The effect of the guide field on energy conversion during collisionless magnetic reconnection

Abstract

It is well known that magnetic reconnection is an efficient mechanism to transfer magnetic energy into plasma energy. However, how the energy conversion and partition between different species are influenced by the shear angle of the reconnecting magnetic component (i.e., the guide field strength) is not well understood. Employing 2.5-D particle-in-cell simulations, we investigate the energy conversion in reconnection with different guide fields. We find that the overall energy conversion first decreases steeply and then increases slowly when the guide field increases from B_g = 0 to 4. The increase of the energy conversion in large guide field regime is due to the electron energy gain through the perpendicular channel J_⊥⋅E_⊥. The overall energy conversion is predominantly contributed by J_⊥ 〖⋅E〗_⊥ rather than J_∥ E_∥. We further find that energy conversion mainly occurs within the reconnection front and the flux pileup region. However, the contribution from the fore reconnection front becomes important in large guide field regimes (3<B_g≤4) due to the enhanced electron energy gain.