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.

*Physics o fAuroral Phenomena'’, Proc. XXXIIIAnnual Seminar, Apatity, pp. 1 3 - 1 6 , 2011 © Kola Science Centre, Russian Academyof Science, 2011 Polar Geophysical Institute Kp INDEX CORRECTION IN ORDER TO ELIMINATE EXCESS IMPACT OF HIGH LATITUDE MAGNETOSPHERIC DISTURBANCES N.A. B arkhatov1, A.E. Levitin2, S.E. Revunov1 1. Nizhniy Novgorod State Pedagogical University, Nizhny Novgorod, Russia 2. Pushkov Institute o f Terrestrial Magnetism, Ionosphere and Propagation o fRadio Waves (IZMIRAN), Russian Academy o f Sciences, Troitsk, Russia Abstracts. The present research working out of a technique of correction of the Kp-index is devoted. It will allow to avoid superfluous influence of foreign polar sources and is more reliable to estimate planetary geomagnetic disturbance. The algorithm of preliminary magnetogram clearing used for calculation o f the specified index of planetary geomagnetic activity is offered. 1. Introduction Recently with the advent of the new narrowly focused indices for description the solar and geomagnetic activity, which offered by various institutes (for example, ULF-index Institute of Physics o f the Earth, RAS [Kozyreva and Kleymenova, 2008]), a question of reliability of early create the planetary indices is arising. So, Kp index has been created in 1949 by Bartels (Julius Bartels, till 1964 the director of Institute of Researches of Solar System of Max Plank, Germany). This index intended for representation of planetary geomagnetic disturbances in a simple scale from 28 values. In 1951 it has been officially recognized by the International Association on studying of problems of Geomagnetism and Aeronomy (IAGA). More detailed information one can be found on Helmholtz Centre Potsdam GFZ German Research Centre for Geosciences: http:// www-app3.gfz-potsdam.de/kp_index, http:// www.gfz-potsdam.de/pb2/pb23/niemegk/kp_index/kp.html. Kp index under the geomagnetic data received at 13 earth stations is calculated, distributed on globe in subauroral latitudes (49°-62°). Today it is widely at studying of dynamic communications between a solar wind and magnetosphere, in problems of estimation of plasma-pause position and other plasma regions. Also it used as an input parameter of various mathematical magnetospheres and ionospheres models. It well known that strong magnetospheric disturbances the excessive contribution to settlement values of Kp index can give. The algorithm of calculation of Kp index existing now called to describe planetary geomagnetic disturbance does not allow to consider dynamics o f existential change magnetosphere-ionosphere current systems, resulting change of topology of a magnetic field during the periods magnetospheric disturbances. Errors of an existing planetary Kp index during the periods strong magnetospheric disturbances are shown. At this time the sizes and position o f borders of a polar cap and auroral zones change. There can be a situation when the network of stations o f calculation of Kp partially appears in polar region so calculated during these moments value o f Kp index local subauroral activity is correspond, instead of planetary geomagnetic activity. 2. Check of existence Kp index error The prospective error o f an index not with a technique of its calculation is connected, but with a base material - magnetograms from observatories. Really, in disturbed day observatories in subauroral latitudes on magnetograms the same dynamics of disturbances, as high-latitude stations is register. Influence substorm activity on magnetometer indications at stations of calculation Kp on an example of 2004 can be shown. It was found out that ~30% from observatories influence of the general in middle-latitude and high-latitude area magnetosphere source of disturbances contain. As a result calculate values of the Kp-index overestimated is appear. It is clearly visible on an example magnetograms from two observatories located at different latitudes approximately on one magnetic meridian (station of calculation of Kp-index Meanook (MEA, geom. latitude 61,7°/longitude 305,7°) and high- latitude station of calculation of AE-index Yellowknife (YKC, geom. latitude 69,2°/longitude 296,6°)). The Fig. 1 shows magnetograms for horizontal components o f geomagnetic field during disturbed day on January, 7th, 2004. Other situation during the periods of absence strong magnetospheric disturbances is observed. The Fig. 2 illustrates magnetograms from the same observatories, but already in quiet day on April, 29th, 2004. 13