Observational evidence for new instabilities in the midlatitude E and F region

Other literature type, Article English OPEN
D. L. Hysell ; M. Larsen ; M. Sulzer (2016)
  • Publisher: Copernicus Publications
  • Journal: Annales Geophysicae (issn: 0992-7689, eissn: 1432-0576)
  • Related identifiers: doi: 10.5194/angeo-34-927-2016
  • Subject: Geophysics. Cosmic physics | Q | Science | Physics | QC1-999 | QC801-809
    arxiv: Physics::Space Physics

Radar observations of the <i>E</i>- and <i>F</i>-region ionosphere from the Arecibo Observatory made during moderately disturbed conditions are presented. The observations indicate the presence of patchy sporadic <i>E</i> (<i>E</i><sub>s</sub>) layers, medium-scale traveling ionospheric disturbances (MSTIDs), and depletion plumes associated with spread <i>F</i> conditions. New analysis techniques are applied to the dataset to infer the vector plasma drifts in the <i>F</i> region as well as vector neutral wind and temperature profiles in the <i>E</i> region. Instability mechanisms in both regions are evaluated. The mesosphere–lower-thermosphere (MLT) region is found to meet the conditions for neutral dynamic instability in the vicinity of the patchy <i>E</i><sub>s</sub> layers even though the wind shear was relatively modest. An inversion in the MLT temperature profile contributed significantly to instability in the vicinity of one patchy layer. Of particular interest is the evidence for the conditions required for neutral convective instability in the lower-thermosphere region (which is usually associated with highly stable conditions) due to the rapid increase in temperature with altitude. A localized <i>F</i>-region plasma density enhancement associated with a sudden ascent up the magnetic field is shown to create the conditions necessary for convective plasma instability leading to the depletion plume and spread <i>F</i>. The growth time for the instability is short compared to the one described by [Perkins(1973)]. This instability does not offer a simple analytic solution but is clearly present in numerical simulations. The instability mode has not been described previously but appears to be more viable than the various mechanisms that have been suggested previously as an explanation for the occurrence of midlatitude spread <i>F</i>.
  • References (71)
    71 references, page 1 of 8

    Behnke, R. A.: F layer height bands in the nocturnal ionosphere over Arecibo, J. Geophys. Res., 84, 974-978, 1979.

    Bernhardt, P. A.: The modulation of sporadic-E layers by KelvinHelmholtz billows in the neutral atmosphere, J. Atmos. Sol.-Terr. Phy., 64, 1487-1504, 2002.

    Bernhardt, P. A., Selcher, C. A., Siefring, C., Wilkens, M., Compton, C., Bust, G., Yamamoto, M., Fukao, S., Takayuki, O., Wakabayashi, M., and Mori, H.: Radio tomographic imaging of sporadic-E layers during SEEK-2, Ann. Geophys., 23, 2357- 2368, doi:10.5194/angeo-23-2357-2005, 2005.

    Bernhardt, P. A., Werne, J., and Larsen, M. F.: Modeling of Sporadic-E Structures from Wind-Driven Kelvin-Helmholtz Turbulence, in: Characterising the Ionosphere, Meeting Proceedings RTO-MP-IST-056, Neuilly-sur-Seine, France, 34, 31-1-31-14, 2006.

    Cabrit, B. and Kofman, W.: Ionospheric composition measurement by EISCAT using a global fit procedure, Ann. Geophys., 14(12), 1496-1505, 1996.

    Chu, Y. H. and Wang, C. Y.: Interferometry observations of 3- dimensional spatial structures of sporadic E using the Chung-Li VHF radar, Radio Sci., 32, 817-832, 1997.

    Chu, Y. H., Wang, C. Y., Su, S. L., and Kuong, R. M.: Coordinated sporadic E layer observations made with Chung-Li 30 MHz radar, ionosonde and FORMOSAT-3/COSMIC satellites, J. Atmos. Sol.-Terr. Phy., 73, 883-894, 2011.

    Cosgrove, R. B.: Generation of mesoscale F layer structure and electric fields by the combined Perkins and Es layer instabilities, in simulations, Ann. Geophys., 25, 1579-1601, doi:10.5194/angeo-25-1579-2007, 2007.

    Cosgrove, R. B. and Tsunoda, R. T.: A direction-dependent instability of sporadic-E layers in the nighttime midlatitude ionosphere, Geophys. Res. Lett., 29, 1864, doi:10.1029/2002GL014669, 2002.

    Cosgrove, R. B. and Tsunoda, R. T.: Instability of the E-F coupled nighttime midlatitude ionosphere, J. Geophys. Res., 109, A04305, doi:10.1029/2003JA010243, 2004.

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