Investigation of GPS-TEC Inconsistency and Correlation with SSN, Solar Flux (F10.7 cm) and Ap-index during Low and High Solar Activity Periods (2008 and 2014) Over Indian Equatorial Low Latitude Region

The international reference ionosphere (IRI) models have been widely used for correcting the ionospheric scintillations at different altitude levels. An evaluation on the performance of VTEC correction from IRI models (version 2007, 2012 and 2016) over Sukkur, Pakistan (27.71º N, 68.85º E) is presented in this work. Total Electron Content (TEC) from IRI models and GPS in 2019 over Sukkur region are compared. The main aim of this comparative analysis is to improve the VTEC in low latitude Sukkur, Pakistan. Moreover, this study will also help us to identify the credible IRI model for the correction of Global Positioning System (GPS) signal in low latitude region in future. The development of more accurate TEC finds useful applications in enhancing the extent to which ionospheric influences on radio signals are corrected. VTEC from GPS and IRI models are collected between May 1, 2019 and May 3, 2019. Additionally, Dst and Kp data are also compared in this work to estimate the geomagnetic storm variations. This study shows a good correlation of 0.83 between VTEC of GPS and IRI 2016. Furthermore, a correlation of 0.82 and 0.78 is also recorded for IRI 2012 and IRI 2007 respectively, with VTEC of GPS. The IRI TEC predictions and GPS-TEC measurements for the studied days reveal the potential of IRI model as a good candidate over Pakistan.

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The statistical properties of spread F observed at Hainan station during the declining period of the 23rd solar cycle

Annales Geophysicae ◽

10.5194/angeo-28-1263-2010 ◽

2010 ◽

Vol 28 (6) ◽

pp. 1263-1271 ◽

Cited By ~ 12

Author(s):

G. J. Wang ◽

J. K. Shi ◽

X. Wang ◽

S. P. Shang ◽

G. Zherebtsov ◽

...

Keyword(s):

Solar Activity ◽

Solar Cycle ◽

Temporal Variations ◽

High Solar Activity ◽

Positive Relation ◽

Low Latitude ◽

23Rd Solar Cycle ◽

Reversal Time ◽

Spread F ◽

Maximum Occurrence

Abstract. The temporal variations of the low latitude nighttime spread F (SF) observed by DPS-4 digisonde at low latitude Hainan station (geog. 19.5° N, 109.1° E, dip lat. 9.5° N) during the declining solar cycle 23 from March 2002 to February 2008 are studied. The spread F measured by the digisonde were classified into four types, i.e., frequency SF (FSF), range SF (RSF), mixed SF (MSF), and strong range SF (SSF). The statistical results show that MSF and SSF are the outstanding irregularities in Hainan, MSF mainly occurs during summer and low solar activity years, whereas SSF mainly occurs during equinoxes and high solar activity years. The SSF has a diurnal peak before midnight and usually appears during 20:00–02:00 LT, whereas MSF peaks nearly or after midnight and occurs during 22:00–06:00 LT. The time of maximum occurrence of SSF is later in summer than in equinoxes and this time delay can be caused by the later reversal time of the E×B drift in summer. The SunSpot Number (SSN) dependence of each type SF is different during different season. The FSF is independent of SSN during each season; RSF with SSN is positive relation during equinoxes and summer and is no relationship during the winter; MSF is significant dependence on SSN during the summer and winter, and does not relate to SSN during the equinoxes; SSF is clearly increasing with SSN during equinoxes and summer, while it is independent of SSN during the winter. The occurrence numbers of each type SF and total SF have the same trend, i.e., increasing as Kp increases from 0 to 1, and then decreasing as increasing Kp. The correlation with Kp is negative for RSF, MSF, SSF and total SF, but is vague for the FSF.

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Statistical analysis of TEC perturbations over a low latitude region during 2009–2013 ascending solar activity phase

Advances in Space Research ◽

10.1016/j.asr.2015.09.021 ◽

2015 ◽

Vol 56 (11) ◽

pp. 2542-2551 ◽

Cited By ~ 1

Author(s):

Geoffrey Andima ◽

Edward Jurua ◽

Emirant Bertillas Amabayo ◽

John Bosco Habarulema

Keyword(s):

Solar Activity ◽

Statistical Analysis ◽

Low Latitude ◽

Activity Phase ◽

Latitude Region

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Assessment of IRI-2012 profile parameters by comparison with the ones inferred using NeQuick2, ionosonde and FORMOSAT-1 data during the high solar activity over Brazilian equatorial and low latitude sector

Journal of Atmospheric and Solar-Terrestrial Physics ◽

10.1016/j.jastp.2014.09.014 ◽

2014 ◽

Vol 121 ◽

pp. 10-23 ◽

Cited By ~ 10

Author(s):

K. Venkatesh ◽

P.R. Fagundes ◽

R. de Jesus ◽

A.J. de Abreu ◽

V.G. Pillat ◽

...

Keyword(s):

Solar Activity ◽

High Solar Activity ◽

Low Latitude

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Impact of Solar Activity on Global Atmospheric Circulation Based on SD-WACCM-X Simulations from 2002 to 2019

Atmosphere ◽

10.3390/atmos12111526 ◽

2021 ◽

Vol 12 (11) ◽

pp. 1526

Author(s):

Chen-Ke-Min Teng ◽

Sheng-Yang Gu ◽

Yusong Qin ◽

Xiankang Dou

Keyword(s):

Solar Activity ◽

Atmospheric Circulation ◽

Southern Oscillation ◽

Upper Atmosphere ◽

Lower Atmosphere ◽

High Solar Activity ◽

Low Latitude ◽

Quasi Biennial Oscillation ◽

Global Atmospheric Circulation ◽

The Impact

In this study, a global atmospheric model, Specified Dynamics Whole Atmosphere Community Climate Model with thermosphere and ionosphere eXtension (SD-WACCM-X), and the residual circulation principle were used to study the global atmospheric circulation from the lower to upper atmosphere (~500 km) from 2002 to 2019. Our analysis shows that the atmospheric circulation is clearly influenced by solar activity, especially in the upper atmosphere, which is mainly characterized by an enhanced atmospheric circulation in years with high solar activity. The atmospheric circulation in the upper atmosphere also exhibits an ~11 year period, and its variation is highly correlated with the temporal variation in the F10.7 solar index during the same time series, with a maximum correlation coefficient of up to more than 0.9. In the middle and lower atmosphere, the impact of solar activity on the atmospheric circulation is not as obvious as in the upper atmosphere due to some atmospheric activities such as the Quasi-Biennial Oscillation (QBO), El Niño–Southern Oscillation (ENSO), sudden stratospheric warming (SSW), volcanic forcing, and so on. By comparing the atmospheric circulation in different latitudinal regions between years with high and low solar activity, we found the atmospheric circulation in mid- and high-latitude regions is more affected by solar activity than in low-latitude and equatorial regions. In addition, clear seasonal variation in atmospheric circulation was detected in the global atmosphere, excluding the regions near 10−4 hPa and the lower atmosphere, which is mainly characterized by a flow from the summer hemisphere to the winter hemisphere. In the middle and low atmosphere, the atmospheric circulation shows a quasi-biennial oscillatory variation in the low-latitude and equatorial regions. This work provides a referable study of global atmospheric circulation and demonstrates the impacts of solar activity on global atmospheric circulation.

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Effect of solar cycle on topside ion temperature measured by SROSS C2 and ROCSAT 1 over the Indian equatorial and low latitudes

Annales Geophysicae ◽

10.5194/angeo-30-1645-2012 ◽

2012 ◽

Vol 30 (12) ◽

pp. 1645-1654 ◽

Cited By ~ 5

Author(s):

A. Borgohain ◽

P. K. Bhuyan

Keyword(s):

Solar Activity ◽

Solar Cycle ◽

Significant Negative Correlation ◽

Solar Flux ◽

High Solar Activity ◽

Topside Ionosphere ◽

Ion Temperature ◽

Ion Density ◽

Positive Correlation ◽

June Solstice

Abstract. The effect of solar activity on the diurnal, seasonal and latitudinal variations of ion temperature Ti and its relationship with corresponding ion density Ni over the Indian low and equatorial topside ionosphere within 17.5° S to 22.5° N magnetic latitudes are being investigated, combining the data from SROSS C2 and ROCSAT 1 for the 9-year period from 1995 to 2003 during solar cycle 23. Ti varies between 800 K and 1100 K during nighttime and rises to peak values of ~1800 K in the post sunrise hours. Daytime Ti varies from 1000 K to 1500 K. The time of occurrence, magnitude and duration of the morning enhancement show distinct seasonal bias. For example, in the June solstice, Ti increases to ~1650 K at ~06:00 h and exhibits a daytime plateau till 17:00 LT. In the equinoxes, enhanced ion temperature is observed for a longer duration in the morning. There is also a latitudinal asymmetry in the ion temperature distribution. In the equinoxes, the daytime Ti is higher at off equatorial latitudes and lower over the Equator, while in the solstices, Ti exhibits a north–south gradient during daytime. Nighttime Ti is found to be higher over the Equator. Daytime ion temperature exhibits insignificant positive correlation with F10.7 cm solar flux, while nighttime ion temperature decreases with increase in solar flux. Daytime ion temperature and ion density are negatively correlated during solar minimum, while nighttime Ti does not exhibit any correlation. However, during high solar activity, significant positive correlation of Ti with Ni has been observed over the Equator, while at 10° S and 10° N temperature and density exhibit significant negative correlation. The neutral temperature Tn derived from the MSISE 90 model is found to be higher than measured Ti during nighttime, while daytime Ti is higher than model Tn.

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Characteristics of VHF radiowave scintillations over a solar cycle (1983−1993) at a low-latitude station: Waltair (17.7°N, 83.3°E)

Annales Geophysicae ◽

10.1007/s00585-997-0729-3 ◽

1997 ◽

Vol 15 (6) ◽

pp. 729-733 ◽

Cited By ~ 12

Author(s):

P. V. S. Rama Rao ◽

P. T. Jayachandran ◽

P. Sri Ram ◽

B. V. Ramana Rao ◽

D. S. V. V. D. Prasad ◽

...

Keyword(s):

Solar Activity ◽

Solar Cycle ◽

High Solar Activity ◽

Night Time ◽

Low Latitude ◽

Latitude Station ◽

Maximum Occurrence

Abstract. The characteristics of VHF radiowave scintillations at 244 MHz (FLEETSAT) during a complete solar cycle (1983–93) at a low-latitude station, Waltair (17.7°N, 83.3°E), are presented. The occurrence of night-time scintillations shows equinoctial maxima and summer minima in all the epochs of solar activity, and follows the solar activity. The daytime scintillation occurrence is negatively correlated with the solar activity and shows maximum occurrence during the summer months in a period of low solar activity. The occurrence of night-time scintillations is inhibited during disturbed days of high solar activity and enhanced during low solar activity.

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