant heating effects for the midlatitude upper F region.

Elaborate methods have been developed for identification of future managers, based on certain assumptions of traits or qualities of the individual. On the other hand, behavioral and situational models of the managerial-leadership function imply quite different identification and developmental strategies. Between the two poles lie a variety of alternatives and more realistic approaches to the selection process.

Ionospheric F-region heating by a high-frequency transmitter (100 kW at 5.62 MHz fed into a 1000-ft dish producing a beam with an angular half-width of 10 deg) was observed with a 430-MHz incoherent scatter radar, an ionosonde, and several photometers. The electron temperature of the ionosphere was increased by as much as 30% at and just below the height where the local plasma frequency was equal to the frequency of the heating transmitter. Calculations show time constants of 40 sec for electron heating and less than 10 sec for the cooling at 308 km when the heating transmitter was operated in a pulsed mode.

Comparison of radar backscatter and rocket probe measurements of ionospheric electron temperature