Unusual behavior of quiet-time zonal and vertical plasma drift velocities over Jicamarca during the recent extended solar minimum of 2008

Santos, A. M.; Abdu, M. A.; Souza, J. R.; Batista, I. S.; Sobral, J. H. A.

doi:10.5194/angeo-35-1219-2017

Cited by 3 publications

(3 citation statements)

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“…In general, the ILs duration was higher during solar minimum than during solar maximum period, for both CP and SL. As the ILs are mainly a diurnal phenomenon with a behavioral pattern very similar to that of the E layer (Dos Santos et al, 2019), the longest lifetime in 2009 can be partially attributed to the weakening of the E region dynamo in this period (Santos et al, 2017). On the other hand, over the equatorial station, the duration of the ILs was lower when compared with the low‐latitude region.…”

Section: Resultsmentioning

confidence: 99%

Some Differences in the Dynamics of the Intermediate Descending Layers Observed During Periods of Maximum and Minimum Solar Flux

et al. 2020

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In this paper, ionograms from São Luís (SL, 2°S; 44°W, I: −3.8°) and Cachoeira Paulista (CP, 22.42°S; 45°W, I: −34.4°) are analyzed to examine the characteristics of the intermediate descending layers (ILs) over the Brazilian equatorial and low-latitude regions under different solar flux conditions. The solar flux effects on the ILs are investigated in terms of the rate of occurrence of the IL; the seasonal behavior of some parameters such as the height, frequency, and velocity; and the duration and the number of ILs events observed per day. One of the main results of this work is that unlike over CP, the ILs over SL presented some peculiarities, such as a lower rate of occurrence during a period of solar maximum activity (2003) when compared with a period of solar minimum activity (2009). This apparent variation was likely caused by the magnetic equator moving away from SL during this period. The duration of the ILs was also investigated, and it was found that in 2009, the ILs presented higher life time than in 2003. The descending velocity of the ILs is compatible with the semidiurnal and quarter-diurnal tides. Over SL, the larger descending rate in some cases (>10 km/hr) may reveal the additional influence of the gravity waves in the IL's dynamics. Recently, Dos Santos et al. (2019) presented a climatological study of the ILs over the equatorial and low-latitude regions in Brazil during a period of extreme solar minimum activity. They found an ILs' rate of occurrence higher than 90% over the low-latitude sector and higher than 60% over the equator. The day-today variability observed in the ILs parameters such as the height, frequency of occurrence, and descent velocity may result from variations of tides, the electric fields, the metallic ion, or due to the influences of gravity waves (

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Section: Resultsmentioning

confidence: 99%

Some Differences in the Dynamics of the Intermediate Descending Layers Observed During Periods of Maximum and Minimum Solar Flux

et al. 2020

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“…In this modified version some input parameters, such as atmospheric neutral densities and solar EUV flux, were updated and the field line calculation was extended to lower altitudes in order to include the E region (Bravo et al, 2017;Santos et al, 2016;Souza et al, 2010Souza et al, , 2013. Some studies have demonstrated that this model reproduces well the ionosphere of equatorial, low, and middle latitudes during quiet conditions (Balan et al, 1995;Batista et al, 2011;Nogueira et al, 2013;Santos et al, 2017;Souza et al, 2013;Thampi et al, 2011) and at equatorial-low latitudes during geomagnetic storms (Abdu et al, 2013;Bravo et al, 2017;Santos et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

Ionospheric Response to Disturbed Winds During the 29 October 2003 Geomagnetic Storm in the Brazilian Sector

et al. 2019

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Modeling the ionosphere during disturbed periods is one of the most challenging tasks due to the complexity of the phenomena that affect the electric fields and the whole thermosphere environment. It is well known that both, prompt penetration electric fields and large amounts of energy deposited in the polar region during disturbed periods, produce significant disturbances in the global electron density distribution, in particular, in the equatorial ionization anomaly development. Besides, the disturbance dynamo, traveling atmospheric disturbances, and traveling ionospheric disturbances also affect the equatorial ionization anomaly density distribution. In this work we use the Sheffield University Plasmasphere-Ionosphere Model at Instituto Nacional de Pesquisas Espaciais, to simulate the drastic effects that were observed at the low-latitude ionosphere in the Brazilian region during a very intense magnetic storm event, the so-called 2003 Halloween storms. In the absence of measured vertical drift during the storm, a new vertical drift deduced from the interplanetary electric field combined with the time variation of the F region virtual height is used as input. The simulation results showed that, in the case of the disturbed thermospheric wind, the ionospheric observations are better explained when a novel traveling wave-like disturbance propagating from north to south, at a velocity equal to 300 m/s, is considered.

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“…Chen et al () investigated the effect of lower geomagnetic activity on ionospheric electron content, Chaitanya et al () analyzed E × B drift impacts on the F 2 and F 3 layers, Ji et al () compared TEC from the JASON‐1 satellite to the International Reference Ionosphere model, Perna and Pezzopane () found good correspondence between the Mg II solar proxy and ionosonde data (cf. Perna et al, ), and Santos et al () observed anomalous zonal plasma drift over Jicamarca in 2008.…”

Section: Introductionmentioning

confidence: 93%

Ionospheric Electron Content During Solar Cycle 23

2018

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The solar minimum period between solar cycles 23 and 24 has generated extensive study, in part because the changes in the upper atmosphere and ionosphere were so dramatic. Thermospheric density during 2008-2009, at the benchmark 400-km altitude, was shown to be approximately 30% lower than the previous solar minimum during 1996, in observations and in model simulations. Ionospheric densities were also estimated to be lower, by 10% to 20%. However, earlier analyses using data from the global network of Global Navigation Satellite System receivers did not find any significant reduction in global mean total electron content. Recent work reexamining those data using a limited set of receivers, but with consistent processing, identified a 19% reduction (Emmert et al., 2017, https://doi.org/10.1002/2016JA023680). In this study, we compare model simulations of the thermosphere-ionosphere system during the 2008-2009 solar minimum to its predecessor and estimate a 16% reduction in global mean total electron content. This is consistent with the neutral thermosphere density change seen in model simulations and in satellite drag observations. In the model simulations, the primary driver is a 10% reduction in solar extreme ultraviolet irradiance, with a smaller contribution from lower geomagnetic activity, and a very small decrement due to increase in atmospheric carbon dioxide.Plain Language Summary The Sun goes through 11-year activity cycles, best known with regard to the number of sunspots. At solar minimum, when sunspots mostly vanish, the extreme ultraviolet region of the solar spectrum also diminishes. This causes lower temperature and density in the ionosphere and upper atmosphere above 100 km, where the extreme ultraviolet radiation is absorbed. Past solar minimum periods have seemed basically similar with regard to extreme ultraviolet radiation, and other manifestations of solar activity. However, the solar minimum during 2008-2009 was longer and had fewer sunspots than its predecessor during 1996, or than any minimum period in the past century. The thermosphere was also lower in density, and the ionosphere also appeared to be lower in density, but there were some contradictory measurements. Recent reanalysis of ionospheric measurements found better agreement with the thermospheric measurements. Modeling studies attempting to explain the changes in the ionosphere and thermosphere have suggested that they were caused by a decrease of about 10% in solar extreme ultraviolet radiation. Here we show that the model results and the ionospheric measurements are now in good agreement. This demonstrates that solar minima are not all the same and may have implications for understanding the Sun during extended periods of very low activity.

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Unusual behavior of quiet-time zonal and vertical plasma drift velocities over Jicamarca during the recent extended solar minimum of 2008

Cited by 3 publications

References 31 publications

Some Differences in the Dynamics of the Intermediate Descending Layers Observed During Periods of Maximum and Minimum Solar Flux

Some Differences in the Dynamics of the Intermediate Descending Layers Observed During Periods of Maximum and Minimum Solar Flux

Ionospheric Response to Disturbed Winds During the 29 October 2003 Geomagnetic Storm in the Brazilian Sector

Ionospheric Electron Content During Solar Cycle 23

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