Research ArticleGEOPHYSICS

Relativistic electrons generated at Earth’s quasi-parallel bow shock

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Science Advances  03 Jul 2019:
Vol. 5, no. 7, eaaw1368
DOI: 10.1126/sciadv.aaw1368
  • Fig. 1 Evolution of magnetic field lines around a foreshock bubble in the GSE-XY plane (z = 0): Results of a hybrid simulation.

    (A) to (C) are at t = 364, 393, and 421 s, respectively. Colors denote field strength in nanotesla. The vertical dashed black line represents the position of the RD except when it interacts with the bow shock [indicated by the dashed white line in (A)]. The solid black lines represent solar wind magnetic field lines.

  • Fig. 2 THEMIS observations of a foreshock bubble.

    From top to bottom: (A) magnetic field in GSE coordinates (X, Y, Z, and total are in blue, green, red, and black, respectively); (B) electron density (e Density) from the onboard moment (black) and calculated from the high-resolution spacecraft potential (blue); (C) ion energy flux (i+ Eflux); (D) ion bulk velocity along the foreshock bubble shock normal Vn (n = [0.91, 0.24, −0.31] in GSE) compared with ion bulk velocity in GSE-X (blue); (E) ion bulk velocity tangential to the foreshock bubble shock normal Vt and bulk velocity in GSE-YZ (green and red, respectively); (F) electron PSD (e PSD) spectrum from 30 to 700 keV (9 s smoothed to lower noise level; for unsmoothed spectrum, see fig. S2B); (G) electron PSD spectrum from 10 eV to 25 keV. The solid purple line indicates the smoothed magnetic field strength scaled by a factor of 100 for comparison with the PSD spectrum contour (dotted line). The expansion region and the compression region are labeled in the core and separated by a vertical dotted line. The colored vertical dashed lines indicate the times at which electron PSD in Fig. 3 is measured.

  • Fig. 3 Electron PSD in various regions.

    (A to C) PSD in directions perpendicular, parallel, and anti-parallel to the magnetic field, respectively. The PSD from 30 to 700 keV is smoothed over 9 s to lower the instrument noise level. The colors correspond to the colored vertical dashed lines in Fig. 2. The dotted lines indicate the slopes, −3 and −4. The dashed lines indicate the noise levels for two particle instruments.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/7/eaaw1368/DC1

    Additional events

    Fig. S1. Energy increase ratio versus field strength increase ratio.

    Fig. S2. The unsmoothed electron PSD spectrum from 30 to 700 keV and the PSD ratio of perpendicular to parallel and anti-parallel directions from 10 eV to 25 keV.

    Fig. S3. Electron distributions corresponding to the colored vertical dashed lines in Figs. 2 and 3.

    Fig. S4. THEMIS observations of event 2.

    Fig. S5. Electron PSD from event 2.

    Fig. S6. THEMIS observations of event 3.

    Fig. S7. Electron PSD from event 3.

    Movie S1. Hybrid simulation results of magnetic field evolution of a foreshock bubble.

  • Supplementary Materials

    The PDF file includes:

    • Additional events
    • Fig. S1. Energy increase ratio versus field strength increase ratio.
    • Fig. S2. The unsmoothed electron PSD spectrum from 30 to 700 keV and the PSD ratio of perpendicular to parallel and anti-parallel directions from 10 eV to 25 keV.
    • Fig. S3. Electron distributions corresponding to the colored vertical dashed lines in Figs. 2 and 3.
    • Fig. S4. THEMIS observations of event 2.
    • Fig. S5. Electron PSD from event 2.
    • Fig. S6. THEMIS observations of event 3.
    • Fig. S7. Electron PSD from event 3.
    • Legend for movie S1

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    Other Supplementary Material for this manuscript includes the following:

    • Movie S1 (.avi format). Hybrid simulation results of magnetic field evolution of a foreshock bubble.

    Files in this Data Supplement:

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