A comparative study of night-time enhancement of TEC at a low latitude station on storm and quiet nights including the local time, seasonal and solar activity dependence

Unnikrishnan, K. P.; Nair, R. Balachandran; Venugopal, Chandu

doi:10.5194/angeo-20-1843-2002

Cited by 25 publications

(20 citation statements)

References 26 publications

(36 reference statements)

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“…This leads to severe dissipation of LSTIDs, even if they were traveling during the night. Strong nighttime enhancements in TEC are usually observed at low latitudes during both disturbed and quiet times (Unnikrishnan et al, 2002;Jain et al, 2011), and dissipation of LSTIDs due to ion drag has previously been reported by Tsugawa et al (2004) and Ding et al (2012).…”

Section: Annmentioning

confidence: 56%

Observations of poleward-propagating large-scale traveling ionospheric disturbances in southern China

et al. 2013

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Abstract. We report here on two cases of poleward-propagating large-scale traveling ionospheric disturbances (LSTIDs) in China during a medium-scale storm between 27 May and 1 June 2011. The observations were conducted by making use of the Global Positioning System network and ionosondes in China and Southeast Asia. One northeastward-propagating LSTID occurred on the morning of 30 May, while the other was observed during the nighttime of 1 June. Both poleward-traveling LSTIDs occurred during the storm's recovery phase in southern China's low-latitude region (geomagnetic latitude ~ 7.3–24° N) and experienced severe dissipation during their propagation from south to north. Although the initial relative amplitude of the nighttime LSTID was ~ 60% larger than that of the morning event, the nighttime event dissipated more quickly than the morning event because of a strong nighttime enhancement in background total electronic content (TEC) during storm time, which led to strong ion-drag dissipation during the evening. The poleward-propagating LSTIDs exhibit a narrower latitudinal range, a smaller amplitude, and a slightly higher elevation compared with the equatorward-moving LSTIDs observed in the same region. Given these features, the poleward-propagating LSTIDs were likely excited by some local source near southern China. Excitation of secondary LSTIDs during the dissipation of some primary medium-scale disturbances from the lower atmosphere is a possible mechanism.

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Section: Annmentioning

confidence: 56%

Observations of poleward-propagating large-scale traveling ionospheric disturbances in southern China

et al. 2013

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“…Nighttime enhancements in TEC had been reported in previous studies (e.g. Mukherjee et al, 2010;Adewale et al, 2012;D'ujanga et al, 2012;Oron et al, 2013;Aggarwal, 2011;Unnikrishnan et al, 2002). This enhancement in TEC could be attributed to enhancement of eastward electric field which causes the equatorial ionization anomaly.…”

Section: Diurnal Tec Variationsmentioning

confidence: 59%

Investigation of TEC variations over the magnetic equatorial and equatorial anomaly regions of the African sector

Oryema

Jurua

D’ujanga

et al. 2015

Advances in Space Research

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“…The observed features of the nighttime enhancements in the total ionospheric electron content, TEC, at low geomagnetic latitudes, were reported by various workers (e.g. Young et al, 1970;Nelson and Cogger, 1971;Lanzerotti et al, 1975;Tyagi et al, 1982;Balan et al, 1994;Su et al, 1994;Jain et al, 1995;Unnikrishnan et al, 2002). The post-sunset enhancements in TEC and NmF2 of the low-latitude ionosphere during geomagnetically quiet conditions were studied by Anderson and Klobuchar (1983), Dasgupta et al (1985), Balan et al (1995), and Su et al (1995Su et al ( , 1997, using theoretical modeling techniques.…”

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confidence: 99%

A modeling study of ionospheric F2-region storm effects at low geomagnetic latitudes during 17-22 March 1990

2006

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Abstract.We have presented a comparison between the modeled NmF2 and hmF2, and NmF2 and hmF2, which were observed in the low-latitude ionosphere simultaneously by the Kokubunji, Yamagawa, Okinawa, Manila, Vanimo, and Darwin ionospheric sounders, by the middle and upper atmosphere (MU) radar during 17-22 March 1990, and by the Arecibo radar for the time period of 20-22 March 1990. A comparison between the electron and ion temperatures measured by the MU and Arecibo radars and those produced by the model of the ionosphere and plasmasphere is presented. The empirical zonal electric field, the meridional neutral wind taken from the HWM90 wind model, and the NRLMSISE-00 neutral temperature and densities are corrected so that the model results agree reasonably with the ionospheric sounder observations, and the MU and Arecibo radar data. It is proved that the nighttime weakening of the equatorial zonal electric field (in comparison with that produced by the empirical model of Fejer and Scherliess (1997) or Scherliess and Fejer (1999)), in combination with the corrected wind-induced plasma drift along magnetic field lines, provides the development of the nighttime enhancements in NmF2 observed over Manila during 17-22 March 1990. As a result, the new physical mechanism of the nighttime NmF2 enhancement formation close to the geomagnetic equator includes the nighttime weakening of the equatorial zonal electric field and equatorward nighttime plasma drift along magnetic field lines caused by neutral wind in the both geomagnetic hemispheres. It is found that the latitudinal positions of the crests depend on the E×B drift velocity and on the neutral wind velocity. The relative role of the main mechanisms of the equatorial anomaly suppression observed during geomagnetic storms is studied for the first time in terms of storm-time variations of the model crest-to-trough ratios of the equatorial anomaly. During most of the studied time Correspondence to: A. V. Pavlov (pavlov@izmiran.rssi.ru) period, a total contribution from meridional neutral winds and variations in the zonal electric field to the equatorial anomaly changes is larger than that from geomagnetic storm disturbances in the neutral temperature and densities. Vibrationally excited N 2 and O 2 promote the equatorial anomaly enhancement during the predominant part of the studied time period, however, the role of vibrationally excited N 2 and O 2 in the development of the equatorial anomaly is not significant. The asymmetries in the neutral wind and densities relative to the geomagnetic equator are responsible for the northsouth asymmetry in NmF2 and hmF2, and for the asymmetry between the values of the crest-to-trough ratios of the Northern and Southern Hemispheres. The model simulations provide evidence in favor of an asymmetry in longitude of the energy input into the auroral region of the Northern Hemisphere on 21 March 1990.

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A comparative study of night-time enhancement of TEC at a low latitude station on storm and quiet nights including the local time, seasonal and solar activity dependence

Cited by 25 publications

References 26 publications

Observations of poleward-propagating large-scale traveling ionospheric disturbances in southern China

Observations of poleward-propagating large-scale traveling ionospheric disturbances in southern China

Investigation of TEC variations over the magnetic equatorial and equatorial anomaly regions of the African sector

A modeling study of ionospheric F2-region storm effects at low geomagnetic latitudes during 17-22 March 1990

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