A plasma channel is a conductive channel of
plasma. A plasma channel can be formed in the following ways.
# With a high-powered
laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word ''laser'' originated as an acronym for light amplification by stimulated emission of radi ...
that operates at a certain
frequency
Frequency is the number of occurrences of a repeating event per unit of time. Frequency is an important parameter used in science and engineering to specify the rate of oscillatory and vibratory phenomena, such as mechanical vibrations, audio ...
that will provide enough energy for an
atmospheric gas to break into its
ion
An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...
s, or form a plasma, such as in a
Laser-Induced Plasma Channel, for example in an
electrolaser
An electrolaser is a type of electroshock weapon that is also a directed-energy weapon. It uses lasers to form an electrically conductive ''laser-induced plasma channel'' (LIPC). A fraction of a second later, a powerful electric current is sent ...
.
# With a voltage higher than the
dielectric breakdown
In electronics, electrical breakdown or dielectric breakdown is a process that occurs when an electrically insulating material (a dielectric), subjected to a high enough voltage, suddenly becomes a conductor and current flows through it. All ...
voltage applied across a dielectric, and dielectric breakdown occurs.
A plasma channel has a low
electrical resistance
The electrical resistance of an object is a measure of its opposition to the flow of electric current. Its reciprocal quantity is , measuring the ease with which an electric current passes. Electrical resistance shares some conceptual paral ...
and, once formed, will permit continuous
current flow if the energy source that heats the plasma can be maintained. Unlike a normal electrical conductor, the resistance (and voltage drop) across an unconfined plasma channel decreases with increasing current flow, a property called
negative resistance. As a result, an
electric spark
An electric spark is an abrupt electrical discharge that occurs when a sufficiently high electric field creates an Ionization, ionized, Electric current, electrically conductive channel through a normally-insulating medium, often air or other ga ...
that initially required a very high voltage to initiate
avalanche breakdown
Avalanche breakdown (or the avalanche effect) is a phenomenon that can occur in both insulating and semiconducting materials. It is a form of electric current multiplication that can allow very large currents within materials which are otherwis ...
within the insulating gas will rapidly evolve into a hot, low-voltage
electric arc
An electric arc (or arc discharge) is an electrical breakdown of a gas that produces a prolonged electrical discharge. The electric current, current through a normally Electrical conductance, nonconductive medium such as air produces a plasma ( ...
if the electrical power source can continue to deliver sufficient power to the arc. Plasma channels tend to self constrict (see
plasma pinch) due to
magnetic force
Magnetism is the class of physical attributes that occur through a magnetic field, which allows objects to attract or repel each other. Because both electric currents and magnetic moments of elementary particles give rise to a magnetic field, m ...
s stemming from the current flowing through the plasma.
On Earth, plasma channels are most frequently encountered in
lightning
Lightning is a natural phenomenon consisting of electrostatic discharges occurring through the atmosphere between two electrically charged regions. One or both regions are within the atmosphere, with the second region sometimes occurring on ...
storms.
References
Channel, plasma
Electromagnetism
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