Below are the scientific results, achieved during the STELLAR project.
Scientific publications
[1] Petkova, D.B., Petkov, P.Z, Aperture-Coupled Microstrip Patch Antenna Design Using FEM Simulation Technique (2021) 2021 56th International Scientific Conference on Information, Communication and Energy Systems and Technologies, ICEST 2021 – Proceedings, art. no. 9483494, pp. 149-152. DOI: 10.1109/ICEST52640.2021.9483494
Full text freely available at: http://e-university.tu-sofia.bg/e-publ/search-det.php?id=8280
[2] Pavlina Aleksieva, title: Astronomy at low frequencies with the International LOFAR telescope, Bachelor degree thesis, 2021, Sofia University St. Kliment Ohridski, Faculty of Physics, successfully defended with the highest possible grade; supervisor Assoc. Prof. Antoaneta Antonova.
Full text freely available at:
[3] Zhang, P., Zucca, P., Kozarev, K., Carley, E., Wang, C., Franzen, T., Dabrowski, B., Krankowski, A., Magdalenic, J. and Vocks, C., Imaging of the Quiet Sun in the Frequency Range of 20–80 MHz (2022), The Astrophysical Journal, 932, 17, Open access, DOI: 10.3847/1538-4357/ac6b37
[4] Zhang, P., Chen, J., Liu, R. and Wang, C., FastQSL: A Fast Computation Method for Quasi-separatrix Layers (2022) The Astrophysical Journal, 937, 26, Open access, DOI: 10.3847/1538-4357/ac8d61
[5] Zhang P., Offringa A. R., Zucca P., Kozarev K., Mancini M., RFI flagging in solar and space weather low frequency radio observations, (2023), MNRAS, 521, 630. Open access, DOI:10.1093/mnras/stad491
[6] I. Nachev and P. Petkov, “VLF system for SID monitoring,” 2023 33rd International Conference Radioelektronika (RADIOELEKTRONIKA), Pardubice, Czech Republic, 2023, pp. 1-4, doi:10.1109/RADIOELEKTRONIKA57919.2023.10109027
[7] P. Z. Petkov and E. Lyubenov, “Passive Retranslation with Space Wave Coupled Antennas,” 2023 33rd International Conference Radioelektronika (RADIOELEKTRONIKA), Pardubice, Czech Republic, 2023, pp. 1-4, doi:10.1109/RADIOELEKTRONIKA57919.2023.10109006.
[8] P. Aleksieva and P. Z. Petkov, “Log-periodic Antenna for Solar Observations in 100 MHz – 500 MHz,” 2023 58th International Scientific Conference on Information, Communication and Energy Systems and Technologies (ICEST), Nis, Serbia, 2023, pp. 77-80, doi:10.1109/ICEST58410.2023.10187221.
[9] D. B. Petkova, T. S. Tsekov and P. Z. Petkov, “Application of Electromagnetic Bandgap Structures for Mutual Coupling Reduction in Microstrip Antenna Arrays,” 2023 58th International Scientific Conference on Information, Communication and Energy Systems and Technologies (ICEST), Nis, Serbia, 2023, pp. 73-76, doi: 10.1109/ICEST58410.2023.10187394.
[10] T. Valkovski, I. Nachev and P. Z. Petkov, “Optical Communication System Investigation with Application for VLF Solar Flares Monitoring System,” 2023 58th International Scientific Conference on Information, Communication and Energy Systems and Technologies (ICEST), Nis, Serbia, 2023, pp. 249-252, doi: 10.1109/ICEST58410.2023.10187279.
Submitted or in Preparation
[1] Mohamed Nedal, Kamen Kozarev, Peijin Zhang and Pietro Zucca, Coronal Diagnostics of Solar Type-III Radio Bursts Using LOFAR and PSP Observations, 2023, accepted at Astronomy & Astrophysics
http://arxiv.org/abs/2310.02677
[2] J. Rigney, D. M. Long, P. T. Gallagher, G. Ramsay, J. G. Doyle, O. Stepanyuk, and K. Kozarev, “Low Frequency Radio Emission Associated with a CME Shock and EUV Wave”, 2023, in prep. for Astronomy & Astrophysics
[3] Kamen Kozarev, Pietro Zucca, Peijin Zhang, Low-Frequency Coronal Gyrosynchrotron Radio Emission as a Tracer for the Early Solar Wind, 2023, in prep for Astronomy & Astrophysics
[4] Pavlina Aleksieva, “Novel Modeling of LOFAR`s High Band Antenna, Using the Finite Element Method”, conf. paper, submitted
[5] Nicole Christoff, Feature Extraction of VLF Radio Signal for Solar Flares Detection, conf. paper, submitted
[6] Peter Petkov, Array Element Model with Improved Accuracy for LOFAR Radio telescope, conf. paper, submitted
Conference participation
[1] Petkov P., THE BULGARIAN LOFAR PROJECT, XXI Gamow International Astronomical Conference-School “Astronomy and beyond: Astrophysics, Cosmology and Gravitation, High Energy Physics, Astroparticle Physics, Radio astronomy and Astrobiology”, 15-21 August, 2021, Odessa, Ukraine
[2] Antoaneta Antonova, Astronomy at radio wavelengths, invited talk at the 46 National Astronomical Youth Conference, 4 Sept. 2020 (https://astro-varna.com/index.html#!art=234)
[3] Antoaneta Antonova, The Universe at radio wavelengths, invited public talk, Sofia Science Festival, 26 – 27 Sept. 2020 (https://www.britishcouncil.bg/sites/default/files/programata_2020_preview_final.pdf)
[4] K. Kozarev, P. Zhang, P. Zucca, O. Stepanyuk, M. Nedal, Towards Lucky Imaging for Quiet-Time Low-Frequency Radio Solar Observations, Second Machine Learning in Heliophysics conference, Boulder, USA, 21-25 March 2022
[5] Kozarev, Kamen; Zhang, Peijin; Zucca, Pietro, Metric-Decametric Gyrosynchrotron Radio Emission From the Quiet Solar Corona. EGU22, the 24th EGU General Assembly, held 23-27 May, 2022, id.EGU22-5067
[6] A. Antonova, K. Kozarev, A. Avramova-Boncheva, R. Mitevа, M. Dechev, P. Zucca, E. Carley, S. Maloney, P. Petkov, STELLAR :an EU twinning project on LOFAR data analysis and knowledge transfer, poster, MW-Gaia WG5 workshop: Breaking Barriers: Inspiring the Next Generation, Santiago de Compostela, Spain, May 23 – 25, 2022 http://mao.tfai.vu.lt/breakingbarriers
[7] Nedal, Mohamed, Multi-Viewpoint Remote Observations of Solar Radio Bursts, 44th COSPAR Scientific Assembly. Held 16-24 July, 2022, Abstract D2.3-0051-22
[8] J. Rigney: Low Frequency Radio Emission associated with a CME and EUV Wave, talk at the Irish National Astronomy Meeting 2023 (INAM 2023), University College Cork, August 24 – 25, 2023 (https://astronomers.ie/inam-2023/)
[9] Rositsa Miteva, Susan W. Samwel, Svetoslav Zabunov, Kostadinka Koleva, Momchil Dechev , Ramesh Chandra, Recent advances on solar radio burst emissions, eruptive phenomena and geomagnetic storms associated with in situ particles in solar cycles 23 and 24, PLANETARY, SOLAR, AND HELIOSPHERIC RADIO EMISSIONS, 2022 September 26-28, Dublin, Ireland (https://pre2022.dias.ie/programme/ )
[10] Kozarev, Kamen, Observations and Modeling of The Quiet Solar Corona in Low Frequency Imaging, Planetary, Solar, and Heliospheric Radio Emissions, held 26-28 September 2022.
[11] Nedal, Mohamed; Kozarev, Kamen A.; Zhang, Peijin; Zucca, Pietro, Imaging the Sources of Solar Type-III Radio Bursts during the Parker Solar Probe Encounter 2, ESWW18, the European Space Weather Week, held 24-28 October 2022, id. P2.p03
[12] Rositsa Miteva (IANAO-BAS), Susan W. Samwel (NRIAG, Egypt) and Momchil Dechev (IANAO-BAS), Space weather catalogs: energetic particles, radio emissions, flares and geomagnetic storms, XIIIth Bulgarian-Serbian Astronomical Conference, 3-7/10/2022 Velingrad, Bulgaria
[13] A. Antonova, A. Avramova-Bioncheva, H. Korhonen, G. Doyle, J. Rigney, I. Stateva, Looking for the elusive stellar coronal mass ejections. How can LOFAR help?, talk at the STELLAR special session, NAFSKI2022, 10 – 12 November, Sofia, Bulgaria (https://bulgarianspace.online/wp-content/uploads/2022/11/NaFSKI-3_EN_v3.pdf)
[14] K. Kozarev, Presentation of the Project STELLAR, talk at the STELLAR special session, NAFSKI2022, 10 – 12 November, Sofia, Bulgaria (https://bulgarianspace.online/wp-content/uploads/2022/11/NaFSKI-3_EN_v3.pdf)
[15] Mohamed Nedal, Imaging the Sources of Solar Type-III Radio Bursts during the Parker Solar Probe Encounter 2, talk at the STELLAR special session, NAFSKI2022, 10 – 12 November, Sofia, Bulgaria (https://bulgarianspace.online/wp-content/uploads/2022/11/NaFSKI-3_EN_v3.pdf)
[16] Peijin Zhang, LOFAR Imaging and Spectroscopy of the Sun, talk at the STELLAR special session, NAFSKI2022, 10 – 12 November, Sofia, Bulgaria (https://bulgarianspace.online/wp-content/uploads/2022/11/NaFSKI-3_EN_v3.pdf )
[17] Peter Petkov, Presentation of “The Bulgarian LOFAR project”, poster, Radio2022 and GLOW Annual Assembly, Berlin, Germany https://www.glowconsortium.de/index.php/en/berlin-2022
[18] Nedal, Mohamed; Kozarev, Kamen A.; Zhang, Peijin; Zucca, Pietro, Probing the Coronal Conditions using LOFAR Observations of Type-III Radio Burst, AGU Fall Meeting 2022, 12-16 December 2022, id. SH45D-2367.
[19] Kozarev, Kamen; Zhang, Peijin; Zucca, Pietro. “Modeling and Observations of The Quiet Solar Corona at Metric-Decametric Radio Frequencies”. AGU Fall Meeting 2022, 12-16 December 2022, id. SH25D-2075
[20] Peijin Zhang, Pietro Zucca, Kamen A Kozarev, Peter Gallagher, Mohamed Nedal, Incremental Development of LOFAR Space-weather (IDOLS) , AGU Fall Meeting 2022, held in Chicago, IL, 12-16 December 2022, id. SH35E-1844.
[21] Kozarev, Kamen; Stepanyuk, Oleg; Nedal, Mohamed; Mancini, Mattia; Zucca, Pietro. “Improving LOFAR Solar Radio Imaging Observations With Machine Learning”. MCH23, International Workshop on Machine Learning and Computer Vision in Heliophysics, held 19-21 April 2023, id. MCH23-55
[22] Ivaylo Nachev and Peter Petkov, VLF system for SID monitoring, Paper,Microwave and Radio Electronics Week 2023, Pardubice, Czech Republic, April 19-20, 2023 (https://www.marew.cz/ )
[23] P. Z. Petkov and E. Lyubenov, Passive Retranslation with Space Wave Coupled Antennas, Paper, Microwave and Radio Electronics Week 2023, Pardubice, Czech Republic, April 19-20, 2023 (https://www.marew.cz/ )
[24] Pavlina Aleksieva, “Novel Modeling of LOFAR`s High Band Antenna, Using the Finite Element Method”, paper presentation, Techsys 2023, Plovdiv, Bulgaria, 18-20 May 2023 (http://techsys.tu-plovdiv.bg/)
[25] 5th International Conference on Advances in Signal Processing and Artificial Intelligence (ASPAI’ 2023), 7-9 June 2023 TENERIFE (CANARY ISLANDS), SPAIN (https://aspai-conference.com/)
[26] Pavlina Aleksieva and Peter Petkov, Log-periodic Antenna for Solar Observations in 100 MHz – 500 MHz, paper, 58th International Scientific Conference on Information, Communication and Energy Systems and Technologies, Niš, Serbia, June 29 – July 01, 2023 (https://icestconf.org/ )
[27] Diana Petkova and Peter Petkov, Application of Electromagnetic Bandgap Structures for Mutual Coupling Reduction in Microstrip Antenna Arrays. Paper, 58th International Scientific Conference on Information, Communication and Energy Systems and Technologies, Niš, Serbia, June 29 – July 01, 2023 (https://icestconf.org/ )
[28] Ivaylo Nachev and Peter Petkov, Optical Communication System Investigation with Application for VLF Solar Flares Monitoring System, paper, 58th International Scientific Conference on Information, Communication and Energy Systems and Technologies, Niš, Serbia, June 29 – July 01, 2023 (https://icestconf.org/ )
[29] Peter Petkov, Array Element Model with Improved Accuracy for LOFAR Radio telescope, Paper, IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting, Portland, Oregon, USA, July 23–28, 2023 (https://2023.apsursi.org/ )
Successful LOFAR Observing Proposals
In addition, in the past 18 months, there have been four successful proposals for observations with LOFAR from members of the STELLAR team. The data from these proposals will be included in open access scientific publications.
[1] J. Rigney, A. Antonova, J. G. Doyle, H. Korhonen, E. Carley, G. Ramsay, P. Gallagher, Radio and optical time domain observations of flares and coronal mass ejections from two G dwarfs and implications of space weather on nearby planets – 8 hours observed, data being processed.
[2] K. Vida, A. Antonova, K.Namekata, H. Maehara, H. Korhonen, K. Perger , H. Vedantham, A. Gorgei, A. Avramova-Boncheva, B. Seli, Radio and optical observation of flares and coronal mass ejections in the Hyades open cluster – 40 hours granted, observations are scheduled for autumn 2023.
[3] P. Zucca, P. Gallagher, …, K. Kozarev et al., Observations of the Sun and Heliosphere Using LOFAR for a Coordinated Ground- and Space-Based Approach to Space-Weather Research – 308 hours granted, to be completed in Cycle 20.
[4] P. Zucca, E. Carley, … Peter Gallagher, … P. Zhang, K. Kozarev et al., Advancing solar and heliospheric physics with LOFAR in the era of Parker Solar Probe and Solar Orbiter – Long-term proposal covering four LOFAR observing cycles and a total of over 1000 observing hours. The observations conducted so far are being processed.
STELLAR seminars
[1] “Observation, Modeling, and Wave-Propagation Simulations on the Source of Solar Radio Bursts”
Dr. Peijin Zhang, University of Science and Technology of China
Tuesday, 17 August 2021, at 15:00h CET, over Zoom
[2] “Characterisation of weak transient meterwave solar emissions”
Dr. Rohit Sharma, Fachhochschule Nordwestschweiz, Switzerland
Thursday, 16 September 2021, at 13:00h CET, over Zoom
[3] “Radio flashes from plasma storms around exoplanets”
Dr. Harish Vedantham, ASTRON, The Netherlands Institute of Radio Astronomy
Tuesday, 2 November 2021, at 15:00h CET, over Zoom
[4] “The Sun and the (Low Mass) Stars: Searching for Radio Flares and CMEs on M Dwarfs”
Jeremy Rigney, PhD student at Dublin Institute of Advanced Studies & Armagh Observatory and Planetarium,
November 14 2022, at 13:00h CET, over Zoom
[5] “The Nature and Origin of Moving Solar Radio Bursts Associated With Coronal Mass Ejections on the Sun”
Dr. Diana Morosan, University of Helsinki
December 22 2022, at 13:00h CET, over Zoom
[6] “Remote Measurement of Plasma Parameters of Coronal Mass Ejections using Spectropolarimetric Radio Imaging”
Devojyoti Kansabanik, National Centre for Radio Astrophysics, Tata Institute of Fundamental Research
January 31 2023, at 13:00h CET, over Zoom
Additional Dissemination And Outreach
[1] Participation at the Second National Forum for space exploration and technologies with a promotional stand (07 – 09 Oct. 2021, http://bulgarianspace.online/nafski2021/). The forum was organised by the Space section of the academic and business community in Bulgaria. It took place in the Sofia Tech park over 3 days. It covered three main topics: Business and space; Science, technologies and space; and Education and space. There were participants from several Bulgarian universities (e.g. Sofia University, Varna Naval Academy, Technical University Sofia), several institutes of the Bulgarian Academy of Sciences (Institute of astronomy, Space research and technology institute, Institute for nuclear research and nuclear energy, Climate, atmosphere and water research institute), as well as representatives from education initiatives (Space Education for Bulgaria (SpaceEdu4BG), Astroparty Baikal, Space Academy, Astroparty Varshets, etc.) and businesses (IBM Bulgaria, Sfera Technologies, Endurosat, S-Cosmos). At the Business and Cosmos session, there were invited representatives of ESA, EUSPA, the Bulgariam Ministry for science and education, the National Agency for innovations).
The STELLAR project, together with the LOFAR-BG was presented at the promotional stand of the Institute of astronomy, where LOFAR-BG/STELLAR leaflets were distributed to the participants and visitors and the project was orally presented.
[2] Participation at the Sofia Science Festival (15 – 16 May 2021, https://www.britishcouncil.bg/sofia-science-festival) with a promotional stand, which was visited by the Bulgarian Science and Education Minister at the time Prof. Nikolay Denkov.
The Sofia Science Festival is an annual event encompassing different scientific and cultural spheres. Its main organiser is the British Council in Bulgaria under the patronage of the Bulgarian Ministry of Science and education. The event targets the general public, whereas all presenters are professionals in their respective fields. It includes lectures, hands-on sessions for children and demonstrations. In addition, there are promotional stands at which different scientific institutions can advertise their work. The Institute of Astronomy is now a regular participant in the Festival, both with a promotional stand and with lecturers and demonstrators. In 2021, we presented the STELLAR project at the promotional stand, where we were giving information about the project’s aim and activities. We were also giving away STELLAR leaflets. The stand was visited by the Bulgarian Minister for Science and Education – Prof. Nikolay Denkov (as can be seen in one of the pictures below.)
The Minister for Science and Education – Prof. Nikolay Denkov visiting the promotional stand of IA at the Sofia Science Festival 2021.
There will be two graduate theses to be defended in the very near future that will greatly benefit from the STELLAR and the partnerships formed during the project, namely:
[3] The Master’s thesis of Pavlina Aleksieva, titled ”LOG-PERIODIC ARRAY FOR SOLAR OBSERVATIONS”, Technical University, Sofia, supervisor Peter Petkov. The defense is scheduled for September 2023. Pavlina plans to continue her work (including a PhD) on topics connected both with the engineering and scientific part of radio astronomy.
[4] The PhD thesis of Mohamed Nedal, titled “Solar coronal activity: energetic particles, radio and EUV”, IA and NAO, BAS, supervisor Kamen Kozarev. The expected date of defense is spring of 2024.
We have also performed outreach activities both for scientists from astronomy, other fields in physics and young astronomy enthusiasts from all over the country:
[5] Antoaneta Antonova, “Scientific and Technological Excellence by Leveraging LOFAR Advancements in Radio Astronomy” — STELLAR, talk at the regular Vienna Astro Colloquium, 16.05.2022, University of Vienna, Austria
[6] A promotional stand and mini-event at the NAFSKI2022 conference in Sofia, where besides the special session, we also showed a model of an international LOFAR station and gave away information leaflets about STELLAR.
[7] In the summer of 2022, Mohamed Nedal gave a talk , titled “Overview on LOFAR and STELLAR Projects in Bulgaria” at the 2022 “Beli Brezi” Astronomy school for school children (https://www.astro-brezi.org/index.php#). This is a school with more than 50 years of history. There, school children (ages 12 to 18) and some undergraduate students from all over Bulgaria learn to perform and analyse different kinds of astronomical observations. The school also offers lectures from professional researchers on various topics, connected to astrophysics and space exploration. The lecture was included in the program of the school and met with great interest. We plan to continue this participation at the Beli Brezi summer school by doing a series of lectures in 2024 about the potential and the development of radio astronomy in Bulgaria.
