The southern-hemisphere mid-latitude day-time and night-time trough at low-sunspot numbers

Horvath, Ildiko; Essex, E. A.

doi:10.1016/s1364-6826(03)00113-5

Cited by 21 publications

(35 citation statements)

References 31 publications

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“…Methods of TEC calculation from GPS observations have been described in detail in several papers (Sardón et al, 1994, Breed et al, 1996 and the reference therein). More specifically, Horvath and Essex (2003b) have clearly outlined the algorithm that has been used in this paper, which uses the methods described by Sardón et al (1994). Here we give a brief description of the procedure.…”

Section: Discussionmentioning

confidence: 99%

“…The STEC can be obtained from the difference between the pseudoranges (P 1 and P 2 ), and the difference between the phases (L 1 and L 2 ) of the two GPS signals (Klobuchar, 1996;Horvath and Essex, 2003b). The relevant equations are:…”

Section: Discussionmentioning

confidence: 99%

“…To demonstrate the influence of the magnetic storm on latitudinal gradients and local time behaviour, the longitudinal difference of GPS data from different stations are corrected to a common median longitude (150 • E), using a simple relation described by Horvath and Essex (2003b) A TEC depletion, or negative storm effect, occurred at high-and mid-latitudes before SSC time (prior to 12:22 UT) on 22 September. It persists at high latitudes until SSC time and even extends until about 19:00 UT on the same day at mid-latitudes, as is most obvious in Figs.…”

Section: Observationmentioning

confidence: 99%

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The Southern Hemisphere and equatorial region ionization response for a 22 September 1999 severe magnetic storm

2004

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Abstract. The ionospheric storm evolution process was monitored during the 22 September 1999 magnetic storm over the Australian eastern region, through measurements of the ionospheric Total Electron Content (TEC) from seven Global Positioning Systems (GPS) stations. The spatial and temporal variations of the ionosphere were analysed as a time series of TEC maps. Results of our analysis show that the main ionospheric effect of the storm under consideration are: the long lasting negative storm effect during a magnetic storm at mid-latitude regions; the strong, positive disturbances during the storm's main phase at auroral latitude regions; the effects of storm-induced equatorward directed wind causing a positive disturbance at high and mid-latitude stations with appropriate time shift between higher and lower latitudes; daytime poleward movement of depleted plasma that causes temporary suppression of the equatorial anomaly during the start of the storm recovery phase; and prompt penetration of eastward electric fields to ionospheric altitudes and the production of nearly simultaneous TEC enhancement at all latitudes. In general, we found dominant negative disturbance over mid and high latitudes and positive disturbance at low latitudes. A comparison of storm-time behaviour of TEC determined from GPS satellites, and f o F 2 derived from ionosondes at a range of latitudes, showed reasonable agreement between the two independent measurements.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Observationmentioning

confidence: 99%

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The Southern Hemisphere and equatorial region ionization response for a 22 September 1999 severe magnetic storm

2004

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“…Currently, due to the fast-growing number of ground-based GPS receivers, GPS-TEC measurements have been increasingly used for upper atmospheric research. Horvath and Essex (2003) used TEC measurements from three stations to investigate the features of the Southern Hemisphere trough. Wielgosz et al (2004) showed that the structure of the ionosphere trough can be regularly identified from latitudinal GPS-TEC plots.…”

Section: Introductionmentioning

confidence: 99%

Statistical analysis of ionospheric mid-latitude trough over the Northern Hemisphere derived from GPS total electron content data

Yang

Liu

2015

Earth Planet Sp

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This study statistically investigated the seasonal variation, magnetic local time (MLT) variation, geomagnetic activity dependence, and solar activity dependence of the mid-latitude trough using GPS total electron content (TEC) data from 2000 to 2014. The daily median Kp index was used to characterize the daily geomagnetic activity level. The results showed that the trough minimum position depended primarily on the geomagnetic activity, MLT, and the season. The trough depth depended primarily on the solar flux index (F107) and, to a lesser degree, on MLT. The trough depth increased as F107 increased and as the incidence angle of solar flux decreased. The trough equatorward half-width decreased as the geomagnetic activity increased. These variations in the GPS-TEC trough minimum position were compared with the variations in the TEC trough derived from the International Reference Ionosphere (IRI)-2007 model. The GPS-TEC trough minimum position changed little with respect to F107, whereas the IRI-TEC trough minimum position showed a strong F107 dependence.

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“…The contradictions may origin from differences in the properties of the midlatitude and high-latitude troughs or the dayside and nightside troughs, as well as from a restricted time of observation. Some trough studies are based on limited time intervals (Whalen, 1989) or isolated cases (Jones et al, 1997;Pryse et al, 1998), while others make use of larger databases (Mallis and Essex, 1993;Kersley et al, 1997;Werner and Prölss, 1997;Horvath and Essex, 2003).…”

Section: Introductionmentioning

confidence: 99%

The F-region trough: seasonal morphology and relation to interplanetary magnetic field

2006

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Abstract. We present here the results of a statistical study of the ionospheric trough observed in 2003 by means of satellite tomography. We focus on the seasonal morphology of the trough occurrence and investigate the trough latitude, width and the horizontal gradients at the edges, at different magnetic local times, as well as their relations to geomagnetic activity and the interplanetary magnetic field. A seasonal effect is noticed in the diurnal variation of the trough latitude, indicating that summer clearly differs from the other seasons. In winter the troughs seem to follow the solar terminator. The width of the trough has a diurnal variation and it depends on the season, as well. The broadest troughs are observed in winter and the narrowest ones in summer. A discontinuity in the diurnal variation of the trough latitude is observed before noon. It is suggested that this is an indication of a difference between the generation mechanisms of morningside and eveningside troughs. The density gradients at the edges have a complex dependence on the latitude of the trough and on geomagnetic activity. The photoionization and the auroral precipitation are competing in the formation of the trough walls at different magnetic local times. An important finding is that the interplanetary magnetic field plays a role in the occurrence of the trough at different levels of geomagnetic activity. This is probably associated with the topology of the polar cap convection pattern, which depends on the directions of the IMF components B y and B z .

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The southern-hemisphere mid-latitude day-time and night-time trough at low-sunspot numbers

Cited by 21 publications

References 31 publications

The Southern Hemisphere and equatorial region ionization response for a 22 September 1999 severe magnetic storm

The Southern Hemisphere and equatorial region ionization response for a 22 September 1999 severe magnetic storm

Statistical analysis of ionospheric mid-latitude trough over the Northern Hemisphere derived from GPS total electron content data

The F-region trough: seasonal morphology and relation to interplanetary magnetic field

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