Tidal variability in the ionospheric dynamo region

[1] The seasonal and interannual variability of migrating (Sun-synchronous) and nonmigrating solar atmospheric tides at altitudes between 100 and 116 km are investigated using temperature measurements made with the SABER instrument on the TIMED spacecraft during 2002–2006. Quasi-biennial variations of order ±10–15% in migrating diurnal and semidiurnal tidal amplitudes are found, presumably due to modulation by the quasi-biennial oscillation (QBO) as the tides propagate from their troposphere and stratospheric sources to the lower thermosphere. A number of nonmigrating tidal components are found that have the potential to produce significant longitudinal variability of the total tidal fields. The most prominent of these, i.e., those that appear at amplitudes of order 5–10 K in a 5-year mean climatology, include the zonally symmetric (s = 0) diurnal tide (D0); the eastward propagating diurnal and semidiurnal tides with zonal wave numbers s = −2 (DE2 and SE2) and s = −3 (DE3 and SE3); and the following westward propagating waves: diurnal s = 2 (DW2); semidiurnal s = 1 (SW1), s = 3 (SW3), and s = 4 (SW4); and terdiurnal s = 5 (TW5). These waves can be plausibly accounted for by nonlinear interaction between migrating tidal components and stationary planetary waves with s = 1 or s = 2 or by longitudinal variations of tropospheric thermal forcing. Additional waves that occur during some years or undergo phase cancellation within construction of a 5-year climatology include DW5, SE1, SE4, SW6, TE1, TW1, and TW7. It is anticipated that the winds that accompany all of these waves in the 100–170 km region will impose longitudinal variability in the electric fields produced through the ionospheric dynamo mechanism, thereby modulating vertical motion of the equatorial ionosphere and the concomitant plasma densities. In addition to the wave-4 modulation of the equatorial ionosphere that has recently been discovered and replicated in modeling studies, the waves revealed here will generate wave-1 (SW1, SW3, D0, DW2), wave-2 (SW4, TW1), wave-3 (DE2, SE1), wave-4 (DE3, SE2, DW5, SW6, TE1, TW7), wave-5 (SE3), and wave-6 (SE4) components of this ionospheric variability, depending on year and time of year. However, the absolute and relative efficiencies with which these waves produce electric fields remains to be determined.

[1]  R. Roble,et al.  Connections between deep tropical clouds and the Earth's ionosphere , 2007 .

[2]  Jann‐Yenq Liu,et al.  Plausible effect of atmospheric tides on the equatorial ionosphere observed by the FORMOSAT‐3/COSMIC: Three‐dimensional electron density structures , 2007 .

[3]  J. Forbes,et al.  Seasonal cycle of nonmigrating diurnal tides in the MLT region due to tropospheric heating rates from the NCEP/NCAR Reanalysis Project , 2007 .

[4]  S. Maus,et al.  Longitudinal variation of the E‐region electric fields caused by atmospheric tides , 2006 .

[5]  J. Forbes,et al.  Monthly tidal temperatures 20–120 km from TIMED/SABER , 2006 .

[6]  T. Killeen,et al.  Diurnal nonmigrating tides from TIMED Doppler Interferometer wind data: Monthly climatologies and seasonal variations , 2006 .

[7]  J. Forbes,et al.  Troposphere-Thermosphere Tidal Coupling as Measured by the SABER Instrument on TIMED during July-September, 2002 , 2006 .

[8]  C. Swenson,et al.  Effect of atmospheric tides on the morphology of the quiet time, postsunset equatorial ionospheric anomaly , 2006 .

[9]  J. Russell,et al.  Stratospheric and mesospheric temperature variations for the quasi-biennial and semiannual (QBO and SAO) oscillations based on measurements from SABER (TIMED) and MLS (UARS) , 2006 .

[10]  Larry J. Paxton,et al.  Control of equatorial ionospheric morphology by atmospheric tides , 2006 .

[11]  Dong L. Wu,et al.  Solar tides as revealed by measurements of mesosphere temperature by the MLS experiment on UARS , 2006 .

[12]  Harald U. Frey,et al.  Longitudinal structure of the equatorial anomaly in the nighttime ionosphere observed by IMAGE/FUV , 2005 .

[13]  J. Forbes,et al.  A space-based climatology of diurnal MLT tidal winds, temperatures and densities from UARS wind measurements , 2005 .

[14]  J. Forbes,et al.  Nonmigrating diurnal tides in the thermosphere , 2009 .

[15]  Jeffrey M. Forbes,et al.  Migrating and nonmigrating semidiurnal tides in the upper atmosphere excited by tropospheric latent heat release: MIGRATING AND NONMIGRATING SEMIDIURNAL TIDES , 2003 .

[16]  Jeffrey M. Forbes,et al.  Migrating and nonmigrating diurnal tides in the middle and upper atmosphere excited by tropospheric latent heat release , 2002 .

[17]  D. Offermann,et al.  Sources of nonmigrating tides in the tropical middle atmosphere , 2002 .

[18]  J. Forbes,et al.  Nonlinear interactions in the upper atmosphere: The s = 1 and s = 3 nonmigrating semidiurnal tides , 2002 .

[19]  Y. Miyoshi,et al.  Seasonal variation of non-migrating semidiurnal tide in the polar MLT region in a general circulation model , 2002 .

[20]  R. Roble,et al.  Modeling diurnal tidal variability with the National Center for Atmospheric Research thermosphere‐ionosphere‐mesosphere‐electrodynamics general circulation model , 2001 .

[21]  J. Forbes,et al.  Simulations of diurnal tides due to tropospheric heating from the NCEP/NCAR Reanalysis Project , 2001 .

[22]  James M. Russell,et al.  Retrieval of mesospheric and lower thermospheric kinetic temperature from measurements of CO2 15 µm Earth Limb Emission under non‐LTE conditions , 2001 .

[23]  J. Forbes.  Wave coupling between the lower and upper atmosphere: case study of an ultra-fast Kelvin Wave , 2000 .

[24]  Dale N. Anderson,et al.  Longitude structure of ionospheric total electron content at low latitudes measured by the TOPEX/Poseidon satellite , 1999 .

[25]  J. Forbes,et al.  QBO effects on the diurnal tide in the upper atmosphere , 1999 .

[26]  D. Fritts,et al.  Zonal mean and tidal dynamics from space: an empirical examination of aliasing and sampling issues , 1997 .

[27]  E. Ekanayake,et al.  Background wind effect on propagation of nonmigrating diurnal tides in the middle atmosphere , 1997 .

[28]  J. Forbes,et al.  First results from the meteor radar at South Pole: A large 12‐hour oscillation with zonal wavenumber one , 1995 .

[29]  Raymond G. Roble,et al.  A thermosphere-ionosphere-mesosphere-electrodynamics general circulation model (time-GCM): Equinox solar cycle minimum simulations (30–500 km) , 1994 .

[30]  J. Forbes,et al.  Variability in the upward propagating semidiurnal tide due to effects of QBO in the lower atmosphere , 1992 .

[31]  H. Teitelbaum,et al.  On tidal variability induced by nonlinear interaction with planetary waves , 1991 .

[32]  A. Hedin.  Extension of the MSIS Thermosphere Model into the middle and lower atmosphere , 1991 .

[33]  R. Stening.  A calculation of ionospheric currents due to semidiurnal antisymmetric tides , 1989 .

[34]  J. Forbes,et al.  Effects of mean winds and dissipation on the diurnal propagating tide: An analytic approach , 1989 .

[35]  R. Roble,et al.  Electrodynamic effects of thermospheric winds from the NCAR Thermospheric General Circulation Model , 1987 .

[36]  M. Takeda.  Three dimensional ionospheric currents and field aligned currents generated by asymmetrical dynamo action in the ionosphere , 1982 .

[37]  J. Forbes,et al.  Theoretical studies of atmospheric tides , 1979 .

[38]  R. Lindzen,et al.  Atmospheric Tides: Thermal and Gravitational , 1969 .

[39]  Michael Selwyn Longuet-Higgins,et al.  The eigenfunctions of Laplace's tidal equation over a sphere , 1968, Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences.