The Heaviside Layer, also known as the Kennelly–Heaviside Layer, is a region of the Earth's ionosphere that reflects radio waves. Its name is derived from Oliver Heaviside, a British mathematician and physicist, and Arthur Edwin Kennelly, an American electrical engineer. The correct spelling of this term is [ˈhɛvɪsaɪd ˌleɪər]. The "Heaviside" part is pronounced with a short "e" sound, represented by the IPA symbol /ɛ/, while the "Layer" part is pronounced with a long "a" sound, represented by the IPA symbol /eɪ/.
The Heaviside Layer refers to a region in the Earth's upper atmosphere, specifically found within the ionosphere, which is a portion of the atmosphere that is ionized by solar radiation. Named after the British physicist Oliver Heaviside, the Heaviside Layer is also known as the Kennelly-Heaviside Layer, as it was simultaneously discovered by Arthur E. Kennelly.
Situated at an altitude ranging between 90 and 150 kilometers (55 to 90 miles) above the Earth's surface, the Heaviside Layer is characterized by a high concentration of free electrons that result from the ionization process. These free electrons play a crucial role in the propagation of radio waves, as they reflect or refract radio signals, enabling long-distance communication.
Due to its ability to refract radio waves, the Heaviside Layer serves as an important communication medium for long-distance wireless transmissions. Its presence allows radio waves to be bent back towards the Earth's surface, enabling them to travel beyond the line of sight. This phenomena, known as skywave propagation, is utilized in various applications including long-range broadcasting, air traffic control, and even military communication.
The Heaviside Layer's height and density can vary depending on a range of factors such as the time of day, season, and solar activity. Understanding its characteristics is of great importance for radio engineers and telecommunications experts to optimize the effectiveness and reliability of long-range radio communications.
The term "Heaviside Layer" is named after the English electrical engineer and physicist Oliver Heaviside. Oliver Heaviside made significant contributions to the study of electromagnetic theory and transmission of telegraph signals in the late 19th and early 20th centuries.
Heaviside adopted the concept of an electrically conductive layer in the upper atmosphere, also known as the Kennelly–Heaviside layer. This layer was independently proposed by Arthur E. Kennelly and Oliver Heaviside around the same time in the early 1900s. However, the term "Heaviside Layer" gained more popularity and is commonly used to refer to this layer.
The prefix "Heavi-" in "Heaviside Layer" comes from the last name of Oliver Heaviside, while "side" simply refers to the layer's presence in the upper atmosphere.