The role of electric field and neutral wind direction in the formation of sporadic E-layers

Nygrén, T.; Jalonen, L.; Oksman, J.; Turunen, T.

doi:10.1016/0021-9169(84)90122-3

Cited by 143 publications

(93 citation statements)

References 38 publications

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“…Both converging and diverging windshear nulls were found, with the typical pattern of descent followed by stagnation. Nygren et al (1984), Bristow and Watkins (1991) and Kirkwood and Von Zahn (1991) focused on the formation of layers at high latitudes (I = 75°) where electric ®elds are considered the predominant driving force, in contrast to the more important role of neutral winds at mid-latitudes. These works, which neglected neutral winds, showed that thin ion layers formed in the 90± 130 km region provided the E-®eld was suitably oriented.…”

Section: Laboratory Measurements Of Reaction Rates and Previous Theomentioning

confidence: 99%

Global transport and localized layering of metallic ions in the upper atmospherer

Carter

Forbes

1999

Ann. Geophys.

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Abstract. A numerical model has been developed which is capable of simulating all phases of the life cycle of metallic ions, and results are described and interpreted herein for the typical case of Fe + ions. This cycle begins with the initial deposition of metallics through meteor ablation and sputtering, followed by conversion of neutral Fe atoms to ions through photoionization and charge exchange with ambient ions. Global transport arising from daytime electric ®elds and poleward/ downward diusion along geomagnetic ®eld lines, localized transport and layer formation through descending convergent nulls in the thermospheric wind ®eld, and ®nally annihilation by chemical neutralization and compound formation are treated. The model thus sheds new light on the interdependencies of the physical and chemical processes aecting atmospheric metallics. Model output analysis con®rms the dominant role of both global and local transport to the ion's life cycle, showing that upward forcing from the equatorial electric ®eld is critical to global movement, and that diurnal and semidiurnal tidal winds are responsible for the formation of dense ion layers in the 90±250 km height region. It is demonstrated that the assumed combination of sources, chemical sinks, and transport mechanisms actually produces F-region densities and E-region layer densities similar to those observed. The model also shows that zonal and meridional winds and electric ®elds each play distinct roles in local transport, whereas the ion distribution is relatively insensitive to reasonable variations in meteoric deposition and chemical reaction rates.

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Section: Laboratory Measurements Of Reaction Rates and Previous Theomentioning

confidence: 99%

Global transport and localized layering of metallic ions in the upper atmospherer

Carter

Forbes

1999

Ann. Geophys.

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“…The zonal wind structure shows an EW (east below, west above) wind shear, which could form sporadic E-layers (Whitehead, 1989). The electric field has a NW orientation favorable to the high-latitude E s formation (Nygrén et al, 1984). The examination of the velocity profiles depicted in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…It has been assumed that the wind shear, which is the main factor of the E s layers formation at middle latitudes (Whitehead, 1989), cannot be very effective at high-latitudes, due to the large inclination of the geomagnetic lines. Nygrén et al (1984) showed that when the electric field direction lies in the NW sector, ions would ascend at low altitudes and descend at high altitudes, compressing the plasma into dense and thin sheets at 120-125 km. This mechanism is effective at high latitudes, because the values of the electric field are considerably higher.…”

Section: Introductionmentioning

confidence: 99%

The role of total wind in the vertical dynamics of ions in the E-region at high latitudes

Voiculescu

Ignat

2005

Ann. Geophys.

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Abstract.A seasonally dependent total neutral wind model obtained from experimental data is used to evaluate the diurnal variation of the vertical ion velocity in the E-region at a high-latitude location (Tromsø), for each season, in the presence of an electric field with a typical diurnal variation for quiet auroral days. The diurnal variation and spatial locations of the vertical convergence of ions are analyzed and the effect of the total wind on the occurrence of sporadic E-layers is inferred. The results show that the structure of the wind is an important factor in controlling the vertical velocities of ions, favoring or hindering the sporadic E-layer formation. The ion convergence conditions are improved when the permanent wind is removed, which suggests that sporadic E-layers occur when the mean wind has small values, thus allowing the electric field and/or the semidiurnal tide to control the ion dynamics. We conclude that for quiet days the formation of the sporadic layers is initiated by the electric field, while their evolution and dynamics is controlled by the wind. We also find that the seasonal variation of the E s layers cannot be related to the seasonally dependent wind shear. Although we focus on sporadic E-layers, our results can be used in the analysis of other processes involving the vertical dynamics of ions in the E-region at high latitudes.

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“…At polar latitudes, convection electric fields often provide the important driver for convergence or divergence in the ion motion (Nygren et al, 1984;Turunen et al, 1993;Watkins, 1991, 1993;von Zahn, 1991, 1993;Kirkwood and Nilsson, 2000;Williams et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

Observation of electron biteout regions below sporadic E layers at polar latitudes

2015

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Abstract. The descent of a narrow sporadic E layer near 95 km altitude over Poker Flat Research Range in Alaska was observed with electron probes on two consecutive sounding rockets and with incoherent scatter radar during a 2 h period near magnetic midnight. A series of four trimethyl aluminum chemical releases demonstrated that the Es layer remained just slightly above the zonal wind node, which was slowly descending due to propagating long-period gravity waves. The location of the layer is consistent with the equilibrium position due to combined action of the wind shear and electric fields. Although the horizontal electric field could not be measured directly, we estimate that it was ∼ 2 mV m −1 southward, consistent with modeling the vertical ion drift, and compatible with extremely quiet conditions. Both electron probes observed deep biteout regions just below the Es enhancements, which also descended with the sporadic layers. We discuss several possibilities for the cause of these depletions; one possibility is the presence of negatively charged, nanometer-sized mesospheric smoke particles. Such particles have recently been detected in the upper mesosphere, but not yet in immediate connection with sporadic E. Our observations of electron depletions suggest a new process associated with sporadic E.

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The role of electric field and neutral wind direction in the formation of sporadic E-layers

Cited by 143 publications

References 38 publications

Global transport and localized layering of metallic ions in the upper atmospherer

Global transport and localized layering of metallic ions in the upper atmospherer

The role of total wind in the vertical dynamics of ions in the E-region at high latitudes

Observation of electron biteout regions below sporadic E layers at polar latitudes

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