Abstract
By performing twodimensional particleincell simulations, we investigate the transfer between electron bulk kinetic and electron thermal energy in collisionless magnetic reconnection. In the vicinity of the X line, the electron bulk kinetic energy density is much larger than the electron thermal energy density. The evolution of the electron bulk kinetic energy is mainly determined by the work done by the electric field force and electron pressure gradient force. The work done by the electron gradient pressure force in the vicinity of the X line is changed to the electron enthalpy flux. In the magnetic island, the electron enthalpy flux is transferred to the electron thermal energy due to the compressibility of the plasma in the magnetic island. The compression of the plasma in the magnetic island is the consequence of the electromagnetic force acting on the plasma as the magnetic field lines release their tension after being reconnected. Therefore, we can observe that in the magnetic island the electron thermal energy density is much larger than the electron bulk kinetic energy density.
This work was supported by the National Science Foundation of China (NSFC) under Grant Nos. 41174124 and 41121003, 973 Program (2013CBA01503, 2012CB825602), Ocean Public Welfare Scientific Research Project, State Oceanic Administration People's Republic of China (No. 201005017), and the Fundamental Research Funds for the Central Universities (WK2080000010).
I. INTRODUCTION
II. SIMULATION MODEL
III. SIMULATION RESULTS
IV. CONCLUSIONS
Key Topics
 Magnetic reconnection
 27.0
 Magnetic islands
 25.0
 Energy transfer
 16.0
 Enthalpy
 13.0
 Magnetic fields
 9.0
Figures
Contours of the electron bulk kinetic energy density for the cases (a) at and (b) at . In the figure, the magnetic field lines are also plotted for reference. The electron bulk kinetic energy density is normalized by .
Contours of the electron bulk kinetic energy density for the cases (a) at and (b) at . In the figure, the magnetic field lines are also plotted for reference. The electron bulk kinetic energy density is normalized by .
Contours of the electron thermal energy density for the cases (a) at and (b) at . In the figure, the magnetic field lines are also plotted for reference. The electron bulk kinetic energy density is normalized by .
Contours of the electron thermal energy density for the cases (a) at and (b) at . In the figure, the magnetic field lines are also plotted for reference. The electron bulk kinetic energy density is normalized by .
Time evolutions of the righthandside terms of Eq. (3) integrated in the selected region denoted with red rectangles (in the vicinity of the X line) in Figs. 1 and 2 for the cases (a) and (b) , respectively. The green curve represents the electron bulk kinetic energy flux term , the red curve denotes the power density of the work done by the electric field , and the power density of the work done by the electron pressure gradient is described by the blue curve. The black curves are the sums of the three terms. All these terms are normalized by .
Time evolutions of the righthandside terms of Eq. (3) integrated in the selected region denoted with red rectangles (in the vicinity of the X line) in Figs. 1 and 2 for the cases (a) and (b) , respectively. The green curve represents the electron bulk kinetic energy flux term , the red curve denotes the power density of the work done by the electric field , and the power density of the work done by the electron pressure gradient is described by the blue curve. The black curves are the sums of the three terms. All these terms are normalized by .
Time evolutions of the righthandside terms of Eq. (4) integrated in the selected region denoted by red rectangles (in the vicinity of the X line) in Figs. 1 and 2 for the cases (a) and (b) . The green, blue, and red curves represent the electron enthalpy flux term , the electron heat flux term , and the thermal energy source term , respectively. The black curves are the sums of the three terms. All these terms are normalized by .
Time evolutions of the righthandside terms of Eq. (4) integrated in the selected region denoted by red rectangles (in the vicinity of the X line) in Figs. 1 and 2 for the cases (a) and (b) . The green, blue, and red curves represent the electron enthalpy flux term , the electron heat flux term , and the thermal energy source term , respectively. The black curves are the sums of the three terms. All these terms are normalized by .
Time evolutions of the righthandside terms of Eq. (4) integrated in the selected region denoted by black rectangles (in the magnetic island) in Fig. 2 for the cases (a) and (b) . The green, blue, and red curves represent the electron enthalpy flux term , the electron heat flux term , and the thermal energy source term , respectively. The black curves are the sums of the three terms. All these terms are normalized by .
Time evolutions of the righthandside terms of Eq. (4) integrated in the selected region denoted by black rectangles (in the magnetic island) in Fig. 2 for the cases (a) and (b) . The green, blue, and red curves represent the electron enthalpy flux term , the electron heat flux term , and the thermal energy source term , respectively. The black curves are the sums of the three terms. All these terms are normalized by .
Tables
The difference in the ion and electron kinetic energy in magnetic reconnection. denotes the ion kinetic energy (it includes the ion bulk kinetic energy and ion thermal energy), and denotes the electron kinetic energy (it includes the electron bulk kinetic energy and electron thermal energy). The electron bulk kinetic energy is denoted by , and the electron thermal energy is denoted by . “D” means the energy difference, which is calculated by subtracting the energy, when the reconnection attains its maximum rate, to its initial value. The energy is integrated over the entire simulation domain, and it is normalized by . An approximate conservation of the total energy is kept in our simulation models, and the percentage of energy nonconservation is within 0.4%.
The difference in the ion and electron kinetic energy in magnetic reconnection. denotes the ion kinetic energy (it includes the ion bulk kinetic energy and ion thermal energy), and denotes the electron kinetic energy (it includes the electron bulk kinetic energy and electron thermal energy). The electron bulk kinetic energy is denoted by , and the electron thermal energy is denoted by . “D” means the energy difference, which is calculated by subtracting the energy, when the reconnection attains its maximum rate, to its initial value. The energy is integrated over the entire simulation domain, and it is normalized by . An approximate conservation of the total energy is kept in our simulation models, and the percentage of energy nonconservation is within 0.4%.
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