Abstract
Abstract. The formation of ice particle density irregularities with a meter scale in the mesopause region is explored in this paper by developing a growth and motion model of ice particles based on the motion equation of a variable mass object. The growth of particles by water vapor adsorption and the action of gravity and the neutral drag force on particles are considered in the model. The evolution of the radius, velocity, and number density of ice particles is then investigated by solving the growth and motion model numerically. For certain nucleus radii, it is found that the velocity of particles can be reversed at a particular height, leading to a local gathering of particles near the boundary layer, which then forms small-scale ice particle density structures. The spatial scale of the density structures can be affected by vertical wind speed, water vapor density, and altitude, and it remains stable as long as these environmental parameters do not change. The influence of the stable small-scale structures on electron and ion density is further calculated by a charging model, which considers the production, loss, and transport of electrons and ions, along with dynamic particle charging processes. Results show that the electron density is anti-correlated to the charged ice particle density and ion density for particles with radii of 11 nm or less due to plasma attachment by particles and plasma diffusion. This finding is in accordance with most rocket observations. The small-scale electron density structures created by small-scale ice particle density irregularities can produce the polar mesosphere summer echo (PMSE) phenomenon.
Highlights
Polar mesosphere summer echoes (PMSEs) are strong radar echoes from the polar mesopause in summer (Rapp and Lübken, 2004)
A growth and motion model of ice particles was developed based on the equation of variable mass object motion in order to explain the formation of ice particle density irregularities with a meter scale in the polar mesopause region
For a certain radius of the condensation nucleus, ice particles can bounce near the boundary layer, which leads to a local gathering phenomenon of ice particles and the creation of meter scale ice particle density structures
Summary
Polar mesosphere summer echoes (PMSEs) are strong radar echoes from the polar mesopause in summer (Rapp and Lübken, 2004). The size of initial condensation nuclei has a certain distribution These factors can cause complex trajectories of ice particles and result in an inhomogeneous distribution of particle number density, leading to small-scale structures of electron density. The water vapor is supersaturated in the polar mesopause region (Lübken, 1999), and it is assumed that the size of condensation nuclei is larger than the condensation critical size, so stable growth of ice particles will continue when water molecules collide with particles during thermal motion. The particles continue to enter and leave the condensation region, and as long as the external environment does not change, the distribution of particle density and radius will remain unchanged The influence of these stable nd and rd profiles on electron and ion density is calculated.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
