Magnetic reconnection during collisionless , stressed , X-point collapse was studied using kinetic , 2.5D , fully electromagnetic , relativistic Particle-in-Cell numerical code .
Two cases of weakly and strongly stressed X-point collapse were considered .
Here descriptors weakly and strongly refer to 20 % and 124 % unidirectional spatial compression of the X-point , respectively .
In the weakly stressed case , the reconnection rate , defined as the out-of-plane electric field in the X-point ( the magnetic null ) normalised by the product of external magnetic field and Alfvén speeds , peaks at 0.11 , with its average over 1.25 Alfvén times being 0.04 .
During the peak of the reconnection , electron inflow into the current sheet is mostly concentrated along the separatrices until they deflect from the current sheet on the scale of electron skin depth , with the electron outflow speeds being of the order of the external Alfvén speed .
Ion inflow starts to deflect from the current sheet on the ion skin depth scale with the outflow speeds about four times smaller than that of electrons .
Electron energy distribution in the current sheet , at the high-energy end of the spectrum , shows a power law distribution with the index varying in time , attaining a maximal value of -4.1 at the final simulation time step ( 1.25 Alfvén times ) .
In the strongly stressed case , magnetic reconnection peak occurs 3.4 times faster and is more efficient .
The peak reconnection rate now attains value 2.5 , with the average reconnection rate over 1.25 Alfvén times being 0.5 .
Plasma inflow into the current sheet is perpendicular to it , with the electron outflow seeds reaching 1.4 Alfvén external Mach number and ions again being about four times slower than electrons .
The power law energy spectrum for the electrons in the current sheet attains now a steeper index of -5.5 , a value close to the ones observed near X-type region in the Earth ’ s magneto-tail .
Within about one Alfvén time , 2 % and 20 % of the initial magnetic energy is converted into heat and accelerated particle energy in the case of weak and strong stress , respectively .
In the both cases , during the peak of the reconnection , the quadruple out-of-plane magnetic field is generated , hinting possibly to the Hall regime of the reconnection .
These results strongly suggest the importance of the collisionless , stressed X-point collapse as an efficient mechanism of converting magnetic energy into heat and super-thermal particle energy .