A.E. Stepanov, V.L. Khalipov, E.K. Zikrach

(Institute of Cosmophysical Research and Aeronomy, Yakutsk, Russia)

V.V. Afonin (Space Research Institute, Moscow, Russia)

On the basis of analysis of ionospheric data of the Yakut meridional chain of ionosondes (Tixie Bay, L=5.57 and Kotelny Island, L=6.00) and the Cosmos-900 satellite the ground-based and satellite signatures of large-scale blobs of ionization in auroral and polar cap zones are revealed. The ionospheric stations of vertical and inclined sounding register plasma blobs, mainly, in midnight and morning sectors of local time. The satellite measures them in the polar cap and auroral zone in various sectors of local magnetic time. The satellite and ground data show that in some cases for period of observations several plasma blobs are registered. Cases of registration of ionization blobs on a polar edge of the main ionospheric trough are revealed. A seasonal course of occurrence frequency of plasma blobs in the polar cap and auroral zone on ground and satellite data has an expressed maxima in winter months.

Horizontal sizes of blobs (129 cases of measurements from the satellite in northern hemisphere) have two peaks at 200-400 km and 600-700 km. The model calculations of drifts trajectories carried out at a stationary model of electric field (IZMEM) show, that the blobs of ionospheric plasma are formed in the dayside cusp/cleft region during sharp changes of interplanetary magnetic field parameters.

This work was supported by the Russian Fund of Basic Research under the grant N98-05-64909.

V.L. Khalipov, A.E. Stepanov, E.K. Zikrach

(Institute of Cosmophysical Research and Aeronomy, Yakutsk, Russia)

After the data of high-latitude ionospheric stations from Tixie Bay (InvLat = 65.1) and Kotelny Island (InvLat = 69.5) the boundary of the polar wall of the main ionospheric trough (MIT) in the morning sector (00 - 06 LT) during magneto-quiet conditions are analysed. After the statistics study, carried out after a large number of data, in the morning sector during periods of very quiet geomagnetic conditions (Kp = 0-1) positions of a MIT polar wall boundary have two branches dispersing to the pole and equator from the common approximation line. The purpose of the present work is to explain such behaviour of the polar wall at morning hours. The hourly values of interplanetary magnetic field (IMF) parameters were considered in cases when the boundary of a polar wall displaced either to the pole or to equator. It is discovered, that in the morning sector the displacement of the boundary toward the pole is observed only for negative B_y and large positive B_z IMF values. For specific events the pictures of a large-scale convection designed on a model dependent from IMF parameters are obtained.

V. D. Tereshchenko, V. A. Tereshchenko (Polar Geophysical Institute, Murmansk, Russia)

It is known that the presence of an enhanced electric field in the polar ionosphere leads to an anisotropic ion velocity distribution for the F-region. An analytical expression for the ion distribution function has been derived recently by solving the kinetic equation with BGK and Lenard - Bernstein collision operators. In this paper the problem was solved by Larmor circles method for weakly inhomogeneous plasma.

According to the method of orbits, first of all, find the distribution function of Larmor circles in phase space and then determine the charged particle velocity distribution, using the relation of coordinates of a particle and the centre of orbit. It is necessary to take into account, that the electric field influences particles and changes the mean velocity and the randon velocity related to it. This simple method allows to deeper understand physical nature of the plasma phenomena. The derived formulas coincide with those inferred from the solution of the kinetic equation with the simple BGK collision term for low collision frequencies.

The non-Maxwellian features of the ion distributions need to be taken into consideration when studying necessary and sufficient conditions for instability of plasma waves. General criterion for electrostatic plasma instabilities is established in an inhomogeneous plasma with anisotropic velocity distributions. It is shown that the growth of an external electric field can result in stabilization of electrostatic modes in the areas with the negative plasma density gradient. In this case the instability grows only for the areas with the positive density gradient.

S.M.Chernyakov (Polar Geophysical Institute, Murmansk, Russia)

I.I.Shagimuratov (West Department of IZMIRAN, Kaliningrad, Russia)

The preliminary analysis of the ionospheric delays of GPS signals for the high-latitude ionosphere are presented. The first observations at high-latitude in Russia have been made in Murmansk since July 1998. A dual-frequency receiver is used for the observations providing measurements of the group (code) and phase delays of a signal at two coherent frequencies. Differential delay depends on the total electron content (TEC) along the path. Code measurements allow to determine an absolute value of the signal delay at the satellite-Earth track. Phase measurements yield information on relative variations, but since the noise level is an order of magnitude less, than that for the code one enables to detect fine effects in the ionosphere.

It is known, that ionospheric delay obtained from dual-frequency GPS observation is biased on the instrumental (satellite/receiver) delays. For reducing the absolute TEC we have applied a procedure allowing to separate the instrumential delay and the ionospheric part of delay. Algorithm of reduction of mid-latitude measurements has been modified for the high-latitude features observations taken into account. As a result of reduction the instrumential biases are found for all satellites and the diurnal variations of TEC is determined. In spit of an essential unhomogenious structure of the high-latitude ionosphere the algorithm permit to obtain the distribution of the absolute TEC over station.

The results of analysis of the GPS data for quiet and disturbed days are presented. It is found out, that TEC behaviour for the polar ionosphere is very variable as against the one at middle latitudes. During magnetic disturbance the increased level of TEC is indicated. At that time differential Doppler clearly identify unhomogeneous structure of ionosphere as well as wave-type disturbances.

The first result show the efficiency of using GPS for study of the structure and dynamics of the polar ionosphere. The regular GPS observations may be a good indicator of ionosphere state.

A.A. Namgaladze^1,2, A.N. Namgaladze²

We have obtained the first numerical results of modeling the behavior of the sub-auroral and auroral ionosphere over Scandinavia in November 1995 using the global upper atmosphere model (Namgaladze et al., 1998) and compared these results with the data of mapping the ionospheric F region by means of satellite tomography presented by Nygren et al.(1997) and with the data of the empirical reference ionospheric model by Chusovitin et al.(1987).

Several electron density maps on the vertical plane between the satellites and the receivers have been reproduced in the model calculations for various days and UT moments with the latitudinal resolution of 1.0 - 0.3 deg. After correction of the total solar EUV flux intensity, a good similarity has been achieved between the theoretical model calculation results and the ionospheric tomography data including the shape and intensity of the soft electron precipitation effects.

This work was supported by the Grant No.98-05-64145 of Russian Foundation for Basic Research.

Yu.K. Chusovitin, A.V.Shirochkov, A.S.Besprozvannaya, et al. An empirical model for the global distributions of density, temperature and effective collision frequency of electrons in the ionosphere. Adv.Space Res., v.7, p.49-52, 1987.

A.A. Namgaladze, O.V.Martynenko, M.A.Volkov, A.N.Namgaladze, R.Yu.Yurik. High-latitude version of the global numerical model of the Earth’s upper atmosphere. Proceedings of the MSTU., v.1, No.2, p.23-84, 1998.

T. Nygren, E.D.Tereshchenko, B.Z.Khudukon, O.V.Evstafiev, M.Lehtinen, M.Markkanen. Mapping the ionospheric F region by means of satellite tomography. Acta Geod. Geoph.Hung., v.32, No.3-4, p.395-405, 1997.

A.A.Namgaladze^1,2, M.Foerster³, R.Yu.Yurik ^1,2

To test various hypotheses about positive ionospheric storm development, we performed a numerical simulation case study for the magnetic storm of 24-27 January 1974 to obtain the global pattern of the thermospheric and ionospheric effects of this magnetic storm. This typical northern winter solstice storm under low solar activity has an advantage, that good neutral gas measurements from the AE-C and ESRO-4 satellites are available as well as some plasma observations.

The global upper atmosphere model (UAM) by Namgaladze et al. (1998) has been used in the investigation with the resolution of the numerical integration of the modeling equations 2-d degree in latitude for all ionospheric and thermospheric parameters. This model describes the Earth's mesosphere, thermosphere, ionosphere, plasmasphere, and the inner part of the magnetosphere confined by the closed geomagnetic field lines as a single system including its electrodynamics. The cross-polar cap electric potential was estimated from the hourly AE index according to Weimer et al. (1990) and served as main model input parameter.

The results of the numerical simulation of the neutral composition changes agree in general with observations of the AE-C and ESRO-4 satellite and with the MSISE90 model. The perturbation regions at northern and southern mid- to high latitudes are clearly visible. Their equatorward boundaries show diurnal and/or longitudinal variations. The disturbance zone at the summer (southern) hemisphere is more extended, while the comparison of the absolute values is in favour of the winter (northern) hemisphere. The steepness of the gradient of the perturbation zone boundary is much different for the simulation results and satellite measurements on the one hand and for the MSISE90 empirical model on the other (especially in the northern, winter hemisphere). The MSISE90 model obviously fails to reproduce these gradients.

Although the ratio [N₂]/[O] during storm maximum is increased by more than a factor 10 in comparison with the quiet time level at high latitudes, at low latitudes it does not decrease (at fixed height) below it, while the absolute density of all neutral constituents is enhanced. Meanwhile, the ionospheric storm is positive at low latitudes. We conclude that the positive phase of ionospheric storm is mainly due to upwelling of ionospheric F2-region plasma at mid-latitudes and moving of this plasma equatorward at low latitudes caused by large-scale neutral wind circulation and the passage of travelling atmospheric disturbances (TADs). The negative phase is a combination of the effects of the neutral composition changes and those of ion transport and heating due to electric fields.

This work was supported by the Grant No.98-05-64145 of Russian Foundation for Basic Research.

A.A. Namgaladze, O.V.Martynenko, M.A.Volkov, A.N.Namgaladze, R.Yu.Yurik. High-latitude version of the global numerical model of the Earth’s upper atmosphere. Proceedings of the MSTU., v.1, No.2, p.23-84, 1998.

D.R. Weimer, N.C. Maynard, W.J. Burke, and C.Liebrecht, Polar cap potentials and the auroral electrojet indices, Planet. Space Sci., v. 38, p.1207--1222, 1990.

А.А. Боголюбов, В.A. Власков, О.Ф. Оглоблина (Полярный геофизический институт, Мурманск)

Известно, что такое явление как Полярное мезосферное летнее эхо (PMSE), происходит на высотах летней мезопаузы ((85 км) и связано с периодическими вариациями параметров нейтральной атмосферы на этих высотах ( в основном с вариациями температуры). С другой стороны для более глубокого понимания природы PMSE, необходимо более тщательное исследование периодов характерных вариаций нейтральной атмосферы на этих высотах.

Поскольку частичные отражения связаны с параметрами нейтральной атмосферы, возможно изучение периодов ее вариаций при анализе интенсивности частичных отражений. Исследование процессов с достаточно большими периодами требует наличия непрерывного ряда данных. К сожалению, в эксперименте не всегда удается получить достаточный для анализа непрерывный массив данных.

Была разработана методика объединения и стыковки отдельных массивов данных, с использованием Фурье разложения, которая позволяет заполнять пустые промежутки между массивами исходных данных и получать фактически непрерывные массивы за периоды до 1,5 месяцев.

На основе этой методики были обработаны данные радара частичных отражений ПГИ за летний период 1996 года. Это позволило достаточно четко выделить суточную и полусуточную компоненты вариаций. Исследование спектров полученных массивов позволило выделить также 7-8 дневную компоненту вариаций, которая может быть связана с фазами Луны.

В высокоширотной нижней термосфере часто наблюдаются высотные профили зональной и меридиональной составляющих термосферного ветра, которые имеют противоположные направления на близко расположенных уровнях. В частности, такие профили могут сформироваться при прохождении волны Россби. Ранее при помощи метода математического моделирования нами были исследованы те изменения, которые должны претерпевать высотные распределения заряженных частиц в ионосферных слоях E и F1 при возмущениях нейтрального ветра, обусловленных прохождением волны Россби, в ночное время [1].

В настоящей работе приводятся результаты аналогичного исследования, но только для дневного времени. Применяется та же, что и в [1], многоионная нестационарная модель высокоширотной ионосферы, позволяющая рассчитывать высотные профили концентраций 5 сортов положительных ионов в пределах высот 90-164 км. Расчеты проводились для точки, лежащей на широте Мурманска, для момента MLT=12 час при средней солнечной и низкой магнитной активностях в условиях равноденствия.

Установлено, что возмущения термосферного ветра, обусловленные прохождением волны Россби, стремятся сформировать на профиле электронной концентрации на уровне слоев E и F1 точно такие же слоистые структуры, как и в ночных условиях; механизм, приводящий к формированию этих слоистых структур, оказывается тем же самым, что и в ночных условиях. Однако последствия, к которым приводит действие этого механизма, в дневных условиях оказываются гораздо менее выраженными, чем в ночных условиях. В частности, относительные максимальные отклонения электронной концентрации оказываются в десятки раз меньшими, чем в ночных условиях, что делает их практически слабо заметными. Характерное время установления слоистых структур в дневных условиях не превышает 2 мин., в то время как в ночных условиях оно составляет около часа.

[1] T.N. Lukicheva, V.S. Mingalev In: "Physics of Auroral Phenomena". Proc. XXI Annual Seminar, Apatity, pp. 67-70, 1998.

S.S. Parfenov, D.D. Reshetnikov (Yakut State University, Yakutsk, Russia)

V.L. Khalipov, A.E. Stepanov (Institute of Cosmophysical Research and Aeronomy, Yakutsk, Russia)

By the method of spatially-diverse reception of radio signals (D1 method) at Yakutian meridional stations we measured the speed and direction of the ionospheric plasma drifts at subauroral latitudes. The joint analysis of interplanetary magnetic field variations and drift measurements by the method D1 showed, that the moment of reversal of drift plasma speed from the west eastward in an early evening sector is bound to turn in negative values of an IMF B_y - component for B_z < 0. For B_y > 0 (B_z < 0) changes of the drift’s sign are not observed till the morning hours of local time.

E E Timofeev (Polar Geophysical Institute, Murmansk)

M K Vallinkoski, J Kangas, P Pollari (Department of Physics, University of Oulu, Finland)

T Virdi, P J Williams (Department of Physics, University of Aberystwyth, Wales, U.K.)

E Nielsen (Max-Planck-Institute fuer Aeronomie, Katlenburg-Lindau, Germany)

Properties of the threshold E-fields of a radar echo appearance are analyzed from statistics of the coordinated STARE-EISCAT measurements stored during the multi-event ERRRIS campaign. The selected data pool with 0 dB < SNR < 1dB contains 64 cases observed by the Finnish STARE radar (F-radar). The radar echo is supposed to come from the zero-aspect angle layer (echo-layer): 108*6 km altitudes over Tromso. Electron (Te) and ion (Ti) temperatures are analyzed as being averaged over the echo-layer width and over 30-deg flow angle bins. The present paper deals with analysis of the flow angle properties of the electron (Te) and ion (Ti) temperatures as averaged within the echo layer and over flow angle bins.

It is found that:

1) the primary cone of the modified Farley-Buneman (FB) waves with about 45 degree half-width exists permanently within the Finnish STARE radar echo layer for small (near-threshold radar echo) level of the DC ionospheric electric fields.

2) both temperatures are minimal in the center of the cone while their local maxima are at the edges of the cone; the temperatures decrease beyond the cone limits;

3) both temperatures are essentially flow angle asymmetric. Ti (Te) has its absolute maximum at -45 (+45) degree flow angle bin;

4) standard deviation of the Ti (Te) sharply (2-5 times) increases near the negative (positive) flow angle edge of the cone, respectively.

As a result, such a puzzling phenomenon as cooling of electrons relatively to ions stationary exists near the negative flow angle edge of the cone. The difference of temperatures (Ti-Te) is of about 50 K degrees.

It is interpreted that areas of local maximal heating are, in fact, strong turbulence boundary layers constraining the quasi-stationary field-plasma configuration. The effect of dynamical electron cooling is discussed in terms of the classical thermoelectricity effects (Peltier, Seeback, Thomson) as applied to the Pedersen ion and electron currents transverse to the edges of the cone.

Хорошо известно, что главной причиной возникновения нейтрального ветра является неравномерный нагрев атмосферы солнечным излучением. Заряженные же частицы ионосферной плазмы, являющиеся сильно замагниченными в слое F, движутся главным образом под действием крупномасштабных электрических полей, которые в высоких широтах могут достигать значительных величин. Поэтому типичной ситуацией в земной ионосфере является несовпадение скоростей движения нейтрального газа и заряженных частиц, следствием чего может явиться повышение температуры ионосферной плазмы, обусловленное "фрикционным" нагревом, происходящим благодаря упругим столкновениям между нейтральными и заряженными частицами.

[1] Г.И. Мингалева, В.С. Мингалев В сб. :Моделирование процессов в верхней полярной атмосфере, с. 251-265, Мурманск, 1998.

[2] J.M. Meriwether, J.P. Heppner, J.D. Stolaric, E.M. Wescott J.Geophys.Res.,v.78,6643-6661,1973.

Для исследования свойств ионосферной плазмы успешно применяется метод искусственной модификации ионосферы мощными короткими радиоволнами, излучаемыми наземным нагревным стендом. Однако высокоширотные нагревные стенды удавалось использовать для модификации только D- и E-слоев ионосферы, высокоширотный F-слой пока модифицировать не удавалось, хотя среднеширотные нагревные стенды для этой цели успешно применялись. Это происходит, по-видимому, вследствие того, что поведение плазмы в F-слое высокоширотной ионосферы при воздействии на нее мощной греющей волны принципиально отличается от ее поведения в средних широтах. Главное отличие обусловлено конвекцией, которая не позволяет выделенному объему плазмы находиться в зоне облучения нагревным стендом также долго, как в средних широтах, а заставляет его перемещаться над нагревным стендом с довольно большой скоростью. Как показали результаты ранее проведенных расчетов [1,2] нагретый возмущенный объем плазмы может быть перенесен на расстояние в несколько сотен километров за то время, пока ионосферные параметры будут релаксировать к своим естественным невозмущенным значениям.

Настоящая работа является продолжением [1,2], ее целью является получение результатов модельных расчетов, которые могли бы быть использованы при организации новых экспериментов на норвежском нагревном стенде (Тромсе) и при планировании работы диагностических средств.

В работе приводятся полученные при помощи математической модели [1] результаты расчетов отклика F-слоя на воздействие мощных греющих волн КВ-диапозона при различных значениях эффективной поглощаемой энергии (от 5 до 120 МВт), которые могут быть достигнуты на норвежском нагревном стенде при его работе в различных энергетических режимах.

[1] G.I. Mingaleva, V.S. Mingalev Ann. Geophys., v.15, pp. 1291-1300, 1997.

A. Osepian¹, S. Kirkwood², L. Borovkov¹, L. Lazutin¹

1Polar Geophysical Institute, Murmansk region, Russia

2. At the substorm onset increase of the precipitating flux is observed in all electron energies with bigger changes for Е>10 keV. During expansion electron energy spectrum can be approximated by the superposition of two specters – for Е<10 and E>10 keV with larger variations in the later one.

3. For the electron precipitation in the morning sector most variable flux is situated at E>30 keV and spectrum is harder than in the evening and midnight sector. For the same typical substorm intervals electron spectrum were investigated using direct measurements in the equatorial region at 4.5-6.6 Re. It is shown, that measured and calculated specter are comparable in general, with certain deviations.

The results are discussed in an assumption of the joint action of different mechanisms of the acceleration and precipitation of the electrons in soft and hard energy regions.

A.B. Pashin (Polar Geophysical Institute, Apatity)

N.A. Ryumochkina (Kola Branch of Petrozavodsk State University, Apatity)

The results of numerical modelling of the heating/cooling time constants are presented. Their dependencies from pump wave parameters are comparatively weak. Strong dependence on altitude is related with fast decrease of electron-neutral collision frequency with altitude. The cooling time constant is longer than the heating one. Calculations show that for frequency of the pump wave modulation higher than 500 Hz one should take into account heating/cooling time constants. In the calculations of the disturbed ionospheric parameters time integration of electron energy balance equation is needed.

В.А.Турянский, А.А.Боголюбов (Полярный геофизический институт, Мурманск)

А.С.Елохов, И.Б.Беликов (Институт физики атмосферы, Москва)

S.V. Leontyev, N.N. Bogdanov (Polar Geophysical Institute, Apatity)

Neutral vertical wind velocity in the E-layer of ionosphere was measured with Fabry-Perot interferometer (FPI) in Lovozero (68.0 N, 35.1 E). FPI was thermostabilized and isolated from outer pressure. It was regularly calibrated with 557.0 nm Kr emission. Observations during one night show that the vertical velocity of the neutral gas may have a very big variation. Its magnitude may be more then 100 m/s and it depends on the aurora intensity. Moreover, vertical wind velocity varies from one night to another. The vertical velocity averaged through a night has 100 m/s changes. As a result there is a large problem with finding of the true wavelength of the green (557.7 nm) emission and, as consequence, with absolute determination of vertical and horizontal wind velocities.

This work has been supported by the grant N 98-05-64435 from the Russian Foundation for Fundamental Researches.

A.A.Danilov, V.D.Sokolov (Institute of Cosmophysical Research and Aeronomy, Yakutsk, Russia)

Diurnal variations of the auroral absorption using riometer data in Tixie Bay have been analyzed. The components depending and independing on the IMF sector structure sign have been found. The first of them has the maximum in the evening hours at By>0 and in the morning hours - at By<0; the component independing on the IMF sign has the maximum in early morning hours. The explanation for observed variations are given: the effect of the sector IMF structure is caused by the change of an angle between two electric fields in the boundary layer of the magnetosphere (the field of quasi-viscous friction and the electric field of the solar wind); the component independing on the IMF is due to the change of the mutual position of the plasma magnetotail sheet and geomagnetic equator planes.

V.A.Kuzmin, V.D.Sokolov, I.P.Bezrodnykh

(Institute of Cosmophysical Research & Aeronomy, Yakutsk, Russia)

The experimental results showing the frequency change of auroral absorptions, registered with the riometer in Tixie during the 22nd solar activity cycle are presented. The auroral absorption frequency is measured a few hours a day, during which the cosmic radioemission absorption amplitude, by the ionosphere D- region, exceeds the 0.3 dB threshold and the duration is more then 10 minutes. The comparative analysis of the absorption frequency, and the change of sun spot number, solar wind velocity, interplanetary medium parameters and geomagnetic activity indices showed that the observed decrease of the riometer absorption frequency in the solar activity maximum (1989-1991) coincides in time with the absence of polar coronal holes. At the same time, the maximum value of the absorption frequency registered in 1994 at the 22nd cycle decrease phase is caused by the high- speed solar wind streams outflowing from the extended polar coronal holes.

V.A. Kuzmin, V.D. Sokolov, I.P. Bezrodnykh

(Institute of Cosmophysical Research & Aeronomy, Yakutsk, Russia)

The calculation results of the power spectrum of the energetic particle precipitation frequency registered with the 32 MHz riometer in Tixie Bay (L=5.6) during the 22nd solar activity cycle are presented. The analysis of the spectrum dynamics showed that the largest power of absorption frequency variations took place at the decay phase of solar activity in 1994-1995. This is related to the recurrent high-speed streams of solar wind observed in this period. The harmonics of oscillation periods about of 9 and 13.5 days have been found.

V.G. Vlasov, G.O. Zhizhko (Irkutsk State Technical University, Irkutsk, Russia)

An auroral thermal wave is the phenomenon results from the collective interaction of the auroral electron beams with the F-region ionospheric plasma [1]. Auroral electron beams resulting in the auroral arcs undergo the collective interaction with the ionospheric plasma, through which they pass. However, the collective dissipation of the electron beam energy is possible only in the region of small gradients, which always takes place near the F2-region maximum. The beams are stabilized by the large-scale inhomogeneity of plasma density on the rest of their path from the acceleration region up to the E-region of the ionosphere. The stabilization results from rapid escape of the generated waves from the generation area in the wave number space. As a numerical simulation of the auroral thermal wave shows, the collective dissipation of the beam energy occurs in a small (tens of kilometers) region, where is very intensive plasma heating. Electron and ion temperature can reach 8000 K and 6000 K respectively. This heating results in the ion upflows with the velocity around 1000 cm s^-1 and density 10¹⁴ cm^-2 s^-1. Similar ion flows are repeatedly observed by the EISCAT radar over auroral arcs and approximately 80% of events are associated with either ion or electron increased temperatures [2]. Hence here is good reason to believe the auroral thermal wave is an important source of the auroral ion upflows in the ionospheric F-region.

1. V.G. Vlasov, G.O. Zhizhko, Stabilized electron beams: An auroral thermal wave, J. Geophys. Res., 103, 9421-9431, 1998

2. C. Foster, M. Lester, J.A. Davies, A statistical study of diurnal, sesonal and solar cycle variations of F-region and topside auroral upflows observed by EISCAT between 1984 and 1996, Ann. Geophys., 16}, 1144-1158, 1998.