Effects of the midnight temperature maximum observed in the thermosphere–ionosphere over the northeast of Brazil

Figueiredo, C. A. O. B.; Buriti, R. A.; Paulino, Igo; Meriwether, J. W.; Makela, J. J.; Batista, I. S.; Barros, Diego; Medeiros, A. F.

doi:10.5194/angeo-35-953-2017

Cited by 10 publications

(8 citation statements)

References 49 publications

(75 reference statements)

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“…When this occurs, it is called the critical level and, as a result, the gravity waves cannot propagate upward (Vadas, 2007). Barros et al (2018), Figueiredo, Buriti, et al (2017), and Makela et al (2013) reported that the nighttime thermospheric neutral wind magnitude, observed by Fabry-Perot interferometer in the Brazilian northeast, is not greater than 150 m/s. Moreover, Drob et al (2015) updated the Horizontal Wind Model and verified that the diurnal thermospheric neutral wind does not exceed 160 m/s on quiet days.…”

Section: Propagation Directionmentioning

confidence: 99%

Medium‐Scale Traveling Ionospheric Disturbances Observed by Detrended Total Electron Content Maps Over Brazil

et al. 2018

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A ground‐based network of Global Navigation Satellite Systems receivers has been used to monitor medium‐scale traveling ionospheric disturbances (MSTIDs). MSTIDs were studied using total electron content perturbation maps and keograms over south‐southeast of Brazil during the period from December 2012 to February 2016. In total, 826 MSTIDs were observed mainly in daytime, thus presenting median values of horizontal wavelength, period, and horizontal phase velocity of 452 ± 107 km, 24 ± 4 min. and 323 ± 81 m/s, respectively. The direction of propagation varies on the season: during the winter (June–August), the waves preferentially propagated to north‐northeast, while in the other seasons the waves propagated to other directions. The anisotropy observed in the MSTID propagation direction could be associated with the region of the gravity wave generation that takes place in the troposphere. We also found that the MSTIDs were observed most frequently during the daytime, between 11 and 15 local time in winter and near to dusk solar terminator (17–19 local time) in the other seasons. Furthermore, the occurrence of MSTIDs was higher in winter. We suggest that atmospheric gravity waves in the thermosphere, mesosphere, and troposphere could play an important role in generating the MSTIDs and the propagation direction may depend on location of the wave sources.

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Section: Propagation Directionmentioning

confidence: 99%

Medium‐Scale Traveling Ionospheric Disturbances Observed by Detrended Total Electron Content Maps Over Brazil

et al. 2018

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“…The authors observed that MSTIDs rarely propagate to magnetic latitudes less than 15°, and it occurs during the low solar activity period. Narayanan et al (2014) pointed out two physical explanations for that: first, the increasing intensity due to midnight pressure bulge shift to the poles (further details about midnight pressure bulge can be found in Figueiredo, Buriti, et al, 2017;Mesquita et al, 2018) when MSTIDs occur late at night and second, when MSTIDs propagate before midnight, it encounters the equatorial ionization anomaly that limits its propagation toward the equator. Amorim, and Candido (2008), which presented velocities ranging from 50 to 100 m/s.…”

Section: Journal Of Geophysical Research: Space Physicsmentioning

confidence: 99%

Investigation of Nighttime MSTIDS Observed by Optical Thermosphere Imagers at Low Latitudes: Morphology, Propagation Direction, and Wind Filtering

et al. 2018

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Different types of medium‐scale traveling ionospheric disturbances (MSTIDs) have been observed at Cachoeira Paulista (22.4°S; 45.0°W), Brazil, from June 2013 to December 2015, using airglow OI 630.0‐nm images. During the period, 58 MSTIDs were identified and classified as follows: dark band MSTIDs (around 10 events) and periodic MSTIDs (48 events). Dark band MSTIDs present phase velocity between 50 and 200 m/s and propagation direction to northwestward. On the other hand, periodic MSTIDs have phase velocity of 50 to 200 m/s, horizontal wavelengths from 80 to 160 km, periods ranging between 5 and 45 min, and propagation directions are mainly north‐northeastward. The wave parameters indicate that periodic MSTIDs have different characteristics when compared to dark band MSTIDs, suggesting that periodic MSTIDs are not generated through the well‐known Perkins and E‐F coupling instability. In addition to it, the present study indicates that the spectral characteristics found in Brazil are different from other regions such as Japan and Indonesia. Therefore, we intend to do the statistics of the wave parameters (wavelength, phase velocity, period, propagation direction, and time occurrence) and investigate the generation mechanisms of periodic MSTIDs at low to middle latitude for the first time. Furthermore, the anisotropy observed in periodic MSTID propagation direction can be explained by different mechanisms.

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“…The MTM peak is commonly observed in the equatorial region with typical amplitudes of 150-200 K (Figueiredo et al, 2017). An example of an amplitude of as much as 300 K associated with sudden stratospheric warming events has been presented (Gong et al, 2016). In the local summer as addressed by Meriwether et al (2008) and Meriwether et al (2011), the MTM was seen to move with an average velocity of 300 m s −1 (as observed by Sobral et al, 1978).…”

Section: Introductionmentioning

confidence: 76%

New results on the mid-latitude midnight temperature maximum

et al. 2018

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Abstract. Fabry–Perot interferometer (FPI) measurements of thermospheric temperatures and winds show the detection and successful determination of the latitudinal distribution of the midnight temperature maximum (MTM) in the continental mid-eastern United States. These results were obtained through the operation of the five FPI observatories in the North American Thermosphere Ionosphere Observing Network (NATION) located at the Pisgah Astronomic Research Institute (PAR) (35.2∘ N, 82.8∘ W), Virginia Tech (VTI) (37.2∘ N, 80.4∘ W), Eastern Kentucky University (EKU) (37.8∘ N, 84.3∘ W), Urbana-Champaign (UAO) (40.2∘ N, 88.2∘ W), and Ann Arbor (ANN) (42.3∘ N, 83.8∘ W). A new approach for analyzing the MTM phenomenon is developed, which features the combination of a method of harmonic thermal background removal followed by a 2-D inversion algorithm to generate sequential 2-D temperature residual maps at 30 min intervals. The simultaneous study of the temperature data from these FPI stations represents a novel analysis of the MTM and its large-scale latitudinal and longitudinal structure. The major finding in examining these maps is the frequent detection of a secondary MTM peak occurring during the early evening hours, nearly 4.5 h prior to the timing of the primary MTM peak that generally appears after midnight. The analysis of these observations shows a strong night-to-night variability for this double-peaked MTM structure. A statistical study of the behavior of the MTM events was carried out to determine the extent of this variability with regard to the seasonal and latitudinal dependence. The results show the presence of the MTM peak(s) in 106 out of the 472 determinable nights (when the MTM presence, or lack thereof, can be determined with certainty in the data set) selected for analysis (22 %) out of the total of 846 nights available. The MTM feature is seen to appear slightly more often during the summer (27 %), followed by fall (22 %), winter (20 %), and spring (18 %). Also seen is a northwestward propagation of the MTM signature with a latitude-dependent amplitude. This behavior suggests either a latitudinal dependence of thermosphere tidal dissipation or a night-to-night variation of the composition of the higher-order tidal modes that contribute to the production of the MTM peak at mid-latitudes. Also presented in this paper is the perturbation on the divergence of the wind fields, which is associated with the passage of each MTM peak analyzed with the 2-D interpolation. Keywords. Ionosphere (mid-latitude ionosphere)

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Effects of the midnight temperature maximum observed in the thermosphere–ionosphere over the northeast of Brazil

Cited by 10 publications

References 49 publications

Medium‐Scale Traveling Ionospheric Disturbances Observed by Detrended Total Electron Content Maps Over Brazil

Medium‐Scale Traveling Ionospheric Disturbances Observed by Detrended Total Electron Content Maps Over Brazil

Investigation of Nighttime MSTIDS Observed by Optical Thermosphere Imagers at Low Latitudes: Morphology, Propagation Direction, and Wind Filtering

New results on the mid-latitude midnight temperature maximum

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