B.V. Kozelov, E.E. Titova (Polar Geophysical
Institute, Apatity, Russia)
V.Y. Trakhtengerts (Institute of Applied
Physics, Nizhny Novgorod, Russia)
F. Jiricek, P. Triska (Institute of
Atmospheric Physics, Praha, Czech Republic)
We consider the VLF emissions observed
by MAGION-5 in the morning sector. The chorus emissions on dynamic spectra
in the range of time scales 0.1-10 Hz look like a self-similar set. The
scaling features in chorus observation have been tested. It was found that
the distribution of time between chorus is power-law with the exponent
d = 2.0e2.3. It was found that fluctuations in hiss at the same frequencies
have the similar shape of distribution, but for plasmaspheric hiss such
distribution is different. We suppose that the similar power-law distribution
for chorus and hiss could be a result of the same mechanism of self-organization
in the magnetospheric plasma.
INCOMING MHD WAVES AS POSSIBLE TRIGGERS OF MAGNETIC RECONNECTION
I.V. Alexeev, V.S. Semenov (St.Petersburg State University, Institute of Physics)
We consider a reconnection process on a
thin current sheet in the highly conductive plasma. This kind of process
may be responsible for the various events of fast magnetic energy releases
in space and laboratory plasma, particulary in substorms in the Earth magnetosphere.
Here we present theoretical study of this phenomena based on MHD approach.
Our study is based on well known Petschek reconnection model. In order
to investigate effects of incoming waves we took into account second order
terms of perturbation theory. Using this model we found out that incoming
MHD wave can locally change reconnection rate. Also we found dependence
of reconnection rate perturbations and plasma flow speed disturbances in
outflow region of reconnection. We formulated a criterion which allows
to recognize incoming waves which can stimulate reconnection. This result
can be used to study origins of reconnection generation in the Earth magnetosphere,
solar flares and other astrophysical objects.
ОДНОВРЕМЕННЫЕ ПЕЛЕНГАЦИОННЫЕ НАБЛЮДЕНИЯ ИОНОСФЕРНЫХ ТОЧЕК ВЫХОДА ОНЧ-ИЗЛУЧЕНИЙ В ДВУХ БЛИЗКОРАСПОЛОЖЕННЫХ ПУНКТАХ
В.А. Муллаяров, С.И. Львов, В.И. Козлов
(Институт космофизических исследований
и аэрономии СО РАН, г. Якутск)
Представлены результаты двухпунктовых пеленгационных
наблюдений точек выхода магнитосферных ОНЧ-излучений из ионосферы в магнитовозмущенный
день 19.02.98. На двух станциях, разнесенных на 150 км, в течение всех
суток регистрировалось ОНЧ-излучение из разных ионосферных областей, хотя
и с совпадающих азимутальных направлений. Хоры и шипения приходили, как
правило, из противоположных секторов. Точки выхода из ионосферы шипений
располагались обычно в южном и юго-восточном квадрантах от зенита обеих
станций, а хоров - в северном. Результаты указывают, что в магнитосфере
имело место канализированное (дактовое) распространение излучения. Выход
ОНЧ-шипений из дактов происходил, по-видимому, на более низких высотах
по сравнению с хорами. При этом, на уровень ионосферы над пунктами регистрации
ОНЧ-шипения выходили из нескольких близко-расположенных дактов.
VLF CHORUS AND PULSATING AURORA
I.A. Kornilov (Polar Geophysical Institute, Apatity, Russia)
Using ground based TV data on auroral pulsations
and VLF emissions some predictions of BWO (back wave oscillator) chorus
generation theory have been checked. Statistical study of the dependence
of chorus frequency change rate (dF/dT) and average amplitude versus chorus
repetition period have not revealed theory confirmation yet. Time dependence
of dF/dT demonstrates rather good correlation with aurora motions and pulsations
intensity. Two types of chorus - in low (700-1200 Hz) and high (2000-4000
Hz) frequency bands was also studied. These emissions correspond to the
different types of auroral pulsations and have a tendency to anticorrelate.
SELF-CONSISTENT THEORY OF CYCLOTRON INTERACTION IN THE WHISTLER WAVEGUIDED
L. Pasmanik and V.Y. Trakhtengerts (Institute of Applied Physics RAS, Nizhny Novgorod, Russia)
Further analysis of self-consistent theory
of the cyclotron interactions of energetic electrons and whistler waves
in the case of ducted waves propagation is performed. Such theory can be
applied when the waveguide for whistler waves is formed by plasmapause
(whispering gallery propagation) or by ducts of enhanced background plasma
density. As a model of magnetospheric duct the cylindrically symmetric
cold plasma density enhancement is considered. The spatial structure of
eigenmodes of such a waveguide with azimuthal dependency taken into account
is analyzed. The development of cyclotron instability due to interaction
of energetic electrons injected into this waveguide and whistler waves
with eigenmodes structure taken into account is studied. The efficiency
of excitation of a different eigenmodes and energetic electron precipitation
spatial structure is analyzed.
MODELING OF RADIOWAVE SOURCE DIRECTION BASED ON INTERBALL-2 SATELLITE MEASUREMENTS ONBOARD (POLRAD EXPERIMENT)
E.A. Morozova, M.M.Mogilevsky (Space
Research Institute, Moscow, Russia)
J. Hanasz (Space Research Center, Torun,
Poland)
The numerical model of onboard experiment
and procedure for POLRAD data treatment were developed. In that model of
POLRAD device the signal is a set of waves regarded as a quasi-monochromatic,
partly polarized noise, which is splitted into two components corresponding
to polarized and unpolarized parts of radiation. The modeling consists
of two parts: a model of POLRAD device and a program for data treatment.
The output of POLRAD model is covariance
matrix (in POLRAD this matrix corresponds to 9 channels of the radio-spectro-polarimeter
(J. Hanasz et al., POLRAD Description of Experiment, 1995).) The direction
of radio source and its polarization characteristics are obtained from
this covariance matrix in data treatment program by means of Stokes parameter
theory (V.V. Zheleznyakov, Electromagnetic waves in space plasma, Moscow,
Nauka, 1977). In order to determine the accuracy of our treatment procedure
the input parameters of POLRAD device model are verified (noise level,
multiple source case, which determines angular accuracy of the procedure).
Thus the analysis for deferent imperfect sources was performed and the
influence of source imperfection on the result of data treatment was obtained
in different cases.
There is another method for source direction
obtaining described by W. Calvert, Measuring wave direction with INTERBALL,
1999. It is based on direct calculation from nine channels of POLRAD radio-specto-polarimeter.
It has been applied also and the results of these methods were compared.
СВЯЗЬ ВАРИАЦИЙ ОНЧ-ШУМОВ С СЕКТОРНОЙ СТРУКТУРОЙ МЕЖПЛАНЕТНОГО МАГНИТНОГО ПОЛЯ
Р.Р. Каримов, В.И. Козлов, В.А. Муллаяров
(Институт космофизических исследований
и аэрономии СО РАН)
Для исследования связи вариаций амплитуды
ОНЧ-шумов на частоте 8,7 кГц, регистрируемых в Якутске, с секторной структурой
межпланетного магнитного поля (ММП) использован метод наложения эпох. Даты
пересечения Землей границ секторов ММП за период 1979-1994 гг. установлены
по каталогу Кинга и по данным наземной антарктической станции "Восток".
Систематические вариации амплитуды ОНЧ-шумов в летние ночные часы при смене
знака направления ММП от отрицательного к положительному не обнаружены.
В то же время, при смене положительного сектора отрицательным амплитуда
ОНЧ-шумов резко падает во второй день. В зимние ночные часы наблюдается
повышение амплитуды ОНЧ-шумов в положительных секторах как в 21 солнечном
цикле, так и в 22 солнечном цикле. Подобное повышение амплитуды наблюдается
и в летние ночные часы. В то же время, в дневные часы зимой наблюдается
понижение амплитуды ОНЧ-шумов до минимального значения приблизительно в
середине отрицательного сектора ММП. Причем такое поведение вариаций ОНЧ-шумов
характерно для периодов максимума и минимума солнечной активности в обоих
рассмотренных циклах, т.е. не зависит от четности цикла и от уровня солнечной
активности. Регулярные ОНЧ-шумы на частоте 8,7 кГц, регистрируемые в Якутске,
отражают грозовую активность (летом - местную, зимой - в мировых грозовых
центрах). Следовательно, полученные результаты указывают, что вариации
грозовой активности могут быть связаны с секторной структурой ММП. Однако
конкретизировать причинную связь в настоящее время затруднительно.
THE FEATURES OF SPECTRAL RESONANCE STRUCTURES OBSERVED ON FEBRUARY, 27th , 1999 AT LOVOZERO GEOMAGNETIC OBSERVATORY
V.V. Safargaleev, V.K. Roldugin, A.N. Vasil’ev,
A.I. Voronin, S.N. Noskov
(Polar Geophysical Institute, Apatity,
Russia)
The recent measurements by the use of high-sensitive
induction magnetometers have proved that the effects of the ionospheric
Alfven resonator, IAR, in the electromagnetic background noise are also
observed at high latitudes. The main obstacle to the IAR detection is the
low signal-to-noise ratio. Due to this, the time intervals of 5-20 minute
duration have to be used to calculate a series of spectra (sonogram). We
present here an unique case when the ionospheric conditions were favorable
so that the spectral resonance structures, SRS, were clearly seen for one
hour on the sonogram obtained at ~1 minute resolution. The higher temporal
resolution allows us to conclude that the SAR-event represents a sequence
of the short-time enhancements in the background noise at 2.0, 2.7, 3.5
and 4.2 Hz. Another feature is the decrease in the spectral intensity of
the first Schumann resonance during the interval of SRS observation. Both
features are discussed in light of IAR theory. We assume that the single
bursts of a few second duration, which are rather frequently observed on
the sonograms and having the spectral maxima at the frequencies mentioned,
are the IAR signature, too.
CUSP LATITUDE Pc3-Pc5 GEOMAGNETIC PULSATIONS TRIGGERED BY SSC
N.G. Kleimenova, O.V. Kozyreva (Institute of the Earth Physics, Moscow, Russia)
We have analyzed geomagnetic pulsations
in frequency range of ~0.6-50 mHz (Pc3, Pc4, Pc5) at antarctic Dumont-d'Urwill
(DRV) obs. (¦=80.5) during 36 events of SSC which have happened near the
local magnetic noon under the quiet geomagnetic conditions (Kp<2) in
the period of 1978-1995. Under such conditions DRV is located near the
ionosphere cusp projection. It was found that all of given daytime SSC's
triggered the bursts of geomagnetic pulsations with spectral maxima at
the ipcl-range (2-4 mHz) and at two frequency bands of the Pc4-range (~8-12
mHz and ~18-20 mHz). Sometimes the Pc3 pulsations also could be seen mostly
in relative broad bands (~30-40 mHz and ~40-50 mHz). As a rule, SSC are
accompanied by several hours lasting Pc4 range pulsations observed in a
global scale.
PC~1 WAVES AND IONOSPHERIC ALFVEN RESONATOR: GENERATION AND FILTRATION
A. G. Demekhov 1, V. Y. Trakhtengerts
1, T. Boesinger 2, S. V. Isaev 3, P. P.
Belyaev 3, J. Kangas 4
1 Institute of Applied Physics,
Nizhniy Novgorod, Russia
2 Oulu University, Oulu,
Finland
3 Radiophysical Research
Institute, Nizhny Novgorod, Russia
4 Sodankyla Geophysical
Observatory, Sodankyla, Finland
We report continuation of our studies of
two peculiar phenomena in ULF range related to each other via the ionospheric
Alfven resonator (IAR). These are Pc 1 pearl emissions and the spectral
resonance structure of ULF electromagnetic noise in frequency range 0.1-10
Hz. We calculate the optimal conditions for the Pc 1 generation in the
magnetosphere and their detection on the ground. These conditions depend
on the reflection coefficient of Alfven waves from the IAR, the transmission
coefficient through the IAR, and the growth rate of the cyclotron instability.
The calculations are used to find out how the optimal frequency of Pc 1
pearl generation region varies with local time and latitude. We compare
the expected variation in spectra of Pc 1 pearls with those of spectral
resonance structure of the ULF electromagnetic background noise and discuss
the influence of ionospheric parameters on the relation between these spectra.
The morphological features of Pc 1 pulsations
resulting from the model are compared with satellite and ground-based measurements.
AURORAL ELECTROMAGNETIC ION CYCLOTRON WAVES AND EXTERNAL IONOSPHERE CONDITIONS
V.S. Smirnov, A.A. Lubchich, T.A. Yahnina (Polar Geophysical Institute, Apatity, Russia)
Observations of auroral electromagnetic
ion cyclotron (EMIC) waves obtained onboard the low-altitude (h=400-2000
km) Aureol-3 satellite and received at ground station Apatity during the
period October, 1981 - February, 1984 are considered. These waves are narrow-banded
emissions with frequency f=130-260 Hz. It has been found that the frequency
of the emissions varies between the local hydrogen and helium cyclotron
frequencies, but it is closer to the later one. Analysis of the wave spectra
suggests that wave source lies at the altitude between 2000 and 4000 km.
The probability of the wave observation strongly depends on sunlight conditions:
It increases when the zenith angle of the Sun achieves 90 degrees. In addition,
the superposition epoch analysis has shown that the emissions are observed
during the recovery phases of geomagnetic disturbance. These findings are
discussed taking into account the effect of the external ionosphere composition
on generation and propagation of the EMIC waves.
MAGION-5 VLF CHORUS OBSERVATIONS AT EQUATORIAL REGION
E.E. Titova, B.V. Kozelov (Polar Geophysical
Institute, Apatity, Russia)
F. Jiricek, J. Smilauer (Institute
of Atmospheric Physics, Praha, Czech Republic)
A.G. Demekhov, V.Y. Trakhtengerts (Institute
of Applied Physics, Nizhny Novgorod, Russia)
We analyze new data on chorus emissions
obtained from Magion-5 satellite. The emissions are recorded at latitudes
of 10-30 degrees from the geomagnetic equator. The data have high temporal
resolution (sampling frequency 44 kHz) and thus provide a valuable information
on chorus dynamical spectra at high altitudes, i.e., not very far from
the generation region which is believed to be near the magnetic equator.
We seek for statistical relationships between experimentally determined
parameters of chorus such as the mean frequency of an element, frequency
sweep rate, growth rate, peak amplitude, repetition period of elements,
etc. These relationships are compared to scalings based on theoretical
ideas concerning chorus formation.
SPECTRAL RESONANCE STRUCTURE IN THE AURORAL ULF ELECTROMAGNETIC NOISE: CALCULATIONS USING THE IRI-95 MODEL AND COMPARISON WITH OBSERVATIONS
N.V.Semenova 1,2, A.G.Yahnin
1, A.A.Ostapenko 1, J.Manninen 3, J.Kangas
3
1 Polar Geophysical Institute,
Apatity, Russia
2 Kola Branch of Petrozavodsk
State University, Apatity, Russia
3 Sodankyla Geophysical
Observatory, Sodankyla, Finland
Spectral Resonance Structure (SRS) is often seen in the ULF range spectra of electromagnetic noise in auroral zone. According to the theory of ionospheric Alfven resonator (IAR) the SRS characteristics mainly depend on parameters of ionosphere above the observational point. On the basis of the IAR theory and using the International Reference Ionosphere model (IRI-95), which provides the altitude profiles of ionospheric parameters for any given location and time, we calculated the SRS characteristics for auroral zone station Sodankyla, Finland for whole year 1996. The result has been compared with the SRS observations at the same point. We found that, in general, the calculations correctly reproduce the diurnal behaviour of observed resonant frequencies as well as the seasonal dependence. We consider these facts as confirmation of the IAR theory. Some inconsistencies, which however occur, are explained by a difference between real ionosphere parameters and that obtained from the ionosphere model. For some cases such difference has been documented comparing the calculated electron density with the data of ionospheric station situated at Sodankyla. This means that the SRS parameters do reflect the ionosphere conditions, and they can be used for diagnostics of the ionosphere.