Electrodynamics of Ionosphere–Thermosphere Coupling

Richmond, A. D.

doi:10.1007/978-94-007-0326-1_13

Cited by 11 publications

(9 citation statements)

References 79 publications

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“…The thermospheric wind acts to distribute energy and momentum from high‐latitude drivers to the global thermosphere‐ionosphere system, and likewise from sources in the lower and middle atmosphere to near‐Earth space. In the lower thermosphere, a region with high electrical conductivity, neutral winds generate dynamo electric fields which transport ionospheric plasma (Heelis, 2004; Richmond, 2011). In the upper thermosphere, winds force the ionosphere via drag and via advection of compositional changes (Rishbeth, 1972).…”

Section: Introductionmentioning

confidence: 99%

Validation of ICON‐MIGHTI Thermospheric Wind Observations: 2. Green‐Line Comparisons to Specular Meteor Radars

Harding

Chau

et al. 2021

JGR Space Physics

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We compare coincident thermospheric neutral wind observations made by the Michelson Interferometer for Global High-Resolution Thermospheric Imaging (MIGHTI) on the Ionospheric Connection Explorer (ICON) spacecraft, and four ground-based specular meteor radars (SMRs). Using the green-line MIGHTI channel, we analyze 1158 coincidences between Dec 2019 and May 2020 in the altitude range from 94 to 104 km where the observations overlap. We find that the two datasets are strongly correlated (r = 0.82) with a small mean difference (4.5 m/s). Although this agreement is good, an analysis of known error sources (e.g., shot noise, calibration errors, and analysis assumptions) can only account for about a quarter of the disagreement variance. The unexplained variance is 27.8% of the total signal variance and could be caused by unknown errors. However, based on an analysis of the spatial and temporal averaging of the two measurement modalities, we suggest that some of the disagreement is likely caused by temporal variability of the wind on scales ≲70 min. The observed magnitudes agree well during the night, but during the day, MIGHTI observes 16%-25% faster winds than the SMRs. This remains unresolved but is similar in certain ways to previous SMR-satellite comparisons. Plain Language Summary Although Earth's atmosphere becomes less dense at high altitudes where it transitions to space, the wind speed grows faster, often exceeding 100 m/s (225 mph). One barrier to better predictions of conditions in the near-Earth space environment is obtaining knowledge of the wind in the thermosphere, the uppermost layer of the atmosphere. Measurements of the thermospheric wind are difficult to make and historically sparse. ICON, a new NASA mission launched in October 2019, carries the MIGHTI instrument to measure the wind from 90 to 300 km altitude. In this study we compare the observations of MIGHTI to those of meteor radars, which measure the wind from the ground by analysis of radio waves reflected by meteor trails. The results indicate good agreement between the datasets when they measure the wind at the same time and place. Specifically, with 1158 coincidences over the first 6 months of the ICON mission, the correlation is 0.82 and the average difference is 4.5 m/s. This study is important because it validates the MIGHTI data, giving confidence for subsequent studies using its data. It also quantifies limits to the agreement between space-based and ground-based winds, which is useful information for future studies combining them. HARDING ET AL.

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Section: Introductionmentioning

confidence: 99%

Validation of ICON‐MIGHTI Thermospheric Wind Observations: 2. Green‐Line Comparisons to Specular Meteor Radars

Harding

Chau

et al. 2021

JGR Space Physics

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“…Electrodynamics of ionosphere-thermosphere coupling. Richmond [2011] presented an overview of ionosphere-thermosphere electrodynamic coupling. Collisions between the charged and neutral constituents of the upper atmosphere couple their respective dynamics and energetics.…”

Section: Work Carried Out and Results Obtainedmentioning

confidence: 99%

Modeling Density Variation in the Thermosphere

Richmond¹

2011

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“…Auroral ionization will not be considered although at high‐latitude conductivities are often dominated by this ionization source, especially at night (Richmond, ).…”

Section: Methodsmentioning

confidence: 99%

Ionospheric Conductance Spatial Distribution During Geomagnetic Field Reversals

2018

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The conductivity of the ionosphere is extremely important in geophysical processes and plays a critical role in magnetosphere‐ionosphere‐thermosphere coupling. Understanding its nature is essential to understand the physics of ionospheric electrodynamics. Earth's magnetic field, which varies greatly in geological time scales, is among the main variables involved in ionospheric conductivity. The present field can be approximated by a magnetic dipole that accounts for ~80% of the magnetic field at the Earth's surface, plus multipolar components making up the remaining ~20%. During a polarity transition the field magnitude diminishes to about 10% of its normal value at the expense, most likely, of decreasing the dipolar component and becoming mostly multipolar in nature. The effects of geomagnetic field variations on the spatial structure of Hall and Pedersen conductances are analyzed in the present work considering some possible reversal scenarios. The spatial structure of both conductances changes significantly with sharp spatial gradients. The conductivity peak heights also change, moving to upper heights as expected for weaker field configurations.

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Electrodynamics of Ionosphere–Thermosphere Coupling

Cited by 11 publications

References 79 publications

Validation of ICON‐MIGHTI Thermospheric Wind Observations: 2. Green‐Line Comparisons to Specular Meteor Radars

Validation of ICON‐MIGHTI Thermospheric Wind Observations: 2. Green‐Line Comparisons to Specular Meteor Radars

Modeling Density Variation in the Thermosphere

Ionospheric Conductance Spatial Distribution During Geomagnetic Field Reversals

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