On the propagation of bubbles in the geomagnetic tail
By Juhani Birn, Joachim Raeder, Y. Wang, R. Wolf, M. Hesse. 2004
239 citations recorded by the source corpus.
Abstract. Using three-dimensional magnetohydrodynamic simulations, we investigate the propagation of low-entropy magnetic flux tubes ("bubbles") in the magnetotail. Our simulations address fundamental properties of the propagation and dynamics of such flux tubes rather than the actual formation process. We find that the early evolution, after a sudden reduction of pressure and entropy on a localized flux tube, is governed by re-establishing the balance of the total pressure in the dawn-dusk and north-south directions through compression on a time scale less than about 20s for the typical magnetotail. The compression returns the equatorial pressure to its original unperturbed value, due to the fact that the magnetic field contributes only little to the total pressure, while farther away from the equatorial plane the magnetic field compression dominates. As a consequence the pressure is no longer constant along a flux tube. The subsequent evolution is characterized by earthward propagation at speeds of the order of 200-400km/s, depending on the initial amount of depletion and the cross-tail extent of a bubble. Simple acceleration without depletion does not lead to significant earthward propagation. It hence seems that both the entropy reduction and the plasma acceleration play an important role in the generation of fast plasma flows and their propagation into the near tail. Earthward moving bubbles are found to be associated with field-aligned current systems, directed earthward on the dawnward edge and tailward on the duskward edge. This is consistent with current systems attributed to observed bursty bulk flows and their auroral effects. Key words. Magnetospheric physics (magnetospheric configuration and dynamics; magnetotail; plasma sheet)nguage:
Subfields: Astronomy and Astrophysics, Molecular Biology
View Paper: https://www.semanticscholar.org/paper/39177ea19194749424f97c182e42810b9ae38171
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Citations in the corpus
- On the current sheets surrounding dipolarizing flux bundles in the magnetotail: The case for wedgelets (2013, methodology): “The electron energization may be due to betatron or Fermi acceleration [Birn et al., 2004b; Fu et al., 2011] or both.”
- Entropy and plasma sheet transport (2007, background): “shown by Chen and Wolf [1999] reached a velocity of about 500 km/s, consistent with bursty bulk flows, but the 3-D Birn et al. [2004] simulations showed a peak at a somewhat lower velocity.”
- Bursty bulk flows and dipolarization in MHD simulations of magnetotail reconnection (2011, result): “[6] Three‐dimensional MHD simulations have confirmed that entropy reduction is indeed a crucial factor in enabling earthward transport of magnetic flux tubes [ Birn et al., 2004b ], although the speeds of depleted flux tubes in these simulations without underlying reconnection were more modest than ”
- Average thermodynamic and spectral properties of plasma in and around dipolarizing flux bundles (2015, background): “In addition, the vortex motion of plasma around the DFB [e.g., Birn et al., 2004; Gabrielse et al., 2012] and turbulence [e.g., Antonova, 1985] in the wake of the dipolarization front may transport thermal plasma between the ambient plasma sheet and DFBs.”
- Average properties of the magnetic reconnection ion diffusion region in the Earth's magnetotail: The 2001–2005 Cluster observations and comparison with simulations (2009, background): “Flow reversals without a reversal in Bz were discarded, since they are often observed in association with bursty bulk flows (BBFs) and associated flow vortices [Birn et al., 2004].”
- Multiple overshoot and rebound of a bursty bulk flow (2010, methodology): “[3] Observations and theory [Goertz and Baumjohann, 1991; Chen and Wolf, 1999; Birn et al., 2004] have suggested that BBFs can be thought of as thin filaments inside the plasma sheet with entropy that is substantially lower than that of the surrounding plasma, resulting in earthward acceleration by…”
- THEMIS observations of an earthward‐propagating dipolarization front (2009, methodology): “These are also predicted by the plasma bubble model [e.g., Birn et al., 2004, and references therein].”