The global climatology of the intensity of the ionospheric sporadic <i>E</i> layer

Abstract

Abstract. On the basis of S4max data retrieved from COSMIC GPS radio occultation measurements, the long-term climatology of the intensity of Es layers is investigated for the period from December 2006 to January 2014. Global maps of Es intensity show the high-spatial-resolution geographical distribution and strong seasonal dependence of Es layers. The maximum intensity of Es occurs over the mid-latitudes, and its value in summer is 2–3 times larger than that in winter. A relatively strong Es layer is observed at the North Pole and South Pole, with a distinct boundary dividing the mid-latitudes and high latitudes along the 60–80∘ geomagnetic latitude band. The simulation results show that the convergence of vertical ion velocity could partially explain the seasonal dependence of Es intensity. Furthermore, some disagreements between the distributions of the calculated divergence of vertical ion velocity and the observed Es intensity indicate that other processes, such as the vertical motions of gravity waves, magnetic-field effects, meteoric mass influx into Earth's atmosphere, and the chemical processes of metallic ions, should also be considered as they may also play an important role in the spatial and seasonal variations in Es layers.

The intensification of metallic layered phenomena above thunderstorms through the modulation of atmospheric tides

“…The relative change of critical frequency, f 0 E s () is shown in blue dotted and solid lines, in which is the average background frequency of f 0 E s . Since f 0 E s is a function of layer height 35 , for each point was calculated from all layers within our dataset which had a similar height (within ± 0.5 km). These were then subtracted from each time after lightning in our study.…”

Derivation of global ionospheric Sporadic E critical frequency ( f o Es) data from the amplitude variations in GPS/GNSS radio occultations

“…Patches of ionization within Es layers form as a result of the vertical ion convergence driven by vertical shears in the zonal neutral wind (a westward wind increasing with altitude) and meridional neutral wind (a northward wind increasing with altitude for the Northern Hemisphere, or a southward wind increasing with altitude in the Southern Hemisphere). The wind shear theory indicates that the formation of Es layers should be inhibited on the magnetic equator, because the ions fail to converge vertically into a layer when the magnetic field is horizontal [ 16 ]. The equatorial Es arises from the gradient instability and is associated with the enhanced electro-jet current [ 17 , 18 ].…”

“…The equatorial Es arises from the gradient instability and is associated with the enhanced electro-jet current [ 17 , 18 ]. Based on the expression for the vertical ion drift in wind shear theory [ 16 ], the vertical velocity of ions is very small when cosI ∼ 0. Here, I denotes the magnetic dip angle.…”

“…Model simulations show that the seasonal variation in the occurrence rate of the Es layer is potentially attributed to the convergence of the metal ions driven by wind shears [ 52 ]. A global map of the amplitude scintillation index (S4), a proxy of the intensity of Es layers, also presents a strong seasonal dependence [ 16 ]. However, one weak point in explaining the seasonal dependence of Es remains; that the geographical distribution of the Es minimum in the winter hemisphere cannot be simulated by the neutral wind shears.…”

Gravity Waves induced Wind Shears Derived from SABER Temperature Observations

“…It is now accepted that the large winds and shears are a common phenomenon in the MLT region (Liu, 2007;2017). The large winds and shears play important roles in forming the middle latitudes sporadic E layers and driving the equatorial electrojet (Mathews 1998;Hysell et al, 2002;Haldoupis, 2012;Shinagawa et al, 2017;Yu et al, 2019), in controlling atmospheric stabilities and the propagation of GWs, and in transporting and mixing tracers locally and/or globally (Fritts et al, 2004;Liu 2007Liu , 2017Yue et al, 2013;Stevens et al, 2014).…”