Physics of auroral phenomena : proceedings of the 33rd Annual seminar, Apatity, 02 - 05 March, 2010 / [ed.: A.G. Yahnin, A. A. Mochalov]. - Апатиты : Издательство Кольского научного центра РАН, 2011. - 206 с. : ил.

“P hysics o f Auroral P henom ena", Proc. XXXIII A n n u a l Seminar, Apatity, pp. 137 -1 3 9 , 2011 Polar © Kola Science Centre, Russian Academy of Science, 2011 v v y ^ Geophysical STU DY OF GENERAT ION OF ARTIFICIAL MAGNETIC PULSAT IONS IN P c i RANGE AT SPITSBERGEN Institute A.A. M ochalov1, A.B. Pash in1, and T. Yeoman2 ‘ Polar Geophysical Institute, Apatity, Russia 2 University o fLeicester, Leicester, UK Abstract. Excitation of artificial magnetic pulsations in Pci frequency range occurs rather rare. Moreover observation of the ionosphere response to ionosphere heating is not clear in the frame of a conventional model of their generation. Frequently for two events with very similar ionospheric condition artificial emissions may to be observed or not observed. This peculiarity was named as a sporadic nature of the artificial pulsations. Possible explanation o f the sporadic nature is disturbances of neutral particle densities in the ionosphere. This parameter included in the numerical model is not controlled during experiments on ionosphere heating. Series of the heating experiments on the pulsation excitation at Spitsbergen give more features to the sporadic nature. Probability of their excitation is independent from local magnetic activity, although the artificial pulsation amplitude depends strictly on ionospheric magnetic field magnitude. The event study of the convection velocity also shows its insignificant correlation with the emission intensity. New ideas are needed to fit the experimental findings with the numerical model. Introduction Heating experiments at Spitsbergen on the artificial magnetic pulsations excitation in Pci frequency range carried out in 2006 through different seasons, local time, geophysical conditions, etc. Numerical calculations of the effects of the modulated heating with ground based HF powerful transmitter predict simple dependence o f the pulsation amplitude on the ionospheric electric field (Pashin et a l, 1995). Probability of the pulsation excitation is expected to be statistically increased with the magnetic activity growth; however it does not show clear dependence from magnetic activity (Mochalov and Pashin, 2010). In cases of the artificial pulsation observations a relationship of the emission parameters with ionospheric convection also is not observed (Mochalov and Pashin, 2010). Such behavior of the emissions contradicts to the conventional model o f their generation and more extensive analysis of the intervals of''he ionosphere response observations is needed. Observations o f ionospheric drift velocity by radar systems such as SuperDARN (Greenwald et a l, 1995; Chisham et a l, 2007) provide one frame o f the convection map in 10 minutes. Intensity of the artificial emissions may vary faster so its comparison with the convection is not reliable. In simple case of one dimensional current system one may to estimate its location from ratio of horizontal component to vertical one. Magnetometer site at LYR is close to the SPEAR Heating Facility and magnetic variations recorded there are used to deduce ionospheric currents for comparison with artificial emission parameters. For this purpose it is very significant to determine a quite level corresponding to the zero density of ionospheric current. Also it should be noted that at high latitudes ionospheric currents frequently are arbitrary directed so we used variations of horizontal component calculated its direction as well. For our study we choose the heating intervals when a clear ionospheric response is observed, namely: July 12, interval 05.30-06.30 UT; July 15, interval 05.30-06.30 UT; July 11, interval 15.50-16.50 UT. «V ’f t ? 4 и------ 1------ !------ 1------ !------ 1---- £"!------ !------ !------ 1----- 20 25 20 35 40 Ориентацияглавнейосизлдипсаполяризации Г... jr W f 1 L...... * Figure 1. Artificial pulsation parameters deduced from spectral density for July 12, 2006 experiment. Data analysis Artificial magnetic pulsations were observed at the Barentsburg observatory of the Polar Geophysical Institute by a three component magnetometer with a 40 seconds sampling rate. The 137