The discovery of ETI as a high-consequence, low-probability event

The authors use the opportunity of presenting a paper during the 51st International Astronautical Congress in Rio de Janeiro to introduce a numerical method of characterizing the potential significance of any announcement of discovery of extraterrestrial intelligence. This approach uses the Torino Scale (for characterizing asteroid impacts) as a model for constructing a proposed “Rio Scale” to assist the discussion and interpretation of any claimed discovery of ETI

Neutral density depletions attributed to plasma bubbles

Neutral density measurements in the equatorial thermosphere by the accelerometer of the San Marco V satellite in 1988 indicate from time to time sudden density depletions of 10-20 s. As the occurrence of such events maximizes between 1700 and 0300 hours local solar time, we interpret them as manifestations of the crossings of plasma bubbles by the satellite

New results concerning the geomagnetic effect in the upper atmosphere

89 equivalent duration values based on more than 30000 satellite observations were used to derive relations between different geomagnetic parameters and the correlated changes in upper atmospheric density during magnetospheric storms. The results demonstrate how the storm-time relative density increase depends on the intensity of the magnetospheric storm, on the altitude of the perigee and on its geocentric distance from the center of the diurnal bulge

Investigation of the density wave activity in the thermosphere above 220 km

Based on CACTUS (Capteur Accélérométrique Capacitif Triaxial Ultra Sensible) microaccelerometer measurements it has been demonstrated that — after taking into account all effects included in the MSIS'86=CIRA'86 (COSPAR, 1988) model - there are residual fluctuations in the density of the upper atmosphere much larger than that the accuracy of the measurements can account for. These fluctuations are attributed to some kind of wave activity (Illés-Almár, 1993, Illés-Almár et al. 1996a). The average deviations from a model are considered as a measure of the amplitude of the waves in the atmosphere and are analysed as a function of geomagnetic coordinates, altitude and local solar time, in order to identify possible wave sources either in the lower lying atmosphere or in the thermosphere/ionosphere system. As a first step, the present investigation intends to make a map of the wave pattern by this method

Ring current heating of the low latitude thermosphere connected with geomagnetic disturbances

The excess thermospheric density at low latitudes during the recovery phase of geomagnetic disturbances found in earlier studies has been related to the ring current belt. This would mean that the geomagnetic effect is due not only to an auroral but also to an equatorial source. The low latitude excess density could be separated into a storm time dependent and a local time dependent component. Thus, the morphology of this effect is similar to that of the geomagnetic disturbance field. The heating can be attributed mainly to the precipitation of energetic neutral particles produced by charge exchange, as well as to the dumping of energetic charged particles due to wave-particle interaction. The local time dependent component could be connected also with the asymmetry of the composition of the ring current and with the irregular shape of the plasmasphere

Investigation of the thermosphere-ionosphere interaction by means of the neutral post-storm effect,

Previous investigations of the authors based on the decay rates of many satellites have demonstrated the existence of a post-storm effect in the neutral atmosphere after geomagnetic storms. Its maximum appears 4–6 days after the storm onset. It generally lasts 8–10 days, but if there is also an ionospheric post-storm effect, then it is about twice as long at mid-latitudes and in the evening hours. The observed characteristics of the post-storm effect seem to indicate that it is related to the precipitation of ring current particles due to charge exchange and wave-particle interaction

On a possible ring current effect in the density of the neutral upper atmosphere

The neutral post-storm effect is reconsidered by means of accelerometric data. Since Δρ has proved to be different function of Kp during and outside recovery phases, but a unique function of Dst, the latter is considered as a better index for correcting the effect of geomagnetic activity in models, i.e. it seems that the ring current plays an important role in the geomagnetic effect of the equatorial thermosphere