Sounding of sporadic E layers from CSES radio occultation and comparing with ionosonde measurements

GNSS radio occultation (RO) plays an important role in ionospheric electron density inversion and sounding of sporadic E layers. As the China's first electromagnetic satellite, China Seismo Electromagnetic Satellite (CSES) has collected the RO data from both GPS and BDS-2 satellites since March 2018. In this study, we extracted the carrier to noise density ratio (CNR) data of CSES and calculated the standard deviation of normalized CNR. A new criterion is developed to determine the Es events, that is when the mean value of the absolute value of the difference between the normalized CNR is greater than 3 times of the standard deviation. The statistics show that sporadic E layers have strong seasonal variations with highest occurrence rates in summer season at middle latitudes. It is also found that the occurrence height of Es is mainly located at 90–110 km, and the period of local time 15:00–18:00 is the high incidence period of Es. In addition, the geometric altitudes of a sporadic E layer detected in CSES radio occultation profiles and the virtual heights of a sporadic E layer obtained by the Wuhan Zuo Ling Tai (ZLT) ionosonde show four different space-time matching criterions. Our results reveal that there is a good agreement between both parameters which is reflected in the significant correlation.

Interhemispheric transport of metallic ions within ionospheric sporadic <i>E</i> layers by the lower thermospheric meridional circulation

Long-lived metallic ions in the Earth's atmosphere (ionosphere) have been investigated for many decades. Although the seasonal variation in ionospheric “sporadic E” layers was first observed in the 1960s, the mechanism driving the variation remains a long-standing mystery. Here, we report a study of ionospheric irregularities using scintillation data from COSMIC satellites and identify a large-scale horizontal transport of long-lived metallic ions, combining the simulations of the Whole Atmosphere Community Climate Model with the chemistry of metals and ground-based observations from two meridional chains of stations from 1975–2016. We find that the lower thermospheric meridional circulation influences the meridional transport and seasonal variations of metallic ions within sporadic E layers. The winter-to-summer meridional velocity of ions is estimated to vary between −1.08 and 7.45 m/s at altitudes of 107–118 km between 10–60∘ N. Our results not only provide strong support for the lower thermospheric meridional circulation predicted by a whole atmosphere chemistry–climate model, but also emphasize the influences of this winter-to-summer circulation on the large-scale interhemispheric transport of composition in the thermosphere–ionosphere.

Investigation on the role of E-F region coupling processes on the generation of nighttime MSTIDs: Case studies over northern Germany

&lt;p&gt;Northwest to southeast phase fronts with southwestward moving features are commonly observed in the nighttime midlatitude ionosphere during the solstice months at low solar activity. These features are identified as nighttime MSTIDs (medium scale traveling ionospheric disturbances). Initially, they were considered to be a manifestation of neutral atmospheric gravity waves. Later on, investigations showed that the nighttime MSTIDs are electrified in nature and mostly confined to the mid and low latitude ionosphere. Although the overall characteristics of the nighttime MSTIDs are mostly well understood, the causative mechanisms are not well known. Perkins instability mechanism was believed to be the cause of nighttime MSTIDs, however, the growth rate of the instability is too small to explain the perturbations observed. Recently, model simulations and observational studies suggest that coupling between sporadic-E layers and other type of E-region instabilities, and the F region may be relevant to explain the generation of the MSTIDs.&lt;/p&gt;&lt;p&gt;In the present study simultaneous observation from OI 630 nm all-sky airglow imager, GPS-TEC, ionosonde and Meteor radars, are used to investigate the role of E and F region coupling on the generation of MSTIDs .Nighttime MSTIDs observed on three nights (14 March 2020, 23 March 2020 and 28 May 2020) in the OI 630 nm airglow images over Kuehlungsborn (54&amp;#176;07'N; 11&amp;#176;46'E, 53.79N&amp;#160; mag latitude), Germany, are presented. Simultaneous detrended GPS-TEC measurements also shows presence of MSTIDs on these nights. In addition, simultaneous ionosonde observations over Juliusruh (54&amp;#176;37.7'N 13&amp;#176;22.5'E) show spread-F in the ionograms as well as sporadic-E layer occurrence.&amp;#160; Furthermore, we also investigate the MLT region wind variations during these nights. The role of Es-layers and the interplay between the winds and Es-layers role on the generation of the MSTIDs will be discussed in detail in this presentation.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;

Numerical prediction of sporadic E layer occurrence using GAIA

A sporadic E layer has significant influence on radio communications and broadcasting, and predicting the occurrence of sporadic E layers is one of the most important issues in space weather forecast. While sporadic E layer occurrence and the magnitude of the critical sporadic E frequency (foEs) have clear seasonal variations, significant day-to-day variations as well as regional and temporal variations also occur. Because of the highly complex behavior of sporadic E layers, the prediction of sporadic E layer occurrence has been one of the most difficult issues in space weather forecast. To explore the possibility of numerically predicting sporadic E layer occurrence, we employed the whole atmosphere–ionosphere coupled model GAIA, examining parameters related to the formation of sporadic E layer such as vertical ions velocities and vertical ion convergences at different altitudes between 90 and 150 km. Those parameters in GAIA were compared with the observed foEs data obtained by ionosonde observations in Japan. Although the agreement is not very good in the present version of GAIA, the results suggest a possibility that sporadic E layer occurrence can be numerically predicted using the parameters derived from GAIA. We have recently developed a real-time GAIA simulation system that can predict atmosphere–ionosphere conditions for a few days ahead. We present an experimental prediction scheme and a preliminary result for predicting sporadic E layer occurrence.

Sporadic sodium layer: A possible tracer for the conjunction between the upper and lower atmospheres

In this research, we reveal the inter-connection between lightning strokes, reversal of the electric field, ionospheric disturbances, and a trigger of sporadic sodium layer event (NaS), based on the joint observations by three lidars, an ionosonde, an atmospheric electric mill, a fluxgate magnetometer, and World Wide Lightning Location Network (WWLLN). Our results suggest that lightning strokes would probably have an influence on the ionosphere and thus give rise to the occurrence of NaS, with the overturning of electric field playing an important role. Statistical results reveal that the sporadic E layers (ES) could hardly be formed or maintained when the atmospheric electric field turns upward. A conjunction between the lower and upper atmospheres could be established by these inter-connected phenomena, and the key processes could be suggested as follows: lightning strokes→overturning of electric field→different collisional frequencies for ions and electrons→depletion of ES/generation of NaS.

Numerical prediction of sporadic E layer occurrence using GAIA

A sporadic E layer has significant influence on radio communications and broadcasting, and predicting the occurrence of sporadic E layers is one of the most important issues in space weather forecast. While sporadic E layer occurrence and the magnitude of the critical sporadic E frequency ( foEs ) have clear seasonal variations, significant day-to-day variations as well as regional and temporal variations also occur. Because of the highly complex behavior of sporadic E layers, the prediction of sporadic E layer occurrence has been one of the most difficult issues in space weather forecast. To explore the possibility of numerically predicting sporadic E layer occurrence, we employed the whole atmosphere–ionosphere coupled model GAIA, examining parameters related to the formation of sporadic E layer such as vertical ions velocities and vertical ion convergences at different altitudes between 90 km and 150 km. By comparing those parameters in GAIA with observed foEs data obtained by ionosonde observations in Japan, we found that variations in the vertical ion convergence at 120 km altitude agree fairly well with variations in foEs . This result suggests that sporadic E layer occurrence can be numerically predicted using the parameters derived from GAIA. We have recently developed a real-time GAIA simulation system that can predict atmosphere–ionosphere conditions for a few days ahead. We present an experimental prediction scheme and a preliminary result for predicting sporadic E layer occurrence.

Numerical prediction of sporadic E layer occurrence using GAIA

A sporadic E layer has significant influence on radio communications and broadcasting, and predicting the occurrence of sporadic E layers is one of the most important issues in space weather forecast. While sporadic E layer occurrence and the magnitude of the critical sporadic E frequency ( foEs ) have clear seasonal variations, significant day-to-day variations as well as regional and temporal variations also occur. Because of the highly complex behavior of sporadic E layers, the prediction of sporadic E layer occurrence has been one of the most difficult issues in space weather forecast. To explore the possibility of numerically predicting sporadic E layer occurrence, we employed the whole atmosphere–ionosphere coupled model GAIA, examining parameters related to the formation of sporadic E layer such as vertical ions velocities and vertical ion convergences at different altitudes between 90 km and 150 km. By comparing those parameters in GAIA with observed foEs data obtained by ionosonde observations in Japan, we found that variations in the vertical ion convergence at 120 km altitude agree fairly well with variations in foEs . This result suggests that sporadic E layer occurrence can be numerically predicted using the parameters derived from GAIA. We have recently developed a real-time GAIA simulation system that can predict atmosphere–ionosphere conditions for a few days ahead. We present an experimental prediction scheme and a preliminary result for predicting sporadic E layer occurrence.

Interhemispheric transport of metallic ions within ionospheric sporadic E layers by the lower thermospheric meridional circulation

Long-lived metallic ions in the Earth's atmosphere/ionosphere have been investigated for many decades. Although the seasonal variation in ionospheric sporadic E layers was first observed in the 1960s, the mechanism driving the variation remains a long-standing mystery. Here we report a study of ionospheric irregularities using scintillation data from COSMIC satellites and identify a large-scale horizontal transport of long-lived metallic ions, combined with the simulations of the Whole Atmosphere Community Climate Model with the chemistry of metals and ground-based observations from two meridional chains of stations from 1975–2016. We find that the lower thermospheric meridional circulation influences the meridional transport and seasonal variations of metallic ions within sporadic E layers. The winter-to-summer, meridional velocity of ions is estimated to vary between −1.08 and 7.45 m/s at altitudes of 107–118 km between 10°–60° N latitude. Our results not only provide strong support for the lower thermospheric meridional circulation predicted by a whole atmosphere chemistry-climate model, but also emphasise the influences of this winter-to-summer circulation on the large-scale interhemispheric transport of composition in the thermosphere/ionosphere.

Numerical prediction of sporadic E layer occurrence using GAIA

A sporadic E layer has significant influence on radio communications and broadcasting, and predicting the occurrence of sporadic E layers is one of the most important issues in space weather forecast. While sporadic E layer occurrence and the magnitude of the critical sporadic E frequency (foEs) have clear seasonal variations, significant day-to-day variations as well as regional and temporal variations also occur. Because of the highly complex behavior of sporadic E layers, the prediction of sporadic E layer occurrence has been one of the most difficult issues in space weather forecast. To explore the possibility of numerically predicting sporadic E layer occurrence, we have examined various parameters related to sporadic E layer formation using the whole atmosphere–ionosphere coupled model GAIA. By comparing the parameters in GAIA with observed foEs data obtained by ionosonde observations in Japan, we found that variations in the vertical ion convergence at 120 km altitude agree fairly well with variations in foEs. This result suggests that sporadic E layer occurrence can be numerically predicted using the parameters derived from GAIA. We have recently developed a real-time GAIA simulation system that can predict atmosphere–ionosphere conditions for a few days ahead. We present an experimental prediction scheme and a preliminary result for predicting sporadic E layer occurrence.