Flare Events Research Articles

Variability of Ionosphere Over Indian Longitudes to a Variety of Space Weather Events During December 2006

AbstractThis paper highlights the impact of intense solar events over India during 3–20 December 2006. Ionospheric effects of a major solar flare (X9) on December 5 (10:35 UT) have been investigated by using dayside and nightside magnetometer data, dayside ionosondes, and dayside GPS vTEC observations. On the next day, a stream of fast solar wind hits the magnetosphere, causing a HILDCAA (High Intensity Long Duration Continuous Auroral Activity) preceded by moderate geomagnetic storm. The origin and characteristics of a positive ionospheric storm which occurred over Tirunelveli (TIR, geomagnetic latitude: −0.18°N) in the recovery phase of storm due to simultaneous presence of enhanced O/N2 and WEJ or weakened EEJ during the HILDCAA (7th and 8th of December) is investigated. Subsequently, on December 14, the most powerful CME since the Halloween event impacts the Earth, and three SSCs are recorded on December 14, 16, and 18. The variability of the ionosphere over the Indian longitude sector due to these intense space weather fluctuations is presented by utilizing the magnetometers, ionosonde, GPS vTEC, and satellite‐based observations in the same region. This study reports the influence of prompt penetration of the magnetospheric convection electric field and the disturbance dynamo on several key ionospheric and magnetic parameters within the Indian longitude sector.

A Catalog of Geoefficient Flare Events of the Current 25th Solar Cycle in a Modern Presentation

To study the phenomena occurring on the Sun and in interplanetary space and their influence on near-Earth space and on processes in the outer and inner shells of the Earth, the results of continuous long-term observations of solar activity become very valuable. A representative collection of such long-term homogeneous series of systematic observations obtained by the worldwide network of solar and astronomical observatories, as well as by spacecraft, has been collected at the World Data Center for Solar–Terrestrial Physics in Moscow. The article describes a cumulative interactive catalog of the main characteristics of significant solar-flare events of the current 25th cycle of solar activity.

Understanding the Duration of Solar and Stellar Flares at Various Wavelengths

Recent irradiance measurements from numerous heliophysics and astrophysics missions including Solar Dynamics Observatory (SDO), GOES, Kepler, TESS, Chandra, the X-ray Multi-Mirror Mission, and NICER have provided critical input into understanding the physics of the most powerful transient events on the Sun and magnetically active stars:solar and stellar flares. The light curves of flare events from the Sun and stars show remarkably similar shapes, typically with a sharp rise and protracted decay phase. The duration of solar and stellar flares has been found to be correlated with the intensity of the event in some wavelengths, such as white light, but not in other wavelengths, such as soft X-rays, but it is not evident why this is the case. In this study, we use a radiative hydrodynamics code to examine factors affecting the duration of flare emission at various wavelengths. The duration of a light curve depends on the temperature of the plasma, the height in the atmosphere at which the emission forms, and the relative importance of cooling due to radiation, thermal conduction, and enthalpy flux. We find that there is a clear distinction between emission that forms low in the atmosphere and responds directly to heating, and emission that forms in the corona, indirectly responding to heating-induced chromospheric evaporation, a facet of the Neupert effect. We discuss the implications of our results for a wide range of flare energies.

Classification and Analysis of Solar X-ray Monitoring Data for Intensity Monitoring

Abstract: Scientists have focused on solar flares because they are violent phenomena that take place on the Sun's surface and atmosphere and pose threats to the highly advanced civilization on Earth. Electromagnetic radiation from these eruptions primarily manifests as X-rays, UV light, and sporadically visible light. The energy released by these eruptions is equivalent to that of millions of atomic bombs. The beauty of auroras is enhanced but communication systems are disrupted by geomagnetic storms, which frequently accompany flares via coronal mass ejections (CMEs). Long-distance radio communication is hampered by ionospheric ionization caused by X-rays, and GPS navigation may become less precise, especially in high-latitude areas. Increased radiation levels during solar flares pose a concern to both astronaut safety and satellite operations. Geomagnetic disruptions pose a threat to electrical networks, which could result in widespread blackouts. Complex observatories like the Solar Dynamics Observatory (SDO) and the Solar and Heliospheric Observatory (SOHO) are used to predict and reduce the effects of solar flares. Classifying and analyzing solar flares precisely can assist determine their possible effects, which can range from modest interruptions brought on by Class C flares to major disruptions brought on by X-class flares. This study advances our knowledge of solar-terrestrial interactions and helps with space weather forecasting, both of which are essential in today's highly developed society.

Study of the energetic X-ray superflares from the active fast rotator AB doradus

ABSTRACT We present the analyses of intense X-ray flares detected on the active fast rotator AB Dor using observations from the XMM–Newton. A total of 21 flares are detected, and 13 flares are analysed in detail. The total X-ray energy of these flares is found to be in the range of 1034−36 erg, in which the peak flare flux increased up to 34 times from the pre-/post-flaring states for the strongest observed flare. The duration of these flaring events is found to be 0.7 to 5.8 h. The quiescent state X-ray spectra are found to be explained by a three-temperature plasma with average temperatures of 0.29, 0.95, and 1.9 keV, respectively. The temperatures, emission measures, and abundances are found to be varying during the flares. The peak flare temperature was found in the 31–89 MK range, whereas the peak emission measure was 1052.5–54.7 cm−3 . The abundances vary during the flares and increase by a factor of ∼3 from the quiescent value for the strongest detected flare. The variation in individual abundances follows the inverse-FIP effect in quiescent and flare phases. The X-ray light curves of AB Dor are found to exhibit rotational modulation. The semi-loop lengths of the flaring events are derived in the range of 109.9−10.7 cm, whereas the minimum magnetic field to confine the plasma in the flaring loop is estimated between 200 and 700 G.

ANTIHISTAMINE AS AN ADJUNCTIVE TREATMENT IN ACNE VULGARIS: A SYSTEMATIC REVIEW AND META-ANALYSIS

Approximately one-tenth of the global population suffer from acne vulgaris, which is a skin disease with considerable psychological impact. Recently, antihistamines have been used in the treatment of acne. However, their overall treatment effects for this indication remain unclear. This systematic review and meta-analysis aim to evaluate the clinical efficacy and safety of the antihistamines in the treatment of acne vulgaris. The following databases were searched: PubMed, Scopus, Embase, Cochrane Central Register of Controlled Clinical Trials, and Google Scholar. We included the randomized controlled trials on acne vulgaris patients which compared any H1- antihistamine drug in combination with other medications to placebo, no treatment, or other medications, with acne lesion (non-inflammatory and inflammatory) counts, acne severity score, patient satisfaction, acne flare, or adverse events as an outcome of interest. Six studies contributing to 388 patients were included, involving two H1 antihistamines (i.e., levocetrizine and desloratadine), isotretinoin, azithromycin, and topical azelaic acid cream. From the network meta–analysis, levocetirizine+isotretinoin was better than the isotretinoin alone in the inflammatory lesion count, but not in the non-inflammatory lesion count. The desloratadine+isotretinoin retained the best balance in terms of non-inflammatory lesion count, inflammatory lesion count, acne flare, and mucocutaneous adverse events. The desloratadine+isotretinoin and levocetirizine+isotretinoin were considered safe.

Flares confirmed for the first time to be from the primary component of an eclipsing binary

Abstract Only a handful of precise observations of flare detected from a contact binary so far. This paper presents the photometric and spectroscopic analysis of a contact binary (ASAS J082243+1927.0). Two flare events detected from this object were observed in the data of TESS. The two flare events both occurred at the secondary minimum. Considering the totally eclipsing secondary minimum, it is pretty sure that the two flares are both from the primary component. This is the first time to definitely identify a flare that comes from which component in an eclipsing binary system. This system is a low mass ratio (q ∼ 0.094) and deep contact binary ($f\sim 69.4~{{\%}}$). LAMOST spectra of this object exhibit excess emissions in the Hα line, indicating its chromospheric activity. The continuous variation of the TESS light curves is explained by using the variation of a dark spot added to the secondary component. Through analyzing the relationship between the variation of the longitude of the spot and the O-C variation of the primary minima, we discover the spot rotation is prograde as viewed in the frame rotating with the orbital motion.

On Some Challenges for National and Global Space Weather Services

Space Weather (SW) hazards are discussed in terms of the operation of national SW services and global SW centers for the International Civil Aviation Organization (ICAO). The definition of threshold values of monitored parameters which are used to identify moderate and severe SW events is one of the critical problems. Due to the lack of both physical data on severe events and user feedback, we tried to approach the problem statistically. In particular, we pursued the answer to the question about what intensity of ionospheric storms and flare effects should be reported by national and global SW entities to their users. We also discussed the possible role of an active region on the Sun, and the cosmic rays’ issues that may be helpful regarding SW operational work. The presented considerations are based on examples of the ionosphere state assessment for the low-latitude American sector with a focus on the Mexican region. This work attempts to argue the possible approaches to resolve the tasks that the SW national services and global centers face.

Ionospheric TEC prediction using FFNN during five different X Class solar flares of 2021 and 2022 and comparison with COKSM and IRI PLAS 2017

Abstract The Ionospheric Total Electron Content (TEC) measured in the ray path of the signals directly contributes to the Range Error (RE) of the satellite signals, which affects positioning and navigation. Employing the Co-Kriging-based Surrogate Model (COKSM) to predict TEC and RE correction has proven prolific. This research attempted to test and compare the prediction capability of COKSM with an Artificial Intelligence-based Feed Forward Neural Network model (FFNN) during five X-Class Solar Flares of 2021–22. Also, the results are validated by comparing them with the IRI PLAS 2017 model. TEC, solar, and geomagnetic parameters data for Hyderabad GPS station located at 17.31° N latitude and 78.55° E longitude were collected from IONOLAB & OMNIWEB servers. The COKSM uses six days of input data to predict the 7th day TEC, whereas prediction using the FFNN model is done using 45 days of data before the prediction date. The performance evaluation is done using RMSE, NRMSE, Correlation Coefficient, and sMAPE. The average RMSE for COKSM varied from 1.9 to 9.05, for FFNN it varied from 2.72 to 7.69, and for IRI PLAS 2017 it varied from 7.39 to 11.24. Likewise, evaluation done for three different models over five different X-class solar flare events showed that the COKSM performed well during the high-intensity solar flare conditions. On the other hand, the FFNN model performed well during high-resolution input data conditions. Also, it is notable that both models performed better than the IRI PLAS 2017 model and are suitable for navigational applications.

Characteristics of the Accelerated Electrons Moving along the Loop Derived from Cyclical Microwave Brightenings at the Footpoints

Many particles are accelerated during solar flares. To understand the acceleration and propagation processes of electrons, we require the pitch-angle distributions of the particles. The pitch angle of accelerated electrons has been estimated from the propagation velocity of a nonthermal microwave source archived in Nobeyama Radioheliograph data. We analyzed a flare event (an M-class flare on 2014 October 22) showing cyclical microwave brightenings at the two footpoint regions. Assuming that the brightenings were caused by the accelerated electrons, we approximated the velocity parallel to the magnetic field of the accelerated electrons as ∼7.7 × 104 and 9.0 × 104 km s −1. The estimated pitch angle of the accelerated electrons is 69°–80° and the size of the loss cone at the footpoint (estimated from the magnetic field strength in the nonlinear force-free field model) is approximately 43°. Most of the accelerated electrons could be reflected at the footpoint region. This feature can be interpreted as brightenings produced by bouncing motion of the accelerated electrons.

Two-fluid reconnection jets in a gravitationally stratified atmosphere

Context. Density decreases exponentially with height in the gravitationally stratified solar atmosphere, and therefore collisional coupling between the ionized plasma and the neutrals also decreases. Reconnection is a process observed at all heights in the solar atmosphere. Aims. Here, we investigate the role of collisions between ions and neutrals in the reconnection process occurring at various heights in the atmosphere. Methods. We performed simulations of magnetic reconnection induced by a localized resistivity in a gravitationally stratified atmosphere, in which we varied the height of the initial reconnection X-point. We compared a magnetohydrodynamic (MHD) model and two two-fluid configurations: one in which the collisional coupling was calculated from local plasma parameters, and another in which the coupling was decreased so that collisional effects would be enhanced. The latter setup has a more representative solar collisionality regime. Results. Simulations in a stratified atmosphere show similar structures in MHD and two-fluid simulations, with strong coupling. However, when collisional effects are increased to attain representative parameter regimes, we find a nonlinear runaway instability, which separates the plasma-neutral densities across the current sheet (CS). With increased collisional effects, the initial decoupling in velocity heats the neutrals and this sets up a nonlinear feedback loop, according to which neutrals migrate outside the CS, replacing charged particles that accumulate toward the center of the CS. Conclusions. The reconnection rate has a maximum value of around 0.1 for both reconnection heights, and is consistent with the locally enhanced resistivity used in all three models. The early-stage plasmoid formation observed near the end of our simulations is influenced by the outflow from the primary reconnection point, rather than by collisions. We synthesized optically thin emission for both MHD and two-fluid models, which can show a very different evolution when the charged-particle density is used instead of the total density. Our simulations have relevance for observed plasmoid features associated with chromospheric to low-coronal flare events.

Statistical analysis of microflares as observed by the 4–8 GHz spectropolarimeter

Radio observations of weak events are one of the promising methods for studying energy release and non-thermal processes in the solar corona. The development of instrumental capabilities allows for radio observations of weak transient coronal events, such as quasi-stationary brightenings and weak flares of X-ray class B and below, which were previously inaccessible for analysis. We have measured the spectral parameters of microwave radiation for thirty weak solar flares with X-ray classes ranging from A to C1.5, using observations from the Badary Broadband Microwave Spectropolarimeter (BBMS). The spectra indicate that plasma heating is caused by the appearance of non-thermal electron fluxes, which can be detected by bursts of microwave radiation, predominantly with an amplitude ~5–6 solar flux units (SFU) at 4–5 GHz frequencies. One solar flux unit (SFU) of radio emission is equal to 10–22 W/(m•Hz). The range of low-frequency spectrum growth indices fα varies widely from α=0.3 to 15. The distribution of high-frequency decay indices is similar to the distributions of regular flares. One of the explanations for the appearance of large fα values is the Razin effect, which can influence the shape of the gyrosynchrotron spectrum during the generation of bursts in dense plasma under relatively weak magnetic fields. We have detected two events in which the appearance of non-thermal electrons led to the generation of narrowband bursts at frequencies near the double plasma frequency. SRH test trials have shown the potential for measuring the structure of flare sources with fluxes of the order of 1 SFU, indicating the high diagnostic potential of the radioheliograph for detecting acceleration processes in weak flare events and their localization in active regions.

Статистический анализ микровспышек по данным Cпектрополяриметра 4-8 ГГц

Radio observations of weak events are one of the promising methods for studying energy release and non-thermal processes in the solar corona. The development of instrumental capabilities allows for radio observations of weak transient coronal events, such as quasi-stationary brightenings and weak flares of X-ray class B and below, which were previously inaccessible for analysis. We have measured the spectral parameters of microwave radiation for thirty weak solar flares with X-ray classes ranging from A to C1.5, using observations from the Badary Broadband Microwave Spectropolarimeter (BBMS). The spectra indicate that plasma heating is caused by the appearance of non-thermal electron fluxes, which can be detected by bursts of microwave radiation, predominantly with an amplitude ~5–6 solar flux units (SFU) at 4–5 GHz frequencies. One solar flux unit (SFU) of radio emission is equal to 10–22 W/(m•Hz). The range of low-frequency spectrum growth indices fα varies widely from α=0.3 to 15. The distribution of high-frequency decay indices is similar to the distributions of regular flares. One of the explanations for the appearance of large fα values is the Razin effect, which can influence the shape of the gyrosynchrotron spectrum during the generation of bursts in dense plasma under relatively weak magnetic fields. We have detected two events in which the appearance of non-thermal electrons led to the generation of narrowband bursts at frequencies near the double plasma frequency. SRH test trials have shown the potential for measuring the structure of flare sources with fluxes of the order of 1 SFU, indicating the high diagnostic potential of the radioheliograph for detecting acceleration processes in weak flare events and their localization in active regions.

Two-stage Hierarchical Framework for Solar Flare Prediction

Solar flares, often accompanied by coronal mass ejections and other solar phenomena, are one of the most important sources affecting space weather. It is important to investigate the forecast approach of solar flares to mitigate their destructive effect on the Earth. Statistical analysis, associated with data from 2010 to 2017 in Space-weather HMI Active Region Patches (SHARPs) collected by the Solar Dynamics Observatory's Helioseismic and Magnetic Imager, reveals that there is a distribution divergence between the two types of active regions (ARs) of solar flares. A two-stage hierarchical prediction framework is formulated to better utilize this intrinsic distribution information. Specially, we pick up the ARs where at least one solar flare event occurs within the next 48 hr as flaring ARs through balanced random forest and naive Bayesian methods and then predict the events from flaring ARs by a cascade module of learning models. The empirical evaluation of SHARPs data from 2016 to 2019 verifies the promising performance of our framework, e.g., 0.727 for the true skill statistic.

P20.09.A FRACTIONATED STEREOTACTIC RADIOTHERAPY (FSRT) AS A TREATMENT FOR TRIGEMINAL SCHWANNOMAS

Abstract BACKGROUND Trigeminal schwannomas (TS) represent 1-8% of all intracranial schwannomas and 0.1-0.5% of all intracranial tumors Treatment strategies are mainly based on limited published data and case reports. The most common treatment is surgical resection. However, it can rarely be completed. Fractionated stereotactic radiotherapy (FSRT) has the potential to be a valuable and safe alternative to control growing or symptomatic TS. The aim of this review is to analyze clinical RESULTS , toxicity and tumor control rates obtained with this technique when treating this pathology in our short series of cases. MATERIAL AND METHODS Medical records of 18 patients treated from January 2007 to December 2018 were reviewed. 15 of them presented symptoms at the moment of diagnosis (83.3%) and the remaining 3 were radiological findings. Surgery was previously performed in 2 cases. Regarding radiotherapy scheme, all patients received 1.8-2Gy daily fractions to a median of 50,0 Gy. The median follow-up time was 62.7 months. RESULTS The outcome after radiotherapy was favourable in 16 of 18 patients (88.8%), clinical improvement was achieved in 52.94% while stability of symptoms was reached in 35.29%. Tumor growth was controlled in 82.35% of cases, even with tumor decrease observed in 5.88%. Acute toxicity was detected in 23.53% and it consisted in increased pain, sensitive alterations and diplopia. All well tolerated with adjusted corticoids and pain medication scheme. Clinical worsening and radiographic progression was shown in 2 out 17 patients and surgery was needed as salvage treatment in both cases (11.76%). However, one of them presented these outcomes in a period in which pseudoprogression could not be excluded (less than 2 years after treatment). CONCLUSION FSRT such as primary or adjuvant treatment accomplishes good clinical results and tumoral control, being an alternative for those patients with comorbidities not suitable for a surgical treatment or who preferred a non-invasive treatment. Regarding toxicity, FSRT is mainly a well tolerated treatment among patients. Prospective multicenter studies should be run in order to accomplish statistically significant results. Also, it is the second case series that reports the flare effect.

Modelling of the multitransition periodic flaring in G9.62+0.20E

ABSTRACT We present detailed modelling of periodic flaring events in the 6.7 GHz and 12.2 GHz methanol lines as well as the OH 1665 MHz and 1667 MHz transitions observed in the G9.62+0.20E star-forming region. Our analysis is performed within the framework of the one-dimensional Maxwell–Bloch equations, which intrinsically cover the complementary quasi-steady state maser and transient superradiance regimes. We find that the variations in flaring time-scales measured for the different species/transitions, and sometimes even for a single spectral line, are manifestations of and are best modelled with Dicke’s superradiance, which naturally accounts for a modulation in the duration of flares through corresponding changes in the inversion pump. In particular, it can explain the peculiar behaviour observed for some features, such as the previously published result for the OH 1667 MHz transition at vlsr = +1.7 km s−1 as well as the methanol 6.7 GHz line at vlsr = −1.8 km s−1, through a partial quenching of the population inversion during flaring events.

TESS Photometric Variability of Young Brown Dwarfs in the Taurus Star-forming Region

We present a comprehensive analysis of TESS high-quality light curves from sectors 43 and 44 of a few samples of young (∼2–3 Myr) brown dwarfs in the Taurus molecular cloud. They are well characterized and bona fide members of Taurus. We aim to search for the fast rotations of brown dwarfs and to picturize their dynamic atmosphere and surface features. Out of 11 young BDs, we found that 72% are periodic, in the period range of 1–7 days; among them, three BDs have periods <1.5 day and the period of one object is estimated for the first time. The sinusoidal periodic variations are related to a large spot or group of small spots corotating with the objects. Interestingly, we have detected four flare events in three young BDs, with one object, MHO 4, showing two flares in two different sectors. From the flared light curves, we have estimated the total bolometric flared energy in a range of 1035–1036 erg, which is close to the superflare energy range (≥1034 erg). To produce such kinds of superflare events, we have calculated the required magnetic field strength, which comes out at the order of a few kilogauss. Such superflares have a strong effect on the habitability of planets around M dwarfs.

A multiple spacecraft detection of the 2 April 2022 M-class flare and filament eruption during the first close Solar Orbiter perihelion

Context. The Solar Orbiter mission completed its first remote-sensing observation windows in the spring of 2022. On 2 April 2022, an M-class flare followed by a filament eruption was seen both by the instruments on board the mission and from several observatories in Earth’s orbit, providing an unprecedented view of a flaring region with a large range of observations. Aims. We aim to understand the nature of the flaring and filament eruption events via the analysis of the available dataset. The complexity of the observed features is compared with the predictions given by the standard flare model in 3D. Methods. In this paper, we use the observations from a multi-view dataset, which includes extreme ultraviolet (EUV) imaging to spectroscopy and magnetic field measurements. These data come from the Interface Region Imaging Spectrograph, the Solar Dynamics Observatory, Hinode, as well as several instruments on Solar Orbiter. Results. The large temporal coverage of the region allows us to analyse the whole sequence of the filament eruption starting with its pre-eruptive state. Information given by spectropolarimetry from SDO/HMI and Solar Orbiter PHI/HRT shows that a parasitic polarity emerging underneath the filament is responsible for bringing the flux rope to an unstable state. As the flux rope erupts, Hinode EIS captures blue-shifted emission in the transition region and coronal lines in the northern leg of the flux rope prior to the flare peak. This may be revealing the unwinding of one of the flux rope legs. At the same time, Solar Orbiter SPICE captures the whole region, complementing the Doppler diagnostics of the filament eruption. Analyses of the formation and evolution of a complex set of flare ribbons and loops, of the hard and soft X-ray emissions with STIX, show that the parasitic emerging bipole plays an important role in the evolution of the flaring region. Conclusions. The extensive dataset covering this M-class flare event demonstrates how important multiple viewpoints and varied observations are in order to understand the complexity of flaring regions. While the analysed data are overall consistent with the standard flare model, the present particular magnetic configuration shows that surrounding magnetic activity such as nearby emergence needs to be taken into account to fully understand the processes at work. This filament eruption is the first to be covered from different angles by spectroscopic instruments, and provides an unprecedented diagnostic of the multi-thermal structures present before and during the flare. This complete dataset of an eruptive event showcases the capabilities of coordinated observations with the Solar Orbiter mission.

The effects of gas flaring as moderated by government quality in leading natural gas flaring economies

This study seeks to address pertinent economic and environmental issues associated with natural gas flaring, especially for the world's leading natural gas flaring economies (i.e. Russia, Iraq, Iran, the United States, Algeria, Venezuela, and Nigeria). By applying relevant empirical panel and country-specific approaches, the study found that fuel energy export positively impacts economic growth with elasticity of ~ 0.22 to ~ 0.24 for the panel examination. It is further revealed that environmental quality in the panel is hampered by increase in economic growth, gas flaring, fuel energy export, and urbanization. Moreover, for the country-wise inference, government quality desirably moderates economic and environmental aspects of gas flaring in Venezuela and Nigeria, and in Russia and Iran respectively. However, government quality moderates gas flaring to cause economic downturn in the USA. Additionally, economic growth increased with increase in urbanisation (in Iraq and the USA), gas flaring (in Iran and the USA), government quality (only in the USA), and fuel energy export (only in Algeria) while economic growth downturn is due to increase urbanisation in Russia and the USA, increase in fuel energy export in the USA, and increase in government quality in Russia. Meanwhile, environmental quality is worsened through intense carbon dioxide emission from increased urbanisation activity (in Iraq, Iran, Algeria, and Nigeria), increased fuel energy export (in Nigeria), increased natural gas flaring (in Algeria and Nigeria), increased GDP (in Russia, Iran, USA, Algeria, and Venezuela), and high government quality (in Iran). Interestingly, the result revealed that increase in GDP (in Nigeria), increase in urbanisation (in the USA), and increase in gas flaring (in Algeria and Nigeria) dampens environmental quality. Importantly, this study offers policy insight into sustainable approaches in natural gas production, government effectiveness, and regulatory quality.

The Effect of Solar Flares on HF Radio Communications over Turkey

The Effect of Solar Flares on HF Radio Communications over Turkey