Effects of space environment on path loss for stratospheric channels

Abstract

Today, 6th generation (6G) networks are being developed, and the number of studies in this field is increasing. It is thought that high-speed and wide-coverage communication, which has been targeted for many years, will be possible with the development and dissemination of High Altitude Platform Stations (HAPS) models. HAPS are facilities designed to be positioned between 20 and 50 km above the sea level and serve as an intermediary to transmit electromagnetic waves between Low Earth Orbit (LEO) satellites. As electromagnetic waves travel between HAPS and LEO satellites, they progress through the ionosphere, one of the Earth's layers. The ionosphere is one of the upper layers of the earth's atmosphere and is considered to start at approximately 50 km above the sea level and continue up to an altitude of 1000 km. These altitudes can change under the effects of many different factors, such as temperature, space weather conditions, and seasonal effects. The ionosphere is the part of the Earth's atmosphere where ions and free electrons are observed. Factors that we generally call space weather or the environment interact with molecules in the atmosphere and cause them to ionize or release their electrons. These ionized molecules, or released electrons, cause the reflection of electromagnetic waves. The biggest question mark in the design of HAPS-LEO satellite models that have emerged in recent years for the development of 6G technology is the effects of free electrons in the ionosphere on the electromagnetic waves of these HAPS-LEO satellite models that will move through the ionosphere. Since the density of free electrons in the ionosphere depends on many different parameters, detailed and comparative analyses are needed to predict and draw definitive conclusions on their effects. In this study, all the factors related to space weather or space environment that may affect the free electron density in the ionosphere are examined, and the path loss they will cause on the electromagnetic wave that will travel through the ionosphere is analyzed. First of all, the effects of solar activities, cosmic rays, and the Earth's magnetosphere on ionization and free electron density in the ionosphere, which are within the scope of space weather, are investigated. Cosmic rays in the interstellar medium have very high energy, and their sources are thought to be supernovae and radio galaxies. Although they have high energy, their effect on the free electron density in the ionosphere is not very large and was not taken into account in this study.