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.

О. V. Martynenko, М. G. Botova 2.3. Mid-latitudinal maximum Instead of disappearing near-auroral maximum another one forms during 3rd-5th days of modeling time at the middle latitudes of night ionosphere. It clearly corresponds with accumulation o f H+ ions in upper parts o f these tubes (Fig.3). Such night mid-latitude areas of high electron content were observed in the experiments. Their existence was explained by Knyazeva [6,7] as the influence of neutral wind. But our simulation shows that this structure can be generated by diffusion process only. In order to discover physical mechanism of its formation we ran another simulation, in which the ion temperature was set constant in whole space. In this modeling mid-latitudinal maximum did not appear. Therefore spatial inhomogeneity of Tj plays determining role in its generation. The formation o f this maximum results from coincidence o f the two factors. Diffusional ion flux velocity increases with increasing Tj. On the other hand, the tube volume grows very rapidly with latitude (Fig.6). At the latitudes of 30-40° the diffusional fluxes are strong enough in order to fill relatively small volume of tubes during the daytime and to return big part of accumulated ions back to ionosphere in the night (Fig.5, right panel). As a result the night maximum appears here. At shorter tubes the ion temperature and diffusion rate are too low, and longer ones have too big volume to fill it. Figure 6. The latitudinal dependence of: 1 - ion temperature in the tube upper part 2 - tube volume 0 20 40 60 geomagnetic latitude, deg. 3. Conclusions Thus, in our 3D simulation we have reproduced the formation of the plasmasphere under the influence solely of ionization / recombination and charge exchange reactions and field-aligned diffusion of 0 + and H ' ions for fully symmetrical statement or problem. We have got physically plausible picture o f plasmasphere-ionosphere with a few large-scale structural features of plasma density and ion composition. In the ionosphere they appear as 3 night-time maxima at some latitudinal areas: sub-auroral, near-equatorial and mid-latitudinal. We have explained physical mechanisms of generation of each of these maxima which complete previously known mechanisms. References 1. Кринберг И .А , Тащилин A.B. Ионосфера и плазмосфера, Москва, Наука, 1984 , 190 с. 2. Carpenter D .L , Giles B .L , Chappell C .R , Decreau P.M .E , Anderson R .R , Persoon A .M , Smith A .J, Corcuff Y , Canu P. Plasmaspheric dynamic in the duskside bulge region: a new look at an old topic // J.Geophys. Res V.98. P. 19243-19271. 1993. 3. Green J.L , Reinisch B/W. An overview of results from the RPI on IMAGE // Space Sci. Rev. V.109 P 183- 210.2003. 4. http://uam.mstu.edu.ru 5. Namgaladze, A .A , O.V. Martynenko, A.N. Namgaladze. Global model o f the upper atmosphere with variable latitudinal integration step. Geomagnetism and Aeronomy International, v .l, N o .l. P.53-58, 1998. 6. Knyazeva M .A , Namgaladze A.A. An investigation o f the night-time increases o f the plasma density in the middle-latitude ionospheric F2-layer by the mathematical modeling method // Physics of Auroral Phenomena, Proc. XXXI Annual Seminar. Apatity. Kola Science Centre. Russian Academy o f Science. P. 145-148. 2008. 7. Knyazeva M .A , Namgaladze A.A. The influence of the northward wind on the latitudinal location of the enhanced electron density regions in the night-time ionospheric F2-layer and plasmasphere of the Earth // Problems of Geocosmos: Proceedings of the 7th International Conference (St. Petersburg, Petrodvorets, 26 - 29 May 2008) - St. Petersburg, 2008. 1 3 2