Supplementary material to "Geomagnetic pulsations in the Pc5/Pi3 frequency range and fluctuations of foF2 frequency"

2019 ◽  
Author(s):  
Nadezda Yagova ◽  
Alexander Kozlovsky ◽  
Evgeny Fedorov ◽  
Olga Kozyreva
Keyword(s):  
Geomagnetic Pulsations ◽  
Frequency Range ◽  
Supplementary Material

scholarly journals Geomagnetic Pulsations, Blackout and Low-Latitude Aurorae Associated with Power Magnetic Storm

2021 ◽  
Vol 3 (4) ◽  
pp. 279-289
Author(s):  
Vladimir Parkhomov ◽  
Aleksandr Mikhalev ◽  
Konstantin Ratovskyi
Keyword(s):  
Solar Flare ◽  
Magnetic Storm ◽  
Geomagnetic Pulsation ◽  
Spectral Lines ◽  
Geomagnetic Pulsations ◽  
Radio Waves ◽  
Frequency Range ◽  
Low Latitude ◽  
Ionospheric Absorption ◽  
Solar Filament

The research analyzed the regularities of the dynamics of geomagnetic pulsation regimes in the frequency range 0.002–5 Hz, the generation of which reflects the interaction with the Earth's magnetosphere of the solar filament ejected by a powerful solar flare of 3B. We compared the dynamics of the change in the types and modes of geomagnetic pulsations with the dynamics of the atmosphere glow in two spectral lines and the total ionospheric absorption of radio waves. The study developed a possible model of the observed phenomenon.

scholarly journals Non-triggered auroral substorms and long-period (1–4 mHz) geomagnetic and auroral luminosity pulsations in the polar cap

2017 ◽  
Vol 35 (3) ◽  
pp. 365-376 ◽  
Author(s):  
Nadezda Yagova ◽  
Natalia Nosikova ◽  
Lisa Baddeley ◽  
Olga Kozyreva ◽  
Dag A. Lorentzen ◽  
...  
Keyword(s):  
Auroral Oval ◽  
Geomagnetic Pulsations ◽  
Frequency Range ◽  
Polar Cap ◽  
Time Intervals ◽  
Spectral Parameters ◽  
Long Period ◽  
Power Spectral ◽  
Auroral Substorms ◽  
Auroral Luminosity

Abstract. A study is undertaken into parameters of the polar auroral and geomagnetic pulsations in the frequency range 1–4 mHz (Pc5∕Pi3) during quiet geomagnetic intervals preceding auroral substorms and non-substorm background variations. Special attention is paid to substorms that occur under parameters of the interplanetary magnetic field (IMF) conditions typical for undisturbed days (non-triggered substorms). The spectral parameters of pulsations observed in auroral luminosity as measured by a meridian scanning photometer (Svalbard) in the polar cap and near the polar boundary of the auroral oval are studied and compared with those for the geomagnetic pulsations measured by the magnetometer network IMAGE in the same frequency range. It is found that Pc5∕Pi3 power spectral density (PSD) is higher during pre-substorm time intervals than for non-substorm days and that specific variations of pulsation parameters (substorm precursors) occur during the last 2–4 pre-substorm hours.

Bursts of geomagnetic pulsations in the frequency range 0.2-5 Hz excited by large changes of the solar wind pressure

2010 ◽  
Vol 48 (1) ◽  
pp. 86-100 ◽  
Author(s):  
V. A. Parkhomov ◽  
G. N. Zastenker ◽  
M. O. Riazantseva ◽  
B. Tsegmed ◽  
T. A. Popova
Keyword(s):  
Solar Wind ◽  
Wind Pressure ◽  
Geomagnetic Pulsations ◽  
Frequency Range ◽  
Solar Wind Pressure

scholarly journals New type of ensemble of quasi-periodic, long-lasting VLF emissions at the auroral zone

2012 ◽  
Vol 30 (12) ◽  
pp. 1655-1660 ◽  
Author(s):  
J. Manninen ◽  
N. G. Kleimenova ◽  
O. V. Kozyreva
Keyword(s):  
Temporal Dynamics ◽  
Low Frequency ◽  
Auroral Zone ◽  
Spectral Structure ◽  
Geomagnetic Pulsations ◽  
Frequency Range ◽  
Theoretical Investigations ◽  
New Type ◽  
Periodic Signals ◽  
Vlf Emissions

Abstract. A new type of the series of quasi-periodic (QP) very low frequency (VLF) emissions in frequency range of 1–5 kHz, and not associated with geomagnetic pulsations, has been discovered at auroral latitudes (L = 5.3) during the Finnish VLF campaign (held in December 2011). At least five unusually spectacular events, each with a duration of several hours, have been observed during the night under conditions of quiet geomagnetic activity (Kp = 0–1), although QPs usually occur during the daytime. Contrary to the QP emissions typically occurring during the day, the spectral structure of these QP events represented an extended, complicated sequence of repeated discrete rising VLF signals. Their duration was about 2–3 min each, with the repetition periods ranging from ~1 min to ~10 min. Two such nighttime non-typical events are reported in this paper. The fine structure of the separated QP elements may represent a mixture of the different frequency band signals, which seem to have independent origins. It was found that the periodic signals with lower frequency appear to trigger the strong dispersive upper frequency signals. The temporal dynamics of the spectral structure of the QPs studied were significantly controlled by some disturbances in the solar wind and interplanetary magnetic field (IMF). This finding is very important for future theoretical investigations because the generation mechanism of this new type of QP emissions is not yet understood.

scholarly journals Geomagnetic pulsations in the Pc5/Pi3 frequency range and fluctuations of foF2 frequency

2019 ◽  
Author(s):  
Nadezda Yagova ◽  
Alexander Kozlovsky ◽  
Evgeny Fedorov ◽  
Olga Kozyreva
Keyword(s):  
Spatial Distribution ◽  
Critical Frequency ◽  
Dynamic Pressure ◽  
Pressure Fluctuations ◽  
Automatic Detection ◽  
Geomagnetic Pulsations ◽  
Frequency Range ◽  
Spectral Content ◽  
Using Data ◽  
Fof2 Critical Frequency

Abstract. Using data of the ionosonde in Sodankyla, (SOD, 67° N, 27° E, Finland), parameters of variations of foF2 critical frequency in the Pc5/Pi3 (1–5 mHz) frequency range are studied. For that, a technique of automatic detection of critical frequency from an ionogram is developed. The variations of foF2 are compared with the Pc5/Pi3 geomagnetic pulsations on the ground and in the magnetosphere. The variations of foF2 are in the majority of cases decoupled from the Pc5/Pi3 on the ground. Meanwhile, the analysis of geomagnetic and foF2 variations at SOD show intervals with noticeable coherence for both horizontal components. These coherent pulsations are predominantly registered in the afternoon MLT sector. Statistically, their spectral content, polarization and spatial distribution differs from those of background variations. Coherent pulsation tend to occur under moderate geomagnetic and auroral activity, SW speed, and dynamic pressure fluctuations. The fraction of coherent geomagnetic and foF2 pulsations is higher for the geomagnetic pulsations registered in the magnetosphere, than on the ground.

Global impulse burst of geomagnetic pulsations in the frequency range of 0.2–5 Hz as a precursor of the sudden commencement of St. Patrick’s Day 2015 geomagnetic storm

2017 ◽  
Vol 55 (5) ◽  
pp. 307-317 ◽  
Author(s):  
V. A. Parkhomov ◽  
N. L. Borodkova ◽  
A. G. Yahnin ◽  
A. V. Suvorova ◽  
B. V. Dovbnya ◽  
...  
Keyword(s):  
Geomagnetic Storm ◽  
Sudden Commencement ◽  
Geomagnetic Pulsations ◽  
Frequency Range

Density-based discrimination of protein and RNA in the ribosome

1992 ◽  
Vol 50 (1) ◽  
pp. 464-465
Author(s):  
Joachim Frank
Keyword(s):  
Transfer Function ◽  
Spatial Frequency ◽  
Three Dimensional ◽  
Wiener Filter ◽  
Dark Field Image ◽  
Dark Field ◽  
Frequency Range ◽  
Bright Field ◽  
Contrast Transfer Function ◽  
Pass Filter

Cryo-electron microscopy combined with single-particle reconstruction techniques has allowed us to form a three-dimensional image of the Escherichia coli ribosome.In the interior, we observe strong density variations which may be attributed to the difference in scattering density between ribosomal RNA (rRNA) and protein. This identification can only be tentative, and lacks quantitation at this stage, because of the nature of image formation by bright field phase contrast. Apart from limiting the resolution, the contrast transfer function acts as a high-pass filter which produces edge enhancement effects that can explain at least part of the observed variations. As a step toward a more quantitative analysis, it is necessary to correct the transfer function in the low-spatial-frequency range. Unfortunately, it is in that range where Fourier components unrelated to elastic bright-field imaging are found, and a Wiener-filter type restoration would lead to incorrect results. Depending upon the thickness of the ice layer, a varying contribution to the Fourier components in the low-spatial-frequency range originates from an “inelastic dark field” image. The only prospect to obtain quantitatively interpretable images (i.e., which would allow discrimination between rRNA and protein by application of a density threshold set to the average RNA scattering density may therefore lie in the use of energy-filtering microscopes.

Evaluation of Special Hearing Aids for Deaf Children

1971 ◽  
Vol 36 (4) ◽  
pp. 527-537 ◽  
Author(s):  
Norman P. Erber
Keyword(s):  
Hearing Aids ◽  
High Frequency ◽  
Hearing Aid ◽  
Low Frequency ◽  
Acoustic Stimulation ◽  
Deaf Children ◽  
Frequency Range ◽  
Frequency Limit ◽  
Unpublished Studies ◽  
Published Research

Two types of special hearing aid have been developed recently to improve the reception of speech by profoundly deaf children. In a different way, each special system provides greater low-frequency acoustic stimulation to deaf ears than does a conventional hearing aid. One of the devices extends the low-frequency limit of amplification; the other shifts high-frequency energy to a lower frequency range. In general, previous evaluations of these special hearing aids have obtained inconsistent or inconclusive results. This paper reviews most of the published research on the use of special hearing aids by deaf children, summarizes several unpublished studies, and suggests a set of guidelines for future evaluations of special and conventional amplification systems.

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