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A Long-Lived Relativistic Electron Storage Ring Embedded in Earth’s Outer Van Allen Belt

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Science  12 Apr 2013:
Vol. 340, Issue 6129, pp. 186-190
DOI: 10.1126/science.1233518

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  1. Fig. 1 Relativistic Electron Probe Telescope data.

    Energetic electron data from the RBSP satellites in eccentric orbits around Earth showing several discrete energy channels of the REPT instruments on board the spatially separated RBSP-A and RBSP-B spacecraft. Each panel’s left y axis shows the L* parameter; the x axis shows time from 1 September to 4 October 2012. Electron differential flux values (in units of electrons per square centimeter·second·steradian·megaelectron volt) are in a color-coded logarithmic scale as shown to the right of the figure. (A) Electrons in the energy range 3.2 ≤ E ≤ 4.0 MeV. (B) Electrons with 4.0 ≤ E ≤ 5.0 MeV. (C) Electrons with 5.0 ≤ E ≤ 6.2 MeV.

  2. Fig. 2 Meridional plane projections.

    Projections of the REPT-A and REPT-B electron flux (4.0 to 5.0 MeV) values, as shown according to the logarithmic color scale to the right of the figure. Each panel shows a limited interval of time in a magnetic latitude L* coordinate system. (A) For 1 to 3 September 2012, the expected two-belt Van Allen zone structure consists of an inner-zone electron population (L* < ~2.5), a relatively empty slot region (2.5 < L* < 3.0), and an outer-zone population (L* > 3.0). (B) From 3 to 6 September, only an intense belt of electrons remains in the range 3.0 < L* < 3.5; the inner zone and traditional slot region have not changed. (C) The storage-ring belt, or torus, feature persists at 3.0 < L* < 3.5, whereas a new slot region is seen at 3.5 < L* < 3.8, and a completely new outer-zone population has formed at L* > 3.8. (D) The storage-ring feature remains, whereas the outer zone at L* > 3.8 decays away. (E) The entire outer zone (L* > ~3.0) has virtually disappeared at these energies.

  3. Fig. 3 Development of the storage ring.

    (A) Image similar to Fig. 1B, but also including the plasmapause, the outer boundary of the plasmasphere (26) for the period 1 September to 7 October 2012. The white curve overplotted on the color-coded electron particle flux data in Fig. 3A shows the modeled, 3-day averaged plasmapause radial location that is in agreement with concurrent plasma wave data (17, 27, 28). (B) Concurrently measured solar wind speed upstream of Earth’s magnetosphere. (C) Interplanetary magnetic field for the interval under study. |B|, the magnitude of the interplanetary magnetic field components parallel to the ecliptic in nanotesla (nT); Bz, the values of the components perpendicular. (D) Geomagnetic activity index (Dst) for the period under study.

  4. Fig. 4 Radiation belt structures.

    Diagrams providing a cross-sectional view of Earth’s radiation belt structure and relation to the plasmasphere. (A) Schematic diagram showing Earth, the outer and inner radiation belts, and the normal plasmaspheric location. (B) Similar to (A), but showing a more highly distended plasmasphere and unexpected triple radiation belt properties during the September 2012 period. The radiation belts are really “doughnut-” or torus-shaped entities in three dimensions. Earth is portrayed at the center. White denotes the highest electron fluxes; blue indicates the lowest fluxes. The translucent green overlay denotes the plasmasphere.