The Earth’s ionosphere is a weakly ionized plasma that forms an interface between outer space and the atmosphere. Ionospheric plasma can refract radio signals used for satellite navigation, causing significant positioning errors. Irregularities in ionospheric plasma distribution can cause diffraction and scintillation of trans-ionospheric radio signals, leading to disruptions in satellite communication and navigation services in severe cases.
Ionospheric irregularities appear at various altitudes and latitudinal regions. Equatorial plasma bubbles (EPBs), are regions of lower plasma density that occur in the F-region ionosphere, particularly near the Earth's geomagnetic equator. These bubbles form after sunset when the sun stops ionizing the ionosphere. The ions recombine, creating a lower-density layer that can rise through the more ionized layers above via convection, resulting in a plasma bubble. The formation of EPBs is believed to be driven by the Rayleigh–Taylor instability, which occurs when a less dense fluid rises through a denser fluid. The occurrence of EPBs is influenced by factors such as solar activity and seasonal variations, with higher frequencies during the spring and autumn equinoxes.
Sporadic E layers are electron density enhancements that typically appear at around 100 km altitude in mid-latitudes of the summer hemisphere during daytime. These layers result from complex interactions involving meteoroids bringing metallic ions into our atmosphere, dynamics of the upper mesosphere and lower thermosphere, Earth's magnetic field parameters, and geomagnetic activity.
The main goal of the project is to improve our understanding of the formation and propagation of ionospheric disturbances throughout the entire ionosphere. We are investigating the occurrence and evolution of disturbances related to electric fields, ion drift velocities, mesospheric and thermospheric winds, magnetic field parameters, and space weather events. Therefore, we use large satellite-based datasets, which we augment with selected ground-based observations.
References
Arras, C., Resende, L.C.A., Kepkar, A. et al. Sporadic E layer characteristics at equatorial latitudes as observed by GNSS radio occultation measurements. Earth Planets Space 74, 163 (2022). https://doi.org/10.1186/s40623-022-01718-y
Arras, C. and Wickert, J. (2018). Estimation of ionospheric sporadic E intensities from GPS radio occultation measurements. JASTP, 171, 60-63, https://doi.org/10.1016/j.jastp.2017.08.006
Kepkar, A., Arras, C., Wickert, J., Schuh, H., Alizadeh, M., & Tsai, L.-C. (2020). Occurrence climatology of equatorial plasma bubbles derived using FormoSat-3 ∕ COSMIC GPS radio occultation data. Annales Geophysicae, 38, 611-623. https://doi:10.5194/angeo-38-611-2020
Sobhkhiz-Miandehi, S., Jadhav, A. P., Arras, C., Shinagawa, H., Miyoshi, Y., & Yamazaki, Y. (2024). Planetary Wave Signature in Sporadic E Layer Obtained from Multi-Mission Radio Occultation Observations. Earth and Space Science, 11(10): e2024EA003757. https://doi:10.1029/2024ea003757
Yamazaki, Y., Arras, C., Andoh, S., Miyoshi, Y., Shinagawa, H., Harding, B. J., et al. (2022). Examining the wind shear theory of sporadic E with ICON/MIGHTI winds and COSMIC-2 radio occultation data. Geophysical Research Letters, 49, e2021GL096202. https://doi.org/10.1029/2021GL096202
Resende, L. C. A., Zhu, Y., Denardini, C. M., Moro, J., Arras, C., Chagas, R. A. J., et al. (2022). Worldwide study of the Sporadic E (Es) layer development during a space weather event. J. Atmos. Solar-Terrestrial Phys. 241, 105966. https://doi.org/10.1016/j.jastp.2022.105966
Link to the project in the DFG's GEPRIS project database: gepris.dfg.de/gepris/projekt/468463584