Dr. Yi Duann is a postdoctoral researcher in space science, engineering, and astronomy, currently specializing in exoplanetary atmospheres and spectral analysis. She is an interdisciplinary scientist with extensive experience managing satellite missions and fostering international collaborations. She previously served as the Project Manager for the INSPIRESat-1 Taiwan team and IDEASSat at National Central University. Her earlier research focused on ionospheric variability and its underlying drivers, leveraging expertise in areas such as visible-light airglow, machine learning applications, and the study of dual acceleration scales in elliptical galaxies. More recently, she has expanded her work into the field of exoplanets, with a particular emphasis on ultra-hot Jupiters and their near-ultraviolet spectral characteristics.
EDUCATION
2019-02 to 2023-06 | Doctor of Philosophy (Department of Space Science and Engineering)
2015-09 to 2018-05 | Master of Science (Graduate Institute of Space Science)
RESEARCH, TEACHING, or OTHER INTERESTS
Space and Planetary Science, Atmospheric Science, Earth and Planetary Sciences
10
Scopus Publications
Scopus Publications
Magnetohydrodynamic simulation assessment of a potential near-ultraviolet early ingress in WASP-189b Y. Duann, S.-H. Lai, H. J. Hoeijmakers, A. Johansen, C.-L. Lin, L.-C. Huang, Y.-Y. Chang, A. G. Sreejith, K. France, L. C. Chang, W.-H. Ip Astronomy and Astrophysics, 2025 Context . Ultra-hot Jupiters (UHJs) in close orbits around early-type stars provide natural laboratories for studying atmospheric escape and star-planet interactions under extreme irradiation and wind conditions. The near-ultraviolet (NUV) regime is particularly sensitive to extended upper atmospheric and magnetospheric structures. Aims . We investigate whether star-planet interactions in the WASP-189 system could plausibly account for the early ingress feature suggested by NUV transit fitting models. Methods . We analysed three NUV transits of WASP-I89b observed as part of the Colorado Ultraviolet Transit Experiment (CUTE), which employs a 6U CubeSat dedicated to exoplanet spectroscopy. To explore whether the observed transit asymmetry could plausibly arise from a magnetospheric bow shock (MBS), we performed magnetohydrodynamic (MHD) simulations using representative stellar wind velocities and planetary atmospheric densities. Results . During Visit 3, we identified a ~31.5-minute phase offset that is consistent with an early ingress. Our MHD simulations indicate that, with a wind speed of 572.97 km s −1 and a sufficient upper atmospheric density (~4.59 × 10 −11 kg m −3 ), a higher-density zone due to compression can form ahead of the planet within five planetary radii in regions where the fast-mode Mach number falls below ~0.56, even without a MBS. Shock cooling and crossing time estimates from the simulations further suggest that such a pileup could, in principle, produce detectable NUV absorption. Conclusions . Our results indicate that while MBS formation is feasible for WASP-189b, low stellar-wind speeds favour NUV-detectable magnetic pileups over classical bow shocks. Immediately after the shock formation, the post-shock plasma is too hot for strong NUV absorption, but a high-to-low wind-speed transition shortens the cooling time while preserving the compressed plasma, increasing its opacity. Pressure-balance estimates show that magnetic pressure dominates across wind regimes in the low-density case, and at low wind speeds in the high-density case, favouring pileup and reconnection near the magnetopause and enhancing the potential detectability of early-ingress signatures.
Atomic oxygen ion retrieval from 630.0 nm airglow during geomagnetically quiet periods: a mid-latitude case study near Irkutsk Y. Duann, L. C. Chang, Y.-C. Chiu, C. C. J. H. Salinas, A. V. Dmitriev, K. G. Ratovsky, I. V. Medvedeva, R. Vasilyev, A. V. Mikhalev, J. Y. Liu, C. H. Lin, T.-W. Fang Geoscience Letters, 2024 This study develops and validates three photochemical inversion models to retrieve atomic oxygen ion density ([O+]) profiles from 630.0 nm airglow emissions in the mid-latitude ionosphere during geomagnetically quiet period. Using passive ground-based instruments and empirical models, the models were tested and compared against electron density data from FORMOSAT-3/COSMIC (F3/C) and DPS-4 digisonde at Irkutsk. Among the models, Inversion Model 3 showed the strongest agreement with observations, particularly in capturing seasonal variations such as the June–July peak and a secondary March–April peak, which were absent in IRI-2012 predictions. These results highlight the potential of Inversion Model 3 for accurate [O+] retrieval, offering a novel approach for monitoring ionospheric variability using passive photometric observations.
Application of the Bagged Trees Technique on Retrieving the Nighttime Ionospheric Peak Density From OI-135.6 nm Airglow Chi‐Yen Lin, Jann‐Yenq Liu, Charles Chien‐Hung Lin, P. K. Rajesh, Yi Duann, Yun‐Cheng Wen Earth and Space Science, 2024 The NASA global‐scale observations of the limb and disk (GOLD) mission is a measurement opportunity to scan the far ultraviolet airglow at ∼134–162 nm over the American Hemisphere since October 2018. The FORMOSAT‐7/COSMIC‐2 (F7/C2) satellite mission has provided thousands of daily radio occultation soundings in the low‐ and mid‐latitude regions since July 2019. The nighttime OI–135.6 nm emission is mainly through radiative recombination, and the radiance is used to derive the peak electron density. Comparison with corresponding F7/C2 observations demonstrates good correlation in low‐latitudes, while is overestimated near mid‐latitudes in winter, induced by the photoelectrons emanating from magnetically conjugate Hemisphere. The machine learning technique Bagged Trees is implemented to develop an intensity to peak density model training from GOLD and F7/C2 observations. The validation demonstrates that Bagged Trees peak‐density has less influence from conjugate photoelectrons and indicates the power of machine learning techniques for geophysics data processing.
Variability and distribution of nighttime equatorial to mid latitude ionospheric irregularities and vertical plasma drift observed by FORMOSAT-5 Advanced Ionospheric Probe in-situ measurements from 2017 – 2020 Loren C. Chang, Yueh-Chun Hsieh, Chi-Kuang Chao, Yi Duann, Cornelius Csar Jude H. Salinas, Jann-Yenq Liu, Charles C.H. Lin Advances in Space Research, 2024 Irregularities in ionospheric plasma distribution can result in severe scintillation and disruption to the radio frequencies utilized for satellite communications and navigation. In the low and mid latitudes, these irregularities can include Equatorial Plasma Bubbles (EPBs) and Travelling Ionospheric Disturbances (TIDs). EPBs are irregularities manifesting in low latitude nighttime ionosphere plasma density that can extend along magnetic field lines with zonal scales on the order of 100 km or less, while TIDs are propagating wave disturbances. High frequency in-situ measurements of ionospheric plasma aboard spacecraft in Low Earth Orbit (LEO) are a direct measurement of irregularities in plasma density and are therefore valuable for resolving EPB and TID occurrences, variability, and relation to other ionospheric parameters that are believed to play a driving role in the formation of such irregularities. In this study, we utilize observations taken over a three-year period between 2017 – 2020 by the Advanced Ionospheric Probe (AIP) carried aboard the FORMOSAT-5 satellite to examine the spatial, seasonal, and interannual variability of equatorial to mid latitude ionospheric irregularities and vertical ion drift during this time. AIP provides in-situ measurements of ion density and vertical ion drift in the equatorial to mid latitude ionosphere at approximately 720 km altitude with local times between 22:00 – 23:00 local time. Our global scale results resolve distinct and inter-annually recurrent seasonal patterns in the distribution of nighttime ionospheric irregularities and vertical plasma drift during this time. Elevated occurrences of ion density irregularities are resolved along the Equatorial Ionization Anomaly (EIA) latitudes, while notable occurrences with variability consistent with EPBs also observed along the low and equatorial magnetic latitudes. Zonal variability of equatorial irregularities consistent with the signatures of nonmigrating atmospheric tides are observed. It is also notable that the occurrences and geographic distribution of ion density irregularities showed a considerable level of interannual variability, especially at mid latitudes over the South Atlantic and Southern African sectors, which showed much higher levels of irregularities in 2017 - 2018, compared to 2019 and 2020. In comparison, the spatial and interannual variation of the co-located vertical ion drifts were much more consistent during the years examined, indicating that the driver for the observed interannual variability in ion density irregularities cannot be attributed to the vertical ion drift at the same time and location of the observations. This highlights the need for in-situ instruments distributed across multiple satellites in different local time zones.
Impact of the February 3–4, 2022 geomagnetic storm on ionospheric S4 amplitude scintillation index: Observations and implications Yi Duann, Loren C. Chang, Jann-Yenq Liu Advances in Space Research, 2023 The coincidental loss of 38 out of 49 SpaceX Starlink satellites during their launch on February 3, 2022, concurrent with two moderate geomagnetic storms, opens a unique window into the study of ionospheric irregularities and their potential impacts on Low Earth Orbit assets. This research provides evidence for the first time on the influence of Prompt Penetration Electric (PPE) fields and Disturbance Dynamo (DD) fields on the GNSS S4 amplitude scintillation indices of this particular geomagnetic storm, using observed variations in the distance of Equatorial Ionospheric Anomaly (EIA) crests and the O/N2 density ratio. By examining observations from the F7/C2 (FORMOSAT-7/COSMIC-2) mission, the NASA/GSFC’s OMNI data set, the TIMED/GUVI (Thermosphere Ionosphere Mesosphere Energetics and Dynamics/Global Ultraviolet Imager) O/N2 density ratio, and the GIM-TEC (Global Ionosphere Map of Total Electron Content) data, the study uncovers the complex dynamics of storm-induced irregularities and their correlation with suppressed S4 at low latitudes. It reveals the roles of PPE and DD in augmenting and mitigating S4 occurrences, respectively, during different storm phases. These findings contribute to enhancing the understanding of irregularity occurrence rates, scintillation effects, and geomagnetic storms across various longitudinal sectors, thereby providing a case study of changes to the scintillation environment during this moderate but high-profile geomagnetic event.
Classifying MaNGA velocity dispersion profiles by machine learning Yi Duann, Yong Tian, Chung-Ming Ko Ras Techniques and Instruments, 2023 We present a machine-learning (ML) approach for classifying kinematic profiles of elliptical galaxies in the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey. Previous studies employing ML to classify spectral data of galaxies have provided valuable insights into morphological galaxy classification. This study aims to enhance the understanding of galaxy kinematics by leveraging ML. The kinematics of 2624 MaNGA elliptical galaxies are investigated using integral field spectroscopy by classifying their one-dimensional velocity dispersion (VD) profiles. We utilized a total of 1266 MaNGA VD profiles and employed a combination of unsupervised and supervised learning techniques. The unsupervised K-means algorithm classifies VD profiles into four categories: flat, decline, ascend, and irregular. A bagged decision trees classifier (TreeBagger)-supervised ensemble is trained using visual tags, achieving 100 ${{\\ \\rm per\\ cent}}$ accuracy on the training set and 88 ${{\\ \\rm per\\ cent}}$ accuracy on the test set. Our analysis identifies the majority (68 ${{\\ \\rm per\\ cent}}$) of MaNGA elliptical galaxies presenting flat VD profiles, which requires further investigation into the implications of the dark matter problem.
A Methodology of Retrieving Volume Emission Rate from Limb-Viewed Airglow Emission Intensity by Combining the Techniques of Abel Inversion and Deep Learning Yi Duann, Loren C. Chang, Chi-Yen Lin, Yueh-Chun Hsieh, Yun-Cheng Wen, Charles C. H. Lin, Jann-Yenq Liu Atmosphere, 2023 The conversion of airglow intensity to volume emission rate (VER) is a common method for studying the ionosphere, but the contribution of the intensity conversion process to the uncertainty in estimated electron or ion density is significant. The Abel inversion is a commonly used method for retrieving VERs from vertical profiles of airglow intensities accumulated along the rays horizontally at the tangent point, but it requires that the intensities converge to zero at their uppermost height, which is often not the case due to observational limitations. In this study, we present a method for optimizing the retrieval of VER from satellite-measured airglow intensities using the techniques of deep learning and Abel inversion. This method can be applied to fill in unobserved or discontinuous observations in airglow intensity profiles with the Chapman function, allowing them to be used with the Abel inversion to determine VERs. We validate the method using limb 135.6 nm airglow emission intensity data from the NASA Global-scale Observations of the Limb and Disk (GOLD) mission. Our training process involves using three hidden layers with varying numbers of neurons, and we compare the performance of the best-performing deep learning models to Abel-transformed results from real-time observations. The combination of Abel inversion and deep learning has the potential to optimize the process of converting intensity to VER and improve the capacity for analyzing ionospheric observations.
The INSPIRESat-1: Mission, science, and engineering Amal Chandran, Tzu-Wei Fang, Loren Chang, Priyadarshan Hari, Thomas N. Woods, Chi-Kuang Chao, Richard Kohnert, Ankit Verma, Spencer Boyajian, Yi Duann, William Evonosky, Mallikarjun Kompella, Rong Tsai-Lin, Anant Kumar, Sarthak Srivastava, Bennet Schwab, Robert Sewell, Mayuresh Sarpotdar Advances in Space Research, 2021
IDEASSat: A 3U CubeSat mission for ionospheric science Yi Duann, Loren C. Chang, Chi-Kuang Chao, Yi-Chung Chiu, Rong Tsai-Lin, Tzu-Ya Tai, Wei-Hao Luo, Chi-Ting Liao, Hsin-Tzu Liu, Chieh-Ju Chung, Ru Duann, Cheng-Ling Kuo, Jann-Yenq Liu, Zhe-Ming Yang, Glenn Franco Gacal, Amal Chandran, Hari Priyardarshan, Ankit Verma, Tzu-Wei Fang, Sarthak Srivastava Advances in Space Research, 2020
On the Relationship Between E Region Scintillation and ENSO Observed by FORMOSAT-3/COSMIC Loren C. Chang, Pei‐Yun Chiu, Cornelius Csar Jude H. Salinas, Shih‐Ping Chen, Yi Duann, Jann‐Yenq Liu, Chien‐Hung Lin, Yan‐Yi Sun Journal of Geophysical Research Space Physics, 2018 Global Navigation Satellite System radio occultation signals often show extremely strong levels of scintillation when passing through the ionospheric E region. This is related to sporadic E(Es)—dense layers of metallic ions that can form in the E region, influencing terrestrial and satellite radio propagation. In our report on the 2007–2014 variation of E region S4 amplitude fluctuation indices measured by the FORMOSAT‐3/Constellation Observing System for Meteorology Ionosphere and Climate (COSMIC) satellite constellation, we find that the spatial and temporal variation of the maximum S4 index in the E region is proportionate to the occurrence rate of extreme scintillation and by extension, sporadic E. We also find that the monthly median extreme S4 amplitude fluctuation index in the E region midlatitudes shows a dependence on variation of the El Niño–Southern Oscillation (ENSO) in the troposphere that has not been previously reported. The ENSO‐related variation of the E region median extreme S4 indices varies closely with the tropopause height, with both parameters lagging the Oceanic Niño Index by roughly 1 to 2 months, while also displaying a similar spectrum of periodicities. This similarity is especially strong in the southern midlatitudes. These results indicate that ENSO signatures can be transmitted to Es formation mechanisms, potentially through modulation of vertically propagating atmospheric tides that alter lower thermospheric wind shears. The end result is the modulation of the interannual variation of extreme Es values by ENSO.
GRANT DETAILS
2025-02 to 2026-02
National Science and Technology Council (Taipei, TW)
NSTC 114-2917-I-564-044
