Reconnection has been with us for a very long time, and although it has been happening very near our planet, people have been unaware of it.  As the Sun propels plasma particles at the Earth at supersonic speeds, the solar wind is diverted around the magnetosphere forming a bow shock just ahead of our planet like a wave in front of race boat speeding through the water. 

The boundary layer which separates the solar wind from the magnetosphere is called the magnetopause.  While the magnetosphere is there to protect the Earth from this solar offensive, it is not a perfect shield.  The magnetopause is more like a house with doors; just as a door can be opened to let in the outside air, a door at the magnetopause can be opened to let in solar plasma.  The doors are not continuously open though, because they open only under certain conditions.

The solar wind is constantly changing directions.  Sometimes the direction of the solar wind magnetic lines are directed in the opposite to those of the earthly magnetic lines of force.  When solar magnetic lines carried by the solar wind interconnect with Earth’s oppositely directed magnetic lines, the lines can break and recombine.  This reconnecting of oppositely directed magnetic lines is just exactly the event that opens doors.

This process that also converts energy at the nose of the magnetosphere was explained in1961 by James Dungey of England when he introduced the concept of "magnetic reconnection." At a point near the magnetospheric nose, the solar magnetic lines of force and the terrestrial magnetic lines of force break the no touchy rule and become intertwined.  The result is that solar plasma is injected into the terrestrial realm. 

Here we have two magnetic lines of force.  One belongs to the solar wind and the other belongs to the terrestrial field.  Notice that one is going from north to south, while the other is going from south to north.  At times these two lines are pinched together.

In a plasma if two magnetic field line going in opposite directions get close enough they can break and reconnect in what is called a X line.This causes magnetic stress which accelerates the plasma away from point where the lines intersect.  The reconnected lines snap like a rubber band with great force.  In the process terrestrial plasma and solar plasma mix.  What is more magnetic energy is convert to kinetic energy and heat.

In actuality the process is a little more complicated as a close up of the magnetic lines shows that they twist together like intertwining corkscrews. Scientists are still working on understanding exactly what is happening during this process.

Modification to the fields then allows solar plasma to flow across the magnetopause explosively as the magnetic energy is converted to kinetic energy and heat. This burst of energy is felt throughout the magnetosphere in the form of rolling global oscillations.  Only when the solar magnetic lines are oriented opposite the earthly magnetic lines does this magnetic reconnection takes place, so it is not a steady event because the solar wind is constantly changing directions.  The pressure of the solar wind against the magnetosphere is also constantly changing the shape of the magnetopause.  More pressure causes the Sun side of the magnetosphere to squish even tighter.  Pressure of the solar wind and its direction are the important ingredients in making reconnection happen.  Under these circumstances, the door of the magnetosphere opens to the solar plasma and the turbulent kinetic energy fills the magnetosphere. 

Sometimes magnetic reconnection occurs pole ward of the cusps. When the sun's magnetic fields becomes parallel but opposite in polarity to the Earth’s field, the lines can join up and allow the particles to flow easily along the joined lines down to the Earth's ionosphere.In addition to solar wind pressure and direction, magnetic reconnection can also change the shape of the magnetopause.  The entire magnetosphere oscillates during the reconnection process as waves propagate down the entire length.  

Associated with the pole ward of the cusp magnetic reconnection is strong turbulence in the form electrostatic waves generated by what today’s scientist call bump on tail instability. 

Magnetic reconnection can also occur at the X point in the neutral sheet when magnetic lines of opposite polarity are adjacent and very certain conditions are triggered.  On occasion these oppositely directed magnetic lines get pinched together.

Reconnection on the dayside of the magnetosphere opens field lines. The solar wind then drags the reconnected field lines from the dayside to the night side, allowing the solar plasma to pour into the tail of the magnetosphere. This drag stretches the field lines, and stores the energy in the form of magnetic tension. As the field lines pile up on the night side, the system becomes unstable. Reconnection happens again, this time in the middle of the tail; the recently open magnetic field lines reconnect to form closed field lines.

When this occurs, stored particles and energy are released with a snap both earthward and tail ward. These phenomena energize ions and electrons, injecting some 50% of them earthward of the X point. This causes other parts of the magnetosphere to become unstable.

Now the interplanetary field lines penetrate into the plasma sheet and meet at the X point reconnecting and causing the release of a large amount of kinetic energy and heat.   Like a stretched rubber band, part of this energy is flicked earthward: these flowing ions gain energy and penetrate the inner magnetosphere, while another part ("a plasmoid") is jettisoned away from Earth and the energy is lost into outer space.

Large electric currents then transfer the earthward directed energy from the X point to the poles along field align currents (FACs) and precipitate in the polar auroras.