Dayside Field‐Aligned Current Impacts on Ionospheric Irregularities

Follestad, A. Fæhn; Herlingshaw, Katie; Ghadjari, Hossein; Knudsen, D. J.; McWilliams, K. A.; Moen, J.; Spicher, Andres; Wu, Jiashu; Oksavik, K.

doi:10.1029/2019gl086722

Cited by 12 publications

(21 citation statements)

References 63 publications

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“…Magnetic fluctuations have been observed in situ in regions of density irregularity at both high latitudes, in association with field‐aligned currents in the dayside cusp (Fæhn Follestad et al., 2020) and within equatorial plasma bubbles (Lühr et al., 2014; Pottelette et al., 2007; Rodríguez‐Zuluaga et al., 2017; Stolle et al., 2006). Two types of magnetic fluctuations are reported in association with plasma bubbles.…”

Section: Introductionmentioning

confidence: 99%

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Standing Alfvén Waves Within Equatorial Plasma Bubbles

Ghadjari

Knudsen

Skone

2022

Geophysical Research Letters

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Plasma depletions in the disturbed equatorial ionosphere are known to be associated with magnetic fluctuations and Alfvén waves. Here, using data from the Swarm B satellite's vector field magnetometer and electric fields instrument at an altitude of ∼500 km, we present evidence of standing Alfvén modes trapped within strong density depletions. Fourier transforms of electric (δE) and magnetic (δB) perturbations reveal harmonic structure with anticorrelated peaks and relative phase shifts approaching ±90°, in agreement with a simple model of standing waves sampled from a moving spacecraft. The mode frequencies allow us to estimate the field‐aligned length of the bubbles, which we find to be in the range of 110–200 km. This value is much smaller than the overall field line length mapped to the two E‐region footprints, indicating that the waves we observe do not couple to the lower ionosphere.

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Section: Introductionmentioning

confidence: 99%

“…A perturbation in this configuration can lead to the production of plasma bubbles (Balsley et al, 1972;Haerendel, 1973). Magnetic fluctuations have been observed in situ in regions of density irregularity at both high latitudes, in association with field-aligned currents in the dayside cusp (Faehn Follestad et al, 2020) and within equatorial plasma bubbles (…”

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confidence: 99%

Standing Alfvén Waves Within Equatorial Plasma Bubbles

Ghadjari

Knudsen

Skone

2022

Geophysical Research Letters

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“…Focusing on the dayside, Faehn Follestad et al (2020b) combined in-situ Swarm data with ground based GNSS observations to investigate the potential role of filamentary FACs on phase scintillations in the dayside auroral region. They found a colocation between regions of severe phase scintillations and highly filamented FACs with fluctuations measured in the spacecraft frame of the order of 20 Hz.…”

Section: The High-latitude Ionospherementioning

confidence: 99%

Variability of Ionospheric Plasma: Results from the ESA Swarm Mission

et al. 2022

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Swarm is the first European Space Agency (ESA) constellation mission for Earth Observation. Three identical Swarm satellites were launched into near-polar orbits on 22 November 2013. Each satellite hosts a range of instruments, including a Langmuir probe, GPS receivers, and magnetometers, from which the ionospheric plasma can be sampled and current systems inferred. In March 2018, the CASSIOPE/e-POP mission was formally integrated into the Swarm mission through ESA’s Earthnet Third Party Mission Programme. Collectively the instruments on the Swarm satellites enable detailed studies of ionospheric plasma, together with the variability of this plasma in space and in time. This allows the driving processes to be determined and understood. The purpose of this paper is to review ionospheric results from the first seven years of the Swarm mission and to discuss scientific challenges for future work in this field.

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“…These irregularities could be the consequence of density gradients due to the development of Gradient Drift Instability (GDI), driven by field-aligned currents or due to flow shears, which are common in the auroral ionosphere. They also could be direct consequences of cusp dynamics, i.e., precipitation associated with filamentary Field Aligned Currents (FAC) [61]. All of these processes can be responsible for the generation of large-scale inhomogeneities that provide a background on which small-scale instabilities can develop [62,63].…”

Section: Sanae: Scintillation Eventsmentioning

confidence: 99%

Investigation of the Physical Processes Involved in GNSS Amplitude Scintillations at High Latitude: A Case Study

et al. 2021

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The storm onset on 7 September 2017, triggered several variations in the ionospheric electron density, causing severe phase fluctuations at polar latitudes in both hemispheres. In addition, although quite rare at high latitudes, clear amplitude scintillations were recorded by two Global Navigation Satellite System receivers during the main phase of the storm. This work attempted to investigate the physical mechanisms triggering the observed amplitude scintillations, with the aim of identifying the conditions favoring such events. We investigated the ionospheric background and other conditions that prevailed when the irregularities formed and moved, following a multi-observations approach. Specifically, we combined information from scintillation parameters and recorded by multi-constellation (GPS, GLONASS and Galileo) receivers located at Concordia station (75.10°S, 123.35°E) and SANAE IV base (71.67°S, 2.84°W), with measurements acquired by the Special Sensor Ultraviolet Spectrographic Imager on board the Defense Meteorological Satellite Program satellites, the Super Dual Auroral Radar Network, the Swarm constellation and ground-based magnetometers. Besides confirming the high degree of complexity of the ionospheric dynamics, our multi-instrument observation identified the physical conditions that likely favor the occurrence of amplitude scintillations at high latitudes. Results suggest that the necessary conditions for the observation of this type of scintillation in high-latitude regions are high levels of ionization and a strong variability of plasma dynamics. Both of these conditions are typically featured during high solar activity.

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Dayside Field‐Aligned Current Impacts on Ionospheric Irregularities

Cited by 12 publications

References 63 publications

Standing Alfvén Waves Within Equatorial Plasma Bubbles

Standing Alfvén Waves Within Equatorial Plasma Bubbles

Variability of Ionospheric Plasma: Results from the ESA Swarm Mission

Investigation of the Physical Processes Involved in GNSS Amplitude Scintillations at High Latitude: A Case Study

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