Abstract
Localized plasma structures, such as thin current sheets, generally are associated with localized magnetic and electric fields. In space plasmas localized electric fields not only play an important role for particle dynamics and acceleration but may also have significant consequences on larger scales, e.g., through magnetic reconnection. Also, it has been suggested that localized electric fields generated in the magnetosphere are directly connected with quasisteady auroral arcs. In this context, we present a twodimensional model based on Vlasov theory that provides the electric potential for a large class of given magnetic field profiles. The model uses an expansion for small deviation from gyrotropy and besides quasineutrality it assumes that electrons and ions have the same number of particles with their generalized gyrocenter on any given magnetic field line. Specializing to one dimension, a detailed discussion concentrates on the electric potential shapes (such as “U” or “S” shapes) associated with magnetic dips, bumps, and steps. Then, it is investigated how the model responds to quasisteady evolution of the plasma. Finally, the model proves useful in the interpretation of the electric potentials taken from two existing particle simulations.
The work of J.B. was performed at Los Alamos National Laboratory, under the auspices of the U.S. Department of Energy with support by NASA through Grant Nos. NNG08EJ63I, NNH10A045I, and NNH11AQ42I. The work of M.H. was supported by NASA’s MMS mission.
I. INTRODUCTION
II. THE MODEL
III. THE EXPANSION
IV. EXAMPLES
V. SLOW EVOLUTION
VI. APPLICATION TO TWO EARLIER SIMULATIONS
VII. SUMMARY AND DISCUSSION
Key Topics
 Magnetic fields
 17.0
 Electric currents
 7.0
 Electric fields
 6.0
 Plasma expansion
 5.0
 Plasma sheets
 5.0
Figures
Two examples for magnetic dips. The solid and dashed curves shown in the upper graph correspond to two different choices for , picked arbitrarily except that they have the same parameter (in addition to symmetry, single extremum and ). The lower graph shows the corresponding electric potentials given by Eq. (33) with fixed also.
Two examples for magnetic dips. The solid and dashed curves shown in the upper graph correspond to two different choices for , picked arbitrarily except that they have the same parameter (in addition to symmetry, single extremum and ). The lower graph shows the corresponding electric potentials given by Eq. (33) with fixed also.
Parameter space vs. for magnetic dips and bumps as defined in the text. Shown are the regions that correspond to different qualitative shapes of the electric potential sketched inside the boxes. Same qualitative shapes are indicated by the same color. The region above the black curve is unphysical (negative plasma pressure), the green line separates magnetic dips () from magnetic bumps (), on the red curve changes sign, on the blue curve the two side minima on one side merge with the central extremum, and on the magenta line the side minima on one side disappear when their values reach 0.
Parameter space vs. for magnetic dips and bumps as defined in the text. Shown are the regions that correspond to different qualitative shapes of the electric potential sketched inside the boxes. Same qualitative shapes are indicated by the same color. The region above the black curve is unphysical (negative plasma pressure), the green line separates magnetic dips () from magnetic bumps (), on the red curve changes sign, on the blue curve the two side minima on one side merge with the central extremum, and on the magenta line the side minima on one side disappear when their values reach 0.
Two examples for magnetic steps. The solid and dashed curves shown in the upper graph correspond to two different choices for , picked arbitrarily except that they have the same parameter (in addition to monotonic increase with and ). The lower graph shows the corresponding electric potentials given by Eq. (33) with a fixed value of
Two examples for magnetic steps. The solid and dashed curves shown in the upper graph correspond to two different choices for , picked arbitrarily except that they have the same parameter (in addition to monotonic increase with and ). The lower graph shows the corresponding electric potentials given by Eq. (33) with a fixed value of
Parameter space vs. for magnetic steps. Shown are the regions that correspond to different qualitative shapes of the electric potential indicated in the boxes. Steps where decreases with (i.e., ) are left out, because these shapes can be reduced to corresponding shapes with by reversal of the axis and a renormalization.
Parameter space vs. for magnetic steps. Shown are the regions that correspond to different qualitative shapes of the electric potential indicated in the boxes. Steps where decreases with (i.e., ) are left out, because these shapes can be reduced to corresponding shapes with by reversal of the axis and a renormalization.
The figure provides an application of the present model to an earlier particle simulation (Section IV of Ref. 26, interval ). The upper graph shows the magnetic field profile. The lower graph gives the electric potential of the simulation (solid curve), the model curve based on simulation data (dashed line) and the adjusted model potential (finescale broken line). The parameter was determined by a minimum variance fit.
The figure provides an application of the present model to an earlier particle simulation (Section IV of Ref. 26, interval ). The upper graph shows the magnetic field profile. The lower graph gives the electric potential of the simulation (solid curve), the model curve based on simulation data (dashed line) and the adjusted model potential (finescale broken line). The parameter was determined by a minimum variance fit.
This figure corresponds to Figure 5 for the second simulation (Section V of Ref. 26). The parameter was determined by a minimum variance fit.
This figure corresponds to Figure 5 for the second simulation (Section V of Ref. 26). The parameter was determined by a minimum variance fit.
Article metrics loading...
Full text loading...
Most read this month
Most cited this month










Electron, photon, and ion beams from the relativistic interaction of Petawatt laser pulses with solid targets
Stephen P. Hatchett, Curtis G. Brown, Thomas E. Cowan, Eugene A. Henry, Joy S. Johnson, Michael H. Key, Jeffrey A. Koch, A. Bruce Langdon, Barbara F. Lasinski, Richard W. Lee, Andrew J. Mackinnon, Deanna M. Pennington, Michael D. Perry, Thomas W. Phillips, Markus Roth, T. Craig Sangster, Mike S. Singh, Richard A. Snavely, Mark A. Stoyer, Scott C. Wilks and Kazuhito Yasuike

Commenting has been disabled for this content