Jack Chieh Wang

Madden-Julian oscillation in the ionosphere

13, 2023

AGU 2023

This study presents observational evidence of the Madden-Julian Oscillation (MJO) influencing the ionosphere, using FORMOSAT-7/COSMIC-2 data. Analysis reveals a prominent 40–90 day intraseasonal oscillation in low-latitude electron density, indicating a teleconnection between the MJO and ionospheric variations. Preliminary findings show HmF2 and NmF2 peak changes of up to 10% and 80%, respectively, linked to MJO phases. To investigate the underlying mechanisms, the study will utilize NCAR TIE-GCM coupled with SD-WACCMX. These results underscore the MJO's role in coupling intraseasonal oscillations from the tropical troposphere to the ionosphere, with significant implications for space weather modeling.

Circulation at the Edge of Space: Lower-thermospheric Winter-to-Summer Circulation

June 2023

JpGU 2023

The forcing mechanism of the lower-thermospheric circulation is explored using SD-WACCMX simulations, revealing that tides and resolved inertia gravity waves primarily drive this circulation. Contrary to previous assumptions, it is identified as the main driver of intra-annual atomic oxygen variation (~95-130 km), surpassing the influence of eddy and molecular diffusion. Vertical advection effectively transports atomic oxygen from its source to sink, highlighting the critical role of wave propagation and dissipation in whole-atmosphere coupling. Accurate representation of lower-atmospheric wave forcing is essential for reliable ionosphere and thermosphere modeling.

Assessment of ionospheric and thermospheric models during the geomagnetic storm times in low and moderate solar flux years

14, 2022

AGU 2022

This study evaluates the performance of ionospheric and thermospheric models hosted by NASA's CCMC during geomagnetic storms by comparing model outputs to observational data. Total Electron Content (TEC) from the models is compared with GNSS observations during storms in March 2013 and November 2021, covering low and moderate solar flux years. The study aims to improve model selection and advance space weather modeling accuracy.

Numerical Simulations of Coupling Mechanisms in the Thermosphere via Winter-to-Summer Lower-Thermospheric Circulation

13, 2024

AGU 2024

This study highlights a dynamic coupling mechanism between the lower thermosphere (~90-130 km) and the middle-to-upper thermosphere (~150-400 km) via winter-to-summer lower-thermospheric circulation, a process previously overlooked. Using the NCAR TIE-GCM model, researchers show that imposing a lower-thermospheric circulation enhances middle-to-upper thermospheric circulation, improving the model’s ability to reproduce seasonal variations in neutral density without relying on artificial assumptions. The findings underscore the importance of lower-thermospheric circulation in driving seasonal and latitudinal variations in thermospheric density, composition, and ionospheric plasma variability, demonstrating the complexity of whole-atmosphere coupling on seasonal scales.

Lower-thermospheric circulation during the geomagnetically storm times

June 2023

JpGU 2023

This study examines thermospheric meridional circulation patterns during geomagnetically active periods using SD-WACCMX simulations. During quiet times, vertical advection associated with the lower-thermospheric winter-to-summer circulation significantly influences atomic oxygen transport and upper atmospheric variability. During geomagnetically active periods, enhanced Joule heating and ion drag create polar-region circulations, altering vertical transport. Observations of CO2 from SABER validate these dynamics, showing effective mixing and changes in atomic oxygen distribution. The findings highlight the role of altered circulation in driving upper atmospheric changes during storm times.

On the importance of the lower-thermospheric circulation in determining thermospheric density and composition

16, 2022

AGU 2022

This study investigates the lower-thermospheric winter-to-summer residual circulation (~90-130 km) and its role in seasonal and latitudinal variations of thermospheric density and ionospheric plasma. Using SD-WACCMX simulations, it identifies tidal and inertia gravity wave momentum deposition as key drivers of this circulation, which influences atomic oxygen distribution and thermospheric intra-annual variation. Contrary to previous assumptions, the circulation’s impact surpasses that of eddy and molecular diffusion. The findings highlight the importance of accurately modeling wave forcing from the lower atmosphere for reliable ionosphere-thermosphere simulations during geomagnetically quiet periods.

High latitude secondary waves generating from traveling planetary waves during the 2019 Southern Hemisphere sudden stratospheric warming 

2021

AGU 2021

This study investigates the unusual September 2019 Southern Hemisphere sudden stratospheric warming (SSW), which amplified planetary waves (PWs) and their interactions with tides, leading to enhanced secondary waves. For the first time, observational evidence of these secondary waves is identified through meteor radar data from Antarctica. Simulations using the NCAR SD-WACCMX model illustrate the evolution of these waves during the SSW. The findings highlight the critical role of nonlinear wave-wave interactions in coupling the neutral atmosphere with the upper atmosphere, enhancing our understanding of atmosphere-ionosphere dynamics.

Burst of symmetric quasi-10 day wave during the 2019 Southern sudden stratospheric warming 

2020

An unusual sudden stratospheric warming (SSW) occurred in the Southern hemisphere in September 2019. Ground-based and satellite observations show the presence of a transient westward-propagating quasi-10 day planetary wave with zonal wavenumber one during the SSW. The planetary wave activity maximizes in the MLT region approximately 10 days after the SSW onset. Analysis indicates the quasi-10 day planetary wave is symmetric about the equator which is contrary to theory for such planetary waves. Observations from MLS and SABER provide a unique opportunity to study the global structure and evolution of the symmetric quasi-10 day wave with observations of both geopotential height and temperature during these unusual atmospheric conditions. The space-based measurements are combined with meteor radar wind measurements from Antarctica, providing a comprehensive view of the quasi-10 day wave activity in the southern hemisphere during this SSW. We will also present the results of our mesospheric and lower thermospheric analysis along with a preliminary analysis of the ionospheric response to these wave perturbations.