The proposed project explores the boundary between the Earth’s atmosphere and near-Earth space, i.e., the mesosphere and lower thermosphere (MLT) region, with a special emphasis on low-latitudes (MLT-LoLa). The MLT in general has not been well studied given the challenges faced by observing techniques (too high for balloons and too low for satellites to make in situ measurements) and the complex dynamical and chemical processes of the region (e.g., co-existence of plasma and neutrals, large temperature gradients, wind shears). An urgent issue is its day-to-day variability, and its connection to thermospheric and ionospheric (TI) weather. Our knowledge of its variability is highly limited, and a systematic picture across different atmosphere layers and an array of major thermosphere/ionosphere parameters (e.g., plasma density and drift, thermosphere density, ion and neutral concentrations, wind, and temperature) is yet to be achieved. However, the past several years have seen a rapid expansion of datasets probing the MLT (e.g., ICON, Swarm, multistatic meteor radars) as well as unprecedented modeling capability which captures realistic lower-atmosphere forcing (e.g., WACCM-X, GAIA). In this proposed effort, a team of experts on middle atmosphere dynamics and chemistry, thermosphere dynamics, ionosphere electrodynamics, and plasma instabilities, is brought together. By combining ground-to-space whole atmosphere models with ground- and satellite-based observations and statistical inverse problems approaches, this team aims to develop an in-depth understanding of the day-to-day variability (e.g., dynamics, temperatures, composition of both the plasma and neutral atmosphere) by addressing the following questions: (1) How can day-to-day variability of the MLT and TI at low latitudes be systematically quantified? (2) What is the role of troposphere and stratosphere processes in the observed MLT-LoLa day-to-day variability? (3) What is the role of MLT-LoLa processes in the day-to-day variability of the TI (including plasma instabilities)? Answering these questions will provide a significant step forward towards a systematic understanding of the vertical connection between atmospheric layers from ground to space.


(Credits: Header figures are courtesy of  NASA)