[1] The EISCAT radar in Tromsø (67 cgmLat) has been used to estimate statistics of electromagnetic (EM) energy transfer rates by utilizing calculated electric fields, conductivities and E-region neutral winds. It was found that the magnetospheric EM energy input is slightly larger in the evening than morning sector, but due to winds, the Joule heating rate has the largest values in the morning sector. The duskside subauroral region contains large northward electric fields and is a site of significant magnetospheric EM energy input and Joule heating. For quiet conditions (Kp: 0-2 + ), the neutral wind is the major source for Joule heating at all MLT except at the evening maximum of magnetospheric EM input. For medium (Kp: 3 À -4 + ) and high (Kp ≥ 5 À ) activity levels, winds increase Joule heating rates in the morning, but decrease them in the evening. The positive contribution of winds during the morning maximum is 30% and 20% for medium and high activity levels, respectively. The region where winds are a net load for the magnetospheric EM energy input is 17-20 MLT for medium and 13-18 MLT for high activity conditions. The median EM energy transfer to mechanical work made on winds is 20% at maximum. An event with a long-lasting high electric field showed that the ion drag acting on neutrals can decrease the Joule (ion-neutral collisional) heating by more than 50%.Citation: Aikio, A. T., L. Cai, and T. Nygrén (2012), Statistical distribution of height-integrated energy exchange rates in the ionosphere,

[1] The statistical properties of the altitude profiles of the different energy transfer rates in the auroral ionosphere are studied by using the European Incoherent Scatter radar measurements in Tromsø (67 ı cgmLat). Aikio et al. (2012) found that during active conditions, winds reduce the height-integrated Joule heating rates in the evening but enhance them in the morning. Here we show that the reduction in the evening takes place close to and above the peak altitude of Joule heating, so that the Joule heating peak descends from the Pedersen conductivity maximum at 120 km down to about 115 km. Values close to the peak are reduced also in the morning, but the positive effect by winds above the peak makes the net effect positive. The altitude range where the electromagnetic energy of magnetospheric origin is converted to the mechanical energy of the neutrals is only 20-35 km wide in the E region and shows a clear magnetic local time variation. Model calculations are made to study the effect of the angle between the wind and electric field directions on the energy transfer rates and to explain the observed features.

[1] On the basis of ionospheric total electron content (TEC) enhancement over the subsolar region during flares, and combined with data of the peak X-ray flux in the 0.1-0.8 nm region, EUV increase in the 0.1-50 and 26-34 nm regions observed by the SOHO Solar EUV Monitor EUV detector, also with the flare location on the solar disc, the relationship among these parameters is analyzed statistically. Results show that the correlation between ionospheric TEC enhancement and the soft X-ray peak flux in the 0.1-0.8 nm region is poor, and the flare location on the solar disc is one noticeable factor for the impact strength of the ionospheric TEC during solar flares. Statistics indicate clearly that, at the same X-ray class, the flares near the solar disc center have much larger effects on the ionospheric TEC than those near the solar limb region. For the EUV band, although TEC enhancements and EUV flux increases in both the 0.1-50 and 26-34 nm regions have a positive relation, the flux increase in the 26-34 nm region during flares is more correlative with TEC enhancements. Considering the possible connection between the flare location on the solar disc and the solar atmospheric absorption to the EUV irradiation, an Earth zenith angle is introduced, and an empirical formula describing the relationship of TEC enhancement and traditional flare parameters, including flare X-ray peak and flare location information, is given. In addition, the X-ray class of the flare occurring on 4 November 2003, which led the saturation of the X-ray detector on GOES 12, is estimated using this empirical formula, and the estimated class is X44.

Abstract. Similar to the Dst index, the SYM-H index may also serve as an indicator of magnetic storm intensity, but having distinct advantage of higher time-resolution. In this study the NARX neural network has been used for the first time to predict SYM-H index from solar wind (SW) and IMF parameters. In total 73 time intervals of great storm events with IMF/SW data available from ACE satellite during 1998 to 2006 are used to establish the ANN model. Out of them, 67 are used to train the network and the other 6 samples for test. Additionally, the NARX prediction model is also validated using IMF/SW data from WIND satellite for 7 great storms during 1995-1997 and 2005, as well as for the July 2000 Bastille day storm and November 2001 superstorm using Geotail and OMNI data at 1 AU, respectively. Five interplanetary parameters of IMF B z , B y and total B components along with proton density and velocity of solar wind are used as the original external inputs of the neural network to predict the SYM-H index about one hour ahead. For the 6 test storms registered by ACE including two super-storms of min. SYM-H< −200 nT, the correlation coefficient between observed and NARX network predicted SYM-H is 0.95 as a whole, even as high as 0.95 and 0.98 with average relative variance of 13.2% and 7.4%, respectively, for the two super-storms. The prediction for the 7 storms with WIND data is also satisfactory, showing averaged correlation coefficient about 0.91 and RMSE of 14.2 nT. The newly developed NARX model shows much better capability than Elman network for SYM-H prediction, which can partly be attributed to a key feedback to the input layer from the output neuron with a suitable length (about 120 min). This feedback means that nearly real information of the ring current status is effectively directed to take part in the prediction of SYM-H index by ANN. The proper history length of the output-feedback may Correspondence to: S. Y. Ma (syma@whu.edu.cn) mainly reflect on average the characteristic time of ring current decay which involves various decay mechanisms with ion lifetimes from tens of minutes to tens of hours. The Elman network makes feedback from hidden layer to input only one step, which is of 5 min for SYM-H index in this work and thus insufficient to catch the characteristic time length.

The high‐latitude ionosphere‐thermosphere system is strongly affected by the magnetospheric energy input during magnetospheric substorms. In this study, we investigate the response of the upper thermospheric winds to four substorm events by using the Fabry‐Perot interferometer at Tromsø, Norway, the International Monitor for Auroral Geomagnetic Effects magnetometers, the EISCAT radar, and an all‐sky camera. The upper thermospheric winds had distinct responses to substorm phases. During the growth phase, westward acceleration of the wind was observed in the premidnight sector within the eastward electrojet region. We suggest that the westward acceleration of the neutral wind is caused by the ion drag force associated with the large‐scale westward plasma convection within the eastward electrojet. During the expansion phase, the zonal wind had a prompt response to the intensification of the westward electrojet (WEJ) overhead Tromsø. The zonal wind was accelerated eastward, which is likely to be associated with the eastward plasma convection within the substorm current wedge. During the expansion and recovery phases, the meridional wind was frequently accelerated to the southward direction, when the majority of the substorm WEJ current was located on the poleward side of Tromsø. We suggest that this meridional wind acceleration is related to a pressure gradient produced by Joule heating within the substorm WEJ region. In addition, strong atmospheric gravity waves during the expansion and the recovery phases were observed.