Observations of nighttime equatorial-upper-E-valley region irregular structures from São Luís radar and their occurrence statistics: A manifestation of vertical coupling between E and F regions

Kherani, E. A.; Paula, E. R. de; Cueva, Ricardo Yvan de La Cruz; Camargo, L.A.P.

doi:10.1016/j.jastp.2011.08.017

Cited by 10 publications

(22 citation statements)

References 24 publications

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“…2 indicate that the irregularities found at altitudes below the base of the F layer appear simultaneously with irregular F structures of larger scale (bottom-type and/or bottomside F layer and plumes). This feature was observed in previous studies carried out in Brazil (Kherani et al, 2012). In that work, it was noted that the slope of the valley-type irregularities, as observed on an RTI map, was proportional to the ascension rate of bottom-type and/or bottom-side F layer irregularities.…”

Section: Langmuir Probe Measurementssupporting

confidence: 78%

“…Although the RTI map and the N e height profile were obtained at longitudinally separated locations and different times, the comparison can be carried out. As discussed at the end of this section and noted by Kherani et al (2012) and Woodman and Chau (2001), the irregularities that appear in the E and valley regions are closely related to bottom-type and top-side (plumes or bubbles) irregularities.…”

Section: Langmuir Probe Measurementsmentioning

confidence: 71%

“…8) in the E and F valley regions. Previous observations (Woodman and Chau, 2001;Kherani et al, 2012) show that the eastern rise of valley irregularities is more prominent compared with its western counterpart. Our results (see the N e height profiles in Fig.…”

Section: Langmuir Probe Measurementsmentioning

confidence: 86%

“…Unfortunately, the low-power VHF radar located very near CLA and used in other studies (e.g., de de Paula et al, 2011;Kherani et al, 2012) was inoperative between October 2012 and February 2013; thus, it was decided to use the RTI map found in Woodman and Chau (2001) to gain insight about our in situ measurements. This RTI map obtained on 20 October 1993 over Jicamarca is a great example of E and F valley region irregularities and was good enough for our purposes: to make a comparison of the spatial distribution of irregularities as observed by our in situ measurements and the VHF radar in Jicamarca.…”

Section: Langmuir Probe Measurementsmentioning

confidence: 99%

“…Using an aperture synthesis imaging technique, the authors were able to show a striking and complex set of striations evidencing different levels of signal-to-noise ratio (SNR), representing a range of different electron density regions. In the equatorial region over Brazil, a statistical study with observations made during 581 nights (from 2001 to 2008) was conducted by Kherani et al (2012) using a low-power coherent scatter radar located at the São Luís equatorial station. Similar to the results of Woodman and Chau (2001), the structures were observed during occurrences of an ascending irregular bottom-type or bottom-side F layer and at the same time or prior to an ascending and well-developed plume.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Rocket in situ observation of equatorial plasma irregularities in the region between E and F layers over Brazil

Savio¹,

Meneses²,

Muralikrishna³

et al. 2017

Ann. Geophys.

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Abstract. A two-stage VS-30 Orion rocket was launched from the equatorial rocket launching station in Alcântara, Brazil, on 8 December 2012 soon after sunset (19:00 LT), carrying a Langmuir probe operating alternately in swept and constant bias modes. At the time of launch, ground equipment operated at equatorial stations showed rapid rise in the base of the F layer, indicating the pre-reversal enhancement of the F region vertical drift and creating ionospheric conditions favorable for the generation of plasma bubbles. Vertical profiles of electron density estimated from Langmuir probe data showed wave patterns and small-and mediumscale plasma irregularities in the valley region (100-300 km) during the rocket upleg and downleg. These irregularities resemble those detected by the very high frequency (VHF) radar installed at Jicamarca and so-called equatorial quasiperiodic echoes. We present evidence suggesting that these observations could be the first detection of this type of irregularity made by instruments onboard a rocket.

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Section: Langmuir Probe Measurementssupporting

confidence: 78%

Section: Langmuir Probe Measurementsmentioning

confidence: 71%

Section: Langmuir Probe Measurementsmentioning

confidence: 86%

Section: Langmuir Probe Measurementsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Rocket in situ observation of equatorial plasma irregularities in the region between E and F layers over Brazil

Savio¹,

Meneses²,

Muralikrishna³

et al. 2017

Ann. Geophys.

View full text Add to dashboard Cite

show abstract

Parallel plate capacitor analogy of equatorial plasma bubble and associated fringe fields with implications to equatorial valley region irregularities

Mukherjee

Patra

2014

JGR Space Physics

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VHF radar echoes from the valley region plasma irregularities, displaying ascending pattern, are often observed during the active phase of equatorial plasma bubble in the close vicinity of the geomagnetic equator and have been attributed to bubble-related fringe field effect. These irregularities however are not observed at a few degrees away from the equator. In this paper, we attempt to understand this contrasting observational result by comparing fringe field at the geomagnetic equator and low latitudes. We use parallel plate capacitor analogy of equatorial plasma bubble and choose a few capacitor configurations, consistent with commonly observed dimension and magnetic field-aligned property of plasma bubble, for computing fringe field. Results show that fringe field decreases significantly with decreasing altitude as expected. Further, fringe field decreases remarkably with latitude, which clearly indicates the role of magnetic field-aligned property of plasma bubble in reducing the magnitude of fringe field at low latitudes compared to that at the geomagnetic equator. The results are presented and discussed in the light of current understanding of plasma bubble-associated fringe field-induced plasma irregularities in the valley region.

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Fringe field dynamics over equatorial and low‐latitude ionosphere: A three‐dimensional perspective

Kherani

Patra

2015

JGR Space Physics

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This paper presents a three‐dimensional simulation of the collisional interchange instability generating equatorial plasma bubble (EPB) in the evening ionospheric F region and associated fringe field (FF) in the valley‐upper‐E (VE) region. This simulation is primarily intended to address hitherto unexplained radar observations of ascending irregularity structures only in the vicinity of the magnetic equator in association with the EPB phenomenon. Novel results of the present simulation are the following: (1) EPB‐associated FF penetrating into the E region is found to be confined to a latitude belt of ±5∘, (2) ascending irregularity structures from the E region is formed only when perturbation in plasma parameters similar to those responsible for forming EPB are present in the VE region, and (3) perturbation in the VE region provide conditions for the formation of ascending irregularity structures on the eastern wall of the plasma bubble. These results are in excellent agreement with radar observations and also account for the presence of metallic ions in the EPB at and above the F region peak.

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Observations of nighttime equatorial-upper-E-valley region irregular structures from São Luís radar and their occurrence statistics: A manifestation of vertical coupling between E and F regions

Cited by 10 publications

References 24 publications

Rocket in situ observation of equatorial plasma irregularities in the region between E and F layers over Brazil

Rocket in situ observation of equatorial plasma irregularities in the region between E and F layers over Brazil

Parallel plate capacitor analogy of equatorial plasma bubble and associated fringe fields with implications to equatorial valley region irregularities

Fringe field dynamics over equatorial and low‐latitude ionosphere: A three‐dimensional perspective

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