Tests of electrodynamic consistency from daytime ionospheric drift observations

Abstract

Observations of the daytime horizontal ion drift velocity in the ionospheric E and F regions by the incoherent scatter radar at Millstone Hill (42.6°N) during quiet geomagnetic conditions reveal the presence of a clockwise rotation of the drift direction with a semidiurnal period and a lag in the azimuth of the E region drift of 50°–60° behind the F region drift. The F region horizontal ion drifts result from the presence of ionospheric polarization electric fields, while at E region heights the ions are additionally driven by neutral winds. By using the electric fields determined from the F region drifts it is possible to derive information on the neutral winds from the E region drifts. The winds so obtained are found to be in good agreement with appropriately height averaged tidal winds in the lower thermosphere corresponding primarily to the (2, 4) propagating mode. This mode has been identified independently from temperature measurements at Millstone Hill. Conversely, calculations for the E region ion drift as a consequence of the combination of the (2, 4) tidal winds and the observed electric fields are shown to reproduce all features of the observations. Finally, the electric currents in the dynamo region have been computed from these experimental data and are shown to produce a magnetic variation at the ground that is similar to the observed average Sq variation at mid‐latitudes, indicating the overall consistency of our observations.

Sq field characteristics at Phu Thuy, Vietnam, during solar cycle 23: comparisons with Sq field in other longitude sectors

“…The existence of a conductive layer around the Earth was established by ionosonde (Breit and Tuve, 1925) and later on by rocket flights (Davis et al, 1967;Maynard, 1967;Sastri, 1968;Monro et al, 1968;Shuman, 1970;Satya Prakash et al, 1970;Sastry, 1973;Richmond, 1995a) and incoherent scatter sounders (Dougherty, 1963;Brekke et al, 1974;Kamide and Brekke, 1975;Harper, 1977;Salah and Evans, 1977;. In the past and still now the Sq variations were and are still intensively analyzed in all longitude sectors (Matshushita, 1965;Mayaud, 1965a, b;Campbell, 1982;Campbell and Matshushita, 1982;Doumouya, 1998;Campbell andSchiffmacher, 1985, 1986;Campbell et al, 1993;Rastogi et al, 1994;Takeda, 1999Takeda, , 2002Yamazaki et al, 2009).…”

Effects of the induction field on the Sq dynamo currents in the ionosphere

“…The height range is from 90 to 1000 km. The wind model is based on that by Salah and Evans [1977] for (1, À2) mode tidal winds with the extension of the winds up to 1000 km on the assumption that winds above 200 km have the same amplitude and phase as those at 200 km. It should be noted that both the conductivity and the wind system are symmetric with the equator, and thus no field-aligned currents need to be considered, which was stated above.…”

Strange currents over Saint‐Santin

“…Surprisingly, these authors found that the measured currents were northward during the most of 'the daylight hours, even though the location of the station in 'the northern hemisphere would indicate that the currents should be southward in the morning and turn northward in the afternoon. They recognized that this anomalous effect is probably peculiar to the European sector because it has not been observed in the American sector by the Millstone Hill radar [Salah and Evans, 1977] and attributed its cause to field-aligned currents resulting from interhemispherical asymmetries in the manner first suggested by Van Sabben [1964,1966]. In the present study we scrutinize the nature of the current anomaly with a larger body of data (29 days versus 3 days in the aforementioned studies) and, further, distinguish between geomagnetically quiet versus disturbed days.…”