Kinetic electric fields associated with the Earth's dayside magnetopause reconnection: THEMIS observations
Thursday, October 1, 2015
Daiki Koga1, Walter D Gonzalez1, Forrest Mozer2, Marcos V Dias Silveira1 and Flavia R Cardoso3, (1)INPE National Institute for Space Research, Sao Jose dos Campos, Brazil, (2)University of California Berkeley, Berkeley, CA, United States, (3)Escola de Engenharia de Lorena/Universidade de Sao Paulo-EEL/USP, São Paulo, Brazil
Abstract:
We investigate a kinetic electric field associated with asymmetric reconnection at the Earth’s dayside magnetopause using THEMIS observations. On July 20, 2007, three THEMIS satellites detected an asymmetric collisionless reconnection event. This event shows a unipolar Hall electric field signature and a simple deviation from the guide field during the magnetopause crossing. As expected from PIC simulations by Malakit et al. (2013), an earthward pointing normal electric field appears in the magnetospheric side of the ion diffusion region. The electric field satisfies two necessary conditions for the existence of the “Larmor” electric field: 1) the ion Larmor radius (rg2) is larger than the distance between the stagnation point and the edge of the ion diffusion region in the strong magnetic field side (δS2), and 2) the spatial extent of the kinetic electric field (δEL) is of the order of the ion Larmor radius. Furthermore, it is shown that the peak value and size of the Larmor electric field are comparable to the predicted value.
