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Full-Text Articles in Physics

Topology Of Earth's Magnetic Shield, David Alan Smith Dec 2017

Topology Of Earth's Magnetic Shield, David Alan Smith

David Smith

The open-closed boundary (OCB) defines the region where geomagnetic field lines transition from being closed to open. Closed field lines have both foot points at or near Earth in opposing hemispheres. Open field lines have one foot point at Earth; the other maps to the interplanetary magnetic field (IMF). Charged particles are able to follow these open field lines into Earth's upper atmosphere. The OCB also defines the polar cap boundary. Being able to identify and track the OCB allows study of several components of the geomagnetic system. Among them are the electrodynamics of the geomagnetic field and the ...


A Review Of High Frequency Radio Wave Absorption, David Alan Smith Dec 2016

A Review Of High Frequency Radio Wave Absorption, David Alan Smith

David Smith

Although the technology dates back nearly to Marconi and his wireless telegraph, the high-frequency (HF) radio spectrum continues to be a useful communications medium.  Since long-distance HF propagation depends on the ionosphere, HF propagation is subject to variations in ionospheric characteristics.  Chief among these characteristics is the density of free electrons.  The sun provides the energy required to ionize neutral atmospheric constituents.  Hence, the production and loss of free electrons is not constant.  Day/night variations as well as the ebb and flow of the 11-year solar cycle cause changes in the density of free electrons.  In addition, space weather ...