The ionospheric midlatitude trough observed by FORMOSAT-3/COSMIC during solar minimum

Lee, I. T.; Wang, Wenbin; Liu, J. Y.; Chen, C. Y.; Lin, Charles

doi:10.1029/2010ja015544

Cited by 47 publications

(75 citation statements)

References 31 publications

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“…The difference of about 6 • latitude between quiet and active geomagnetic activity can be compared with other earlier studies. Lee et al (2011) report an equatorward shift of about 3-5 • latitude for the trough minimum with increased geomagnetic activity in their study, while Fig. 3 of the statis- Figure 10.…”

Section: Discussionmentioning

confidence: 74%

“…The period provided approximately 1950 latitudinal profiles of the trough, which was significantly larger than the 618 troughs of the earlier NIMS study. The period also provided data that were representative of the general behaviour of the prominent troughs of the earlier paper, with the four months including autumn, a season where the trough is prominent (Lee et al, 2011). The use of the four months as giving a fair representation of the prominent trough is reinforced in Fig.…”

Section: Introductionmentioning

confidence: 74%

“…This reduction was attributed to a loss mechanism such as chemical recombination. Lee et al (2011) considering NmF2 found that its values at the trough minimum were slightly larger under disturbed conditions than under quiet conditions.…”

Section: Discussionmentioning

confidence: 91%

“…In such comparisons, it is important to appreciate that different observing techniques have been used and during different times in the solar cycle. For example, Lee et al (2011) used radio occultation to infer NmF2, while the current study uses the assimilation of slant TEC into EDAM to give the VTEC.…”

Section: Discussionmentioning

confidence: 99%

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Modelling the main ionospheric trough using the Electron Density Assimilative Model (EDAM) with assimilated GPS TEC

et al. 2018

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Abstract. The main ionospheric trough is a large-scale spatial depletion in the electron density distribution at the interface between the high-and mid-latitude ionosphere. In western Europe it appears in early evening, progresses equatorward during the night, and retreats rapidly poleward at dawn. It exhibits substantial day-to-day variability and under conditions of increased geomagnetic activity it moves progressively to lower latitudes. Steep gradients on the trough-walls on either side of the trough minimum, and their variability, can cause problems for radio applications. Numerous studies have sought to characterize and quantify the trough behaviour.The Electron Density Assimilative Model (EDAM) models the ionosphere on a global scale. It assimilates observations into a background ionosphere, the International Reference Ionosphere 2007 (IRI2007), to provide a full 3-D representation of the ionospheric plasma distribution at specified times and days. This current investigation studied the capability of EDAM to model the ionosphere in the region of the main trough. Total electron content (TEC) measurements from 46 GPS stations in western Europe from September to December 2002 were assimilated into EDAM to provide a model of the ionosphere in the trough region. Vertical electron content profiles through the model revealed the trough and the detail of its structure. Statistical results are presented of the latitude of the trough minimum, TEC at the minimum and of other defined parameters that characterize the trough structure. The results are compared with previous observations made with the Navy Ionospheric Monitoring System (NIMS), and reveal the potential of EDAM to model the large-scale structure of the ionosphere.

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Section: Discussionmentioning

confidence: 74%

Section: Introductionmentioning

confidence: 74%

Section: Discussionmentioning

confidence: 91%

Section: Discussionmentioning

confidence: 99%

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Modelling the main ionospheric trough using the Electron Density Assimilative Model (EDAM) with assimilated GPS TEC

et al. 2018

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“…Maximum Pc1 occurrence rates are observed around 60 • MLAT at nighttime (see Figs. 4 and 7), where the "mid-latitude trough" frequently occurs in the ionospheric F region (Lee et al, 2011, Fig. 3).…”

Section: Temporal Variation Of Event Ratesmentioning

confidence: 95%

Global characteristics of Pc1 magnetic pulsations during solar cycle 23 deduced from CHAMP data

2013

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We present a global climatology of Pc1 pulsations as observed by the CHAMP satellite from 2000 to 2010. The Pc1 center frequency and bandwidth are about 1 and 0.5 Hz, respectively. The ellipticity is mostly linear with the major axis almost aligned with the magnetic zonal direction. The diurnal variation of Pc1 occurrences shows a primary maximum early in the morning and a secondary maximum during pre-midnight hours. The annual variations of the occurrence rates exhibit a clear preference for local summer. The solar cycle dependence of the occurrence rate reveals a maximum at the declining phase (2004–2005). Neither magnetic activity nor solar wind velocity controls the Pc1 occurrence rate significantly. Pc1 occurrence rate peaks at subauroral latitudes, but the steep cutoff towards higher latitudes is due to auroral field-aligned currents masking the Pc1 pulsations. The center frequency of Pc1 pulsations does not show a clear dependence on latitude. The global distribution of Pc1 exhibits highest occurrence rates near the longitude sector of the South Atlantic Anomaly. Pc1 events at auroral latitudes, although they are rarely detected, show a clear occurrence peak around local noon. A majority of the auroral Pc1 events are observed during solar minimum years

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Seasonal variation and solar activity dependence of the quiet‐time ionospheric trough

et al. 2014

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We have conducted a statistical analysis of the ionospheric F region trough, focusing on its seasonal variation and solar activity dependence under geomagnetically quiet and moderate conditions, using plasma parameter data obtained via Common Program 3 observations performed by the European Incoherent Scatter (EISCAT) radar between 1982 and 2011. We have confirmed that there is a major difference in frictional heating between the high-and low-latitude sides of the EISCAT field of view (FOV) at 73°0′N-60°5′N (geomagnetic latitude) at an altitude of 325 km, which is associated with trough formation. Our statistical results show that the high-latitude and midlatitude troughs occur on the high-and low-latitude sides of the FOV, respectively. Seasonal variations indicate that dissociative recombination accompanied by frictional heating is a main cause of trough formation in sunlit regions. During summer, therefore, the occurrence rate is maintained at 80-90% in the postmidnight high-latitude region owing to frictional heating by eastward return flow. Solar activity dependence on trough formation indicates that field-aligned currents modulate the occurrence rate of the trough during the winter and equinox seasons. In addition, the trough becomes deeper via dissociative recombination caused by an increased ion temperature with F 10.7 , at least in the equinox and summer seasons but not in winter.

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The ionospheric midlatitude trough observed by FORMOSAT-3/COSMIC during solar minimum

Cited by 47 publications

References 31 publications

Modelling the main ionospheric trough using the Electron Density Assimilative Model (EDAM) with assimilated GPS TEC

Modelling the main ionospheric trough using the Electron Density Assimilative Model (EDAM) with assimilated GPS TEC

Global characteristics of Pc1 magnetic pulsations during solar cycle 23 deduced from CHAMP data

Seasonal variation and solar activity dependence of the quiet‐time ionospheric trough

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