arXiv subjects

Rositsa Miteva

Publications and source records attributed to Rositsa Miteva.

12 recordsLinked to original sources

arXiv2025

Multi-Energy Proton Events and Geomagnetic Storms in Solar Cycles 23 and 24

Solar energetic protons (SEPs) in different energy channels from 10 to above 100 MeV are analyzed and their relationship to solar and geomagnetic activity is investigated. We performed temporal association analysis between the SEPs, solar flares (SFs), coronal mass ejections (CMEs) and geomagnetic storms (GSs) that occurred during solar cycles 23 and 24. The energy dependencies between the SEPs and the strength of the space weather activity are evaluated and presented.

astro-ph.SR↗

arXiv2025

Observational methods for solar origin diagnostics of energetic protons

The aim of the present report is to outline the observational methods used to determine the solar origin - in terms of flares and coronal mass ejections (CMEs) - of the in situ observed solar energetic protons. Several widely used guidelines are given and different sources of uncertainties are summarized and discussed. In the present study, a new quality factor is proposed as a certainty check on the so-identified flare-CME pairs. In addition, the correlations between the proton peak intensity and the properties of their solar origin are evaluated as a function of the quality factor.

astro-ph.SR↗

arXiv2025

The use of astronomical data for satellite tracking

The study explored the usage of astronomical observations for the identification and tracking of artificial satellites. Spacecraft streaks on astronomical images are a growing issue for the astronomical community. The increasing number of satellites in the future will only worsen the situation for ground-based optical and radio observations of cosmic objects. In addition, the spacecraft passages often lead to the discarding of the obtained data. In this analysis, we propose an estimation of the usefulness of dedicated astronomical observation for spacecraft monitoring, identification, and deduction of orbital parameters. We use astronomical data from the Astronomical Observatory Meshtitsa (Bulgaria) and the https://www.tycho-tracker.com/ software for the streak analysis. The results are compared with well-known satellite databases, such as https://celestrak.org/. The findings are discussed in the framework of space weather research.

astro-ph.IM↗

arXiv2025

New Bulgarian-Austrian project 'Joint observations and investigations of solar chromospheric and coronal activity'

We present the bilateral collaboration between Bulgarian and Austrian solar and space weather researchers on the topic of chromospheric and coronal activity. This new project will focus, on one hand, on the technical setup and calibration of the new Rozhen chromospheric telescope at the National Astronomical Observatory (NAO) by means of establishing optimal observational programs for different quiet-Sun and activity phenomena, automating the data collection and storage, implementing machine/deep learning models for feature recognition. The second aim is to carry out joint scientific analyses of solar phenomena using observations from ground-based instruments in both countries, and supplementary spacecraft data. The successful implementation of solar monitoring at NAO-Rozhen will facilitate the overall visibility of the Bulgarian instrument and generate interest towards astronomy and solar physics not only for PhD students and young scientists but also for the general public.

astro-ph.SR↗

arXiv2025

Comparative study between low and high energy SOHO/ERNE protons in solar cycle 23

We present a comparison between low and high energy solar energetic protons (SEPs) as observed by the SOHO/ERNE high energy detector in solar cycle (SC) 23. Observed and corrected peak proton intensities are used in the analyses. The linear correlations are calculated between the proton intensity and the soft X-ray class of solar flares (SFs) on one side and the projected speed of coronal mass ejections (CMEs), on another. The energy trends of these correlations are compared with previous reports.

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arXiv2025

A network for solar optical observations in Bulgaria

The report presents a new initiative for the development of a network of ground-based stations for solar observations in the optical range. Three separate locations in Bulgaria have installed instrumentation for solar dedicated observations. The currently used telescopes (type, mounting, guiding systems) and designated filters (white-light, H-alpha) are described in detail. Test images are also included. Future plans for improvements are briefly discussed.

astro-ph.SR↗

arXiv2025

Band Splitting in m-Type II radio Bursts and their Role in Coronal Parameter Diagnostics

Type II radio bursts are signatures of shock waves generated by solar eruptions, observed at radio wavelengths. While metric (m) type II bursts originate in the lower corona, their longer-wavelength (up to kilometers) counterparts extend into interplanetary space. A rare but valuable feature observed in some type II bursts is band splitting in their dynamic spectra, which provides crucial insights into physical parameters such as shock speed, Alfv\'en Mach number, Alfv\'en speed, and coronal magnetic field strength (B). In this study, we investigate band-splitting in 44 m-type II radio bursts observed by the Radio Solar Telescope Network during solar cycle 24 (2009 -- 2019). These events exhibit splitting in both fundamental and harmonic bands and are analyzed under both perpendicular and parallel shocks. All events are associated to solar flares and 41 (93 \%) with the coronal mass ejections. Shock speeds, derived using a hybrid coronal density model proposed by \cite{Vrsnak2004}, range from $\approx$ 350 to 1727 \kms. The relative bandwidth (BDW) of the split bands remains constant with frequency and height. Alfv\'en Mach numbers indicate moderate shock strength (1.06 -- 3.38), while Alfv\'en speeds and $B$ vary from $\approx$ 230 -- 1294 \kms\ and $\approx$ 0.48 -- 7.13 G, respectively. Power-law relationships are established as $BDW \propto f_L^{-0.4}$ and $BDW \propto R^{\sim1}$, while the coronal magnetic field decreases with height as $B \propto R^{\sim-3}$. These results enhance our understanding of shock dynamics and magnetic field structures in the solar corona.

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arXiv2025

Type II radio bursts and space weather phenomena: A statistical study

In this paper, we present for the first time a comprehensive statistical study between type II radio bursts from the metric (m) to the dekameric-hectometric (DH) domain and their associated solar and space weather (SW) phenomena, namely, solar flares (SFs), sunspot (SN) configurations, filament eruptions, coronal mass ejections (CMEs), their interplanetary (IP) counterparts (ICMEs) and shocks, in situ detected particles and geomagnetic storms (GSs). The m-only and m+DH radio signatures are identified from dynamic spectra provided by the ground-based RSTN stations distributed over the globe together with Wind/WAVES satellite data. The DH-only type IIs are adopted from a ready catalog based on Wind/WAVES spacecraft data. We perform the temporal and spatial association between the radio emission and the listed above activity events during solar cycle (SC) 24, separately for the three sub-categories, m-only, m+DH and DH-only type IIs. A quantitative assessment on the occurrence rates is presented as a function of the strength of the specific SW phenomena: highest rates are obtained with CMEs, SFs, filament eruptions, and SN configurations, whereas a much weaker relationship is found with ICMEs, IP shocks, energetic particles, and GSs. The potential of the obtained rates to be used in empirical or physics-based models for SW forecasting is discussed.

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arXiv2024

Characterization of the Early Dynamics of Solar Coronal Bright Fronts

We present a comprehensive characterization of 26 CME-driven compressive waves known as Coronal Bright Fronts (CBFs) observed in the low solar corona between 2010 and 2017. These CBFs have been found to be associated with SEP events near Earth, indicating their importance in understanding space weather phenomena. The aim of this study is to analyze and describe the early dynamics of CBFs using a physics-based heliospheric SEP forecasting system known as the SPREAdFAST framework. This framework utilizes a chain of data-driven analytic and numerical models to predict SEP fluxes at multiple locations in the inner heliosphere by considering their acceleration at CMEs near the Sun and subsequent interplanetary transport. To estimate the time-dependent plasma and compression parameters of the CBFs, we utilized sequences of base-difference images obtained from the AIA instrument on board the SDO satellite, and measurements of the height-time profiles of the CMEs obtained from the LASCO instrument on board the SOHO satellite. We employed kinematic measurements and plasma model results to derive these parameters. The SPREAdFAST framework facilitated the analysis and correlation of these observations with SEP events near Earth. Our analysis yielded statistical relations and distributions for both the shocks and plasma parameters associated with the 26 CBFs investigated. By combining the observations from the AIA and LASCO instruments, as well as the data products from the SPREAdFAST framework, we obtained a comprehensive understanding of the early dynamics of CBFs, including their temporal evolution, plasma properties, and compressional characteristics. These findings contribute to the growing body of knowledge in the field and have implications for space weather forecasting and the study of SEP events.

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arXiv2022

A Multi-Event Study of Early-Stage SEP Acceleration by CME-Driven Shocks -- Sun to 1 AU

The solar corona below 10 solar radii is an important region for early acceleration and transport of solar energetic particles (SEPs) by coronal mass ejection-driven shock waves. There, these waves propagate into a highly variable dynamic medium with steep gradients and rapidly expanding coronal magnetic fields, which modulates the particle acceleration near the shock or wave surfaces, and the way SEPs spread into the heliosphere. We present a study modelling the acceleration of SEPs in global coronal shock events in the corona, as well as their transport to 1 au, based on telescopic observations coupled with dynamic physical models.

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arXiv2018

The Wind/EPACT proton event catalog (1996-2016)

We present the finalized catalog of solar energetic proton events detected by Wind/EPACT instrument over the period 1996-2016. Onset times, peak times, peak proton intensity and onset-to-peak proton fluence are evaluated for the two available energy channels, at about 25 and 50 MeV. We describe the procedure utilized to identify the proton events and to relate them to their solar origin (in terms of flares and coronal mass ejections). The statistical relationships between the energetic protons and their origin (linear and partial correlation analysis) are reported and discussed in view of earlier findings. Finally, the different trends found in the first eight years of solar cycles 23 and 24 are discussed.

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arXiv2017

Solar energetic particles and radio burst emission

We present a statistical study on the observed solar radio burst emission associated with the origin of in situ detected solar energetic particles. Several proton event catalogs in the period 1996$-$2016 are used. At the time of appearance of the particle origin (flare and coronal mass ejection) we identified radio burst signatures of types II, III and IV by inspecting dynamic radio spectral plots. The information from observatory reports is also accounted for during the analysis. The occurrence of solar radio burst signatures is evaluated within selected wavelength ranges during the solar cycle 23 and the ongoing 24. Finally, we present the burst occurrence trends with respect to the intensity of the proton events and the location of their solar origin.

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