Showing papers on "Total electron content published in 1974"

Behavior of the ionospheric F region during the Great Solar Flare of August 7, 1972

Abstract: The response of the ionospheric F region to the large solar flare that occurred near 1500 UT on August 7, 1972, has been monitored by means of Faraday rotation measurements made at 17 stations in North America, Europe, and Africa. With observations spanning more than 10 hours in local time and more than 70 deg in latitude, the first truly global morphology of a flare-induced F region event was obtained. The sizes of the individual sudden increases in the total electron content (Sitec) ranged from 1.8 to 8.6 × 1016 el/m²; on a percentage basis, all the Sitec fell within the 15 to 30% range. No obvious relationship was found between the sizes of the increases and the solar zenith angles at the various subionospheric points, nor between the observed Sitec and the sudden flare effects (SFE) seen on nearby magnetometer recordings. The latitudinal behavior provided the only simple ordering parameter found in the data, the lower latitudes having larger observed increases than the higher latitudes. Millstone Hill incoherent scatter data showed that nearly 40% of the total content enhancement observed at that site came from heights above 300 km. All the Sitec had a rise time of about 10 min, during which the Tec rate of change showed an excellent correlation with the time development of the solar radio burst monitored at 35,000 MHz.

VHF ionospheric scintillations at L = 2.8 and formation of stable auroral red arcs by magnetospheric heat conduction

Abstract: The 137-MHz amplitude scintillation data obtained from the ATS 3 satellite at a mid-latitude station (L = 2.8) are utilized to study the temporal behavior of electron density irregularities following sudden commencements of intense magnetic storms. Comparison with the equatorial Dst index shows that the onset of scintillations is controlled by the universal time of commencement of the main and rapid recovery phases of storms. Total electron content data obtained simultaneously are used to show that the plasmapause-associated ionospheric trough moves to the vicinity of the observing point during the onsets of such universal time controlled scintillations. The magnetospheric heat conduction into the ionosphere during these storms, which sometimes causes stable auroral red arcs near the plasmapause, is found to produce field-aligned irregularities. A persistence of local time dominated scintillations following such storm time onsets is noted. The results of this study indicate that mid-latitude scintillations following large magnetic storms may have a storm time component in addition to the widely known local midnight component.

An Atlas of the Midlatitude F-Region Response to Geomagnetic Storms.

Abstract: : The ionospheric response to 75 geomagnetic storms has been examined using total electron content (TEC) data obtained at Hamilton, Massachusetts (426N, 708W) Simultaneous measurements of the F2-region critical frequency (N(max)) and equivalent slab thickness (tau = TEC/N(max)) to be monitored during the same events Both graphical and tabulated formats were used to present the response of the parameters for five days of each storm period This broad data base should provide a unique source for examining the variety of possible storm effects, for testing storm models, and for comparison with the storm effects observed at other locations (Author)

Longitudinal effect in the response of total electron content to magnetic storms

Abstract: IN a previous study1 of the response of the ionospheric total electron content (TEC) data to magnetic storms, an average storm time behaviour of TEC for middle latitudes was deduced. On average TEC is enhanced during the first 24 h following the start of a storm, depressed for the next 24 h and near normal through the third 24 h. Another study2 has shown a strong diurnal component in TEC behaviour with the maximum enhancement occurring in the dusk sector (1600 to 1800 LT). The present study of disturbed TEC behaviour generally agrees with that reported above but in addition indicates a longitudinal effect in the behaviour of both the storm time and diurnal components of disturbed TEC.

Seasonal and Diurnal Variations in the Total Electron Content of the Ionosphere at Invariant Latitude 54 Degrees.

Abstract: : Measurements of total ionospheric electron content (TEC) by Faraday rotation of radio waves are given for the period November 1967 to September 1973 for 136 MHz transmissions from the geostationary satellite ATS-3 observed at a sub-ionospheric invariant latitude of 54 degrees N The diurnal curves showed the effects of solar radiation and particle precipitation (Modified author abstract)