scholarly journals The Characteristic Variations of the Eastward Drift Velocities of the Equatorial Plasma Bubbles in East Asia during High Solar Activity Period.

1995 ◽  
Vol 47 (5) ◽  
pp. 431-439
Author(s):  
Kang Cheng ◽  
Yinn-Nien Huano
Keyword(s):  
Solar Activity ◽  
East Asia ◽  
Activity Period ◽  
High Solar Activity ◽  
Plasma Bubbles ◽  
Equatorial Plasma Bubbles ◽  
Solar Activity Period

scholarly journals Comparison of IRI-2016 model with IGS VTEC maps during low and high solar activity period

2019 ◽  
Vol 12 ◽  
pp. 555-561 ◽  
Author(s):  
Chuang Shi ◽  
Tao Zhang ◽  
Cheng Wang ◽  
Zhipeng Wang ◽  
Lei Fan
Keyword(s):  
Solar Activity ◽  
Activity Period ◽  
High Solar Activity ◽  
Solar Activity Period

scholarly journals Occurrence climatology of equatorial plasma bubbles derived using FormoSat-3 ∕ COSMIC GPS radio occultation data

2020 ◽  
Vol 38 (3) ◽  
pp. 611-623
Author(s):  
Ankur Kepkar ◽  
Christina Arras ◽  
Jens Wickert ◽  
Harald Schuh ◽  
Mahdi Alizadeh ◽  
...  
Keyword(s):  
Solar Activity ◽  
Radio Occultation ◽  
Signal To Noise Ratio ◽  
Strong Dependence ◽  
Occurrence Rate ◽  
High Solar Activity ◽  
Altitudinal Distribution ◽  
Plasma Bubbles ◽  
Ionosphere Plasma ◽  
Equatorial Plasma Bubbles

Abstract. The Global Positioning System – Radio Occultation (GPS-RO) observations from FormoSat-3 ∕ COSMIC are used to comprehend the global distribution of equatorial plasma bubbles which are characterized by depletion regions of plasma in the F region of the ionosphere. Plasma bubbles that cause intense scintillation of the radio signals are identified based on the S4 index derived from the 1 Hz raw signal-to-noise ratio measurements between 2007 and 2017. The analyses revealed that bubbles influenced by background plasma density occurred along the geomagnetic equator and had an occurrence peak around the dip equator during high solar activity. The peak shifted between the African and American sectors, depending on different solar conditions. Plasma bubbles usually developed around 19:00 local time (LT), with maximum occurrence around 21:00 LT during solar maximum and ∼22:00 LT during solar minimum. The occurrence of bubbles showed a strong dependence on longitudes, seasons, and solar cycle with the peak occurrence rate in the African sector around the March equinox during high solar activity, which is consistent with previous studies. The GPS-RO technique allows an extended analysis of the altitudinal distribution of global equatorial plasma bubbles obtained from high vertical resolution profiles, thus making it a convenient tool which could be further used with other techniques to provide a comprehensive view of such ionospheric irregularities.

scholarly journals Evaluating the Performance of IRI-2016 Using GPS-TEC Measurements over the Equatorial Region

Atmosphere ◽  
2021 ◽  
Vol 12 (10) ◽  
pp. 1243
Author(s):  
Nouf Abd Elmunim ◽  
Mardina Abdullah ◽  
Siti Aminah Bahari
Keyword(s):  
Solar Activity ◽  
Early Morning ◽  
Equatorial Region ◽  
Activity Period ◽  
High Solar Activity ◽  
Electron Content ◽  
Dual Frequency ◽  
Iri Model ◽  
Total Electron ◽  
Solar Activity Period

Total electron content (TEC) is an important parameter in the ionosphere that is extensively used to study the variability of the ionosphere as it significantly affects radio wave propagations, causing delays on GPS signals. Therefore, evaluating the performance of ionospheric models is crucial to reveal the variety of ionospheric behaviour in different solar activity periods during geomagnetically quiet and disturbed periods for further improvements of the IRI model performance over the equatorial region. This research aimed to investigate the variations of ionospheric VTEC and observe the improvement in the performance of the IRI-2016 (IRI-2001, IRI01-corr, and NeQuick). The IRI-2016 was evaluated with the IRI-2012 using NeQuick, IRI-2001, and IRI01-corr topside electron density options. The data were obtained using a dual-frequency GPS receiver installed at the Universiti Utara Malaysia Kedah (UUMK) (geographic coordinates 4.62° N–103.21° E, geomagnetic coordinates 5.64° N–174.98° E), Mukhtafibillah (MUKH) (geographic coordinates 6.46° N–100.50° E, geomagnetic coordinates 3.32° S–172.99° E), and Tanjung Pengerang (TGPG) (geographic coordinates 1.36° N–104.10°E, geomagnetic coordinates 8.43° S–176.53° E) stations, during ascending to high solar activity at the geomagnetically quiet and disturbed periods in October 2011, March 2012, and March 2013. The maximum hourly ionospheric VTEC was observed during the post-noon time, while the minimum was during the early morning time. The ionospheric VTEC modelled by IRI-2016 had a slight improvement from the IRI-2012. However, the differences were observed during the post-noon and night-time, while the modelled VTEC from both IRI models were almost similar during the early morning time. Regarding the daily quiet and disturbed period’s prediction capability of the IRI-2016 and IRI-2012, IRI-2016 gave better agreement with the measured VTEC. The overall results showed that the model’s prediction performance during the high solar activity period in 2013 was better than the one during the ascending solar activity period. The results of the comparison between IRI-2016 and IRI-2012 in high solar activity exhibited that during quiet periods, all the IRI models showed better agreement with the measured VTEC compared to the disturbed periods.

Thermospheric temperature during a high solar activity period

Eos ◽  
1990 ◽  
Vol 71 (39) ◽  
pp. 1100 ◽  
Author(s):  
J. S. Kim ◽  
G. S. N. Murty ◽  
J. W. Kim ◽  
Y. Kim
Keyword(s):  
Solar Activity ◽  
Activity Period ◽  
High Solar Activity ◽  
Solar Activity Period

scholarly journals Electrodynamic influence on the diurnal behaviour of neutral daytime airglow emissions

2016 ◽  
Vol 34 (11) ◽  
pp. 1019-1030 ◽  
Author(s):  
Deepak K. Karan ◽  
Duggirala Pallamraju ◽  
Kedar A. Phadke ◽  
Tatiparti Vijayalakshmi ◽  
Tarun K. Pant ◽  
...  
Keyword(s):  
Solar Activity ◽  
Electric Field ◽  
Activity Period ◽  
High Solar Activity ◽  
Intensity Measurements ◽  
Airglow Emissions ◽  
Asymmetric Behaviour ◽  
Radio Measurements ◽  
Solar Activity Period ◽  
Diurnal Behaviour

Abstract. The diurnal variations in daytime airglow emission intensity measurements at three wavelengths OI 777.4 nm, OI 630.0 nm, and OI 557.7 nm made from a low-latitude location, Hyderabad (17.5° N, 78.4° E; 8.9° N MLAT) in India have been investigated. The intensity patterns showed both symmetric and asymmetric behaviour in their respective diurnal emission variability with respect to local noon. The asymmetric diurnal behaviour is not expected considering the photochemical nature of the production mechanisms. The reason for this observed asymmetric diurnal behaviour has been found to be predominantly the temporal variation in the equatorial electrodynamics. The plasma that is transported across latitudes due to the action of varying electric field strengths over the magnetic equator in the daytime contributes to the asymmetric diurnal behaviour in the neutral daytime airglow emissions. Independent magnetic and radio measurements support this finding. It is also noted that this asymmetric diurnal behaviour in the neutral emission intensities has a solar cycle dependence with a greater number of days during high solar activity period showing asymmetric diurnal behaviour compared to those during a low solar activity epoch. These intensity variations over a long timescale demonstrate that the daytime neutral optical emissions are extremely sensitive to the changes in the eastward electric field over low and equatorial latitudes.

scholarly journals Further tests of the IRI and DGR model ionospheres

1994 ◽  
Vol 37 (2) ◽  
Author(s):  
K. J. Kecic ◽  
P. A. Bradley ◽  
L. R. Cander ◽  
M. I. Dick ◽  
B. Zolesi
Keyword(s):  
Solar Activity ◽  
Activity Period ◽  
High Solar Activity ◽  
Small Data ◽  
Data Set ◽  
Ionospheric Models ◽  
Small Data Set ◽  
Solar Activity Period

The present study discusses and compares the IRI and DGR ionospheric models using N(h) profiles obtained during a high solar activity period at South Uist ionosonde station. After inversion, N(h) profiles obtained from ionograms at South Uist have been compared with those derived from the IRI-90 and DGR ionospheric models. A small data set has been selected such that both geomagnetically quiet and disturbed conditions are represented. The importance of further comparisons with additional sets of N(h) profiles under different solar-geophysical conditions and at more stations has been recognized.

scholarly journals Occurrence climatology of equatorial plasma bubbles (EPBs) using optical observations over Kolhapur, India during solar cycle-24

2020 ◽  
Vol 63 (6) ◽  
Author(s):  
Onkar Gurav ◽  
Rupesh Ghodpage ◽  
Parashram Patil ◽  
Sripathi Samireddipalle ◽  
Ashok Sharma ◽  
...  
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
Optical Observations ◽  
Occurrence Rate ◽  
High Solar Activity ◽  
Storm Events ◽  
Plasma Bubbles ◽  
Equatorial Plasma Bubbles ◽  
Solar Cycle 24 ◽  
Cycle 24

In this paper, the occurrence characteristics of the equatorial plasma bubbles (EPBs) using OI 630.0 nm all sky imager (ASI) night airglow observations over Kolhapur (16.8o N, 74.2o E, 10.6o dip. Lat.) during the solar cycle-24 are presented. These results are discussed in terms of season, solar and magnetic activity during years 2011 to 2018. The ASI observations were only carried out during January to May and October to December months due to unfavorable weather conditions. The results suggest that while January, February and December are the only months where EPBs were found to occur over Kolhapur in any year, but the percentage of occurrence of EPBs during these months suggests their low occurrence rate during solar minimum. A total of 683 nights of observations were carried, out of which, 93 nights are found to be magnetically disturbed nights having Ap>18. In addition, the ASI observations are also correlated with Pre-Reversal Enhancement of the vertical drift of the evening sector at Tirunelveli on few storm events for comparison. The important findings of this study are: 1) increase in the occurrence of EPBs with respect to the solar activity; 2) suppression of EPBs on 71 disturbed nights, while enhancement of EPBs on 22 nights under magnetic disturbance; 3) EPBs occurrence during equinox months is found to be higher than winter months during ascending phase of solar cycle-24.; and, 4) EPBs are mostly observed in the pre-midnight sector in the high solar activity (HSA) period, while they are seen in the post-midnight to dawn sector during the low solar activity (LSA) period. We also noticed non-occurrence of EPBs during equinox month in the year 2018 which seems to be peculiar and needs further investigations.

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