Abstract. We have determined, based on 28 days of European Incoherent Scatter Common Program 1 mode I data obtained between 1989 and 1991, statistical characteristics of the energycoupling processes between the lower thermosphere, ionosphere, and magnetosphere through an analysis of the electromagnetic energy transfer rate J.E, the Joule heating rate J.E', and the mechanical energy transfer rate U.(JxB) at altitudes of 125, 117, 109, and 101 km. At all altitudes the input electromagnetic energy is distributed to both Joule heating and mechanical energy. The energy distributed to Joule heating is larger than that to mechanical energy, but the latter is generally not negligible. All three rates respectively have two maxima, not in the midnight region but in the dawn and dusk. The enhancements of these rates have positive correlations with the increase of geomagnetic activity represented by the Kp index. The electromagnetic energy transfer rate is greatest at 117 km, becoming smaller with decreasing altitude. It is mostly positive but can be negative. At 117 km the mechanical energy transfer rate is considerably smaller than the electromagnetic energy transfer rate, suggesting that most of the electromagnetic energy at this altitude is converted to Joule heating and a small portion of the electromagnetic energy goes to mechanical energy. At 125 km the mechanical energy transfer rate is larger than that at 117 km. On average, 65% of the input electromagnetic energy is converted to Joule heating and 35% is converted to neutral mechanical energy. At 109 and 101 km altitude the mechanical energy transfer rate becomes negative, hence the Joule heating rate is greater than the electromagnetic energy transfer rate, suggesting that not only electromagnetic energy but also mechanical energy contribute to Joule heating. IntroductionThe magnetosphere and ionosphere exchange energy, in the form of electromagnetic energy flux accompanied by fieldaligned currents j//and electric fields E, particle fluxes associated with plasma precipitation and outflow, or plasma waves. The energy transferred from the magnetosphere to the ionosphere can be a major energy source for driving ionospheric currents J. Most of this energy is eventually absorbed by the neutral gas, but under some conditions it can go partly back to the ionosphere and then to the magnetosphere. The rate of the electromagnetic

The influence of solar activity upon ion upflow in the polar ionosphere was investigated using data obtained by the European Incoherent Scatter (EISCAT) Tromsø UHF radar between 1984 and 2008. In agreement with other work we find that the upward ion flux is generally higher when solar activity is high than when it is low. Ion upflow events and also the upward velocity behave the opposite: they are more frequently seen and higher, respectively, at times of low solar activity. In any year about 30–40% ion upflow is accompanied by ∼500 K higher electron temperature than the background temperature at 400 km altitude. Electron and ion heating in connection with upflow is nearly twice as prevalent during high solar activity as it is at low activity. The acceleration of ions by pressure gradients and ambipolar electric field becomes larger when solar activity is low than when it is high. This variation of the average acceleration is caused by the different shapes of electron density profiles for low and high solar activities. Ions start to flow up at above 450 km altitude when solar activity was high, and lower, at 300–500 km altitude, at low solar activity. It is suggested that the solar activity influences long‐term variations of the ion upflow occurrence because it modulates the density of neutral particles, the formation of the F2 density peak, and ion‐neutral collision frequencies in the thermosphere and ionosphere.

Abstract. Using incoherent scatter radar and magnetometer measurements, we report that during terrestrial magnetic Pc5 pulsations in the afternoon sector, a modulation of particle precipitation and ionospheric conductivities by a factor of 2 occurs in addition to high-amplitude variations of electric and magnetic fields. The event thus seems to be considerably more complicated than previously studied ones where information about conductivities was mostly not available. Our groundbased data set gives us several clues about magnetospheric processes. The origin of the conductivity variations seems to be periodically modulated diffusion of hot electrons into the loss cone that is in turn caused by a ring current instability. The direction of the phase propagation of the observed disturbances is also consistent with the hypothesis of a ring current source. From the ionospheric electron densities we can roughly estimate the equatorial phase space diffusion rate which seems relatively high. In addition, strong electric field and Poynting flux variations suggest that intense coupling to shear Alfv•n modes happens in the magnetosphere. The latitudinal variation of power and wave polarization shows features of a field line resonance. Furthermore, power spectral analysis of conductivities, electric and magnetic fields, reveals that there is a turbulent-like background in all three parameters, which is of magnetospheric origin but modified by the ionosphere. The power law slope of the conductivity spectra is comparable to that of the electric field, while the ground magnetic field shows a steeper decrease with frequency because of the shielding of small-scale current structures. A clear anticorrelation between conductivities and the eastward electric field is interpreted as an ionospheric polarization effect, which transmits Alfv•n waves from the ionosphere upward. Finally, we show that due to the time-varying conductivities only the handedness (ratio of left-and right-handed components) of the Hall current is very close to that of the magnetic field, while the electric field has a significantly different polarization.

On April 21, 1985, an intense Ps 6 pulsation event was observed with the EISCAT radar and the EISCAT magnetometer cross. These measurements serve as a reference for a new electrostatic model for the ionospheric conductances, electric fields, and currents of the auroral structures associated with the pulsations, whose auroral signatures are the g2 bands. All parameters are essentially derived from the input field-aligned current distribution. By varying this distribution and a few free parameters in the relation between the conductances and the upward current, the model is adjusted to the data. We find that by a rearrangement of the upward current from a one-dimensional sheet configuration to tonguelike poleward extensions the observed event is reproduced in a satisfactory way. Compared to previous works, the Hall current is modulated in a different, less symmetric way, and considerably lower field-aligned current densities are required.1.

Abstract. Relations between auroral activities and the generation of neutral-wind oscillations in the polar F region (150-300 kin) were investigated using data from the European Incoherent Scatter (EISCAT) radar, the all-sky auroral camera, and the IMAGE (International Monitor for Auroral Geomagnetic Effects) magnetograms. We dealt with two cases: observations on