Ionospheric Response over Nepal during the 26 December 2019 Solar Eclipse

Silwal, Ashok; Gautam, Sujan Prasad; Chapagain, Narayan P.; Karki, Monika; Poudel, P.; Ghimire, B. D.; Mishra, Roshan Kumar; Adhikari, Binod

doi:10.3126/jnphyssoc.v7i1.36970

Cited by 9 publications

(10 citation statements)

References 10 publications

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“…(2020) and Silwal et al. (2021) have shown a TEC depletion of 20%–50% for the 26 December 2019 solar eclipse. In the present study, we have noticed the presence of gravity wave‐type of oscillations with higher amplitude at stations close to the eclipse path.…”

Section: Discussionmentioning

confidence: 92%

“…Similarly, Silwal et al. (2021) have discussed the ionospheric response to 26 December 2019 over Nepal using GNSS TEC observations. They reported a decrease of 20% in TEC as compared to normal days.…”

Section: Introductionmentioning

confidence: 99%

“…The following results are obtained in their analysis: (a) A reduction in TEC by 30%-50%, (b) significant weakening of EEJ currents over the magnetic equator along the path of annularity, and (c) the altitudinal variation of electron density using SWARM and DMSP satellites showed a considerable reduction in the topside ionosphere but enhancement in temperature at 850 km, (d) increase of 20%-40% in Equatorial Ionisation Anomaly (EIA) after the eclipse in the noon hours are attributed by the eclipse driven neutral winds and electrodynamics. Similarly, Silwal et al (2021) have discussed the ionospheric response to 26 December 2019 over Nepal using GNSS TEC observations. They reported a decrease of 20% in TEC as compared to normal days.…”

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confidence: 99%

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Multi‐Instrument Observations of the Ionospheric Response to the 26 December 2019 Solar Eclipse Over Indian and Southeast Asian Longitudes

2022

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A solar eclipse is a rare astronomical event that occurs when the Sun, Moon, and Earth are aligned in a straight line with the moon in between the sun and earth occulting the Sun as well as its radiation by casting a shadow on different parts of the earth. Solar eclipse observation gives a unique opportunity to study the impact of solar radiation on the atmosphere-ionosphere coupled system. The effect of solar eclipses is noticed as a sudden decrease of ionospheric density due to the cutoff of solar ionizing radiation (Mitra et al., 1933). A combination of ground and space-based observations will give an idea about the ionospheric response to the topside and bottom side ionosphere during a solar eclipse. Past studies of the ionospheric response to solar eclipse showed the generation of atmospheric gravity waves in the earth's atmosphere during the eclipse period because of the passage of the Moon's shadow at a supersonic speed (Chimonas & Hines, 1970). Various experimental and modeling techniques have been performed to study the ionospheric response to solar eclipses in the past (Chernogor & Mylovanov, 2020). A Solar eclipse is known to produce changes in the earth's atmosphere and ionosphere. The most common changes are the decrease in electron density, decrease in ion and electron temperature, compositional changes in the ionosphere, plasma movement, and decrease in lower atmospheric temperature. Past solar eclipse studies showed the generation of Traveling Ionospheric Disturbances (TIDs) and gravity waves during solar eclipse using observations. Chimonas and Hines (1970) have reported for the first time the generation of atmospheric gravity waves during a solar eclipse. Many attempts have been done after this to see the observa-

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Section: Discussionmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

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confidence: 99%

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Multi‐Instrument Observations of the Ionospheric Response to the 26 December 2019 Solar Eclipse Over Indian and Southeast Asian Longitudes

2022

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“…Studies have shown that intense geomagnetic storms are usually caused by coronal mass ejections (CMEs). The solar wind carries energy‐momentum and is transmitted into the magnetosphere, ionosphere, and thermosphere (Adhikari, Dahal, & Chapagain, 2017; Silwal, Gautam, Chapagain, et al., 2021). This may cause different deviation levels in the complex morphology of the electric fields, temperature, winds, and composition and affect all ionospheric parameters.…”

Section: Introductionmentioning

confidence: 99%

Ionospheric Signatures During G2, G3 and G4 Storms in Mid‐Latitude

Dahal¹,

Adhikari

Khadka³

et al. 2022

Radio Science

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This paper presents a wavelet‐based analysis of ionospheric irregularities induced by three different geomagnetic storms of varying strength and interplanetary origin over three mid‐latitudes stations, viz. Moscow, Fairford, and Rome. We observed the highest decrease in ionospheric variables (foF2, total electron content (TEC), and NmF2) during the negative phase of the G4 storm. Interestingly, hmF2 exhibits the opposite trend in terms of variation. The maximum ionization height (hmF2) for the G4 event is 500 km (during the main phase) and 150 km (during the recovery phase). Within 2–3 hr of the G4 event, the value of hmF2 is found to decline by 70%. The largest reduction (80%) in critical frequency (foF2) is observed during the negative phase of this event, which is also confirmed by the continuous wavelet transform results. During the negative phase, we observed noticeable power shifts in the signal of the ionospheric parameters toward the lower Fourier period band. During the G4 storm—Particularly during the negative phase—The lowest power linked with the ionospheric parameter's signal was discovered. Additionally, we used detrended cross‐correlation analysis to investigate the correlation and time lag between geomagnetic indices (Symmetric H‐component (SYM‐H) & auroral electrojet) and ionospheric parameters (foF2, NmF2, hmF2 & TEC). The significant association between SYM‐H and ionospheric parameters suggests that the magnetosphere‐ionosphere interaction produces intense electric field disturbances and winds in the mid‐latitudes, resulting in the perturbation of hmF2, foF2, TEC, and NmF2.

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“…(Otsuka et al, 2002;Bagiya et al, 2009;Silwal et al, 2021a).TEC is a prime source of error for ground-based receivers to space satellite communication and navigation system (Dabas, 2000;Jin et al, 2007); thus, significant efforts have been made over the last few decades to understand the spatial and temporal variation of ionospheric TEC (e.g. Fejer, 1997;Bhuyan, 2003;Olwendo & Cesaroni, 2016;Ogwala et al, 2019;Silwal et al, 2021b) and to develop TEC models (e.g. Bilitza, 1990;Radicella & Zhang, 1995;Okoh et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

A study of vTEC above Nepal exploring different calibration techniques, including a comparison with the NeQuick-2 model

Poudel

Silwal

Ghimire

et al. 2022

Astrophys Space Sci

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In this paper, we investigate the performance of the NeQuick 2 (NeQ-2) model with respect to Ciraolo's and Gopi's derived ionospheric vertical TEC (vTEC) during the years 2014 and 2015.GPS observables derived from dual-frequency receivers over western Nepal (Simikot, Bhimchula and Nepalganj) are processed to obtain the experimental vTEC utilizing Gopi's and Ciraolo's calibration procedures. The monthly and seasonal behavior of vTEC obtained from each calibration technique is compared with the vTEC obtained from the NeQ-2 model during a quiet period. It is observed that the vTEC value obtained from all studied approaches started to increase from 00:00 UT, reached a maximum around 08:00 UT, followed by declination, attaining a minimum value around 23:00 UT. Moreover, a comparative study showed that vTEC computed using the Ciraolo calibration technique overestimates GPS vTEC, calculated in all hours and months by Gopi's approach. In the spring and summer, vTEC derived using Ciraolo's TEC calibration overestimates NeQ-2 and underestimates it in the autumn and winter. Except for a few day hours in March and April 2014 (solar maximum), NeQ-2 prediction overestimated Gopi calibrated GPS vTEC. In daytime hours, a considerable difference is noted between one vTEC estimate with respect to another. NeQ-2 model vTEC is favourably associated with GPS vTEC obtained using the Gopi procedure in spring and correlates with the Ciraolo technique in autumn. Two GPS vTEC estimations demonstrate superior consistency in summer and winter 2 seasons over all studied stations. The study on geomagnetically disturbed conditions demonstrates that NeQ-2 is not responding to the storm influence. However, the mean absolute difference between NeQ-2 prediction and GPS vTEC procured through the Gopi approach is less on the storm event day. By contrast, it is discovered less by the Ciraolo technique when the storm is recovering (except for few cases).

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Ionospheric Response over Nepal during the 26 December 2019 Solar Eclipse

Cited by 9 publications

References 10 publications

Multi‐Instrument Observations of the Ionospheric Response to the 26 December 2019 Solar Eclipse Over Indian and Southeast Asian Longitudes

Multi‐Instrument Observations of the Ionospheric Response to the 26 December 2019 Solar Eclipse Over Indian and Southeast Asian Longitudes

Ionospheric Signatures During G2, G3 and G4 Storms in Mid‐Latitude

A study of vTEC above Nepal exploring different calibration techniques, including a comparison with the NeQuick-2 model

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