From decadal to hourly time-scales, Radio Occultation enables a deeper probe into the Ionospheric E-region’s Response to Solar and Geomagnetic Variabilities
Despite being the first ionospheric layer discovered, the ionospheric E-region’s global-scale variabilities are still poorly observed. This is because the E-region is too low for in-situ satellite-based instruments to observe. From limited ground-based observations, all we know is that E-region electron density’s variability follows the changes in solar zenith angle and that during geomagnetic storms, E-region electron density over the high-latitudes is increased. In this work, a new E-region electron density dataset retrieved from radio occultation (RO) measurements is used to probe the global-scale variabilities of E-region electron density driven by solar and geomagnetic activity. The radio occultation measurements come from theCOSMIC-1, COSMIC-2, Spire RO and Feng Yun missions. This work first shows E-region electron density’s global-scale variabilities on monthly to decadal time-scales as observed by COSMIC-1 from 2007 till 2016. These include the seasonality and solar cycle-dependence of E-region electron density. Then, this work shows the day-to-day variabilities that are observed by COSMIC-2 and Spire RO. These include observations of the impacts of solar rotation and geomagnetic activity. Finally, the impacts of geomagnetic activity are probed deeper by looking at hourly variabilities of E-region electron density as well as Sporadic-E perturbations. Comparisons with the Whole Atmosphere Community Climate Model with Ionosphere/Thermosphere eXtension as well as the Thermosphere Ionosphere Electrodynamics– General Circulation model reveal that the models do simulate some of these observed variabilities. This provides the first RO-based support that these models do simulate reasonable E-region electron density variabilities.
Dr. Salinas is an Assistant Research Scientist at NASA Goddard Space Flight Center (GSFC). He works with NASA GSFC through the Goddard Earth Sciences Technology and Research 2 (GESTAR-2) program under University of Maryland, Baltimore County. He earned his B.S. in Applied Physics in 2012 from Ateneo de Manila University in the Philippines. He then earned his PhD in Earth Systems Science in 2019 under the Taiwan International Graduate Program - Earth Systems Science, a program under both the National Central University (NCU) and the Academia Sinica in Taiwan. For his PhD, he did research under the tutelage of Prof. Loren Chang from the NCU Department of Space Science and Engineering as well as under Prof. Danie Mao-chang Liang from the Academia Sinica Institute of Earth Sciences. He then proceeded to do a postdoctoral research fellowship under Prof. Chang’s group from 2019 till 2022 before finally joining NASA GSFC. His host at NASA GSFC is Dr. Dong L. Wu. At NASA, he primarily does research on aeronomy, ionospheric physics and solar-terrestrial physics using space and ground-based observations as well as first principles Physics-based models.