Mechanism of the post-midnight winter night-time enhancements in NmF2 over Millstone Hill during 14–17 January 1986

Павлов, А. В.; Павлова, Н. М.

doi:10.1016/j.jastp.2004.11.004

Cited by 31 publications

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“…Many theories have been put forward to explain these nighttime enhancements in NmF2. The mechanism which can account for the observed nighttime NmF2 enhancements at middle geomagnetic latitudes is a combination of the plasmaspheric heating and refilling, and chemical and plasma transport effects (Pavlov and Pavlova, 2005a). 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.…”

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confidence: 62%

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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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confidence: 62%

“…It has been well established that the F2-peak electron density shows anomalous nighttime enhancements under various geophysical conditions (see Pavlov and Pavlova, 2005a, and references therein). Many theories have been put forward to explain these nighttime enhancements in NmF2.…”

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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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“…Nighttime increases of the midlatitude F2 region electron density, Ne, (critical frequency, foF2, maximum electron density, NmF2, and total electron content, TEC) are wellknown phenomena (Evans, 1965;Da Rosa and Smith, 1967;Rao et al, 1982;Krinberg and Tashchilin, 1984;Bailey et al, 1991;Jakowski and Fö rster, 1995;Mikhailov and Fö rster, 1999;Mikhailov et al, 2000aMikhailov et al, , 2000bRichards et al, 2000;Belehaki and Tsagouri, 2002;Farelo et al, 2002;Dabas and Kersley, 2003;Pavlov and Pavlova, 2005;Luan et al, 2008;Pavlov et al, 2008;Yakovets et al, 2009). These phenomena are called also anomalous enhancements/increases of electron density, since the solar EUV radiation as the major source of ion production is absent during the nighttime.…”

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confidence: 99%

“…At midlatitudes, the enhancements are mostly considered to be the result of the net increase of electron density from the downward plasma flux relative to the loss from the recombination (e.g., Krinberg and Tashchilin, 1984;Bailey et al, 1991;Jakowski and Fö rster, 1995;Mikhailov et al, 2000b;Richards et al, 2000;Pavlov and Pavlova, 2005;Tsagouri and Belehaki, 2002). The larger downward fieldaligned plasma flux responsible for winter postmidnight enhancement is associated with the cooling of the ionosphere-plasmasphere system after sunset in the conjugate summer hemisphere (e.g., Krinberg and Tashchilin, 1984;Bailey et al, 1991;Richards et al, 2000).…”

Section: Introductionmentioning

confidence: 99%

“…This flux can be enhanced by cross-L plasmaspheric compression, since a westward electric field will move plasma from higher Lshells with the subsequent effect that the plasma pressure in the lower L-shells will increase (e.g., Dabas and Kersley, 2003). Neutral meridional wind can contribute to the enhancements of electron density by transporting the plasma to higher altitudes where the recombination rate of ions is small (e.g., Krinberg and Tashchilin, 1984;Bailey et al, 1991;Jakowski and Fö rster, 1995;Mikhailov et al, 2000b;Pavlov and Pavlova, 2005). Numerical modeling shows, that an additional electron heating of the plasmasphere, Qad, assumed to occur before midnight, produces the premidnight/postsunset NmF2 decrease and helps to create the winter postmidnight NmF2 enhancement (Pavlov and Pavlova, 2005).…”

Section: Introductionmentioning

confidence: 99%

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Peculiarities of the nighttime winter foF2 increase over Irkutsk

Pirog

Dëminov

Deminova

et al. 2011

Advances in Space Research

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Postmidnight depletion of the high‐energy tail of the quiet plasmasphere

et al. 2015

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The Van Allen Probes Helium Oxygen Proton Electron (HOPE) instrument measures the high‐energy tail of the thermal plasmasphere allowing study of topside ionosphere and inner magnetosphere coupling. We statistically analyze a 22 month period of HOPE data, looking at quiet times with a Kp index of less than 3. We investigate the high‐energy range of the plasmasphere, which consists of ions at energies between 1 and 10 eV and contains approximately 5% of total plasmaspheric density. Both the fluxes and partial plasma densities over this energy range show H+ is depleted the most in the postmidnight sector (1–4 magnetic local time), followed by O+ and then He+. The relative depletion of each species across the postmidnight sector is not ordered by mass, which reveals ionospheric influence. We compare our results with keV energy electron data from HOPE and the Van Allen Probes Electric Fields and Waves instrument spacecraft potential to rule out spacecraft charging. Our conclusion is that the postmidnight ion disappearance is due to diurnal ionospheric temperature variation and charge exchange processes.

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Mechanism of the post-midnight winter night-time enhancements in NmF2 over Millstone Hill during 14–17 January 1986

Cited by 31 publications

References 50 publications

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

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

Peculiarities of the nighttime winter foF2 increase over Irkutsk

Postmidnight depletion of the high‐energy tail of the quiet plasmasphere

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