Nighttime enhancements in ionospheric electron content in the northern and southern hemispheres

Balan, N.; Bailey, G. J.; Nair, R. Balachandran; Titheridge, J. E.

doi:10.1016/0021-9169(94)90177-5

Cited by 52 publications

(63 citation statements)

References 38 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…These results are in line with those reported by other workers, e.g. Davies et al (1979); Essex and Klobuchar (1980);Balan et al (1994), except that local time occurrences vary. Important mechanisms for nighttime enhancements at mid-latitudes are field-aligned plasma flow, cross-L plasmaspheric compression and neutral air winds interactions.…”

Section: Discussionsupporting

confidence: 93%

See 1 more Smart Citation

Study of mid-latitude nighttime enhancement in F-region electron density using tomographic images over the UK

Dabas

Kersley

2003

Ann. Geophys.

View full text Add to dashboard Cite

Abstract. Nighttime enhancements in ionospheric electron content (IEC)/peak electron density (NmF2) have been studied by various workers in the equatorial anomaly and midlatitude regions. Such studies give an idea about their enhancement over that location only. In the present study tomographic images over the UK, which give a latitudinal versus height distributions of ionospheric electron density in a much wider area, have been used to study the anomalous increases in nighttime F-region electron density at mid-latitudes. From the analysis of four seasonal representative months (November 1997, March, June and October 1998) data it was noted that the majority of the cases of nighttime enhancements were observed after local midnight, with a maximum between 03:00-04:00 LT in the month of November 1997. Enhancements were observed mostly between 45-50 • N latitudes, and their positions are not affected by magnetic activity (K p ) variations, whereas the separation between the midlatitude trough and enhancement decreases with increases in magnetic activity. This finding shows that only the trough moves equatorward with the increase in magnetic activity. It is also noted that the electron density gradient from the trough to the enhancement increases with an increase in K p . Results are discussed in terms of downward plasma transport from the protonosphere to the ionosphere and the nighttime neutral winds.

show abstract

Section: Discussionsupporting

confidence: 93%

“…In the equatorial anomaly region the primary source of such nighttime enhancement is the evening increase in the upward E × B drift at the equator (Anderson and Klobuchar, 1983;Balan et al, 1994). At mid-latitudes the primary source has been identified as a downward flow of plasma from the protonosphere to the ionosphere .…”

Section: Introductionmentioning

confidence: 99%

Study of mid-latitude nighttime enhancement in F-region electron density using tomographic images over the UK

Dabas

Kersley

2003

Ann. Geophys.

View full text Add to dashboard Cite

show abstract

“…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.…”

mentioning

confidence: 81%

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

2006

View full text Add to dashboard Cite

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.

show abstract

“…The term Mid-latitude Summer Nighttime Anomaly (MSNA) is now being used to describe the anomalous electron density patterns in both Northern and Southern Hemispheres Lin et al, 2010). It must be mentioned here that the MSNA is different from winter nighttime enhancements (Evans, 1965;Titheridge, 1968;Davies et al, 1979;Balan and Rao, 1987;Luan et al, 2008), and northern hemispheric summer nighttime enhancements reported by Balan and Bailey (1992) and Balan et al (1994) since the latter ones appear as a secondary maximum in electron density, both in the premidnight and post-midnight hours.…”

Section: Introductionmentioning

confidence: 99%

Mid-latitude Summer Nighttime Anomaly (MSNA) – observations and model simulations

et al. 2011

Self Cite

View full text Add to dashboard Cite

Abstract. In this paper, we present model simulations of the Mid-latitude Summer Nighttime Anomaly (MSNA) in the Northern Hemisphere, which is characterized by noontime dip and evening maximum in the diurnal variation of the ionospheric density. The simulations are carried out using SUPIM (Sheffield University Plasmasphere Ionosphere Model) for solar minimum at 135 • E longitude where MSNA is most pronounced in the Northern Hemisphere. The simulations are used to understand the relative importance of electric fields, and zonal and meridional winds in the formation of MSNA. The wind velocities measured by the Middle and Upper atmosphere radar (MU radar) and those obtained from the horizontal wind model (HWM93) are used. The results show that the formation of MSNA is closely related to the diurnal variation of the neutral winds with little contribution from the changes in the electric fields. The observed features of MSNA are better reproduced when MU radar winds are used as model input rather than HWM winds.

show abstract

Nighttime enhancements in ionospheric electron content in the northern and southern hemispheres

Cited by 52 publications

References 38 publications

Study of mid-latitude nighttime enhancement in F-region electron density using tomographic images over the UK

Study of mid-latitude nighttime enhancement in F-region electron density using tomographic images over the UK

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

Mid-latitude Summer Nighttime Anomaly (MSNA) – observations and model simulations

Contact Info

Product

Resources

About