According to classical electromagnetism, all accelerating charged particles emit electromagnetic radiation. This phenomenon is explained by the laws of classical electrodynamics, particularly by the theory of classical electromagnetism formulated by James Clerk Maxwell.
Maxwell's equations describe the behavior of electric and magnetic fields and their interactions with charges and currents. One of these equations, known as the Maxwell-Faraday equation, states that a changing magnetic field induces an electric field. Similarly, the Ampere-Maxwell equation states that a changing electric field induces a magnetic field.
When a charged particle undergoes acceleration, its velocity changes, resulting in a changing electric field around the particle. This changing electric field, in accordance with Maxwell's equations, gives rise to a magnetic field. The interplay between the changing electric and magnetic fields generates electromagnetic waves, which are forms of electromagnetic radiation.
Classically, this radiation is referred to as "acceleration radiation" or "bremsstrahlung," which is German for "braking radiation." The emitted radiation carries away energy from the accelerating charged particle, causing it to lose energy and slow down.
This phenomenon can be explained using classical mechanics by considering the conservation of energy. As the charged particle accelerates, it gains kinetic energy, which must come from a corresponding loss of energy elsewhere. The emitted electromagnetic radiation carries away this energy, resulting in the particle losing speed or decelerating.
It's important to note that the classical explanation of the emission of electromagnetic radiation by moving charged particles is accurate for macroscopic objects with speeds much lower than the speed of light. At relativistic speeds, the classical approach is insufficient, and quantum electrodynamics is required to fully describe the behavior of charged particles and their interaction with electromagnetic fields.