Details

Autor(en) / Beteiligte

• Zhou, Chen
• Yang, Guobin
• Ni, Binbin
• Zhao, Zhengyu
• Hu, Ze-jun
• Shi, Run

Titel

Strong diffusion limit in the realistic magnetosphere: Dependence on geomagnetic condition and spatial location

Ist Teil von

• Journal of geophysical research. Space physics, 2013-01, Vol.118 (1), p.118-131

Ort / Verlag

Washington: Blackwell Publishing Ltd

Erscheinungsjahr

2013

Quelle

Wiley-Blackwell Journals

Beschreibungen/Notizen

• As an essential concept of resonant wave‐particle interactions, the strong diffusion limit DSD is an important variable to explore the efficiency of wave‐induced pitch angle scattering for particle precipitation loss to the atmosphere. Determined by the size of equatorial loss cone on a given field line and the bounce period at a given energy, the value of DSD sets a lower limit to the precipitation timescale for loss cone filling, regardless of the strength of wave‐particle interactions. However, no efforts have ever been made to evaluate DSD in the realistic magnetosphere considering the impact of various geomagnetic activities. To perform a systematic exploration of the dependence of DSD on geomagnetic condition, spatial location, and global magnetic field model, we have numerically computed DSD using the dipolar and non‐dipolar Tsyganenko magnetic field models under three representative (quiet, moderate, and active) geomagnetic conditions. Use of more realistic Tsyganenko magnetic field models introduces non‐negligible or considerable differences in DSD magnitude from that obtained using a dipolar field. The difference can be over an order of magnitude at the field lines with equatorial crossings ≥6 Re during geomagnetically disturbed times. We also report that in the realistic magnetosphere both DSD magnitude and its variations have a strong dependence on the spatial location. Computed DSD shows the maximum tending to occur on the dayside (MLT = 12 and 16) and the minimum DSD more likely to occur at MLT = 00. Compared to the dipolar results, largest deviation in DSD occurs for MLT = 00, 04, and 20, while DSD variations on the dayside are relatively small. Our results demonstrate that accurate evaluation of DSD besides scattering rates in the realistic magnetosphere, especially at high spatial locations and under geomagnetically disturbed conditions for which a dipolar approximation fails, can make an important contribution to quantifying the wave effect on particle resonant diffusion, which should be incorporated into future modeling efforts for comprehending the role of resonant wave‐particle interactions and the dynamics of magnetospheric electrons under a variety of geomagnetic conditions. Key Points SD is computed by four magnetic field models for three geomagnetic conditions SD is strongly dependent on geomagnetic activity and spatial location Accurate SD is important to modeling magnetospheric electron dynamics