Finding the Ionospheric Fluctuations Reflection in the Pulsar Signals’ Characteristics Observed with LOFAR

Błaszkiewicz, Leszek; Flisek, Paweł; Kotulak, Kacper; Krankowski, Andrzej; Lewandowski, Wojciech; Kijak, J.; Froń, Adam

doi:10.3390/s21010051

Cited by 4 publications

(3 citation statements)

References 68 publications

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“…Low frequencies are extremely vulnerable to all electromagnetic fields, so ionospheric plasma density gradients may seriously affect the quality of observation [ 6 ]. Błaszkiewicz et al [ 18 ] show that even weak ionospheric total electron content (TEC) fluctuations have a strong reflection in radio pulsar observations—the observed radio wave intensity noticeably drops during occurrence of plasma density gradients in a LOFAR’s field of view.…”

Section: Introductionmentioning

confidence: 99%

Sub-Auroral and Mid-Latitude GNSS ROTI Performance during Solar Cycle 24 Geomagnetic Disturbed Periods: Towards Storm’s Early Sensing

Kotulak

Krankowski

Froń

et al. 2021

Sensors

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Geomagnetic storms—triggered by the interaction between Earth’s magnetosphere and interplanetary magnetic field, driven by solar activity—are important for many Earth-bound aspects of life. Serious events may impact the electroenergetic infrastructure, but even weaker storms generate noticeable irregularities in the density of ionospheric plasma. Ionosphere electron density gradients interact with electromagnetic radiation in the radiofrequency domain, affecting sub- and trans-ionospheric transmissions. The main objective of the manuscript is to find key features of the storm-induced plasma density behaviour irregularities in regard to the event’s magnitude and general geomagnetic conditions. We also aim to set the foundations for the mid-latitude ionospheric plasma density now-casting irregularities. In the manuscript, we calculate the GPS+GLONASS-derived rate of TEC (total electron content) index (ROTI) for the meridional sector of 10–20∘ E, covering the latitudes between 40 and 70∘ N. Such an approach reveals equatorward spread of the auroral TEC irregularities reaching down to mid-latitudes. We have assessed the ROTI performance for 57 moderate-to-severe storms that occurred during solar cycle 24 and analyzed their behaviors in regard to the geomagnetic conditions (described by Kp, Dst, AE, Sym-H and PC indices).

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Section: Introductionmentioning

confidence: 99%

Sub-Auroral and Mid-Latitude GNSS ROTI Performance during Solar Cycle 24 Geomagnetic Disturbed Periods: Towards Storm’s Early Sensing

Kotulak

Krankowski

Froń

et al. 2021

Sensors

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“…In the case of LOFAR, the width of the beam created during the beamforming process has an angular size of 4°for the LBA antennas (Błaszkiewicz et al, 2021). The signal-to-noise of a particular object drives the detection: typically, the signal from a given object is considered as detected when the signal level exceeds the 3r threshold (where r indicates the average noise level).…”

Section: General Considerations About Signal Levelsmentioning

confidence: 99%

Towards the possibility to combine LOFAR and GNSS measurements to sense ionospheric irregularities

Flisek,

Forte,

Fallows

et al. 2023

J. Space Weather Space Clim.

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Inhomogeneities within the ionospheric plasma density affect trans-ionospheric radio signals, causing radio wave scintillation in the amplitude and phase of the signals. The amount of scintillation induced by ionospheric irregularities typically decreases with the radio wave frequency. As the ionosphere affects a variety of technological systems (e.g., civil aviation, financial operations) as well as low-frequency radio astronomy observations, it is important to detect and monitor ionospheric effects with higher accuracy than currently available. Here, a novel methodology for the detection and characterization of ionospheric irregularities is established on the basis of LOFAR (Low-Frequency Array) scintillation measurements at Very High Frequency (VHF) that take into account the lack of ergodicity in the intensity fluctuations induced by scintillation. The methodology estimates the S4 scintillation index originating from irregularities with spatial scales in the inertial sub-range of electron density fluctuations in the ionosphere. The methodology is illustrated by means of observations that were collected through the Polish LOFAR stations located in Bałdy, Borowiec and Łazy: its validation was carried out by comparing LOFAR VHF scintillation observations with independent Global Navigation Satellite Systems (GNSS) observations that were collected through a high-rate receiver located near the LOFAR station in Bałdy as well as through geodetic receivers from the Polish ASG-EUPOS network. Two case studies are presented: 31 March 2017 and 28 September 2017. The comparison between LOFAR S4 observations and independent ionospheric measurements of both scintillation and rate of change of Total Electron Content (TEC) from GNSS reveals that the sensitivity of LOFAR and GNSS to ionospheric structures is different as a consequence of the frequency dependency of radio wave scintillation. Furthermore, it can be noticed that observations of LOFAR VHF scintillation can be utilised to detect plasma structures forming in the mid-latitude ionosphere, including electron density gradients occurring over spatial scales that are not necessarily detected through traditional GNSS measurements: the detection of all spatial scales is important for correct monitoring and modelling of ionospheric processes. Hence, the different sensitivity of LOFAR to ionospheric structures, in addition to traditional GNSS ionospheric measurements, allows us to expand the knowledge of ionospheric processes.

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“…The threshold H is defined as the root of Equation (38) for a given false alarm probability level. The parameter SNR det in Equation ( 39) is calculated in the previous section for pulsar, solar and lunar FSRs depending on the frequency of emission, the size of airplanes, which are crossing the baseline "transmitterreceiver" at the right angle and also their distance [23][24][25]. Equation (39) can only be used when the direct signal is fully compensated.…”

Section: Probability Characteristicsmentioning

confidence: 99%

FSR Systems for Detection of Air Objects Using Cosmic Radio Emissions

Kabakchiev

Behar

Garvanov

et al. 2021

Sensors

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The paper analyses the possibility of Forward Scatter Radar (FSR) systems to detect airplanes using cosmic emission from pulsars and planets (pulsar, Sun, Moon). A suboptimal multichannel algorithm for joint detection and evaluation of the parameters of the forward scattering signal created by an airplane (duration and velocity) is proposed, with preliminary compensation of the powerful direct signal emitted by cosmic sources (pulsar, Sun and Moon). The expressions for calculation of the Signal-to-Noise Ratio (SNR) at the input of the detector and the compensator are obtained. The detection characteristics are also obtained, and the requirements for the suppression coefficient of the compensator are evaluated. A methodology for calculating the maximum distance for detecting an aircraft using a described algorithm is proposed. The obtained results show that due to the Forward Scatter (FS) effect, there is the theoretical possibility to detect airplanes at close ranges by FSRs, which use very weak signals from cosmic sources.

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Finding the Ionospheric Fluctuations Reflection in the Pulsar Signals’ Characteristics Observed with LOFAR

Cited by 4 publications

References 68 publications

Sub-Auroral and Mid-Latitude GNSS ROTI Performance during Solar Cycle 24 Geomagnetic Disturbed Periods: Towards Storm’s Early Sensing

Sub-Auroral and Mid-Latitude GNSS ROTI Performance during Solar Cycle 24 Geomagnetic Disturbed Periods: Towards Storm’s Early Sensing

Towards the possibility to combine LOFAR and GNSS measurements to sense ionospheric irregularities

FSR Systems for Detection of Air Objects Using Cosmic Radio Emissions

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