Article

In situ discovery of an electrostatic potential, trapping electrons and mediating fast reconnection in the Earth's magnetotail.

Massachusetts Institute of Technology, Plasma Science Fusion Center, Cambridge, Massachusetts 02139, USA.
Physical Review Letters (Impact Factor: 7.73). 02/2005; 94(2):025006. DOI: 10.1103/PhysRevLett.94.025006
Source: PubMed

ABSTRACT Anisotropic electron phase space distributions, f, measured by the Wind spacecraft in a rare crossing of a diffusion region in Earth's far magnetotail (60 Earth radii), are analyzed. We use the measured f to probe the electrostatic and magnetic geometry of the diffusion region. For the first time, the presence of a strong electrostatic potential (1 kV) within the ion diffusion region is revealed. This potential has far reaching implications for the reconnection process; it accounts for the observed acceleration of the unmagnetized ions out of the reconnection region and it causes all thermal electrons be trapped electrostatically. The trapped electron motion implies that the thermal part of the electron distributions are symmetric around v( parallel)=0: f(v( parallel),v( perpendicular)) approximately f(-v( parallel),v( perpendicular)). It follows that the field aligned currents in the diffusion region are limited and fast magnetic reconnection is mediated.

0 Bookmarks
 · 
92 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Kinetic simulations and spacecraft observations have documented strong anisotropy in the electron distribution function during magnetic reconnection. The level and role of electron pressure anisotropy is investigated for asymmetric geometries applicable to reconnection in the day-side magnetopause. A previously derived analytic model for the pressure anisotropy is generalized and is applied to the asymmetric geometry. In agreement with the results from a kinetic simulation, the generalized model predicts the strongest pressure anisotropy and parallel electric fields in the in-flow region characterized by low electron pressure.
    Physics of Plasmas 10/2011; 18(10):102901-102901-8. · 2.38 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Based on the magnetic field and plasma data obtained by GEOTAIL in 1992–1995 and WIND in1994–2009, the magnetic field and plasma properties in the magnetotail near lunar orbit were studied statistically using the superposed epoch analysis. The results showed that near the 0° sector the plasma density was negatively correlated with Dst index while the temperature was positively correlated with Dst index. The plasma velocity and magnetic field strength had little correlation with Dst index. Around the current sheet near the lunar orbit, the B x varied between −15-15 nT, the plasma density was less than 0.4 cm−3, the median of plasma density for all events was less than 0.1 cm−3, the temperature varied from 0.016 to 8.98 keV, the median of the plasma temperature for all the events was ∼3 keV, the median of speed was about 200 km/s and the maximum speed was up to 1500 km/s. The tailward and earthward flows could be observed accompanied with the current sheet. For the current sheet cases with tailward flow, the B x varied from −15 to 15 nT, the upper quartile of plasma velocity was more than 400 km/s, the maximum speed was up to 1500 km/s. For the current sheet cases with tailward flow, the B x varied from −10 to 10 nT, the upper quartile of plasma velocity was less than 400 km/s, the maximum speed was up to 1200 km/s. The median of plasma density, temperature and velocity were similar for the two categories. This paper discussed the relationship between above results and magnetic reconnection at magnetic tail, compared the above results with the observation in the far magnetotail. We fitted the statistical results according to the Harris current sheet model, and the observation was consistent with Harris current sheet model. The above results can provide useful information for the design and protection of lunar-orbiting spacecraft and can be used as the background magnetic field and plasma parameters in the numerical simulation of mid-magnetotail reconnection.
    Science China Technological Sciences 55(9). · 1.19 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: There have been many significant advances in understanding magnetic field reconnection as a result of improved space measurements and two-dimensional computer simulations. While reviews of recent work have tended to focus on symmetric reconnection on ion and larger spatial scales, the present review will focus on asymmetric reconnection and on electron scale physics involving the reconnection site, parallel electric fields, and electron acceleration. KeywordsMagnetic field reconnection–Asymmetric reconnection–Electron acceleration–Electric fields
    Space Science Reviews 01/2011; 158(1):119-143. · 5.52 Impact Factor

Full-text

View
0 Downloads
Available from