Multipoint observations of Ionospheric Alfvén Resonance
Among the processes that form properties of the geospace in the circumterrestrial plasma the electromagnetic resonances of the Earth, such as Schummann Resonance (SR) and Ionospheric Alfvén Resonance (IAR) are of great importance. IAR is more localized in space than SR and its properties largely dep...
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irk-123456789-1199502017-06-11T03:04:33Z Multipoint observations of Ionospheric Alfvén Resonance Baru, N.A. Koloskov, A.V. Yampolsky, Y.M. Rakhmatulin, R.A. Among the processes that form properties of the geospace in the circumterrestrial plasma the electromagnetic resonances of the Earth, such as Schummann Resonance (SR) and Ionospheric Alfvén Resonance (IAR) are of great importance. IAR is more localized in space than SR and its properties largely depend on the characteristics of the propagation medium. In contrast to the SR, which has global nature and which is continuously observable at any time of the day, IAR signals are registered mostly during the nighttime and demonstrate more variability of the parameters than SR signals. At the Earth surface IAR is registered as Spectral Resonance Structure of the natural electromagnetic noise at frequency range 0.1-40 Hz. In this work we studied an influence of the environment characteristics on IAR parameters by the means of multipoint observations. Annual data series recorded at Ukrainian Antarctic Station "Akademik Vernadsky", Low Frequency Observatory of the Institute of Radio Astronomy near Kharkov (Ukraine) and magnetic station of Sayan Solar Observatory Mondy near Irkutsk (Russia) were used for the analysis. We investigated the behaviour of IAR parameters, such as probability of resonance lines registration and frequency spacing ∆F, for annual and diurnal intervals. These parameters were compared with characteristics of the ionosphere above all of the observation points and geomagnetic activity. 2016 Article Multipoint observations of Ionospheric Alfvén Resonance / N.A. Baru, A.V. Koloskov, Y.M. Yampolsky, R.A. Rakhmatulin // Advances in Astronomy and Space Physics. — 2016. — Т. 6., вип. 1. — С. 45-49. — Бібліогр.: 19 назв. — англ. 2227-1481 DOI:10.17721/2227-1481.6.45-49 http://dspace.nbuv.gov.ua/handle/123456789/119950 en Advances in Astronomy and Space Physics Головна астрономічна обсерваторія НАН України |
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Among the processes that form properties of the geospace in the circumterrestrial plasma the electromagnetic resonances of the Earth, such as Schummann Resonance (SR) and Ionospheric Alfvén Resonance (IAR) are of great importance. IAR is more localized in space than SR and its properties largely depend on the characteristics of the propagation medium. In contrast to the SR, which has global nature and which is continuously observable at any time of the day, IAR signals are registered mostly during the nighttime and demonstrate more variability of the parameters than SR signals. At the Earth surface IAR is registered as Spectral Resonance Structure of the natural electromagnetic noise at frequency range 0.1-40 Hz. In this work we studied an influence of the environment characteristics on IAR parameters by the means of multipoint observations. Annual data series recorded at Ukrainian Antarctic Station "Akademik Vernadsky", Low Frequency Observatory of the Institute of Radio Astronomy near Kharkov (Ukraine) and magnetic station of Sayan Solar Observatory Mondy near Irkutsk (Russia) were used for the analysis. We investigated the behaviour of IAR parameters, such as probability of resonance lines registration and frequency spacing ∆F, for annual and diurnal intervals. These parameters were compared with characteristics of the ionosphere above all of the observation points and geomagnetic activity. |
| format |
Article |
| author |
Baru, N.A. Koloskov, A.V. Yampolsky, Y.M. Rakhmatulin, R.A. |
| spellingShingle |
Baru, N.A. Koloskov, A.V. Yampolsky, Y.M. Rakhmatulin, R.A. Multipoint observations of Ionospheric Alfvén Resonance Advances in Astronomy and Space Physics |
| author_facet |
Baru, N.A. Koloskov, A.V. Yampolsky, Y.M. Rakhmatulin, R.A. |
| author_sort |
Baru, N.A. |
| title |
Multipoint observations of Ionospheric Alfvén Resonance |
| title_short |
Multipoint observations of Ionospheric Alfvén Resonance |
| title_full |
Multipoint observations of Ionospheric Alfvén Resonance |
| title_fullStr |
Multipoint observations of Ionospheric Alfvén Resonance |
| title_full_unstemmed |
Multipoint observations of Ionospheric Alfvén Resonance |
| title_sort |
multipoint observations of ionospheric alfvén resonance |
| publisher |
Головна астрономічна обсерваторія НАН України |
| publishDate |
2016 |
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http://dspace.nbuv.gov.ua/handle/123456789/119950 |
| citation_txt |
Multipoint observations of Ionospheric Alfvén Resonance / N.A. Baru, A.V. Koloskov, Y.M. Yampolsky, R.A. Rakhmatulin // Advances in Astronomy and Space Physics. — 2016. — Т. 6., вип. 1. — С. 45-49. — Бібліогр.: 19 назв. — англ. |
| series |
Advances in Astronomy and Space Physics |
| work_keys_str_mv |
AT baruna multipointobservationsofionosphericalfvenresonance AT koloskovav multipointobservationsofionosphericalfvenresonance AT yampolskyym multipointobservationsofionosphericalfvenresonance AT rakhmatulinra multipointobservationsofionosphericalfvenresonance |
| first_indexed |
2025-07-08T16:58:45Z |
| last_indexed |
2025-07-08T16:58:45Z |
| _version_ |
1837098783391875072 |
| fulltext |
Multipoint observations of Ionospheric Alfvén Resonance
N.A.Baru1∗, A.V.Koloskov1, Y.M.Yampolsky1, R.A.Rakhmatulin2
Advances in Astronomy and Space Physics, 6, 45-49 (2016) doi: 10.17721/2227-1481.6.45-49
© N.A.Baru, A.V.Koloskov, Y.M.Yampolsky, R.A.Rakhmatulin, 2016
1Institute of Radio Astronomy of NAS of Ukraine, 4, Chervonopraporna Str., Kharkov, 61002, Ukraine
2Institute of Solar-Terrestrial Physics RAS, Siberian Branch, 126-a, Lermontova Str., Irkutsk, 664033, Russia
Among the processes that form properties of the geospace in the circumterrestrial plasma the electromagnetic
resonances of the Earth, such as Schummann Resonance (SR) and Ionospheric Alfvén Resonance (IAR) are of great
importance. IAR is more localized in space than SR and its properties largely depend on the characteristics of the
propagation medium. In contrast to the SR, which has global nature and which is continuously observable at any
time of the day, IAR signals are registered mostly during the nighttime and demonstrate more variability of the
parameters than SR signals. At the Earth surface IAR is registered as Spectral Resonance Structure of the natural
electromagnetic noise at frequency range 0.1�40Hz. In this work we studied an in�uence of the environment char-
acteristics on IAR parameters by the means of multipoint observations. Annual data series recorded at Ukrainian
Antarctic Station �Akademik Vernadsky�, Low Frequency Observatory of the Institute of Radio Astronomy near
Kharkov (Ukraine) and magnetic station of Sayan Solar Observatory Mondy near Irkutsk (Russia) were used for
the analysis. We investigated the behaviour of IAR parameters, such as probability of resonance lines registration
and frequency spacing ∆F , for annual and diurnal intervals. These parameters were compared with characteristics
of the ionosphere above all of the observation points and geomagnetic activity.
Key words: radio science: ionospheric physics, waves in plasma
introduction
The maxima of the Pedersen and Hall conduc-
tivity at the heights of E-layer of the ionosphere
lead to the forming of e�ective re�ection wall for the
Alfvén mode of the magnetohydrodynamic (MHD)
waves spread at the upper ionosphere and magne-
tosphere. This leads to existence of a �eld line res-
onator (FLR) in the closed �eld lines, i. e. the system
of the standing waves along the �eld lines of the ge-
omagnetic �eld [9]. The magnetic structure of FLR
is formed when MHD waves re�ect from the iono-
sphere at the di�erent ends of the �eld line in the
magnetoconjugate regions of the South and North-
ern hemispheres. However, if additional conditions
for MHD waves re�ection appear at 1000�1500 km
then the cavity with existing resonance processes is
decreased and becomes bounded by the plasmapause
at the top and the lower ionosphere at the bottom.
Such a phenomenon is named ionospheric Alfvén res-
onator (IAR) and was �rst described in 1981 by
Polyakov & Rapoport [17]. At the heights of E-layer
of the ionosphere MHD waves transform into elec-
tromagnetic ones and can be registered at the Earth
surface as spectral resonance structure (SRS) of the
natural electromagnetic noise in the frequency band
0.1�5Hz. From that time IAR was studied by many
authors both in theoretical [16, 8, 12] and experimen-
tal means [2, 7, 19]. The analysis of IAR morphol-
ogy and its relationships with ionospheric parameters
were investigated in [5]. Authors of [3] studied IAR
parameters during the solar cycle and have found
the inverse dependence between IAR observability
and solar activity. It was shown theoretically [4] and
experimentally [5] that the upper limit of SRS ob-
servability can be up to 10Hz. It should be noted,
however, that most of the experimental observations
used in the above-mentioned works were cases stud-
ies of fragmentary observations.
Monitoring of horizontal magnetic components of
ULF/ELF �elds has been made at the Ukrainian
Antarctic Station (UAS) from the beginning of the
current century. Together with the data got at the
Antarctic station Arrival Heights [18] these are the
longest series of data in this frequency band. We
used these data for systematic search of SRS cor-
responding to IAR [6]. The data analysis allowed
us to develop a technique for evaluating the criti-
cal frequency of F2 layer of the ionosphere using
the IAR records [1]. In addition, the analysis of
the UAS data shows the existence of SRS at the
frequencies up to 40Hz [10], what is signi�cantly
higher than 10Hz limit reported in [4, 5]. Since these
resonances are global, we are interested in simul-
taneous measurements at stations with big spatial
separation. Therefore, IAR monitoring have been
started in 2008 on the basis of the Institute of Radio
Astronomy of the National Academy of Sciences of
∗
baru@rian.kharkov.ua
45
Advances in Astronomy and Space Physics N.A.Baru, A.V.Koloskov, Y.M.Yampolsky, R.A.Rakhmatulin
Ukraine (IRA NASU) and in 2010 by the initiative
of IRA NASU in the Eastern Siberia at the Institute
of Solar-Terrestrial Physics of the Siberian branch of
the Russian Academy of Sciences (ISTP SB RAS).
In this article, the comparative analysis of the IAR
morphology obtained from the observations on all
three stations was made.
the method of calculations
Comparative analysis of IAR data was performed
at the three receiving sites, namely: UAS �Akademik
Vernadsky� (65◦15′ S, 64◦16′W), Low Frequency Ob-
servatory (LFO) of IRA NASU (49◦56′N, 36◦57′ E)
and magnetic station of the Sayan Solar Observa-
tory (SSO) of ISTP SB RAS (51◦37′N, 100◦55′ E).
Despite the di�erent geographic location, the geo-
magnetic latitudes and McIlwain parameter of the
stations are quite similar (UAS � 2.6, LFO � 2.2,
SSO � 2.1). IAR registrations were performed with
induction-coil magnetometers. The magnetometers
Lemi-419ANT (frequency range: 0.001�80Hz) and
Lemi-30 (frequencies: 0.001�40Hz) made by the
Lviv Centre of the Institute of Space Research were
used at UAS and SSO, respectively. At LFO the
ELF receiver (frequency range: 0.5�40Hz) made by
IRA NASU [14] was used. All magnetometers mea-
sure horizontal components of the geomagnetic �eld
in the directions of the geographical meridian (x) and
parallel (y). They are equipped with GPS systems
to synchronize with absolute time and have similar
characteristics.
Also, there are ionosondes at or near the sites.
This allows comparing IAR parameters with the
characteristics of the ionosphere. At UAS there is
an ionosonde IPS-42 at a distance of 500m from the
magnetometer, so it allows considering that these are
single point measurements. This ionosonde was up-
graded and supplemented with a block of digital reg-
istration therefore ionograms are available in digital
format. All of the ionograms are processed by an
operator within the standard URSI technique [15].
DPS-4 digisonde is located in Irkutsk at the distance
about 200 km from SSO that makes searching for the
reaction on the ionospheric disturbances more com-
plicated at small and medium scales. Nevertheless,
this distance is less than the characteristic large-scale
gradients in the ionosphere that allows making com-
parison with its regular variations. The data is pro-
cessed automatically every 15min. At LFO there is
no ionosonde near the station.
The data received synchronously at all the sta-
tions through the whole 2010 year were used for the
analysis. Such amount of the data allows describing
diurnal and seasonal variations of IAR parameters.
The straight through processing of ELF data was
performed for every station. It included spectral pro-
cessing in which for every x and y component instan-
taneous spectra were made with frequency resolution
0.1Hz (duration of realization is 10 s):
Sx,y(f) =
1
T
T2∫
T1
Bx,y(t)e
−i2πftdt.
Hereafter, instantaneous spectra were used for
computing the power Sxx, Syy and cross Sxy spec-
tra calculated with a time resolution 10min (60 in-
stantaneous spectra were averaged). Values of the
power spectra and absolute values and phases of the
cross spectra were used for computation of the po-
larization parameters (r(f) is ellipticity ratio, Ψ(f)
is position angle of the polarization ellipse, Ip(f) is
intensity of the polarized component, P (f) is degree
of polarization) within the technique described in the
article [11]. In this work we do not stop on the in-
terpreting of the polarization parameters and focus
on the analysis of IAR observability and the aver-
age di�erence between SRS eigenfrequencies � ∆F .
For calculation of these parameters the following al-
gorithm was used. At �rst the daily spectrograms
of the signal intensity for every polarization channel
were calculated. Then an operator chose SRS lines
using specially created software. The frequencies of
IAR modes with equal number from di�erent chan-
nels were averaged if they existed in both channels.
The averaged value of the resonance frequencies were
used for calculation of ∆F . Besides that the fact of
the IAR presence was �xed. It was considered that
IAR is detected if there were three or more resonance
maxima. With the ionosonde data for every 10min
we determine SRS presence (1 � SRS exists, 0 � SRS
does not exist) and, if SRS exists, another two pa-
rameters: ∆F , f0F2.
comparative morphology
of IAR behaviour
The data obtained from the three stations allowed
a comparative analysis of the IAR morphology. For
all observational stations there are identical distinct
seasonal and diurnal dependencies of the behaviour
of IAR parameters. Seasonal-diurnal dependencies
for the probability of IAR registration are shown in
Fig. 1. For easy comparison all the data are shown
for local time and for local seasons. It is seen the
smooth variation of the probability during the day.
The beginning of the increasing and decreasing of
the probability of IAR registration depends on the
sunset and sunrise, respectively. The maximum of
the probability falls on midnight and the minimum
falls on midday. There is clearly expressed depen-
dence on the season of the year as well. In winter
the probability of IAR registration is very high and
almost does not depend on the time of the day (espe-
cially at SSO). In autumn it is high too but there is
clear di�erence between daytime and nighttime. In
46
Advances in Astronomy and Space Physics N.A.Baru, A.V.Koloskov, Y.M.Yampolsky, R.A.Rakhmatulin
spring and summer it is much lower, and SRS are not
observed near midday. However, there are some dif-
ferences between IAR behaviour at di�erent stations.
In winter the probability of IAR registration at LFO
is much lower than at the other stations and has clear
diurnal behaviour. In summer the lowest probability
of SRS registration is observed at UAS. Moreover, as
it is known and as it will be con�rmed onward, the
probability of IAR registration has dependence on
the critical frequency of F2 layer of the ionosphere.
There is an anomaly in f0F2 behaviour at UAS in
summer when the critical frequency in nighttime is
higher than in daytime [13]. This explains why the
probability of IAR registration at UAS in summer is
much lower than at the other stations. But it does
not explain why it is higher in summer night than
in summer day. In daytime f0F2 is lower than in
nighttime so the probability of IAR registration is
supposed to be higher. However, the opposite is ob-
served. Therefore, the critical frequency of the iono-
sphere is not the prime factor of IAR registration.
Perhaps, the conditions at the resonance boundaries
are much important.
Fig. 1: Diurnal-seasonal dependencies for probability of
IAR registration. UAS data are shown with dotted line,
SSO � with dashed line, and LFO data � with solid
line.
Seasonal-diurnal variations of SRS frequency sep-
aration are shown in Fig. 2. The diurnal dependence
of ∆F characterized by smooth variations with the
minimum occurring at the midday. The maximum is
reached on sunset, and during the night∆F is stable.
Seasonally ∆F is slightly higher in the winter and
slightly lower in the summer. In the spring and au-
tumn it has similar values. The diurnal and seasonal
dependencies of ∆F from every station are quali-
tatively similar and have comparable values. But,
as well as for probability of registration, there are
a couple of inconsistencies. First one is much lower
∆F value at UAS in the summer. ∆F has a clearly
seen dependence from the critical frequency so the
anomaly of f0F2 fully explains this fact. Another
one is the maximum of ∆F value at UAS on sunrise.
It is almost imperceptible in the winter, meaning in
the autumn and very large in the spring.
Fig. 2: Diurnal-seasonal dependencies for ∆F . UAS
data are shown with dotted line, SSO � with dashed
line, and LFO data � with solid line.
As it is known SRS was registered at frequen-
cies not higher than 10Hz. Earlier IAR modes at
the frequencies higher than 10Hz were found by the
authors of [10] (further we will call such modes as
high frequency IAR modes). Now we compare the
observability of such events at di�erent stations. A
histogram of the annual distribution of the number
of registered high frequency IAR modes is shown in
Fig. 3. The probability of such events registration
is di�erent at di�erent station. It has seasonal de-
pendence when in the local winter it is much higher
than in the local summer. We should note one fact
does not seen on this histogram: the high frequency
IAR modes are not registered synchronously at dif-
ferent stations. There are less than 20% of days when
such events are registered more than at one station.
Even for LFO and SSO despite similar seasonal de-
pendence of the observability. So it is achieved the
statistical con�rmation that to a greater extent IAR
depends on the local characteristics of the ionosphere
above the observation point, not on a global ones.
An analysis of the relationship between IAR pa-
rameters and geomagnetic activity was made. There
is the dependence of the probability of IAR registra-
tion on the local k-indices in Fig. 4. As it is known
from [3] the probability of SRS observation and ge-
omagnetic activity have inverse relationship. How-
ever, there is no clearly seen inverse dependence be-
tween these parameters in our data (see Fig. 4 left
panel). The expected dependence was found when
47
Advances in Astronomy and Space Physics N.A.Baru, A.V.Koloskov, Y.M.Yampolsky, R.A.Rakhmatulin
we calculated these parameters using only data ob-
tained when high frequency IAR modes were regis-
tered. The result is shown in Fig. 4 (right panel).
Fig. 3: The observability of SRS higher than 10Hz.
Fig. 4: Probability of IAR registration from local k-
indices.
Since IAR is determined by the ionosphere condi-
tions it is advisable to found the relationship between
the resonator parameters and ionosphere characteris-
tics. For this reason the IAR data obtained at UAS
and SSO were compared with the ionosonde data.
Fig. 5 displays the monthly values of the probability
of IAR registration (bars) and the critical frequency
of the ionospheric F2 layer (lines). The inverse re-
lationship between two parameters is clearly seen.
The monthly values of the critical frequency at SSO
have fewer variations than at UAS. In the local sum-
mer the critical frequency at SSO is lower than at
UAS and the probability of IAR registration at SSO
is higher than at UAS. In the local winter f0F2 at
UAS is much lower than at SSO, but the probabil-
ity of IAR registration at UAS is not higher than
at SSO. So, again, it is needed to conclude that the
critical frequency of F2 ionospheric layer is not the
main factor for IAR observability.
Fig. 5: Probability of IAR registration from f0F2.
Fig. 6: The comparison of ∆F and f0F2 behavior at
di�erent stations (a), for the whole year (b), and the
diurnal variation (c) at UAS. Solid line corresponds to
UAS data, dashed line � to SSO data.
Also ∆F was compared with f0F2. Fig. 6 shows
the data for the whole year (b) and the diurnal vari-
ations of these values (c). The critical frequency is
shown by the solid line and for ∆F the dashed line
is used. For the data from both stations the inverse
relation is clearly seen. The dependencies between
∆F and the critical frequency at di�erent stations
are shown in Fig. 6(a). As it can be seen the depen-
dence between f0F2 and ∆F for SSO data di�ers
from those obtained at UAS. In [10] it was shown
that this is caused by di�erences of the magnetic
�eld values over the stations.
48
Advances in Astronomy and Space Physics N.A.Baru, A.V.Koloskov, Y.M.Yampolsky, R.A.Rakhmatulin
results and conclusions
The comparative analysis of the SRS registration
data was made for the purpose of searching and al-
locating the local features of the resonance parame-
ters. It is shown that diurnal-seasonal behaviour of
IAR parameters is qualitatively similar at each sta-
tion and depends on the time of the local sunrise and
sunset. There are some local di�erences but they do
not a�ect the overall picture as a whole.
The annual distribution of the high frequency
IAR modes con�rms that IAR is primary in�uenced
by the local characteristics of the ionosphere and not
by the global ones.
Synchronous analysis of the probability of IAR
registration and local k-indices con�rms the inverse
dependence for the SRS observability on the geomag-
netic activity. It is shown that this dependence is
better expressed for the high frequency IAR modes
than for all events of IAR registration independently
from the frequency range.
The matching of IAR parameters with the critical
frequency of F2 layer of the ionosphere con�rms the
inverse relation between them.
acknowledgement
The authors are thankful to the National Antarc-
tic Scienti�c Center of Ukraine, Ministry of Ed-
ucation and Science of Ukraine for supporting
of the long-term ULF-ELF monitoring at UAS
�Academic Vernadski�. Also we are thankful
to the winterer-geophysics and specialists of IRA
NASU and ISTP SB RAS for the skilled work
for maintaining the receiving devices in Antarc-
tica, Ukraine and Russia that is provided the high
quality data. This research was partially sup-
ported by the National Academy of Sciences of
Ukraine projects �Yatagan-3� (N 0116U000035) and
�Spitsbergen-2016� (N 0116U002874).
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