Opinion: Recent developments and future directions in studying the mesosphere and lower thermosphere

Abstract

Abstract. This article begins with a review of important advances in the chemistry and related physics of the mesosphere and lower thermosphere (MLT) region of the atmosphere that have occurred over the past 2 decades, since the founding of Atmospheric Chemistry and Physics. The emphasis here is on chemistry, but we also discuss recent findings on atmospheric dynamics and forcings to the extent that these are important for understanding MLT composition and chemistry. Topics that are covered include observations, with satellite, rocket and ground-based techniques; the variability and connectedness of the MLT on various length scales and timescales; airglow emissions; the cosmic dust input and meteoric metal layers; and noctilucent/polar mesospheric ice clouds. The paper then concludes with a discussion of important unanswered questions and likely future directions for the field over the next decade.

Dominant role of charged meteoric smoke particles in the polar mesospheric clouds

“…The charged-MSPs have also been proposed as candidates for ice nuclei, given that the charges on MSPs can effectively reduce the critical radius (rc) at low temperatures (Gumbel and Megner, 2009;Megner and Gumbel, 2009). However, the variability, distribution and charging process of MSPs remain unclear (Antonsen et al, 2017;Dawkins et al, 2023;Hervig et al, 2022;Knappmiller et al, 2011;Li et al, 2022), and this proposal has not yet gained widespread support (Duft et al, 2019;Plane et al, 2023). The mobility of electrons is much greater than that of positive ions, so MSPs in the upper mesosphere tend to collect electrons, with rocket-borne measurements showing that about 10% of MSPs are negatively charged (Plane et al, 2014;Robertson et al, 2014).…”

Responses of Mesosphere Temperature to the Geomagnetic Storms on 8 and 15 September 2003

“…Fagundes et al (1996) proposed that storms do not impact the nocturnal mesosphere temperature at low latitudes. While, other researches (e.g., Plane et al, 2023;Sinnhuber et al, 2012) argued that geomagnetic storms could impact the mesosphere through ionization of the major constituents, especially at high latitudes. Unfortunately there is no events reported that storms affect the mesosphere temperature at high latitudes.…”

Experimental modeling of atmospheric discharge phenomena and charged dust particle interactions

“…For a detailed exploration of these processes, readers are referred to the comprehensive literature (J. Plane et al (2023)).…”