A Tutorial Review on Sporadic E Layers

Haldoupis, C.

doi:10.1007/978-94-007-0326-1_29

Cited by 137 publications

(202 citation statements)

References 28 publications

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“…The theories proposed for the formation of E sb do not explain its seasonal dependence and the role of EEJ. Based on long-term observations of meteors from 554 V. Yadav et al: Peculiar solar minimum and E sb occurrence mid-latitude stations, it is shown that the strength and occurrence of E s layer are closely related to the meteor influx (Haldoupis et al, 2007;Haldoupis, 2011). Tsunoda (2008) suggested the transport mechanism for the formation of E sb at the equator and established the dependence of EEJ for the first time.…”

Section: Introductionmentioning

confidence: 99%

Occurrence of blanketing Es layer (Esb) over the equatorial region during the peculiar minimum of solar cycle 24

et al. 2014

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Abstract.A thin and highly dense sporadic E layer, which can occasionally block the upper ionospheric layers, is called blanketing sporadic E (E sb ). We present the statistical seasonal local time occurrence pattern of E sb at equatorial station Tirunelveli (8.7 • N, 77.8 • E, dip latitude 0.7 • N) during the extended minimum of solar cycle 24 (2007-2009). In spite of nearly the same average solar activity during both 2007 and 2009, considerable differences are noticed in the seasonal occurrence of E sb during this period. The percentage of E sb occurrence is found to be the highest during the summer solstice (≥ 50 %) for both 2007 and 2009, which is in general accordance with the earlier studies. The occurrences of E sb during the vernal equinox (∼ 33 %) and January-February (∼ 28 %) are substantial in 2009 as compared to those during the same seasons in 2007. We find that, during winter (January-February), ∼ 75 % of E sb occurred during or just after the period of sudden stratospheric warming (SSW). We suggest that enhanced E sb occurrence during winter (January-February) and the vernal equinox of 2009 could be associated with SSW-driven changes in the E region ambient conditions. Furthermore, the close association of E sb with counter equatorial electrojet (CEEJ) suggested by earlier studies is re-examined carefully using the scenario of E sb occurrence on non-CEEJ days. Such an exercise is crucial as we are unaware whether the physical mechanisms driving E sb and CEEJ are linked or not. We find that, of all the seasons, the association of E sb and CEEJ is strongest during winter (November-December).

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Section: Introductionmentioning

confidence: 99%

Occurrence of blanketing Es layer (Esb) over the equatorial region during the peculiar minimum of solar cycle 24

et al. 2014

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“…Es layers can seriously affect the HF and low-VHF communications, causing over the horizon propagation for signals otherwise restricted to line-ofsight (Rice et al 2011). In the past years, the characteristics of mid-latitude Es layers have been extensively studied by many authors (see reviews by Whitehead 1970Whitehead , 1989Mathews 1998;Haldoupis 2011Haldoupis , 2012. The most accredited theory in explaining the formation of the Es layers is the vertical wind-shear theory, conceived in the 1960s studies mostly associated with the atmospheric gravity waves (Whitehead 1961;Axford 1963;Chimonas & Axford 1968).…”

Section: Introductionmentioning

confidence: 99%

On the influence of solar activity on the mid-latitude sporadic E layer

Pezzopane

Pignalberi

Pietrella

2015

J. Space Weather Space Clim.

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To investigate the influence of solar cycle variability on the sporadic E layer (Es), hourly measurements of the critical frequency of the Es ordinary mode of propagation, foEs, and of the blanketing frequency of the Es layer, fbEs, recorded from January 1976 to December 2009 at the Rome (Italy) ionospheric station (41.8°N, 12.5°E), were examined. The results are: (1) a high positive correlation between the F10.7 solar index and foEs as well as between F10.7 and fbEs, both for the whole data set and for each solar cycle separately, the correlation between F10.7 and fbEs being much higher than the one between F10.7 and foEs; (2) a decreasing long-term trend of the F10.7, foEs and fbEs time series, with foEs decreasing more rapidly than F10.7 and fbEs; (3) clear and statistically significant peaks at 11 years in the foEs and fbEs time series, inferred from Lomb-Scargle periodograms.

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“…The dotted blue line shows the vertical ion drift for the wind profile and zero electrical field. The vertical ion drifts are very small (10 cm s −1 ) and convergence times for a 1 km layer are of the order of hours (Haldoupis, 2011), which requires a persistent wind shear to form and maintain the layer. Note that the horizontal wind shear is westward and generates the correct convergence; however, the condition v iz = 0 is met near 96 km and not near 95 km.…”

Section: Sporadic E Layersmentioning

confidence: 99%

“…Whitehead (1961Whitehead ( , 1970 and Axford (1963) developed the wind shear theory, in which ions are swept together by the combined action of neutral collisions and Lorentz force; for recent reviews see Mathews (1998) or Haldoupis (2011). Observation of persistent, narrow layers implies the important role of long-lived metallic ions (e.g., Fe + , Mg + , Si + , Na + , Ca + ), which are abundant in the upper mesosphere and lower thermosphere through meteor ablation.…”

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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A Tutorial Review on Sporadic E Layers

Cited by 137 publications

References 28 publications

Occurrence of blanketing E<sub>s</sub> layer (E<sub>sb</sub>) over the equatorial region during the peculiar minimum of solar cycle 24

Occurrence of blanketing E<sub>s</sub> layer (E<sub>sb</sub>) over the equatorial region during the peculiar minimum of solar cycle 24

On the influence of solar activity on the mid-latitude sporadic E layer

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

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A Tutorial Review on Sporadic E Layers

Cited by 137 publications

References 28 publications

Occurrence of blanketing E&lt;sub&gt;s&lt;/sub&gt; layer (E&lt;sub&gt;sb&lt;/sub&gt;) over the equatorial region during the peculiar minimum of solar cycle 24

Occurrence of blanketing E&lt;sub&gt;s&lt;/sub&gt; layer (E&lt;sub&gt;sb&lt;/sub&gt;) over the equatorial region during the peculiar minimum of solar cycle 24

On the influence of solar activity on the mid-latitude sporadic E layer

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

Contact Info

Product

Resources

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Occurrence of blanketing E<sub>s</sub> layer (E<sub>sb</sub>) over the equatorial region during the peculiar minimum of solar cycle 24

Occurrence of blanketing E<sub>s</sub> layer (E<sub>sb</sub>) over the equatorial region during the peculiar minimum of solar cycle 24