Observational evidence for new instabilities in the midlatitude &amp;lt;i&amp;gt;E&amp;lt;/i&amp;gt; and &amp;lt;i&amp;gt;F&amp;lt;/i&amp;gt; region

Hysell, D. L.; Larsen, M. F.; Sulzer, M. P.

doi:10.5194/angeo-34-927-2016

Cited by 12 publications

(11 citation statements)

References 68 publications

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“…The observations support the theory with regard to the phase relationship between the MSTIDs and E s , suggesting that the MSTIDs and the plasma density irregularities of the E s layer were electrically coupled through the geomagnetic field line as predicted by the F ‐ F coupling instability theory (Cosgrove & Tsunoda, , ; Yokoyama et al, ). Such direct coupling between the plasma density irregularities of the E s layer and the MSTIDs in the F region could not be revealed by the E region and F region observations from a single site (Hysell et al, ).…”

Section: Resultsmentioning

confidence: 91%

Observation of Synchronization Between Instabilities of the Sporadic E Layer and Geomagnetic Field Line Connected F Region Medium‐Scale Traveling Ionospheric Disturbances

et al. 2019

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A frequency-tunable resonance scattering lidar with high temporal/vertical resolutions (1 min/15 m) observed sporadic calcium ion (Ca + s) layers at~100 km over Tachikawa (geographical/ geomagnetic latitude: 35.7°N/27.1°N), Japan, on 21-22 August 2014. Simultaneously, sporadic E (E s) parameters and medium-scale traveling ionospheric disturbances (MSTIDs) were observed by an ionosonde and Global Navigation Satellite System receiver network, GEONET, respectively. The maximum densities of the Ca + and electrons in the E s layer had a strong positive correlation. As observation started~23:30 LT, the Ca + s layer and the associated E s layer descended at~2.8 km/hr with density irregularities including Kelvin-Helmholtz billow-like structures suggesting the presence of background neutral wind shear and instability. And the total electron content variations showed large amplitude associated with the MSTIDs at an altitude of 300 km in synchronization with the Ca + column abundance surges at 100 km over Tachikawa; in their respective E and F region locations connected by geomagnetic field line these irregularities are found to vary in phase. At~02:00 LT, the Ca + s layer stopped descending at~100 km due to larger ion-neutral collision frequency in the lower altitudes and resided there quietly until sunrise; both Ca + column abundance enhancements and the large total electron content variation disappeared as the descent of the Ca + s layer stopped, implicating that the MSTID structure cannot be sustained without the density irregularities of the E s layer. This is the first synchronous observation of the coupling between the E s density irregularities and the MSTIDs in the F region along a common magnetic flux tube. Plain Language Summary The irregular structures of the sporadic E (E s) layer appearing in altitudes of 90-130 km were observed by a calcium ion (Ca +) resonance scattering lidar and an ionosonde. Simultaneously, medium-scale traveling ionospheric disturbances (MSTIDs) in the F region (150-to 500-km altitude) were observed by the Global Navigation Satellite System receiver array in Japan. Though the electron column abundance variation in the E s irregularities is more than an order of magnitude smaller than that in the MSTIDs, we observed that the MSTIDs decayed with the disappearance of the irregular structure in the E s layer. This observation clearly revealed for the first time that the plasma density irregularities in the E region were coupled to those in the F region by the geomagnetic field line as theory predicted.

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Section: Resultsmentioning

confidence: 91%

Observation of Synchronization Between Instabilities of the Sporadic E Layer and Geomagnetic Field Line Connected F Region Medium‐Scale Traveling Ionospheric Disturbances

et al. 2019

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“…It has also been linked by numerous investigators to a particular plasma instability mechanism thought to operate at middle latitudes attributed to Perkins 27 . Mid-latitude spread F has furthermore been associated with patchy E s layers, observationally and theoretically, although different perspectives exist regarding the causal relationship 28 – 32 . Meter-scale irregularities in the F region are also known to cause coherent scatter 33 , 34 .…”

Section: Introductionmentioning

confidence: 99%

Major upwelling and overturning in the mid-latitude F region ionosphere

et al. 2018

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Profiles of the electron number density in the ionosphere are observed at the Arecibo Radio Observatory in Puerto Rico on a regular basis. Here, we report on recent observations showing anomalous irregularities in the density profiles at altitudes >~300 km. The irregularities occurred during a period of “mid-latitude spread F,” a space-weather phenomenon relatively common at middle latitudes in summer months characterized by instability and electron density irregularities in the bottomside of the ionospheric F layer. Remarkably, electron density irregularities extended well above the layer, through the ionization peak and into the topside which is regarded as being stable. Neither the neutral atmosphere nor the ionosphere is thought to be able to support turbulence locally at this altitude. A numerical simulation is used to illustrate how a combination of atmospheric and plasma dynamics driven at lower altitudes could explain the phenomenon.

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“…They are thought to be directly driven by GWs or result from the Perkins instability, which can be seeded by GWs (Behnke, ; Perkins, ; Shiokawa et al, ). Plasma perturbations due to MSTIDs may create conditions favorable for MSF formation via convective instabilities such as the Perkins instability (Hysell et al, ), although Shiokawa et al () reported MSF coincident with MSTIDs only 10–15% of the time.…”

Section: Introductionmentioning

confidence: 99%

Climatology and Characteristics of Medium‐Scale F Region Ionospheric Plasma Irregularities Observed by COSMIC Radio Occultation Receivers

Watson

Pedatella

2018

JGR Space Physics

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Medium-scale ionospheric ionization structures are a persistent global feature of the Earth's ionosphere. Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) radio occultation measurements are well suited to address the incomplete global observational picture of plasma density irregularities, including the global climatology in both bottomside and topside F region layers, and their structure in the vertical dimension. A climatological database of F region ionospheric irregularities and their characteristics has been developed through detection of total electron content perturbations by Global Positioning System receivers onboard COSMIC satellites. This paper presents global occurrence rates and detailed characteristics of equatorial to midlatitude medium-scale irregularities under quiet geomagnetic conditions. The study covers 4 years, two during solar minimum (2008)(2009) and two during the ascending phase of solar cycle 24 (2012)(2013). Irregularities were found to occur frequently at high latitudes and during nighttime in equatorial to midlatitude regions in both bottom and topside F region layers. Longitudinal-seasonal occurrence trends at equatorial and midlatitudes are consistent with previous irregularity climatology, which reaffirms that localized enhancements in plasma instability growth rates contribute to irregularity occurrence. Seasonal occurrence patterns also indicate a high occurrence of irregularities in regions corresponding to the solar terminator, confined primarily to altitudes below~300 km. The local time-altitude distributions of equatorial and midlatitude irregularity occurrence, amplitude, and scale size provide further insight into irregularity generation mechanisms, and include features consistent with "spread F" irregularities and traveling ionospheric disturbances.

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Observational evidence for new instabilities in the midlatitude <i>E</i> and <i>F</i> region

Cited by 12 publications

References 68 publications

Observation of Synchronization Between Instabilities of the Sporadic E Layer and Geomagnetic Field Line Connected F Region Medium‐Scale Traveling Ionospheric Disturbances

Observation of Synchronization Between Instabilities of the Sporadic E Layer and Geomagnetic Field Line Connected F Region Medium‐Scale Traveling Ionospheric Disturbances

Major upwelling and overturning in the mid-latitude F region ionosphere

Climatology and Characteristics of Medium‐Scale F Region Ionospheric Plasma Irregularities Observed by COSMIC Radio Occultation Receivers

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