TEC

About: TEC is a research topic. Over the lifetime, 5119 publications have been published within this topic receiving 84696 citations.

Study of simultaneous penetration of electric fields and variation of total electron content in the day and night sectors during the geomagnetic storm of 23 May 2002

Abstract: [1] Evidence of simultaneous penetration of storm time electric fields in the day and night sectors of the globe during the geomagnetic storm of 23 May 2002 and the response of low-latitude ionosphere to such electric fields is presented. Using the ground-based magnetometer data, simultaneous penetrations of under-shielding and overshielding electric fields, and those arising owing to the unsteady ring currents, have been inferred in the day and night sectors. The ionospheric response in the day and night sectors near the northern crest of the equatorial ionization anomaly has been studied using total electron content (TEC) data. Multiple episodes of prompt penetration electric fields arising owing to the under-shielding and unsteady ring current conditions resulted in enhancement of the TEC in the day sector. These daytime TEC enhancements were reinforced by the equatorward neutral winds that also produced modulations in TEC. The presence of storm time equatorward neutral winds has been inferred from the increased thermospheric [O/N2] ratio. We also show, probably for the first time, that the same penetration fields in the night sector are responsible for the reductions in TEC on 23 May. Reduced TEC at 120°E longitude on 24 May, the day following the storm, has been attributed to the disturbance dynamo electric fields as well as to the changes in thermospheric chemical composition signified by reduced [O/N2] ratio.

Extracting Ionospheric Measurements from GPS in the Presence of Anti-Spoofing

Abstract: Line-of-sight ionospheric measurements derived from differencing dual-frequency Global Positioning System (GPS) pseudorange data are corrupted by instrumental biases in both the receiver and GPS satellite transmitters due to hardware delays in the Ll and L2 signal paths. Hardware calibration of the instrumental delay is possible for some types of receivers (e.g., Allen Osborne Associate’s Rogue SNR-8), but the satellite biases must be estimated using a remote technique. Ignoring the satellite (receiver) biases when computing line-of-sight TEC measurements from GPS observables may result in an error of +-9 (+-30) TECU (1 TEC unit = 1016 electrons/meter2 = 0.35 nanoseconds of differential delay). Using a global ionospheric shell model to fit GPS-based ionospheric delay data from a world-wide network of 50+ receivers, we can simultaneously estimate a global ionospheric map, satellite biases for the entire GPS constellation, and receiver biases for all the uncalibrated receivers. The uncertainty in the resulting estimates of the satellite biases is a dominant error source in extracting line-of-sight TEC measurements from GPS observables. We present the resuits of daily fits of satellite biases over a period spanning 20 months from Jan. 1993 through Aug. 1994. Seven separate time periods each consisting of IO- 12 consecutive days were processed. The day-to-day variability of the estimates has been computed in an effort to assess their precision. Before anti-spoofing (AS) encryption of the GPS ranging code, the estimated satellite biases exhibited a day-to-day standard deviation of 0.6 nanoseconds or 1.7 TECU. With the advent of AS encryption, the pseudorange observable exhibits a lower signal-to-noise ratio, but the day-to-day reproducibility of the biases has not changed significantly. This preliminary study indicates that AS has not had a significant impact on our estimates of the satellite biases. The current satellite bias estimates (with AS on) are consistent with the pre-AS values to a precision of 0.6 ns or 1.7 TECU.

Latitudinal variation of total electron content in the winter at middle latitudes.

Abstract: Studies of total electron content (TEC) have been made by using data obtained during three winter solstices in Paris, France, and Kiruna, Sweden. A nocturnal winter maximum is clearly shown by these data, and an effort is made to hypothesize its cause. A two-fold hypothesis is offered; the increase in TEC is attributed to an electron flux descending from the protonosphere. This flux is linked to lowering electron temperatures in the force tube after sunset in the conjugate hemisphere. In addition to this production process, a regulatory process is invoked to reconcile the observed values with the maximum flux intensity compatible with the theory. The regulatory process is attributed to an interaction betweenthe neutral winds and the ionospheric plasma in the presence of the earth's magnetic field.

Concentric traveling ionospheric disturbances triggered by the launch of a SpaceX Falcon 9 rocket

Abstract: We report the first observation of concentric traveling ionospheric disturbances (CTIDs) triggered by the launch of a SpaceX Falcon 9 rocket on 17 January 2016. The rocket triggered ionospheric disturbances show shock acoustic wave signature in the time rate change (time derivative) of total electron content (TEC), followed by CTIDs in the 8–15 minutes bandpass filtering of TEC. The CTIDs propagated northward with phase velocity of 241–617 m/s and reached distances more than 1000 km away from the source on the rocket trajectory. The wave characteristics of CTIDs with periods of 10.5–12.7 minutes and wavelength ~200–400 km agree well with the gravity wave dispersion relation. The optimal wave source searching and gravity wave ray-tracing technique suggested that the CTIDs have multiple sources which are originated from ~38–120 km altitude before and after the ignition of the 2nd stage rocket, ~200 seconds after the rocket was launched.