Using GNSS radio occultation data to derive critical frequencies of the ionospheric sporadic E layer in real time

et al. 2021

Atmos. Chem. Phys.

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Abstract. 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.

Section: Resultsmentioning

confidence: 99%

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

et al. 2021

Atmos. Chem. Phys.

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“…Figure 3 shows the density scatter plot of 22 234 h coincident events after removing detecting strong Es layers. Either detection technique will only measure a subset of the distribution of the intensity of Es layers [62]. The correlation between the two techniques will be influenced by these factors.…”

Section: Discussionmentioning

confidence: 99%

“…S4max and fo Es was applied[62]. S4max is an index of an amplitude scintillation resulting from vertical gradients in the ionospheric irregularities.…”

mentioning

confidence: 99%

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

et al. 2020

R. Soc. open sci.

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The ionospheric sporadic E (Es) layer has a significant impact on the global positioning system (GPS)/global navigation satellite system (GNSS) signals. These influences on the GPS/GNSS signals can also be used to study the occurrence and characteristics of the Es layer on a global scale. In this paper, 5.8 million radio occultation (RO) profiles from the FORMOSAT-3/COSMIC satellite mission and ground-based observations of Es layers recorded by 25 ionospheric monitoring stations and held at the UK Solar System Data Centre at the Rutherford Appleton Laboratory and the Chinese Meridian Project were used to derive the hourly Es critical frequency ( f o Es) data. The global distribution of f o Es with a high spatial resolution shows a strong seasonal variation in f o Es with a summer maximum exceeding 4.0 MHz and a winter minimum between 2.0 and 2.5 MHz. The GPS/GNSS RO technique is an important tool that can provide global estimates of Es layers, augmenting the limited coverage and low-frequency detection threshold of ground-based instruments. Attention should be paid to small f o Es values from ionosondes near the instrumental detection limits corresponding to minimum frequencies in the range 1.28–1.60 MHz.

“…It shows that the strong 27 day cyclic change of metallic ions within Es layers occurs not only at solar maximum, but also at solar minimum when there is a strong solar rotation effect. Because plasma irregularities in Es layers can significantly affect radio communications and navigation systems (Yue et al 2016;Yu et al 2021), any predictable influence on the reliability of these systems, even during the solar minimum, is very important to quantify given the growth in demand for high-accuracy and reliable GNSS applications.…”

Section: Discussionmentioning

confidence: 99%

A Signature of 27 day Solar Rotation in the Concentration of Metallic Ions within the Terrestrial Ionosphere

et al. 2021

ApJ

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We present observations during the interval 2006-2014 of 27 day and 13.5 day periodic oscillations in the ionospheric sporadic E (Es) layer. This is a thin, dense layer composed of metallic ions in the Earth's upper atmosphere between 90 and 130 km. Lomb-Scargle spectral and wavelet analyses reveal that these pronounced periodicities observed from ground-based ionosondes and GPS/GNSS radio occultations are associated with highspeed solar winds generated from persistent coronal holes on successive 27 day solar rotations. The 27 day and 13.5 day oscillations in the Es layers are dependent on latitude, showing a higher magnitude of periodicities at low latitudes between 0°and 15°and at high latitudes between 45°and 90°(10%-14%) than those at midlatitudes between 15°and 45°(4%-10%). The 27 day and 13.5 day oscillations in the high-latitude Es layers correlate well with the geomagnetic activity Dst and Ap indices, and these periodic oscillations become more significant at the solar maximum (2000-2003 and 2011-2014) than at the solar minimum.