Sq and EEJ—A Review on the Daily Variation of the Geomagnetic Field Caused by Ionospheric Dynamo Currents

Self Cite

112

138

An exceptionally strong stationary planetary wave with Zonal Wavenumber 1 led to a sudden stratospheric warming (SSW) in the Southern Hemisphere in September 2019. Ionospheric data from European Space Agency's Swarm satellite constellation mission show prominent 6‐day variations in the dayside low‐latitude region at this time, which can be attributed to forcing from the middle atmosphere by the Rossby normal mode “quasi‐6‐day wave” (Q6DW). Geopotential height measurements by the Microwave Limb Sounder aboard National Aeronautics and Space Administration's Aura satellite reveal a burst of global Q6DW activity in the mesosphere and lower thermosphere during the SSW, which is one of the strongest in the record. The Q6DW is apparently generated in the polar stratosphere at 30–40 km, where the atmosphere is unstable due to strong vertical wind shear connected with planetary wave breaking. These results suggest that an Antarctic SSW can lead to ionospheric variability through wave forcing from the middle atmosphere.

Section: Ionospheric Observations By Swarmmentioning

confidence: 99%

September 2019 Antarctic Sudden Stratospheric Warming: Quasi‐6‐Day Wave Burst and Ionospheric Effects

Yamazaki

Matthias

Miyoshi

et al. 2020

Self Cite

112

138

“…The GOLD mission, observing the same longitudes repeatedly and on every night, can provide synoptic measurements of large sections of the EIA. The magnetic equator crosses the geographic equator near the subsatellite point, resulting in longitudinal differences in the orientation of the magnetic field to the geographic coordinate system and hence to the neutral winds (e.g., Anderson & Araujo-Pradere, 2010;Fang et al, 2012;Hagan et al, 2007;Yamazaki & Maute, 2017). This difference in equator location and the simultaneous GOLD observations may help advance comprehension of the EIA.…”

Section: 1029/2019gl084199mentioning

confidence: 99%

Global‐Scale Observations of the Equatorial Ionization Anomaly

Eastes

Solomon

Daniell

et al. 2019

116

The National Aeronautics and Space Administration Global‐scale Observations of the Limb and Disk ultraviolet spectrograph has been imaging the equatorial ionization anomaly (EIA), regions of the ionosphere with enhanced electron density north and south of the magnetic equator, since October 2018. The initial 3 months of observations was during solar minimum conditions, and they included observations in December solstice of unanticipated variability and depleted regions. Depletions are seen on most nights, in contrast to expectations from previous space‐based observations. The variety of scales and morphologies also pose challenges to understanding of the EIA. Abrupt changes in the EIA location, which could be related to in situ measurements of large‐scale depletion regions, are observed on some nights. Such synoptic‐scale disruptions have not been previously identified.

“…The equatorial E region of the ionosphere supports an intense current system called the equatorial electrojet (EEJ) owing to the unique geometry of the Earth's magnetic field (see Yamazaki & Maute, 2017, for a recent review on Sq and EEJ current systems). The EEJ flows eastward (westward) during the day (night) concentrated within ±3°centered at the dip equator.…”

Section: Introductionmentioning

confidence: 99%

Evidence for the Influence of DE3 Tide on the Occurrence of Equatorial Counterelectrojet

Singh

Gurubaran

2018

The long‐term Challenging Minisatellite Payload magnetometer data are analyzed to derive the equatorial counterelectrojet (CEJ) signatures globally over a range of local times. The resultant local time‐longitude map of CEJ occurrence rate shows a strong influence of the diurnal eastward propagating wave number 3 (DE3) nonmigrating tide during July–September months. DE3 is also shown to account for the reduction of CEJ occurrence at certain longitudes. These aspects of DE3 tide‐CEJ relationship have implications for understanding the seasonal and longitudinal variations of CEJ. Observations of zonal winds from the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) Doppler Interferometer instrument on board the TIMED satellite are used to establish these findings.