Low-frequency radio recombination lines: observations and data processing

2017 ◽  
Vol 23 (1) ◽  
pp. 50-53
Author(s):  
A.A. Konovalenko ◽  
◽  
S.V. Stepkin ◽  
E.V. Vasilkovskiy ◽  
◽  
...  
Keyword(s):  
Data Processing ◽  
Low Frequency ◽  
Radio Recombination Lines

scholarly journals Results of the infrasonic array on the Valaam Island primary data processing

2020 ◽  
Vol 2 (1) ◽  
pp. 85-91
Author(s):  
Vladimir Karpinsky ◽  
Vladimir Asming
Keyword(s):  
Data Processing ◽  
Seismic Station ◽  
Sampling Rate ◽  
Low Frequency ◽  
Primary Data ◽  
Joint Analysis ◽  
Main Task ◽  
Significant Difference ◽  
Infrasound Signal ◽  
Short Time

The infrasound array VALS developed in Kola Branch GS RAS has been installed in June 2016 on the Valaam Island in addition to the continuously operating seismic station VALR. The array consists of 3 spaced low-frequency microphones. The data with a sampling rate of 100 Hz is stored continuously at the acquisition computer; the timing is carried out using GPS. In addition to the acquisition system, an infrasound signal detector is installed on the computer. It works in near real-time mode and enables us to find signals and compute their back azimuths. At the end of 2018, a new version of the detector was developed at the Kola Branch GS RAS. The detector began to work much faster, which enabled us to carry out data processing for 2.5 years in two frequency ranges in a short time. The main task of the array is acoustic monitoring, the detection of infrasound events, the determination of their parameters, and the selection of events of natural origin. The data are also used (in combination with the VALR seismic station data) to locate near seismic events, especially weak ones. The analysis of the obtained data revealed the prevailing directions to the signal sources. The change of directions to sources in time was investigated, seasonal features were revealed. Acoustic events were detected in the frequency bands 1–5 Hz and 10–20 Hz, and a significant difference was found in the azimuthal distribution of events for these ranges. A joint analysis of acoustic and seismic data showed that the part of events with both acoustic and seismic components is low – it is almost completely exhausted by career explosions. It was also noted that in addition to explosions in nearby quarries (Kuznechnoye, Pitkäranta) located at a distance of 50–60 km, according to acoustic data, events corresponding to explosions at quarries located at a distance of 100 km or more were repeatedly identified.

scholarly journals Geomagnetic anomaly associated with Fukushima earthquake on February 13th, 2021

2021 ◽  
Vol 331 ◽  
pp. 07012
Author(s):  
Cipta Ramadhani ◽  
Bulkis Kanata ◽  
Abdullah Zainuddin ◽  
Rosmaliati ◽  
Teti Zubaidah
Keyword(s):  
Data Processing ◽  
Geomagnetic Field ◽  
Field Data ◽  
Low Frequency ◽  
Earthquake Precursors ◽  
Polarization Ratio ◽  
Magnetic Polarization ◽  
Central Frequency ◽  
Electromagnetic Data ◽  
Geomagnetic Anomaly

In this study, we performed research on electromagnetic anomalies related to earthquakes as early signs (precursors) that occurred in Fukushima, Japan on February 13th, 2021. The research focused on the utilization of geomagnetic field data which was derived from the Kakioka (KAK), Kanoya (KNY), and Memambetsu (MMB) observatories, particularly in the ultra-low frequency (ULF) to detect earthquake precursors. The method of electromagnetic data processing was conducted by applying a polarization ratio. In addition, we improved the methodology by splitting the ULF data (which ranged from 0.01-0.1 Hz) into 9 central frequencies and picking up the highest value from each central frequency to get the polarization ratio. The anomaly of magnetic polarization was identified 2-3 weeks before the mainshock in a narrowband frequency in the range of 0.04-0.05 Hz.

scholarly journals INTERSTELLAR MEDIUM AND DECAMETER RADIO SPECTROSCOPY

2021 ◽  
Vol 26 (4) ◽  
pp. 314-325
Author(s):  
S. V. Stepkin ◽  
◽  
O. O. Konovalenko ◽  
Y. V. Vasylkivskyi ◽  
D. V. Mukha ◽  
...  
Keyword(s):  
Interstellar Medium ◽  
Radio Telescope ◽  
Radio Astronomy ◽  
Low Frequency ◽  
Spectral Lines ◽  
Physical Parameters ◽  
Recombination Mechanism ◽  
Radio Recombination Lines ◽  
Radio Spectroscopy ◽  
Correlation Spectrum

Purpose: The analytical review of the main results of research in the new direction of the low-frequency radio astronomy, the interstellar medium radio spectroscopy at decameter waves, which had led to astrophysical discovery, recording of the radio recombination lines in absorption for highly excited states of interstellar carbon atoms (more than 600). Design/methodology/approach: The UTR-2 world-largest broadband radio telescope of decameter waves optimally connected with the digital correlation spectrum analyzers has been used. Continuous modernization of antenna system and devices allowed increasing the analysis band from 100 kHzto 24 MHz and a number of channels from 32 to 8192. The radio telescope and receiving equipment with appropriate software allowed to have a long efficient integration time enough for a large line series simultaneously with high resolution, noise immunity and relative sensitivity. Findings: A new type of interstellar spectral lines has been discovered and studied, the interstellar carbon radio recombination lines in absorption for the record high excited atoms with principal quantum numbers greater than 1000. The line parameters (intensity, shape, width, radial velocity) and their relation ship with the interstellar medium physical parameters have been determined. The temperature of line forming regions is about 100 K, the electron concentration up to 0.1 cm–3 and the size of a line forming region is about 10 pc. For the first time, radio recombination lines were observed in absorption. They have significant broadening and are amplified by the dielectronic-like recombination mechanism and are also the lowest frequency lines in atomic spectroscopy. Conclusions: The detected low-frequency carbon radio recombination lines and their observations have become a new highly effective tool for the cold partially ionized interstellar plasma diagnostics. Using them allows obtaining the information which is not available with the other astrophysical methods. For almost half a century of their research, a large amount of hardware-methodical and astrophysical results have been obtained including a record number of Galaxy objects, where there levant lines have been recorded. The domestic achievements have stimulated many theoretical and experimental studies in other countries, but the scientific achievements of Ukrainian scientists prove the best prospects for further development of this very important area of astronomical science. Key words: low-frequency radio astronomy; radio telescope; interstellar medium; radio recombination lines; carbon; hydrogen; spectral analyzer

Localizing the Source of Type II Emission Around a CME with the Sun Radio Interferometer Space Experiment (SunRISE) and MHD Simulations

2021 ◽  
Author(s):  
Alexander Hegedus ◽  
Ward Manchester ◽  
Justin Kasper ◽  
Joseph Lazio ◽  
Andrew Romero-Wolf
Keyword(s):  
Data Processing ◽  
Low Frequency ◽  
Solar Energetic Particle ◽  
Radio Interferometer ◽  
Valuable Insight ◽  
Type Ii ◽  
Plasma Parameters ◽  
Low Frequencies ◽  
The Earth ◽  
Type Ii Bursts

<p>The Earth’s Ionosphere limits radio measurements on its surface, blocking out any radiation below 10 MHz. Valuable insight into many astrophysical processes could be gained by having a radio interferometer in space to image the low frequency window, which has never been achieved. One application for such a system is observing type II bursts that track solar energetic particle acceleration occurring at Coronal Mass Ejection (CME)-driven shocks. This is one of the primary science targets for SunRISE, a 6 CubeSat interferometer to circle the Earth in a GEO graveyard orbit. SunRISE is a NASA Heliophysics Mission of Opportunity that began Phase B (Formulation) in June 2020, and plans to launch for a 12-month mission in mid-2023. In this work we present an update to the data processing and science analysis pipeline for SunRISE and evaluate its performance in localizing type II bursts around a simulated CME.</p><p>To create realistic virtual type II input data, we employ a 2-temperature MHD simulation of the May 13th 2005 CME event, and superimpose realistic radio emission models on the CME-driven shock front, and propagate the signal through the simulated array. Data cuts based on different plasma parameter thresholds (e.g. de Hoffman-Teller velocity and angle between shock normal and the upstream magnetic field) are tested to get the best match to the true recorded emission.  This model type II emission is then fed to the SunRISE data processing pipeline to ensure that the array can localize the emission. We include realistic thermal noise dominated by the galactic background at these low frequencies, as well as new sources of phase noise from positional uncertainty of each spacecraft. We test simulated trajectories of SunRISE and image what the array recovers, comparing it to the virtual input, finding that SunRISE can resolve the source of type II emission to within its prescribed goal of 1/3 the CME width. This shows that SunRISE will significantly advance the scientific community’s understanding of type II burst generation, and consequently, acceleration of solar energetic particles at CMEs.  This unique combination of SunRISE observations and MHD recreations of space weather events will allow an unprecedented look into the plasma parameters important for these processes. </p>

scholarly journals Searching for the largest bound atoms in space

2020 ◽  
Vol 634 ◽  
pp. A138
Author(s):  
K. L. Emig ◽  
P. Salas ◽  
F. de Gasperin ◽  
J. B. R. Oonk ◽  
M. C. Toribio ◽  
...  
Keyword(s):  
High Redshift ◽  
Low Frequency ◽  
Significant Feature ◽  
Starburst Galaxy ◽  
Frequency Spectra ◽  
Cassiopeia A ◽  
Radio Recombination Lines ◽  
Searching Method ◽  
Spectral Searching ◽  
First Time

Context. Radio recombination lines (RRLs) at frequencies ν <  250 MHz trace the cold, diffuse phase of the interstellar medium, and yet, RRLs have been largely unexplored outside of our Galaxy. Next-generation low-frequency interferometers such as LOFAR, MWA, and the future SKA will, with unprecedented sensitivity, resolution, and large fractional bandwidths, enable the exploration of the extragalactic RRL universe. Aims. We describe methods used to (1) process LOFAR high band antenna (HBA) observations for RRL analysis, and (2) search spectra for RRLs blindly in redshift space. Methods. We observed the radio quasar 3C 190 (z ≈ 1.2) with the LOFAR HBA. In reducing these data for spectroscopic analysis, we placed special emphasis on bandpass calibration. We devised cross-correlation techniques that utilize the unique frequency spacing between RRLs to significantly identify RRLs in a low-frequency spectrum. We demonstrate the utility of this method by applying it to existing low-frequency spectra of Cassiopeia A and M 82, and to the new observations of 3C 190. Results. Radio recombination lines have been detected in the foreground of 3C 190 at z = 1.12355 (assuming a carbon origin) owing to the first detection of RRLs outside of the local universe (first reported in A&A, 622, A7). Toward the Galactic supernova remnant Cassiopeia A, we uncover three new detections: (1) stimulated Cϵ transitions (Δn = 5) for the first time at low radio frequencies, (2) Hα transitions at 64 MHz with a full width at half-maximum of 3.1 km s−1 the most narrow and one of the lowest frequency detections of hydrogen to date, and (3) Cα at vLSR ≈ 0 km s−1 in the frequency range 55–78 MHz for the first time. Additionally, we recover Cα, Cβ, Cγ, and Cδ from the −47 km s−1 and −38 km s−1 components. In the nearby starburst galaxy M 82, we do not find a significant feature. With previously used techniques, we reproduce the previously reported line properties. Conclusions. RRLs have been blindly searched and successfully identified in Galactic (to high-order transitions) and extragalactic (to high redshift) observations with our spectral searching method. Our current searches for RRLs in LOFAR observations are limited to narrow (<100 km s−1) features, owing to the relatively small number of channels available for continuum estimation. Future strategies making use of a wider band (covering multiple LOFAR subbands) or designs with larger contiguous frequency chunks would aid calibration to deeper sensitivities and broader features.

scholarly journals Low-frequency Carbon Radio Recombination Lines. I. Calculations of Departure Coefficients

2017 ◽  
Vol 837 (2) ◽  
pp. 141 ◽  
Author(s):  
F. Salgado ◽  
L. K. Morabito ◽  
J. B. R. Oonk ◽  
P. Salas ◽  
M. C. Toribio ◽  
...  
Keyword(s):  
Low Frequency ◽  
Radio Recombination Lines

scholarly journals Low-Frequency Carbon Recombination Lines in the Orion Molecular Cloud Complex

2018 ◽  
Vol 35 ◽  
Author(s):  
Chenoa D. Tremblay ◽  
Christopher H. Jordan ◽  
Maria Cunningham ◽  
Paul A. Jones ◽  
Natasha Hurley-Walker
Keyword(s):  
Synchrotron Radiation ◽  
Molecular Cloud ◽  
Low Frequency ◽  
Beta Transition ◽  
Radiation Mechanism ◽  
Radio Recombination Lines ◽  
Hα Emission ◽  
Mechanism Transition ◽  
Cloud Complex

AbstractWe detail tentative detections of low-frequency carbon radio recombination lines from within the Orion molecular cloud complex observed at 99–129 MHz. These tentative detections include one alpha transition and one beta transition over three locations and are located within the diffuse regions of dust observed in the infrared at 100 μm, the Hα emission detected in the optical, and the synchrotron radiation observed in the radio. With these observations, we are able to study the radiation mechanism transition from collisionally pumped to radiatively pumped within the H ii regions within the Orion molecular cloud complex.

Experiments on excitation and data processing of low frequency vibroseis in permafrost area of Tibetan Plateau

2019 ◽  
Author(s):  
Yu-Kun Tian ◽  
Yan-Hui Mei ◽  
Jie Cao ◽  
Juan Li ◽  
Hui Zhou ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Data Processing ◽  
Low Frequency
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