Radio Events Research Articles

INTOMO operator for GNSS multi-source tomography based on 3D ray tracing technique

AbstractThe current GNSS meteorology literature focuses on ground-based and space-based GNSS observations separately, without exploring potential synergies. In this study, we propose combining the two data sources using GNSS tomography to overcome current limitations in (1) horizontal resolution of GNSS space-based, (2) low vertical resolution of GNSS ground-based tropospheric retrievals when the number of GNSS ground-based observations is limited and (3) instability of the tomography system due to a lack of observations traversing the atmosphere horizontally. Our study on the combination of GNSS ground-based and space-based presents an innovative way for data integration based on uncertainty estimation. The developed integrated tomography operator, based on 3D ray tracing principles, is tested on 30 days of simulated data with 101 ground stations and over 240 radio occultation events, using three different station layouts. The a priori data introduced into the tomography processing is from a deterministic model, while ray tracing uses the ERA5 reanalysis wet refractivity field to obtain input data for individual test cases. The results are verified by comparing tomography output to ERA5 reanalysis. We observed a decrease in tomography RMSE between 2% and 16% in the case of an integrated solution, depending on GNSS station layout and the number and geometry of radio occultation ray paths. We show that a single RO event during one processing epoch can shift the wet refractivity estimates by 2 to 5 ppm closer to the correct solution compared to ground-based-only GNSS tomography.

Short-wave fadeout on mars: Radio absorption in the dayside martian ionosphere enhanced by solar flares

Solar flares can cause radio absorption in the D region of the Earth’s ionosphere and consequently interrupt high-frequency radio communication systems, also known as short-wave fadeout or the Dellinger effect. We present an analogous radio absorption event observed at Mars during a solar flare. In this event, the Mars Express Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) instrument fortuitously operated at low altitudes on the dayside around the terminator in a favorable configuration for surface echo measurements at the flare peak. The surface echo power during the flare is abnormally weak compared to nominal echo powers at corresponding solar zenith angles, suggesting flare-induced radio absorption in the dayside lower ionosphere of Mars. Additionally, long-term MARSIS data statistically demonstrate the radio absorption dependence on solar soft X-ray fluxes. Our results point to the need for Martian space weather prediction including ionospheric effects on radio waves.

Effect of The Density and Height of F2 layer on Ground-Based Observation of Jupiter's Radio Signal

The density and height of the ionospheric F2 layer affect the observation of Jupiter's radio signals. The study aims to determine an approximate observation threshold from the values of the F2 peak density and the height of the F2 peak. The Florida and Lamy stations in the USA were selected. Utilizing actual observation data of Jupiter's radio signals from the Radio JOVE Data Archive for the years 2014-2015. The Radio Jove Pro software was employed to predict radio emissions from Jupiter. Ionospheric data were sourced from the International Reference Ionosphere (IRI) website. The primary focus of this study is to examine the role of the ionosphere in blocking the radio signals emanating from Jupiter. It was found that 49% and 31% (for the Florida and Lamy stations, respectively) of the predicted radio emission events from Jupiter were not observed. The likelihood of observation is higher after sunset and depends on Jupiter's elevation above the horizon relative to the observer. The F2 peak density during nighttime and throughout the year ranged from approximately 1011 to 1012 m-3 at altitudes of about 260-360 km. 89% and 98% (for the Florida and Lamy stations, respectively) of the observations occurred when the F2 peak density was less than around 6×1011 m-3. In contrast, 80% and 56% (for the Florida and Lamy stations, respectively) of the cases of non-observation occurred when the F2 peak density was greater than approximately 6×1011 m-3. As for The height of the F2 peak (hmF2), 85% and 93% of the observations occurred when the hmF2 was greater than about 300 km for the Florida and Lamy stations, respectively. The probability of observation is significantly influenced by the relationship between the electron density and its corresponding altitude.

Effect of The Density and Height of F2 layer on Ground-Based Observation of Jupiter's Radio Signal

The density and height of the ionospheric F2 layer affect the observation of Jupiter's radio signals. The study aims to determine an approximate observation threshold from the values of the F2 peak density and the height of the F2 peak. The Florida and Lamy stations in the USA were selected. Utilizing actual observation data of Jupiter's radio signals from the Radio JOVE Data Archive for the years 2014-2015. The Radio Jove Pro software was employed to predict radio emissions from Jupiter. Ionospheric data were sourced from the International Reference Ionosphere (IRI) website. The primary focus of this study is to examine the role of the ionosphere in blocking the radio signals emanating from Jupiter. It was found that 49% and 31% (for the Florida and Lamy stations, respectively) of the predicted radio emission events from Jupiter were not observed. The likelihood of observation is higher after sunset and depends on Jupiter's elevation above the horizon relative to the observer. The F2 peak density during nighttime and throughout the year ranged from approximately 1011 to 1012 m-3 at altitudes of about 260-360 km. 89% and 98% (for the Florida and Lamy stations, respectively) of the observations occurred when the F2 peak density was less than around 6×1011 m-3. In contrast, 80% and 56% (for the Florida and Lamy stations, respectively) of the cases of non-observation occurred when the F2 peak density was greater than approximately 6×1011 m-3. As for The height of the F2 peak (hmF2), 85% and 93% of the observations occurred when the hmF2 was greater than about 300 km for the Florida and Lamy stations, respectively. The probability of observation is significantly influenced by the relationship between the electron density and its corresponding altitude.

A Prediction about Radio Frequency Envelope Detectors for Implementing a 2.4 GHz Rectenna for IEEE 802.15.4 with MOS Transistors

This study introduces a rectenna, functioning as an RF envelope detector, utilizing a 16 nm bulk MOS transistor (metal-oxide-semiconductor field-effect transistor) for nonlinear detection. A circuit architecture is presented alongside a detailed design methodology and simulations. The detector efficiently demodulates a 2.4 GHz OOK (On/Off Keying) encoded signal, comprising a 32-bit word, within 320 μs. Remarkably, the circuit operates passively, requiring no voltage supply or bias current, and functions effectively with −53 dBm input power at the antenna. This capability enables the decoding of 32-bit unsigned integer radio packets as a wakeup radio event. The effectiveness of the envelope detector is substantiated through comprehensive simulations.

Low-frequency solar radio type II bursts and their association with space weather events during the ascending phase of solar cycle 25

Abstract. Type II solar radio bursts are signatures of the coronal shocks and, therefore, particle acceleration events in the solar atmosphere and interplanetary space. Type II bursts can serve as a proxy to provide early warnings of incoming solar storm disturbances, such as geomagnetic storms and radiation storms, which may further lead to ionospheric effects. In this article, we report the first observation of 32 type II bursts by measuring various plasma parameters that occurred between May 2021 and December 2022 in solar cycle 25. We further evaluated their accompanying space weather events in terms of ionospheric total electron content (TEC) enhancement using the rate of TEC index (ROTI). In this study, we find that at heliocentric distance ∼1–2 R⊙, the shock and the Alfvén speeds are in the range 504–1282 and 368–826 km−1, respectively. The Alfvén Mach number is of the order of 1.2≤MA≤1.8 at the above-mentioned heliocentric distance. In addition, the measured magnetic field strength is consistent with the earlier reports and follows a single power law B(r)=6.07r-3.96G. Based on the current analysis, it is found that 19 out of 32 type II bursts are associated with immediate space weather events in terms of radio blackouts and polar cap absorption events, making them strong indications of space weather disruption. The ROTI enhancements, which indicate ionospheric irregularities, strongly correlate with GOES X-ray flares, which are associated with the type II radio bursts recorded. The diurnal variability in ROTI is proportional to the strength of the associated flare class, and the corresponding longitudinal variation is attributed to the difference in longitude. This article demonstrates that since type II bursts are connected to space weather hazards, understanding various physical parameters of type II bursts helps to predict and forecast the space weather.

Coronal Signatures of Flare Generated Fast-Mode Wave at EUV and Radio Wavelengths

This paper presents a detailed study of the type II solar radio burst that occurred on 06 March 2014 using combined data analysis. It is a classical radio event consisting of type III radio burst and a following type II radio burst in the dynamic spectrum. The type II radio burst is observed between 235 – 130 MHz (120 – 60 MHz) in harmonic (fundamental) bands with the life time of 5 minutes between 09:26 – 09:31 UT. The estimated speed of type II burst by applying two-fold Saito model is ∼ 650 km s−1. An extreme ultraviolet (EUV) wave is observed with Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO). The very close temporal onset association of the EUV wave and flare energy release indicates that the EUV wave is likely produced by a flare pressure pulse. The eruption is also accompanied by a weak coronal mass ejection (CME) observed with the coronagraphs onboard the Solar and Heliospheric Observatory (SOHO) and the twin Solar Terrestrial Relations Observatory (STEREO). The plane of sky speed of the CME was ∼ 252 km s−1 in the SOHO/LASCO-C2 and ∼ 280 km s−1 in the STEREO-B/SECCHI-COR1 images. The EUV wave has two wave fronts, one expanding radially outward and the other one moving along the flare loop arcade. The source position of the type II burst imaged by the Nançay Radio Heliograph (NRH) shows that it was associated with the outward moving EUV wave. The CME is independent of the shock wave as confirmed by the location of NRH radio sources below the CME’s leading edge. Therefore the type II radio burst is probably ignited by the flare. This study shows the possibility of EUV wave and coronal shock triggered by flare pressure pulse, generating the observed type II radio burst.

Observation of solar radio burst events from Mars orbit with the Shallow Radar instrument

Context. Multispacecraft and multiwavelength observations of solar eruptions, such as flares and coronal mass ejections, are essential to understanding the complex processes behind these events. The study of solar burst events in the radio frequency spectrum has relied almost exclusively on data from ground-based observations and a few dedicated heliophysics missions such as STEREO or Wind. Aims. By reanalysing existing data from the Mars Reconnaissance Orbiter (MRO) Shallow Radar (SHARAD) instrument, a Martian planetary radar sounder, we discovered the instrument was also capable of detecting solar radio bursts and that it was able to do so with unprecedented resolution for a space-based solar instrument. In this study, we aim to demonstrate the reliability and value of SHARAD as a new solar radio observatory. Methods. We characterised the sensitivity of the instrument to type III solar radio bursts through a statistical analysis of correlated observations using STEREO and Wind as references. Using 38 correlated detections, we established the conditions under which SHARAD can observe solar bursts in terms of acquisition geometry. As an example of scientific application, we also present the first analysis of type III characteristic times at high resolution beyond 1 AU. Results. A simple logistic model based purely on geometrical acquisition parameters can predict burst show versus no-show in SHARAD data with an accuracy of 79.2%, demonstrating the reliability of the instrument in detecting solar bursts and laying the foundation for using SHARAD as a solar radio observatory. The extremely high resolution of the instrument, both in temporal and frequency directions; its bandwidth; and its position in the Solar System enable SHARAD to make significant contributions to heliophysics. Notably, it could provide data on plasma processes on the site of the burst generation and along the propagation path of associated fast electron beams.

Forecasting constraints on the baryon mass fraction in the IGM from fast radio bursts and type Ia supernovae

Fast Radio Bursts (FRBs) are millisecond transient radio events with a high energy. By identifying the origin of the burst, it is possible to measure the redshift of the host galaxy, which can be used to constrain cosmological and astrophysical parameters and test aspects of fundamental physics when combined with the dispersion measure (DM). However, some factors limit the cosmological application of FRBs: (i) the poor modelling of the fluctuations in the DM due to spatial variation in the cosmic electrons density; (ii) the fact that the fraction of baryon mass in the intergalactic medium (fIGM\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$f_{IGM}$$\\end{document}) is degenerated with some cosmological parameters; (iii) the limited knowledge about host galaxy contribution (DMhost\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$DM_{host}$$\\end{document}). In this work, we investigate the impact of different redshift distribution models of FRBs to constrain the baryon fraction in the IGM and host galaxy contribution. We use a cosmological model-independent method developed in previous work Lemos (EPJC 83:138, 2023) to perform the analysis and combine simulated FRB data from Monte Carlo simulation and supernovae data. We assume four distribution models for the FRBs: gamma-ray bursts (GRB), star formation rate (SFR), uniform and equidistant (ED). Also, we consider samples with N=15,30,100\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$N = 15, 30, 100$$\\end{document} and 500 points and different values of the fluctuations of electron density in the DM, δ=0,100,200,400,230z\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\delta = 0, 100, 200, 400, 230\\sqrt{z}$$\\end{document} pc/cm3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{3}$$\\end{document}. Our analysis shows that all the distribution models present consistent results within 2σ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$2\\sigma $$\\end{document} for the free parameters fIGM\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$f_{IGM}$$\\end{document} and DMhost,0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$DM_{host,0}$$\\end{document} and highlights the crucial role of DM fluctuations in obtaining more precise measurements.

Solar Radio Burst Detection Based on the MobileViT-SSDLite Lightweight Model

Real-time detection of solar radio bursts is crucial in solar physics research and space weather forecasting. However, current research on the automatic detection of solar radio bursts is limited to identifying the presence or absence of solar radio bursts or recognizing only a single type of burst, such as type II or III. Furthermore, existing methods cannot learn spectral and temporal features and often suffer from the drawbacks of large network models, resulting in slow speeds. This paper proposes an automatic recognition and localization method based on a lightweight object detection model for solar radio burst events. We collected observation data from e-CALLISTO and established a data set containing type II, III, IV, and V solar radio bursts. To address the real-time requirements of practical applications and consider the temporal and frequency domain information of spectrogram images, we improved a vision transformer with a self-attention mechanism and adopted a lightweight model for detection. The experimental results demonstrate that our proposed method achieves an average precision at a 50% intersection-over-union threshold of 78.2% and a recall rate of 92% on the established solar radio burst data set. Additionally, the model operates at a detection speed of 54.8 frames s–1, where a frame refers to a spectral image with a duration of 15 minutes, enabling efficient automated detection and localization of type II, III, IV, and V solar radio bursts.

The Solar Origin of an In Situ Type III Radio Burst Event

Solar type III radio bursts are generated by beams of energetic electrons that travel along open magnetic field lines through the corona and into interplanetary space. However, understanding the source of these electrons and how they escape into interplanetary space remains an outstanding topic. Here we report multi-instrument, multiperspective observations of an interplanetary type III radio burst event shortly after the second perihelion of the Parker Solar Probe (PSP). This event was associated with a solar jet that produced an impulsive microwave burst event recorded by the Expanded Owens Valley Solar Array. The type III burst event also coincided with the detection of enhanced in situ energetic electrons recorded by both PSP at 0.37 au and WIND at 1 au, which were located very closely on the Parker spiral longitudinally. The close timing association and magnetic connectivity suggest that the in situ energetic electrons originated from the jet’s magnetic reconnection region. Intriguingly, microwave imaging spectroscopy results suggest that the escaping energetic electrons were injected into a large opening angle of about 90°, which is at least nine times broader than the apparent width of the jet spire. Our findings provide an interpretation for the previously reported, longitudinally broad spatial distribution of flare locations associated with prompt energetic electron events and have important implications for understanding the origin and distribution of energetic electrons in interplanetary space.

Hunting for gamma-ray emission from fast radio bursts

Context. Fast radio bursts (FRBs) are a recently discovered class of GHz-band, ms-duration, Jansky-level-flux astrophysical transients. Although hundreds of models have been proposed so far for FRB progenitors (the most popular ones involve magnetars), their physical origin and emission mechanism are still a mystery, making them one of the most compelling problems in astrophysics. Aims. FRBs are caused by astrophysical processes that are not yet understood. Exploring their high-energy counterpart is crucial for constraining their origin and emission mechanism. Methods. Thanks to more than 13 years of gamma-ray data collected by the Large Area Telescope on board the Fermi Gamma-ray Space Telescope, and to more than 1000 FRB events (from 561 non-repeating and 22 repeating sources), one of the largest samples created thus far, we performed the largest and deepest search for high-energy emission from FRB sources to date (between 100 MeV and 1 TeV). In addition to the analysis involving individual FRB events on different timescales (from a few seconds up to several years), we performed, for the first time, a stacking analysis on the full sample of FRB events as well as a search for triplet photons in coincidence with the radio event. Results. We do not detect significant emission, reporting the most stringent constraints, on short timescales, for the FRB-like emission from SGR 1935+2154 with Eγ < 1041 erg, corresponding to a factor η < 107 with respect to the emitted radio energy. Similarly, for the stacked signal of steady emission from all repeaters, the obtained upper limit (UL) on the FRBs luminosity (Lγ < 1.6 × 1043 erg s−1) is more than two orders of magnitude lower than those derived from the individual sources. Finally, no individual or triplet photons have been significantly associated with FRB events. We derived the LAT ms-sensitivity to be ∼0.3 ph cm−2 s−1 and constrained the gamma-ray energy Eγ,δT = 1 ms ≲ 1047(DL/150 Mpc)2 erg, ruling out a gamma-ray-to-radio energy ratio greater than 109 on ms timescales. Conclusions. The results reported here represent the most stringent UL reported so far on the high-energy emission from FRBs on short and long time scales, as well as on cumulative emission and individual photon searches. While the origin of FRBs is still unclear, our work provides important constraints for FRB modelling, which might shed light on their emission mechanism.

On the Improvement of Cellular Coverage Maps by Filtering MDT Measurements

Cellular networks are constantly evolving, driven by changes in user behavior and device capabilities. To ensure that networks adapt to these changes, it is of vital importance for mobile operators to have a good understanding of how well their network meets subscriber needs. For this purpose, the Minimization of Drive Test (MDT) feature has been standardized, allowing operators the cost-effective provision of geolocated network performance statistics and radio events. However, in practice, positioning errors severely limit the potential of MDT measurements. In this paper, an in-depth analysis of a large MDT dataset taken from a commercial Long-Term Evolution (LTE) network shows for the first time several sources of positioning errors in MDT measurements not previously reported in the literature. To address these, a novel heuristic filtering algorithm is proposed to discard samples with inaccurate location data. Method assessment is done by checking the impact of filtering on the coverage map built with a real MDT dataset. Results show that the proposed filtering method significantly improves the accuracy of coverage maps by eliminating unreliable measurements.

Time-frequency catalogue: JSON implementation and python library

TFCat (Time-Frequency Catalogue) is a data interchange format based on JSON (JavaScript Object Notation), which has been initially designed for exchanging low frequency radio events and features. It defines several types of JSON objects and how they are combined to represent data related to temporal-spectral features of a time spectrogram (a.k.a., dynamic spectrum), their properties, and their temporal and spectral extents. This implementation is inheriting from the GeoJSON file format. The TFCat python library is implementing this specification and provides a software interface permitting to create, update and validate TFCat objects efficiently.

On the detection of a solar radio burst event that occurred on 28 August 2022 and its effect on GNSS signals as observed by ionospheric scintillation monitors distributed over the American sector

As part of an effort to observe and study ionospheric disturbances and their effects on radio signals used by Global Navigation Satellite Systems (GNSS), alternative low-cost GNSS-based ionospheric scintillation and total electron content (TEC) monitors have been deployed over the American sector. During an inspection of the observations made on 28 August 2022, we found increases in the amplitude scintillation index (S4) reported by the monitors for the period between approximately 17:45 UT and 18:20 UT. The distributed, dual-frequency observations made by the sensors allowed us to determine that the increases in S4were not caused by ionospheric irregularities. Instead, they resulted from Carrier-to-Noise (C/No) variations caused by a solar radio burst (SRB) event that followed the occurrence of two M-class X-ray solar flares and a Halo coronal mass ejection. The measurements also allowed us to quantify the impact of the SRB on GNSS signals. The observations show that the SRB caused maximum C/No fadings of about 8 dB-Hz (12 dB-Hz) on L1 ~ 1.6 GHz (L2 ~ 1.2 GHz) for signals observed by the monitor in Dallas for which the solar zenith angle was minimum (~24.4°) during the SRB. Calculations using observations made by the distributed monitors also show excellent agreement for estimates of the maximum (vertical equivalent) C/No fadings in both L1 and L2. The calculations show maximum fadings of 9 dB-Hz for L1 and of 13 dB-Hz for L2. Finally, the results exemplify the usefulness of low-cost monitors for studies beyond those associated with ionospheric irregularities and scintillation.

Relationships between energetic storm particle events and interplanetary shocks driven by full and partial halo coronal mass ejections

We have analysed energetic storm particle (ESP) events in 116 interplanetary (IP) shocks driven by front-side full and partial halo coronal mass ejections (CMEs) with speeds >400 kms−1during the years 1996–2015. We investigated the occurrence and relationships of ESP events with several parameters describing the IP shocks, and the associated CMEs, type II radio bursts, and solar energetic particle (SEP) events. Most of the shocks (57%) were associated with an ESP event at proton energies >1 MeV.The shock transit speeds from the Sun to 1 AU of the shocks associated with an ESP event were significantly greater than those of the shocks without an ESP event, and best distinguished these two groups of shocks from each other. The occurrence and maximum intensity of the ESP events also had the strongest dependence on the shock transit speed compared to the other parameters investigated. The correlation coefficient between ESP peak intensities and shock transit speeds was highest (0.73 ± 0.04) at 6.2 MeV. Weaker dependences were found on the shock speed at 1 AU, Alfvénic and magnetosonic Mach numbers, shock compression ratio, and CME speed. On average all these parameters were significantly different for shocks capable to accelerate ESPs compared to shocks not associated with ESPs, while the differences in the shock normal angle and in the width and longitude of the CMEs were insignificant.The CME-driven shocks producing energetic decametric–hectometric (DH) type II radio bursts and high-intensity SEP events proved to produce also more frequently ESP events with larger particle flux enhancements than other shocks. Together with the shock transit speed, the characteristics of solar DH type II radio bursts and SEP events play an important role in the occurrence and maximum intensity of ESP events at 1 AU.

Complex Type II Solar Radio Event on 4 July 2022

Abstract On 4 July 2022, a complex low-frequency solar radio burst was observed in Metsähovi Radio Observatory of Aalto University. The radio burst was observed at a frequency range between 20 and 80 MHz. In GOES (Geostationary Operational Environmental Satellite) class, the event was classified as C5.1. However, coronal mass ejection (CME) was not associated to this event. The observed radio burst was a long-lasting (~10 minutes) event, and it could be mainly classified as type II solar radio event. Also type III solar events were observed before long-lasting type II event. The event includes common frequency drifting emission structures, both fundamental and harmonic structures, but also rarely observed continuum-like or stationary structure. It is assumed that the continuum-like radio emission structure is originated from the stationary flare (coronal) loop, which was visible over the whole event. The drifting emission structure means accelerated electrons, which are produced by the shock related phenomena. The paper provides the observations from this event on radio wavelength, and also soft-X-ray regime and optical wavelength (AIA 171). In addition, a possible, simplified scenario is presented for forming the drifting and continuum solar radio emissions in type II solar burst.

Solar radio bursts observations by Egypt- Alexandria CALLISTO spectrometer: First results

The newly installed CALLISTO spectrometer, hosted by the Department of Space Environment, Institute of Basic and Applied Sciences- EJUST, commenced operation on August 14, 2021. The system contains a cross dipole long-wavelength array antenna with high sensitivity to monitor solar radio transients. Its antenna was strategically positioned and appeared to be in the center of the CALLISTO network of spectrometers. Moreover, in the northern section of Africa, the Egypt-Alexandria CALLISTO and ALGERIA-CRAAG stations are the only ones operating. There are no stations in the West African region, while stations in the eastern part of Africa are not working. Thus, Egypt- Alexandria station serves as a reference for other stations within the e-CALLISTO network. Despite the low solar activity, the instrument detected several solar radio bursts not limited to type II, type III, and type V. A vigorous case study was conducted on two selected radio burst events to validate the authenticity of the recorded events. Other solar radio stations at different geographical locations recorded all the radio bursts detected by the spectrometer. The case study included brief analyses that indicated a type II radio burst observed on October 09, 2021, between 06:30 and 07:00 UT, was associated with an M1.6 solar flare located at N18E08 within NOAA-AR 2882 and a CME with a shock front speed of ∼ 978 km/s. However, the type III radio burst is neither CME nor solar flare associated. These analyses examine the instrument's capacity to provide real-time solar radio transient data 24 h a day to mitigate the challenges of data gaps faced in the African continent. Hence, the instrument has become an integral part of space weather monitoring and forecasting over the region and other parts of the globe.

Опыт радиохирургического блокирования слезоотведения при недостатке слезопродукции

The purpose of the study was the effective assessment and safety of the lacrimal ducts obturation by using radio wave energy in patient with “dry eye” syndrome with sagnificant damage of the ocular surface. Materials and methods. A retrospective analysis of data as patients radiosurgical blocking of tear flow was performed was carried out. Occlusion of the lacrimal ducts was carried out according to the own method using “Surgitron™” devices. The radio wave low-temperature event leads to persistent closure of the lumen of the lacrimal ducts and blockage of the passage of the lacrimal fluid. Results and discussion. The study included 49 patients (79 eyes), of different age groups, with severe manifestations of the “dry eye” syndrome. All patients after the procedure observd an improvement in their condition, an objective examination showed an increase in tear production, tear test values and visual acuity compared to the initial state. Over the entire period of observation, spontaneous recanalization of the lacrimal ducts occurred only in 2 patients (4 %) (3 eyes), which is significantly less in detection with other surgical methods of occlusion of the lacrimal ducts. Conclusion. Radiosurgical lacrimal blockage is an alternative method of surgical treatment of patients with “dry eye” syndrome wich allows to achieve a good functional result. It is supposed to be clinically atraumatic, bloodless and aesthetic. A small percentage of spontaneous recanalization of open tracts of high efficiency and preservation of the result after radiosurgical blocking of lacrimal drainage. Keywords: “dry eye” syndrome, punctal occlusion surgery, radiosurgical occlusion of lacrimal passage, lacrimal punctum plug.

Flare echoes from relaxation shocks in perturbed relativistic jets

Context. One of the main scenarios to account for the multiwavelength flux variability observed in relativistic jets of active galactic nuclei (AGNs) is based on the diffusive shock acceleration of a population of relativistic electrons on internal shocks of various origins. Any complete AGN emission scenario has to be able to explain the wide range of observed variability timescales, which change over several orders of magnitude between the radio and gamma-ray band. In addition to observations of flux variability, constraints are also provided by very-long-baseline interferometry (VLBI), which shows a large variety of moving and standing emission zones with distinct behaviors. Aims. Combining dynamic hydrodynamic jet simulations with radiative transfer, we aim to characterize the evolution of stationary and moving emission zones in the jet and study their multiwavelength signatures through emission maps and light curves. We focus our study on flare events that occur during strong interactions between moving ejecta and stationary recollimation shocks. Such events are shown to lead to a significant perturbation of the stationary jet structure. Methods. We simulate relativistic jets with the magneto-hydrodynamic code MPI-AMRVAC and inject nonthermal particle distributions of electrons into shock regions. We follow the propagation of a moving shock and its interactions with a structure of standing recollimation shocks in the jet. Synchrotron emission and radiative transfer are calculated in the post-processing code RIPTIDE for given observation angles and frequencies, assuming a turbulent magnetic field and taking the light crossing effect into account. Results. In the case of strong shock–shock interactions, we demonstrate the appearance of trailing components behind the leading moving shock. The latter destabilizes the jet, causing the emergence of oscillating standing shocks and relaxation shocks. Emissions from these regions can dominate the overall flux or lead to “flare echoes” in the light curve. Another observational marker for the presence of relaxation shocks appears in time-distance plots of bright VLBI components of the jet. Our scenario provides a plausible explanation for radio VLBI observations of the radio galaxy 3C 111, where trailing components were observed during a radio outburst event in 1997, and may be applicable to other sources with similar features.