Ever noticed that out of all the things we see around us most of them are either a solid, liquid or gas? We know that a rock is a solid, oil is a liquid and the air around us is in gaseous state as we can perceive them and often come across in our daily life. But are three states enough to categorize everything around us? Or is there a way to create new states ?

The greatest scholars earlier noticed the basic difference between each state is the total kinetic and potential energy of its molecules, and a change of state can be brought about by providing enough kinetic energy to the molecules which lead to rise of the three states of matter – Solid, liquid and gas. But things got really interesting when a solid was further cooled, or a gas was further heated giving birth to the super-heated Plasma, and the super-cooled Bose-Einstein Condensate.

One of these hypothetical states exists during a phenomenon called Corona Discharge. When a conductor is carrying current, the current flows through it without escaping to the air around it, as the air is an insulator. But the whole picture changes, when we increase the amount of potential drop, then the insulator becomes a conductor. As we all know every material has a breakdown point, so does the air around the conductor which completely disintegrates into positively charged ions having nucleus and negatively charged electrons after the voltage drop exceeds a certain limit. Henceforth the air acts as a conducting medium in which the conductor tends to repel the nucleus and simultaneously attract the ejected electrons. This type of phenomenon in which electric discharge occurs around the conductor is said to be Corona Discharge. The effect is not very dominant and tends to be negligible after a certain distance from the conductor. The intensity of this effect also depends upon- air density, presence of ions, the conductor used and the amount of voltage supplied (which should be more than the critical disruptive voltage for that medium).

However, it causes a lot of problems too like power loss in the form of heat, humming noise and pinkish-blue light, causes electromagnetic interference to nearby electronic devices, results in production of ozone and NOx gases, causes noise pollution, and emits visible and ultraviolet light; produces dangerous electrical winds and induces vibrations. For example, one can hear humming noises near the transformer setups of the city electrical supply. The Corona Discharge can be reduced by increasing the conductor size, increasing the distance between the conductors, using bundled conductors and by using corona rings at regular intervals.

Still in a lot of processes we intentionally use it like creation of artificial plasmas, plasma chromatography and gas diagnosis, ignition of vehicles, electrostatic apparatus (as active chargers), etc. The recent advancements have proved corona discharge to have much more potential to that can be used like surface treatment and modifications of different substances, pseudo-sparks and pulse-based generator for corona-assisted combustion, heat dissipation (a silent electronics cooling), cleaning surfaces from organic impurities, reforming H2 rich synthesis gas, formation of electric barriers, etc.

Most significant advancement in the application of corona discharge is Corona spark plug system. Usually, discharge consists of many streamers which produce plasma that contains almost ∼ 10 eV electrons which is much greater than normal sparks (∼ 1 eV). In this system, we use two plug electrodes such that when high voltage is applied, corona wind is produced. This corona wind initiates the spark and also carries the ignited mixture away from both electrodes in order to reduce heat loss and ensure better combustion. Compared to conventional spark ignition, flames ignited by a short-pulse corona discharge have a shorter delay time, faster pressure-rise time, higher maximum pressure, and more complete combustion.

Nevertheless, corona discharges have some very harmful outcomes, but none can deny that they have a very prevalent effect in the coming years. They might become our stepping stones to advanced energy producing or conversion techniques and might even help us in inter-planetary travelling. Although corona discharge causes a lot of problems still it has proven to be beneficial in various fields and has endless potential which is yet to be discovered.