000008104 001__ 8104
000008104 005__ 20260325114153.0
000008104 0247_ $$2DOI$$a10.1051/0004-6361/202555142
000008104 037__ $$aSCART-2026-0141
000008104 100__ $$aDeshpande, Ketaki;
000008104 245__ $$aCoronal electron density: Insights from radio and in situ observations, and EUHFORIA modeling
000008104 260__ $$c2025
000008104 520__ $$aContext. The distribution of the coronal electron density at different distances from the Sun strongly influences the physical processes in the solar corona, and it is therefore a very important topic in solar physics. The majority of the methods used to estimate coronal electron density, including radio observations, were up to now not fully validated due to the absence of in situ observations closer to the Sun. Consequently, space weather forecasting models that simulate coronal density lacked proper validation. Newly available Parker Solar Probe (PSP) in situ observations at distances close to the Sun provide an opportunity to study the properties of plasma near the Sun and to compare observational and modeling results. Aims. The focus of this work is to study type III radio bursts, estimate their propagation path, and validate the coronal electron density obtained from in situ radio observations and modeling with the EUropean Heliospheric FORecasting Information Asset (EUHFORIA). Methods. In this study of type III radio bursts observed during the second PSP perihelion, we employ radio triangulation and modeling to analyze coronal electron density. Using the radio triangulation method, we determined the 3D positions of the radio sources. Additionally, we utilized the state-of-the-art EUHFORIA model to estimate electron densities at various locations. The electron densities derived from radio observations and EUHFORIA modeling were then inter-validated with in situ measurements from PSP. Results. We studied 11 type III radio bursts during the second PSP perihelion, with radio triangulation showing their propagation path in the southward direction from the solar ecliptic plane. The obtained radio source sizes ranged from 0.5 to 40 deg (0.5–25 R⊙), showing no clear frequency dependence. This indicates that scattering of radio waves was not very significant for the studied events and in this frequency range. A comparison of electron densities derived from radio triangulation, in situ PSP data, and EUHFORIA modeling showed a large range of obtained values. This result is influenced by the different propagation paths across different coronal structures and model limitations. Despite these variations, EUHFORIA successfully identified high-density regions along type III burst paths, demonstrating its capability to capture large-scale density structures. Conclusions. Our study emphasizes that type III bursts do not always follow the Parker spiral but instead trace distinct magnetic field lines that can be very differently oriented. The study shows constant radio source sizes and confirms that small-scale density fluctuations in PSP data remain relatively low. These two characteristics indicate that scattering effects do not significantly change observed radio source positions within the studied distances.
000008104 536__ $$aROB PhD Grant, BRIAN.be/$$cSWIM, University start-up grant/$$f3E220031, FEDtWIN/PERIHELION, PRODEX/4000112292,  PRODEX/4000134088,  PRODEX/4000106864,  PRODEX/4000134474,  PRODEX/ 4000136424,  European Union’s Horizon Europe research and innovation programme/101134999/SOLER,  Research Council of Finland/371569
000008104 594__ $$aSTCE
000008104 6531_ $$aSun: atmosphere / Sun: corona / Sun: general / Sun: heliosphere / Sun: radio radiation / solar wind
000008104 700__ $$aMagdalenic, Jasmina;
000008104 700__ $$aJebaraj, Immanuel Christopher;
000008104 700__ $$aValliappan, Senthamizh Pavai;
000008104 700__ $$aNiemela, Antonio ;
000008104 700__ $$aRodriguez, Luciano;
000008104 700__ $$aKrupar, Vratislav 
000008104 773__ $$pAstronomy & Astrophysics$$v 704$$y2025
000008104 8560_ $$fketaki.deshpande@ksb-orb.be
000008104 85642 $$ahttps://www.aanda.org/articles/aa/abs/2025/12/aa55142-25/aa55142-25.html
000008104 905__ $$apublished in
000008104 980__ $$aREFERD