scholarly journals Spread-F characteristics over Tucumán near the southern anomaly crest in South America during the descending phase of solar cycle 24

2021 ◽  
Author(s):  
Gilda de Lourdes González
Keyword(s):  
Solar Activity ◽  
South America ◽  
Communication Systems ◽  
Eastern Region ◽  
Plasma Bubble ◽  
Night Time ◽  
Plasma Bubbles ◽  
Wide Range ◽  
Spread F ◽  
Range Spread

Abstract Ionospheric F-region irregularities can acutely affect navigation and communication systems. To develop predictive capabilities on their occurrence, it is key to understand their variabilities in a wide range of time scales. Previous studies at low latitudes in South America have been performed mostly in the eastern region. However, there are still few reports on the spread-F over Argentina owing to a lack of ionosonde data. This work presents the analysis of the spread-F (range spread-F and frequency spread-F) and plasma bubble occurrence characteristics near the southern crest of the Equatorial Ionization Anomaly in Argentina (Tucumán, 26.8°S, 65.2°W; magnetic latitude 15.5°S). We used ionosonde and Global Positioning System (GPS) data from November 2014 to December 2019 for different solar and geomagnetic conditions. The data show that spread-F and plasma bubble occurrence rates peak in local summer and are minimum in equinox and winter, respectively. There is a negative correlation between each type of spread-F and solar activity, whereas the opposite happens for plasma bubbles. Geomagnetic activity suppresses the generation of spread-F in equinox and summer and enhances it in winter. Plasma bubble occurrence is higher during disturbed days than during quiet days, but under medium solar activity, summer months register more plasma bubbles in quiet conditions. Range spread-F observed in winter under low solar activity is not associated with plasma bubbles originated at the magnetic equator. These results contribute to the knowledge necessary to improve the prediction of the spatial and temporal distribution of the night-time ionospheric irregularities.

scholarly journals Spread-F characteristics at the southern anomaly crest in South America during the descending phase of solar cycle 24

2021 ◽  
Author(s):  
Gilda de Lourdes González
Keyword(s):  
Solar Activity ◽  
South America ◽  
Communication Systems ◽  
Temporal Distribution ◽  
Plasma Bubble ◽  
Night Time ◽  
Plasma Bubbles ◽  
Wide Range ◽  
Spread F ◽  
Range Spread

Abstract Ionospheric F-region irregularities can acutely affect navigation and communication systems. To develop predictive capabilities on their occurrence, it is key to understand their variabilities in a wide range of time scales. Previous studies at low latitudes in South America have been performed mostly for the eastern sector, and fewer efforts have been done in the Argentinian region. This work presents the analysis of the spread-F (range spread-F, frequency spread-F and strong spread-F) and plasma bubble occurrence characteristics near the southern crest of the Equatorial Ionization Anomaly (Tucumán, 26.8°S, 65.2°W; magnetic latitude 15.5°S). We used ionosonde and Global Positioning System (GPS) data from November 2014 to December 2019 for different solar and geomagnetic conditions. The data shows that spread-F and plasma bubble occurrence rates peak in summer and are minimum in equinox and winter, respectively. There is, usually, a negative correlation between each type of spread-F and solar activity, whereas the opposite happens for plasma bubbles. Geomagnetic activity suppresses the generation of spread-F in equinox and summer and enhances it in winter. Plasma bubble occurrence is higher during disturbed days than during quiet days, but under medium solar activity, summer months register more plasma bubbles in quiet conditions. Range spread-F observed in winter under low solar activity is not associated with plasma bubbles originated at the magnetic equator. These results contribute to the knowledge necessary to improve the prediction of the spatial and temporal distribution of the night-time ionospheric irregularities.

scholarly journals Simultaneous observation of ionospheric plasma bubbles and mesospheric gravity waves during the SpreadFEx Campaign

2009 ◽  
Vol 27 (4) ◽  
pp. 1477-1487 ◽  
Author(s):  
H. Takahashi ◽  
M. J. Taylor ◽  
P.-D. Pautet ◽  
A. F. Medeiros ◽  
D. Gobbi ◽  
...  
Keyword(s):  
Gravity Wave ◽  
Ionospheric Plasma ◽  
Bubble Formation ◽  
South American ◽  
Plasma Bubble ◽  
Simultaneous Observation ◽  
Plasma Bubbles ◽  
Spread F ◽  
The Relationship ◽  
Horizontal Wavelength

Abstract. During the Spread F Experiment campaign, under NASA Living with a Star (LWS) program, carried out in the South American Magnetic Equator region from 22 September to 8 November 2005, two airglow CCD imagers, located at Cariri (7.4° S, 36.5° W, geomag. 11° S) and near Brasilia (14.8° S, 47.6° W, geomag. 10° S) were operated simultaneously and measured the equatorial ionospheric bubbles and their time evolution by monitoring the airglow OI 6300 intensity depletions. Simultaneous observation of the mesospheric OH wave structures made it possible to investigate the relationship between the bubble formation in the ionosphere and the gravity wave activity at around 90 km. On the evening of 30 September 2005, comb-like OI 6300 depletions with a distance of ~130 km between the adjacent ones were observed. During the same period, a mesospheric gravity wave with a horizontal wavelength of ~130 km was observed. From the 17 nights of observation during the campaign period, there was a good correlation between the OI 6300 depletion distances and the gravity wave horizontal wavelengths in the mesosphere with a statistically significant level, suggesting a direct contribution of the mesospheric gravity wave to plasma bubble seeding in the equatorial ionosphere.

Large Scale TIDs climatology over Europe using HF Interferometry method

2020 ◽  
Author(s):  
Estefania Blanch ◽  
Antoni Segarra ◽  
David Altadill ◽  
Vadym Paznukhov ◽  
Jose Miguel Juan
Keyword(s):  
Solar Activity ◽  
Propagation Velocity ◽  
Large Scale ◽  
Large Data ◽  
Density Fluctuations ◽  
Night Time ◽  
Wide Range ◽  
Propagation Parameters ◽  
The Difference ◽  
Sporadic E

<p>Travelling Ionospheric Disturbances (TIDs) are ionospheric irregularities that occur as plasma density fluctuations that propagate as waves through the ionosphere over a wide range of velocities and frequencies. It has been demonstrated that Large Scale TIDs (LSTID) can be detected with several ionospheric sensors such as ionosondes and their main characteristics such as velocity, direction of propagation and amplitude can be inferred.</p><p>We have applied the recent developed HF Interferometry (HF-Int) method to detect the occurrence and main characteristics of LSTIDs over Europe for different solar activities (2014 – 2019) in order to perform a climatological analysis. HF-Int determines the dominant period of oscillation and the amplitude of the LSTIDs using spectral analysis, and estimates the propagation parameters of the LSTIDs from the measured time delays of the disturbance detected at different sensor sites.</p><p>The results show that larger diurnal and seasonal occurrence of LSTID happens near sunrise hours and night-time, especially during equinox. In the morning sector, prevailing velocity propagation is westward influenced by the solar terminator effect and it also depends on the season: during winter the dominant propagation velocity is north-westward and during summer is south-westward. In the evening and night sector, the prevailing propagation velocity is southward suggesting auroral origin of the disturbance. The higher activity at night-time might be the result that neutral winds favour equatorward propagation at night whereas at day might prevent to propagate to low latitudes.</p><p>Similar behaviour has been found for high and low solar activity with the difference that during summer at low solar activity, large occurrence of sporadic E layer happens during day time. Then, ionospheric data experience large data gaps at the F region because of screening of the Es (Es Blanketing effect). This results in a poor statistic under such a conditions for daytime summer low solar activity and the number of detected LSTID is lower.</p>

scholarly journals Plasma bubble zonal velocity variations with solar activity in the Brazilian region

2004 ◽  
Vol 22 (9) ◽  
pp. 3123-3128 ◽  
Author(s):  
P. M. Terra ◽  
J. H. A. Sobral ◽  
M. A. Abdu ◽  
J. R. Souza ◽  
H. Takahashi
Keyword(s):  
Solar Activity ◽  
Local Time ◽  
Time Frame ◽  
Maximum Activity ◽  
Bubble Velocity ◽  
Activity Period ◽  
Plasma Bubble ◽  
Plasma Bubbles ◽  
Velocity Magnitude ◽  
Zonal Velocity

Abstract. A statistical study of the zonal drift velocities of the ionospheric plasma bubbles using experimental airglow data acquired at the low-latitude station Cachoeira Paulista (Geogr. 22.5° S, 45° W, dip angle 28° S) during the period of October to March, between 1980 and 1994, is presented here. This study is based on 109 nights of zonal plasma bubble velocity estimations as determined from bubbles signatures on the OI 630nm scanning photometer airglow data. The zonal velocity magnitudes of the plasma bubbles are investigated with respect to solar activity and local time. It is verified that these velocities tend to increase with the solar EUV flux, using the solar 10.7-cm radio flux as a proxy (F10.7). These velocities are seen to be larger during the solar maximum activity period than in the solar minimum period. As to the local time variation, they are seen to peak before midnight, in the 20:30-22:30 LT time frame, depending on the season. The all-data plot based on the 109 nights of airglow experiments shows that the plasma bubble mean zonal drift velocities tend to decrease with local time, but they peak at 22:25 LT, where the velocity magnitude reaches 127.4ms-1. The zonal drift variations with local time and solar flux are shown in Figs. 1 and 2, respectively.

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