Observations of double layers in earth's plasma sheet

Area of Science:

• Space Physics
• Plasma Physics
• Magnetospheric Physics

Background:

• Double layers (DLs) are structures known to accelerate charged particles.
• Previous observations of parallel electric fields within DLs were primarily in Earth's auroral region.
• The plasma sheet is a dynamic region within Earth's magnetosphere, crucial for understanding space weather.

Purpose of the Study:

• To report the first direct observations of parallel electric fields (E_{ parallel}) associated with double layers (DLs) in Earth's magnetosphere plasma sheet.
• To investigate the occurrence and characteristics of DLs in different plasma sheet regions.
• To assess the implications of these observations for understanding plasma behavior in the magnetosphere.

Main Methods:

• Direct in-situ measurements by the THEMIS spacecraft.
• Analysis of electric field and plasma data within the magnetosphere's plasma sheet.
• Identification of double layer signatures during specific plasma phenomena.

Main Results:

• Direct observations of parallel electric fields (E_{ parallel}) carried by double layers (DLs) were made in the plasma sheet.
• DLs were observed in conjunction with bursty bulk flow events, the current sheet, and the plasma sheet boundary layer.
• The observed E_{ parallel} signals in the plasma sheet were analogous to those found in the auroral region.

Conclusions:

• Double layers (DLs) appear to be a universal phenomenon in Earth's magnetosphere, not limited to the auroral zone.
• The presence of DLs in the plasma sheet indicates that strongly nonlinear and kinetic plasma behaviors are intrinsic to this region.
• These findings enhance our understanding of energy transfer and particle acceleration processes within the magnetosphere.