Magnetosphere dynamics during the 14 November 2012 storm inferred from TWINS, AMPERE, Van Allen Probes, and BATS-R-US–CRCM

Abstract

Abstract. During the 14 November 2012 geomagnetic storm, the Van Allen Probes spacecraft observed a number of sharp decreases ("dropouts") in particle fluxes for ions and electrons of different energies. In this paper, we investigate the global magnetosphere dynamics and magnetosphereionosphere (M-I) coupling during the dropout events using multipoint measurements by Van Allen Probes, TWINS, and AMPERE together with the output of the two-way coupled global BATS-R-US-CRCM model. We find different behavior for two pairs of dropouts. For one pair, the same pattern was repeated: (1) weak nightside Region 1 and 2 Birkeland currents before and during the dropout; (2) intensification of Region 2 currents after the dropout; and (3) a particle injection detected by TWINS after the dropout. The model predicted similar behavior of Birkeland currents. TWINS low-altitude emissions demonstrated high variability during these intervals, indicating high geomagnetic activity in the near-Earth tail region. For the second pair of dropouts, the structure of both Birkeland currents and ENA emissions was relatively stable. The model also showed quasi-stationary behavior of Birkeland currents and simulated ENA emissions with gradual ring current buildup. We confirm that the first pair of dropouts was caused by large-scale motions of the OCB (open-closed boundary) during substorm activity. We show the new result that this OCB motion was associated with global changes in Birkeland (M-I coupling) currents and strong modulation of low-altitude ion precipitation. The second pair of dropouts is the result of smaller OCB disturbances not related to magnetospheric substorms. The local observations of the first pair of dropouts result from a global magnetospheric reconfiguration, which is manifested by ion injections and enhanced ion precipitation detected by TWINS and changes in the structure of Birkeland currents detected by AMPERE. This study demonstrates that multipoint measurements along with the global model results enable the reconstruction of a more complete system-level picture of the dropout events and provides insight into M-I coupling aspects that have not previously been investigated.

Global ENA Imaging and In Situ Observations of Substorm Dipolarization on 10 August 2016

“…At each UT and energy ( E j ) we recorded the peak flux as a single global metric of the postmidnight low‐altitude ion response. This metric is quantitatively similar to the low‐altitude emission (LAE) index used in previous work (Buzulukova et al, , , Valek et al, , , ). A peak low‐altitude ion flux versus UT curve at 8 keV is shown in Figure d.…”

“…Observation of this type of structure within the N17 event's very weak ring current suggests that the energetics and dynamics of individual substorms can be similar regardless of whether or not a storm is occurring. Buzulukova et al () observed multiple instances of TWINS low‐altitude ENA flux modulation synchronized to flux dropouts in Van Allen Probes ion data during the large 14 November 2012 storm. For the N17 event only the ∼1003‐UT dropout seems coincident with a change in TWINS low‐altitude flux.…”

The Big Picture: Imaging of the Global Geospace Environment by the TWINS Mission

“…Both the model and measured FACs showed intensifications of the region 2 currents after the dropouts. The new result by Buzulukova et al () confirmed that the dropouts were caused by the open‐closed boundary motion in the tail. Moreover, the TWINS‐BATSRUS‐CRCM‐AMPERE comparison established that the dropouts were a locally observed manifestation of a system‐level effect coupling together plasmas in the magnetotail and the ionosphere.…”

“…Causal connections in the ring current. TWINS model‐data comparisons reveal dynamic linkages between ions and currents, and between different regions of the magnetosphere (Buzulukova et al, ). (a) Flux dropouts across 0.1–500 keV measured by RBSP A probe of the Van Allen Probes mission.…”

“…The temperature maps provide global, dynamic, event-specific observations that can make a positive difference in the performance of global models. Buzulukova et al (2018) used a combination of modeling and data (both imaging and in situ) to understand system-level dynamic linkages between the magnetosphere and ionosphere during the 14 November 2012 storm (peak Dst −108 nT). RBSP A measured several steep decreases ("dropouts") in particle flux over a broad range (0.1-500 keV) of energy (Figure 13a).…”