Skip to main content
Article thumbnail
Location of Repository

Midnight sector observations of auroral omega bands

By J.A. Wild, E.E. Woodfield, E. Donovan, R.C. Fear, A. Grocott, M. Lester, A.N. Fazakerley, E. Lucek, Y. Khotyaintsev, M. Andre, A. Kadokura, K. Hosokawa, C. Carlson, J.P. McFadden, K.H. Glassmeier, V. Angelopoulos and G. Björnsson

Abstract

We present observations of auroral omega bands on 28 September 2009. Although generally associated with the substorm recovery phase and typically observed in the morning sector, the features presented here occurred just after expansion phase onset and were observed in the midnight sector, dawnward of the onset region. An all‐sky imager located in northeastern Iceland revealed that the omega bands were ∼150 × 200 km in size and propagated eastward at ∼0.4 km s−1 while a colocated ground magnetometer recorded the simultaneous occurrence of Ps6 pulsations. Although somewhat smaller and slower moving than the majority of previously reported omega bands, the observed structures are clear examples of this phenomenon, albeit in an atypical location and unusually early in the substorm cycle. The THEMIS C probe provided detailed measurements of the upstream interplanetary environment, while the Cluster satellites were located in the tail plasma sheet conjugate to the ground‐based all‐sky imager. The Cluster satellites observed bursts of 0.1–3 keV electrons moving parallel to the magnetic field toward the Northern Hemisphere auroral ionosphere; these bursts were associated with increased levels of field‐aligned Poynting flux. The in situ measurements are consistent with electron acceleration via shear Alfvén waves in the plasma sheet ∼8 RE tailward of the Earth. Although a one‐to‐one association between auroral and magnetospheric features was not found, our observations suggest that Alfvén waves in the plasma sheet are responsible for field‐aligned currents that cause Ps6 pulsations and auroral brightening in the ionosphere. Our findings agree with the conclusions of earlier studies that auroral omega bands have a source mechanism in the midtail plasma sheet

Topics: QC Physics
Year: 2011
DOI identifier: 10.1029/2010JA015874
OAI identifier: oai:eprints.lancs.ac.uk:39968
Provided by: Lancaster E-Prints

Suggested articles

Citations

  1. (2007). A decade of the Super Dual Auroral Radar Network (SuperDARN): Scientific achievements, new techniques and future directions, doi
  2. (2002). A model of the near magnetosphere with a dawn‐dusk asymmetry: 1. Mathematical structure, doi
  3. (2002). A model of the near magnetosphere with a dawn‐dusk asymmetry: 2. Parameterization and fitting to observations, doi
  4. (1997). A new functional form to study the solar wind control of the magnetopause size and shape, doi
  5. (1993). A numerical ionosphere‐ magnetosphere coupling model with variable conductivities, doi
  6. (1999). A study of omega bands and Ps6 pulsations on the ground, at low altitude and at geostationary orbit, doi
  7. (2009). Alfvén waves and their roles in the dynamics of the Earth’s magnetotail: A review, doi
  8. (1991). Auroral signatures of substorm recovery phase: A case study, doi
  9. (1993). Auroral torches: Results of optical observations, doi
  10. Auster (2008b), THEMIS ESA first science results and performance issues, doi
  11. (1984). Can substorm expansive phase effects and low frequency Pc magnetic pulsations be attributed to the same source mechanism?, doi
  12. (1983). Characteristic of eastward drifting omega bands in the morning sector, doi
  13. (2001). Cluster peace observations of electrons during magnetospheric flux transfer events, doi
  14. (1997). Cluster—Science and mission overview, doi
  15. (1994). Combined measurements of EISCAT and the EISCAT magnetometer cross to study omega bands, doi
  16. (2005). Combined optical, EISCAT and magnetic observations of the omega bands/Ps6 pulsations and an auroral torch in the late morning hours: A case study, doi
  17. (1984). Conjugacy of electron auroras observed by all‐sky cameras and scanning photometers,
  18. (2003). disturbances: Relation to substorms and the auroral oval, doi
  19. (2004). Diurnal auroral occurrence statistics obtained via machine vision, doi
  20. (2010). Do magnetospheric shear Alfvén waves generate sufficient electron energy flux to power the aurora?, doi
  21. (2009). Electrodynamics of an omega‐band as deduced from optical and magnetometer data, doi
  22. (2002). Excitation of twin‐vortex flow in the nightside high‐ latitude ionosphere during an isolated substorm, doi
  23. (2001). First results of electric field and density observations by Cluster EFW based on initial months of operation, doi
  24. (1997). Formation of auroral omega bands in the paired region 1 and region 2 field‐aligned current system, doi
  25. (1985). Generation of auroral omega bands by shear instability of the neutral winds, doi
  26. (1982). Joint two‐dimensional observations of ground magnetic and ionospheric electric fields associated with auroral currents. 5. Current system associated with eastward drifting omega bands, doi
  27. Kletzing (2002), Correlation of Alfvén wave Poynting flux in the plasma sheet at 4–7 RE with ionospheric electron energy flux, doi
  28. (2005). Mesoscale ionospheric electrodynamics of omega bands determined from ground‐based electromagnetic and satellite optical observations, doi
  29. (1995). Modelling the Earth’s magnetospheric magnetic field confined within a realistic magnetopause, doi
  30. (2000). Multi‐ instrument observations of the electric and magnetic field structure of omega bands, doi
  31. (2004). Multi‐instrument observations of the ionospheric counterpart of a bursty bulk flow in the near‐earth plasma sheet, doi
  32. (2004). Multi‐instrument observations of the ionospheric counterpartofa bursty bulk flowin thenear‐earth plasma sheet, doi
  33. (2009). Observations of omega bands using an imaging riometer, doi
  34. (1997). PEACE: A Plasma Electron and Current instrument,
  35. (1979). Perturbation magnetic fields and current systems associated with eastward drifting auroral structures, doi
  36. (2000). Polar spacecraft based comparisons of intense electric fields and Poynting flux near and within the plasma sheet‐tail lobe boundary to UVI images: An energy source for the aurora, doi
  37. (1994). Recovery phase of magnetospheric substorms and its association with morning‐sector aurora, doi
  38. (2004). Stereo CUTLASS—A new capability for the SuperDARN HF radars, doi
  39. (2004). Substorm onset observations by IMAGE‐FUV, doi
  40. (2001). The Cluster magnetic field investigation: Overview of in‐flight performance and initial results, doi
  41. (1997). The Cluster magnetic fields investigation,
  42. (1964). The development of the auroral substorm, doi
  43. (1964). The dynamics of the aurora: doi
  44. (1997). The electric field and wave experiment for the Cluster mission, doi
  45. (1994). The image magnetometer network, doi
  46. (2008). The THEMIS fluxgate magnetometer, doi
  47. (2008). The THEMISmission,
  48. (1986). Towards a self‐consistent non‐linear theory of radar auroral backscatter, doi
  49. (1988). Tsurutani doi
  50. (2007). Using colour in auroral imaging, doi

To submit an update or takedown request for this paper, please submit an Update/Correction/Removal Request.