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Yuichi Otsuka - One of the best experts on this subject based on the ideXlab platform.
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Observational evidence of interaction between Equatorial Plasma Bubble, Medium-scale Traveling Ionospheric Disturbances, and Midnight Brightness Wave at low latitudes
2020Co-Authors: C. A. O. B. Figueiredo, Kazuo Shiokawa, Yuichi Otsuka, Cristiano Max Wrasse, Hisao Takahashi, Ricardo Arlen Buriti, Igo Paulino, D. BarrosAbstract:An interesting interaction between equatorial plasma bubbles (EPBs), medium-scale Traveling Ionospheric Disturbance (MSTID), and midnight brightness wave (MBW) were observed at Cachoeira Paulista, ...
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disappearance of equatorial plasma bubble after interaction with mid latitude medium scale Traveling Ionospheric Disturbance
Geophysical Research Letters, 2012Co-Authors: Yuichi Otsuka, K Shiokawa, T OgawaAbstract:[1] We report simultaneous observations of an equatorial plasma bubble and a Medium-Scale Traveling Ionospheric Disturbance (MSTID) in 630-nm airglow images taken with an all-sky airglow imager at Shigaraki (34.9°N, 136.1°E; dip angle of the geomagnetic field ∼49°), Japan. Clear depletion of the 630-nm airglow intensity was observed as the equatorial plasma bubble propagated eastward, whereas the MSTID, which had a wavefront aligned from northwest to southeast, propagated southwestward. This result indicates that MSTIDs do not propagate at the same velocity as the ambient plasma, which is clearly shown by the eastward motion of the plasma bubbles. We found that the airglow depletion caused by the plasma bubble disappeared when the plasma bubble encountered the MSTID. The plasma depletion could be filled with ambient rich plasma that moved into the plasma-depleted region byE × B drift associated with the MSTID, indicating that MSTIDs are accompanied by electric field perturbations.
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large scale Traveling Ionospheric Disturbance observed by superdarn hokkaido hf radar and gps networks on 15 december 2006
Journal of Geophysical Research, 2010Co-Authors: H Hayashi, Yuichi Otsuka, T Ogawa, N. Nishitani, Takuya Tsugawa, K Hosokawa, Akinori SaitoAbstract:[1] On 15 December 2006, during the main phase of a relatively large storm, Doppler velocity data from the Super Dual Aural Radar Network (SuperDARN) Hokkaido radar, together with total electron content (TEC) data from the GPS Earth Observation Network (GEONET), recorded daytime large-scale Traveling Ionospheric Disturbances (LSTIDs). We studied two Disturbances propagating southward and one Disturbance propagating northward between 0000 and 0600 UT on 15 December 2006. The former Disturbances were LSTIDs typical of those reported in many previous studies, whereas the latter was confirmed as an LSTID propagating from the Southern into the Northern Hemisphere, reported in a few past studies. From comparisons of SuperDARN Hokkaido radar Doppler velocity and GEONET TEC, we found a positive correlation between downward Ionospheric motion and increasing TEC. This relationship is consistent with results of model calculation. This is the first observation of LSTIDs ranging from high to low latitude combining simultaneous SuperDARN HF radar and GPS network observations.
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statistical study of relationship between medium scale Traveling Ionospheric Disturbance and sporadic e layer activities in summer night over japan
Journal of Atmospheric and Solar-Terrestrial Physics, 2008Co-Authors: Yuichi Otsuka, T Ogawa, T Tani, T Tsugawa, Akinori SaitoAbstract:Abstract We investigate the relationship between medium-scale Traveling Ionospheric Disturbance (MSTID) and sporadic E ( E s ) layer activities in summer nights by analyzing total electron content (TEC) data obtained from a global positioning system (GPS) network in Japan and ionosonde data obtained at Kokubunji, Japan during May–August in 2001–2005. MSTID activity is defined as δ I / I ¯ , where δ I is standard deviation of the TEC perturbations over Kokubunji within 1 h, and I ¯ is the background TEC. By analyzing nighttime-averaged (19-02 LT) values of MSTID activity and E s layer parameters, we find that the MSTID activity is closely correlated with f 0 E s and f 0 E s - f b E s . This result suggests that MSTID and the spatial structures of E s layer could be generated by an electro-dynamical coupling process between the E s layer and F region through polarization electric fields. Furthermore, we suggest that the appearance of the E s layer in the summer hemisphere could play an important role in generating MSTIDs in both hemispheres.
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Ground observation and AMIE‐TIEGCM modeling of a storm‐time Traveling Ionospheric Disturbance
Journal of Geophysical Research: Space Physics, 2007Co-Authors: Kazuo Shiokawa, Yuichi Otsuka, Tadahiko Ogawa, Masayuki Yamamoto, Nozomu Nishitani, Natsuo SatoAbstract:[1] This paper reports the first comparison between comprehensive observations of equatorward moving Traveling Ionospheric Disturbance at midlatitudes and thermospheric general circulation model with high-latitude energy input based on data assimilation. A prominent Traveling Ionospheric Disturbance (TID) was observed during the major magnetic storm of 31 March 2001. The TID propagated from north to south over Japan with phase speeds of 370–640 m/s. The assimilative mapping of Ionospheric electrodynamics (AMIE) technique was used as input to the thermosphere-ionosphere-electrodynamics general circulation model (TIEGCM) to investigate generation and propagation of the observed TID. In the model, two Joule heating enhancements in the high-latitude dayside sector produced two distinct Traveling atmospheric waves (TADs), which propagated to Japan in the midnight sector as enhancements in thermospheric temperature and southward wind speed. The phase speed of the TADs was much faster (∼1100 m/s) in the model, probably due to the overestimation of Joule heating in the model. The second TAD corresponds to the observed prominent TID, while signatures of the first TAD were also seen in the observed ionosonde data. The observed TID was characterized by a decrease in southward wind speed, causing a significant F-layer height decrease and a temporal enhancement of F-layer peak density. These characteristics were reproduced by the model as a rarefaction of the second TAD. The temporal enhancement of F-layer peak density was because of the vertical shear of meridional wind. The absolute value of F-layer electron density in the model was several factors smaller than that observed, probably because of the underestimation of the supply of O+ ions from the plasmasphere.
T Ogawa - One of the best experts on this subject based on the ideXlab platform.
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disappearance of equatorial plasma bubble after interaction with mid latitude medium scale Traveling Ionospheric Disturbance
Geophysical Research Letters, 2012Co-Authors: Yuichi Otsuka, K Shiokawa, T OgawaAbstract:[1] We report simultaneous observations of an equatorial plasma bubble and a Medium-Scale Traveling Ionospheric Disturbance (MSTID) in 630-nm airglow images taken with an all-sky airglow imager at Shigaraki (34.9°N, 136.1°E; dip angle of the geomagnetic field ∼49°), Japan. Clear depletion of the 630-nm airglow intensity was observed as the equatorial plasma bubble propagated eastward, whereas the MSTID, which had a wavefront aligned from northwest to southeast, propagated southwestward. This result indicates that MSTIDs do not propagate at the same velocity as the ambient plasma, which is clearly shown by the eastward motion of the plasma bubbles. We found that the airglow depletion caused by the plasma bubble disappeared when the plasma bubble encountered the MSTID. The plasma depletion could be filled with ambient rich plasma that moved into the plasma-depleted region byE × B drift associated with the MSTID, indicating that MSTIDs are accompanied by electric field perturbations.
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large scale Traveling Ionospheric Disturbance observed by superdarn hokkaido hf radar and gps networks on 15 december 2006
Journal of Geophysical Research, 2010Co-Authors: H Hayashi, Yuichi Otsuka, T Ogawa, N. Nishitani, Takuya Tsugawa, K Hosokawa, Akinori SaitoAbstract:[1] On 15 December 2006, during the main phase of a relatively large storm, Doppler velocity data from the Super Dual Aural Radar Network (SuperDARN) Hokkaido radar, together with total electron content (TEC) data from the GPS Earth Observation Network (GEONET), recorded daytime large-scale Traveling Ionospheric Disturbances (LSTIDs). We studied two Disturbances propagating southward and one Disturbance propagating northward between 0000 and 0600 UT on 15 December 2006. The former Disturbances were LSTIDs typical of those reported in many previous studies, whereas the latter was confirmed as an LSTID propagating from the Southern into the Northern Hemisphere, reported in a few past studies. From comparisons of SuperDARN Hokkaido radar Doppler velocity and GEONET TEC, we found a positive correlation between downward Ionospheric motion and increasing TEC. This relationship is consistent with results of model calculation. This is the first observation of LSTIDs ranging from high to low latitude combining simultaneous SuperDARN HF radar and GPS network observations.
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statistical study of relationship between medium scale Traveling Ionospheric Disturbance and sporadic e layer activities in summer night over japan
Journal of Atmospheric and Solar-Terrestrial Physics, 2008Co-Authors: Yuichi Otsuka, T Ogawa, T Tani, T Tsugawa, Akinori SaitoAbstract:Abstract We investigate the relationship between medium-scale Traveling Ionospheric Disturbance (MSTID) and sporadic E ( E s ) layer activities in summer nights by analyzing total electron content (TEC) data obtained from a global positioning system (GPS) network in Japan and ionosonde data obtained at Kokubunji, Japan during May–August in 2001–2005. MSTID activity is defined as δ I / I ¯ , where δ I is standard deviation of the TEC perturbations over Kokubunji within 1 h, and I ¯ is the background TEC. By analyzing nighttime-averaged (19-02 LT) values of MSTID activity and E s layer parameters, we find that the MSTID activity is closely correlated with f 0 E s and f 0 E s - f b E s . This result suggests that MSTID and the spatial structures of E s layer could be generated by an electro-dynamical coupling process between the E s layer and F region through polarization electric fields. Furthermore, we suggest that the appearance of the E s layer in the summer hemisphere could play an important role in generating MSTIDs in both hemispheres.
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thermospheric wind during a storm time large scale Traveling Ionospheric Disturbance
Journal of Geophysical Research, 2003Co-Authors: K Shiokawa, Yuichi Otsuka, Masayuki Yamamoto, T Ogawa, Seiji Kawamura, S Fukao, Takuji Nakamura, Toshitaka Tsuda, N Balan, K IgarashiAbstract:[1] A prominent large-scale Traveling Ionospheric Disturbance (LSTID) was observed in Japan during the major magnetic storm (Dst ∼ −358 nT) of 31 March 2001. It was detected as enhancements of the 630-nm airglow and foF2, GPS-TEC variations, and a decrease in F-layer virtual height at 1700–1900 UT (0200–0400 LT). It moved equatorward with a speed of ∼600 m/s. The decrease in the F-layer height was also detected by the MU radar at Shigaraki. Thermospheric wind variations were observed by the MU radar through ion drift measurement and by a Fabry-Perot interferometer (FPI) through a Doppler shift of the 630-nm airglow line at Shigaraki. The wind data show a turn of the meridional wind from −94 m/s (equatorward) to +44 m/s (poleward) during the LSTID, indicating that an intense poleward wind in the thermosphere passed over Shigaraki as an atmospheric gravity wave and caused the observed Ionospheric features of the LSTID. Intense poleward wind was also detected at mesospheric altitudes (95–100 km) by the MU radar (through meteor echoes) and by the FPI (through the 558-nm airglow) with a delay of ∼2 hours from the thermospheric wind, indicating downward phase progression of the wave. Generation of the observed poleward wind in the auroral zone was investigated using magnetic field data and auroral energy input estimated by the assimilative mapping of Ionospheric electrodynamics (AMIE) technique. We suggest that simple atmospheric heating and/or the Lorentz force in the auroral zone do not explain the observed poleward wind enhancement.
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ground and satellite observations of nighttime medium scale Traveling Ionospheric Disturbance at midlatitude
Journal of Geophysical Research, 2003Co-Authors: K Shiokawa, Yuichi Otsuka, T Ogawa, C Ihara, F J RichAbstract:[1] We have investigated a nighttime medium-scale Traveling Ionospheric Disturbance (MSTID) observed by an airglow imager at Shigaraki (34.9°N, 25.4°MLAT), Japan, on 17 May 2001. The structure was identified in the airglow images of OI (630.0 nm and 777.4 nm) as NW-SE band structures (horizontal wavelength: 230 km) moving southwestward with a velocity of 50 m/s. Neutral wind velocity was measured simultaneously from the Doppler shift of the 630.0-nm emission by a Fabry-Perot interferometer at Shigaraki. From these parameters, we performed model calculations of MSTIDs generated by gravity waves and by an oscillating electric field. We found that for the case of gravity waves, the estimated vertical wavelength was too small to explain the observed amplitudes of airglow intensity. For the case of the electric field, we found that an electric field oscillation of ∼1.2 mV/m was sufficient to reproduce the observed airglow amplitudes. This modeled electric field was comparable to that observed by the DMSP F15 satellite as it passed over Shigaraki during our observing period on 17 May 2001. The DMSP ion drift data show that the oscillation of the polarization electric field correlated with the MSTID structure in the airglow image, suggesting that the polarization electric field plays an important role in the generation of MSTIDs.
K Shiokawa - One of the best experts on this subject based on the ideXlab platform.
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www.ann-geophys.net/27/2399/2009/ © Author(s) 2009. This work is distributed under the Creative Commons Attribution 3.0 License.
2016Co-Authors: A. Koustov, K Shiokawa, N. Nishitani, P. V. Ponomarenko, S. Suzuki, B. M. Shevtsov, J. W. MacdougallAbstract:Joint observations of a Traveling Ionospheric Disturbance with the Paratunka OMTI camera and the Hokkaido HF rada
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disappearance of equatorial plasma bubble after interaction with mid latitude medium scale Traveling Ionospheric Disturbance
Geophysical Research Letters, 2012Co-Authors: Yuichi Otsuka, K Shiokawa, T OgawaAbstract:[1] We report simultaneous observations of an equatorial plasma bubble and a Medium-Scale Traveling Ionospheric Disturbance (MSTID) in 630-nm airglow images taken with an all-sky airglow imager at Shigaraki (34.9°N, 136.1°E; dip angle of the geomagnetic field ∼49°), Japan. Clear depletion of the 630-nm airglow intensity was observed as the equatorial plasma bubble propagated eastward, whereas the MSTID, which had a wavefront aligned from northwest to southeast, propagated southwestward. This result indicates that MSTIDs do not propagate at the same velocity as the ambient plasma, which is clearly shown by the eastward motion of the plasma bubbles. We found that the airglow depletion caused by the plasma bubble disappeared when the plasma bubble encountered the MSTID. The plasma depletion could be filled with ambient rich plasma that moved into the plasma-depleted region byE × B drift associated with the MSTID, indicating that MSTIDs are accompanied by electric field perturbations.
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joint observations of a Traveling Ionospheric Disturbance with the paratunka omti camera and the hokkaido hf radar
Annales Geophysicae, 2009Co-Authors: K Shiokawa, N. Nishitani, P. V. Ponomarenko, S. Suzuki, B. M. Shevtsov, A V Koustov, J. W. MacdougallAbstract:On 10 September 2007 between 10:00 and 14:00 UT, the OMTI all-sky imager at Paratunka (Kam- chatka, Russia, GLAT 52 ) observed the onset and south- western progression of a localized depletion region in the air- glow intensity. The perturbation, while being stretched in the NW-SE direction, crossed the entire field of view of the cam- era. During the event, the Hokkaido SuperDARN HF radar was monitoring echoes in the Paratunka longitudinal sector. It was detecting a localized band of ground scatter echoes progressing equatorward synchronously with the motion of the optical perturbation. It is suggested that both features re- sulted from the onset and south-western progression of a lo- calized region with enhanced electric field that influenced the distribution of the plasma density in the ionosphere. Model- ing of the HF ground scatter dynamics based on numerical ray tracing demonstrated qualitative consistency with the ob- servations.
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thermospheric wind during a storm time large scale Traveling Ionospheric Disturbance
Journal of Geophysical Research, 2003Co-Authors: K Shiokawa, Yuichi Otsuka, Masayuki Yamamoto, T Ogawa, Seiji Kawamura, S Fukao, Takuji Nakamura, Toshitaka Tsuda, N Balan, K IgarashiAbstract:[1] A prominent large-scale Traveling Ionospheric Disturbance (LSTID) was observed in Japan during the major magnetic storm (Dst ∼ −358 nT) of 31 March 2001. It was detected as enhancements of the 630-nm airglow and foF2, GPS-TEC variations, and a decrease in F-layer virtual height at 1700–1900 UT (0200–0400 LT). It moved equatorward with a speed of ∼600 m/s. The decrease in the F-layer height was also detected by the MU radar at Shigaraki. Thermospheric wind variations were observed by the MU radar through ion drift measurement and by a Fabry-Perot interferometer (FPI) through a Doppler shift of the 630-nm airglow line at Shigaraki. The wind data show a turn of the meridional wind from −94 m/s (equatorward) to +44 m/s (poleward) during the LSTID, indicating that an intense poleward wind in the thermosphere passed over Shigaraki as an atmospheric gravity wave and caused the observed Ionospheric features of the LSTID. Intense poleward wind was also detected at mesospheric altitudes (95–100 km) by the MU radar (through meteor echoes) and by the FPI (through the 558-nm airglow) with a delay of ∼2 hours from the thermospheric wind, indicating downward phase progression of the wave. Generation of the observed poleward wind in the auroral zone was investigated using magnetic field data and auroral energy input estimated by the assimilative mapping of Ionospheric electrodynamics (AMIE) technique. We suggest that simple atmospheric heating and/or the Lorentz force in the auroral zone do not explain the observed poleward wind enhancement.
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ground and satellite observations of nighttime medium scale Traveling Ionospheric Disturbance at midlatitude
Journal of Geophysical Research, 2003Co-Authors: K Shiokawa, Yuichi Otsuka, T Ogawa, C Ihara, F J RichAbstract:[1] We have investigated a nighttime medium-scale Traveling Ionospheric Disturbance (MSTID) observed by an airglow imager at Shigaraki (34.9°N, 25.4°MLAT), Japan, on 17 May 2001. The structure was identified in the airglow images of OI (630.0 nm and 777.4 nm) as NW-SE band structures (horizontal wavelength: 230 km) moving southwestward with a velocity of 50 m/s. Neutral wind velocity was measured simultaneously from the Doppler shift of the 630.0-nm emission by a Fabry-Perot interferometer at Shigaraki. From these parameters, we performed model calculations of MSTIDs generated by gravity waves and by an oscillating electric field. We found that for the case of gravity waves, the estimated vertical wavelength was too small to explain the observed amplitudes of airglow intensity. For the case of the electric field, we found that an electric field oscillation of ∼1.2 mV/m was sufficient to reproduce the observed airglow amplitudes. This modeled electric field was comparable to that observed by the DMSP F15 satellite as it passed over Shigaraki during our observing period on 17 May 2001. The DMSP ion drift data show that the oscillation of the polarization electric field correlated with the MSTID structure in the airglow image, suggesting that the polarization electric field plays an important role in the generation of MSTIDs.
E J Weber - One of the best experts on this subject based on the ideXlab platform.
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equatorial plasma depletion precursor signatures and onset observed at 11 south of the magnetic equator
Journal of Geophysical Research, 1996Co-Authors: E J Weber, Terence Bullett, C E Valladares, G J Bishop, H Kuenzler, P Ning, P J Sultan, K M Groves, S. Basu, R SheehanAbstract:Coordinated radio and optical measurements of the structure and dynamics of the postsunset equatorial ionosphere were conducted on October 1, 1994, from Agua Verde, Chile (11.3°S magnetic latitude (MLat)). The measurements clearly show a north-south aligned undulation or ripple on the bottomside of the F layer at 2000 LT, appearing as an eastward propagating decrease in the 630.0-nm airglow, resembling a Traveling Ionospheric Disturbance in the digital portable ionosonde measurements and causing a total electron content decrease in the Global Positioning System (GPS) satellite measurements. The initial development of this feature, toward the east and away from the magnetic equator, took place in an otherwise smooth, unstructured ionosphere. Spread F began to develop in the ionograms at 2020 LT, and, at this same time, local onset of satellite signal scintillation was detected using the multiple ray paths throughout the sky available from the GPS satellite constellation transmitting at L band frequencies. UHF scintillation measurements from Ancon, Peru, along the same magnetic field line, show that intense scintillation and Ionospheric irregularities had developed over the magnetic equator almost 60 min prior to their development at 11°S MLat. The observations suggest that the east-west electric field expected to be present within the earlier developed depletion and scintillation region at the magnetic equator mapped along magnetic field lines to lower altitudes and higher latitudes, resulting in an undulation or dome-shaped structure, before evolving into a fully developed depletion (with associated Ionospheric irregularities) all along the magnetic flux tube.
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Equatorial plasma depletion precursor signatures and onset observed at 11° south of the magnetic equator
Journal of Geophysical Research, 1996Co-Authors: E J Weber, Terence Bullett, C E Valladares, G J Bishop, H Kuenzler, P Ning, P J Sultan, K M Groves, S. Basu, R. E. SheehanAbstract:Coordinated radio and optical measurements of the structure and dynamics of the postsunset equatorial ionosphere were conducted on October 1, 1994, from Agua Verde, Chile (11.3°S magnetic latitude (MLat)). The measurements clearly show a north-south aligned undulation or ripple on the bottomside of the F layer at 2000 LT, appearing as an eastward propagating decrease in the 630.0-nm airglow, resembling a Traveling Ionospheric Disturbance in the digital portable ionosonde measurements and causing a total electron content decrease in the Global Positioning System (GPS) satellite measurements. The initial development of this feature, toward the east and away from the magnetic equator, took place in an otherwise smooth, unstructured ionosphere. Spread F began to develop in the ionograms at 2020 LT, and, at this same time, local onset of satellite signal scintillation was detected using the multiple ray paths throughout the sky available from the GPS satellite constellation transmitting at L band frequencies. UHF scintillation measurements from Ancon, Peru, along the same magnetic field line, show that intense scintillation and Ionospheric irregularities had developed over the magnetic equator almost 60 min prior to their development at 11°S MLat. The observations suggest that the east-west electric field expected to be present within the earlier developed depletion and scintillation region at the magnetic equator mapped along magnetic field lines to lower altitudes and higher latitudes, resulting in an undulation or dome-shaped structure, before evolving into a fully developed depletion (with associated Ionospheric irregularities) all along the magnetic flux tube.
R Sheehan - One of the best experts on this subject based on the ideXlab platform.
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equatorial plasma depletion precursor signatures and onset observed at 11 south of the magnetic equator
Journal of Geophysical Research, 1996Co-Authors: E J Weber, Terence Bullett, C E Valladares, G J Bishop, H Kuenzler, P Ning, P J Sultan, K M Groves, S. Basu, R SheehanAbstract:Coordinated radio and optical measurements of the structure and dynamics of the postsunset equatorial ionosphere were conducted on October 1, 1994, from Agua Verde, Chile (11.3°S magnetic latitude (MLat)). The measurements clearly show a north-south aligned undulation or ripple on the bottomside of the F layer at 2000 LT, appearing as an eastward propagating decrease in the 630.0-nm airglow, resembling a Traveling Ionospheric Disturbance in the digital portable ionosonde measurements and causing a total electron content decrease in the Global Positioning System (GPS) satellite measurements. The initial development of this feature, toward the east and away from the magnetic equator, took place in an otherwise smooth, unstructured ionosphere. Spread F began to develop in the ionograms at 2020 LT, and, at this same time, local onset of satellite signal scintillation was detected using the multiple ray paths throughout the sky available from the GPS satellite constellation transmitting at L band frequencies. UHF scintillation measurements from Ancon, Peru, along the same magnetic field line, show that intense scintillation and Ionospheric irregularities had developed over the magnetic equator almost 60 min prior to their development at 11°S MLat. The observations suggest that the east-west electric field expected to be present within the earlier developed depletion and scintillation region at the magnetic equator mapped along magnetic field lines to lower altitudes and higher latitudes, resulting in an undulation or dome-shaped structure, before evolving into a fully developed depletion (with associated Ionospheric irregularities) all along the magnetic flux tube.
