A quantitative study of ionospheric density gradients at midlatitudes

Abstract

Abstract. The subauroral ionosphere, at the magnetic latitudes which characterize the northeastern United States, is subject to severe F region ionospheric density structuring due to the space weather effects of magnetospheric disturbance electric fields. Communications and navigation systems relying on transionospheric propagation must be able to compensate for the effects of the sharp changes (> 10X) in total electron content (TEC) associated with the ionospheric trough and storm time disturbance effects at midlatitudes. The Millstone Hill incoherent scatter radar database has been used to investigate the spatial extent and temporal evolution of TEC and density altitude/latitude structure at middle and subauroral latitudes as a function of solar cycle, local time, and level of geomagnetic activity. More than 11,000 radar elevation scans covering >20 ø of latitude and altitudes between 150 and 750 km have been used to identify the characteristics of the density gradient near the equatorward edge of the ionospheric trough in a variety of circumstances spanning 20 years and two solar cycles. Pronounced density gradients can be identified in •35% of the Millstone Hill scans, and we present a statistical characterization of average magnitude and location for these steepest TEC gradients. In some cases (especially near noon) the equatorward edge of the trough lies poleward of our observational field of view, and gradients associated with phenomena other than the trough contribute to our statistics. IntroductionThe subauroral ionosphere, at the magnetic latitudes which characterize the northeastern United States, is subject to severe F region ionospheric density structuring due to the space weather effects of magnetospheric disturbance electric fields [Foster, 1995]. The subauroral ionosphere is not subjected to the precipitation-

Approaches for modeling ionosphere irregularities based on the TEC rate index

“…The ionospheric activity in polar, sub-auroral, and mid-latitude regions is primarily associated with geomagnetic storms, coronal mass ejections, and coronal holes. Processes in the ionosphere during these events result in the formation of horizontal TEC gradients with TEC enhancement, which lead to phase and amplitude scintillation, as reported by many researchers (Vo and Foster, 2001;Stankov et al 2006;Jakowski et al 2004;Krankowski et al 2006;Jakowski et al 2008;Shagimuratov et al 2012). Usually, GPS positioning requires a minimum of four simultaneously tracked satellites with good geometry (Misra and Enge, 2006).…”

Studies of Ionospheric Structures and Their Effects on Systems

“…This unexpected TEC increase and its fluctuations in the midnight time frame caused the largest errors in the WAAS algorithms in the continental United States. Needless to say, the morphology of such trough-wall gradients and auroral blob structures has to be studied using a large data-base such as the one existing at Millstone Hill [Vo and Foster, 2001] so that predictive schemes may be developed for use during magnetic storms. Finally, we come to a consideration of the effects of penetrating electric fields on the equatorial ionosphere.…”

Cold plasma redistribution throughout geospace

“…Calculated from the ISR density-altitude profiles, F-region TEC approached 100 TECu within the SED plume while sharp TEC gradients (~50 TECu/deg latitude) were observed bordering the SED feature [10]. Such sharp spatial gradients pose significant space weather problems (1 TECu represents an integrated column density of 10 16 electrons m 2 ).…”

“…The February 8, 1986 event represents a severe example of the ionospheric density perturbation that can occur over the continental US associated with SED plumes. TEC near 48° N geodetic latitude is ~100 TEC units with latitude gradient in TEC of ~50 TEC/deg [10].…”