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17 results on '"Chapagain, Narayan Prasad"'

2. Study of Total Electron Content-TEC and electron density profile during geomagnetic storms

Author

Bhattarai, Niraj, Chapagain, Narayan Prasad, and Adhikari, Binod

Subjects
Physics - Space Physics, Physics - Atmospheric and Oceanic Physics
Abstract

Total Electron Content (TEC) and electron density are the basic parameters, which determine the major properties of the Ionosphere. Detail study of the ionospheric TEC and electron density variations has been carried out during geomagnetic storms, with longitude and latitude, for four different locations: (24{\deg}W-14{\deg}W, 25{\deg}S-10{\deg}S); (53{\deg}W- 46{\deg}W, 04{\deg}N-14{\deg}N); (161{\deg}E-165{\deg}E, 42{\deg}S-34{\deg}S), and (135{\deg}W- 120{\deg}W, 39{\deg}S-35{\deg}S) using the COSMIC satellite data. In order to find the background conditions of the ionosphere, the solar wind parameters such as north-south component of inter planetary magnetic field (Bz), plasma velocity (Vsw), AE, Dst and Kp indices, have also been correlated with the TEC and electron density. The results illustrates that the observed TEC and electron density profile significantly vary with longitudes and latitudes as well. This study illustrates that the values of TEC and the vertical electron density profile are influenced by the solar wind parameters associated with solar activities. The peak value of electron density and TEC increase as the geomagnetic storms becomes stronger. Similarly, the electron density profile vary with altitudes which peaks around the altitude range of about 180-280 km, depending on the strength of geomagnetic storms. The results clearly show that the peak electron density shifted to higher altitude (from about 180 km to 300 km) as the geomagnetic disturbances becomes stronger.

Published
2018

4. GPS observations of ionospheric TEC variations over Nepal during 22 July 2009 solar eclipse

Author

Ghimire, Basu Dev, Silwal, Ashok, Chapagain, Narayan Prasad, Gautam, Sujan Prasad, Poudel, Prakash, and Khadka, Balaram

Subjects
Solar Eclipse, Global Positioning System, Physics::Space Physics, General Engineering, Cross-Correlation, Astrophysics::Solar and Stellar Astrophysics, General Physics and Astronomy, Astrophysics::Earth and Planetary Astrophysics, Total Electron Content, Physics::Geophysics
Abstract

As the study of ionospheric behavior during various solar activities is an important task, various studies of ionospheric changes during eclipse events have been widely performed in the different regions of the globe. This paper investigates the ionospheric responses to the solar eclipse on 22 July 2009 over Nepal using the total electron content (TEC) measured by dual-frequency Global Positioning System (GPS) receivers. The time-averaged Vertical TEC (vTEC) of ten GPS stations from Nepal is analyzed and it is found that the value of ionospheric TEC decreases due to the reduction of ionizing radiation. In addition, the deviation in the TEC value on eclipse day from the mean vTEC value of the top five quietest days is found to lie in the range ~1–5 TECu at those regions which were associated with the partial eclipse shadow. On the other hand, the region with the total eclipse (BRN2 and RMTE) faced ~6–7 TECu on average reduction in the TEC value. Considering that the eclipse of 22 July 2009 occurred just at sunrise in the Nepalese zone, a maximum reduction of about 5 TECu is very significant. Higher deviation in TEC is therefore linked with the path of totality and the obscuration rate. This study reveals that the ionospheric TEC over Nepal was altered by wave-like energy and momentum transport, as well as obscuration of the solar disc due to the partial and total solar eclipse. Furthermore, the cross-correlation results presented similar type signatures of the eclipse-induced ionospheric modification over Nepal. This research work serves a crucial future reference for the comparative study of change of ionospheric TEC variability over the Nepal region during Eclipse events

Published
2022

7. Pre-Earthquake Ionospheric Anomalies Associated with the 2015 Gorkha Earthquake of Nepal Detected by GPS-TEC Measurements

Author

Karki, Monika, primary, Silwal, Ashok, additional, Chapagain, Narayan Prasad, additional, Poudel, Prakash, additional, Gautam, Sujan Prasad, additional, Adhikari, Binod, additional, Dahal, Ranjan Kumar, additional, Ghimire, Basu Dev, additional, Mishra, Roshan Kumar, additional, Orue, Yenca Migoya, additional, and Calabia, Andres, additional

Published
2021
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