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Papers by Shivangi Bhardwaj

Research paper thumbnail of Variability of ionospheric TEC at low latitude station, Hyderabad during medium solar activity

Russian Journal of Earth Sciences, 2021

The successful operation of communicational and navigational applications requires knowledge of s... more The successful operation of communicational and navigational applications requires knowledge of state and behaviour of ionosphere as well as spatial and temporal changes taking place in it. With this view, we have studied the variability and changes in the low latitude ionosphere by considering a low latitude Indian station Hyderabad (17.41 ∘ N, 78.55 ∘ E). The variability is studied during the year 2014, by using the space borne Global Positioning System (GPS) observations. From GPS observations an important parameter; Total Electron Content (TEC) is obtained, which represents the integral electron density of the ionosphere and is widely used in studies concerning ionospheric variability. We have studied how the ionospheric conditions at Hyderabad change from hour to hour, day to day, month to month and season to season. We found that ionosphere over Hyderabad exhibits significant, interesting and regular variability. Although, the trends followed by the ionospheric changes are similar, but the magnitude of peak values differ on different time scales. Finally we have compared the variability of observed or actual values of TEC with the corresponding values predicted by International Reference Ionosphere (IRI) model-2016 and found good agreement between hourly values, while IRI model overestimates or underestimates the daily values.

Research paper thumbnail of Geomagnetic and Ionospheric Response to Solar Eruptive Phenomenon

The Sun is an extremely dynamic star and strong changes take place on it on different time scales... more The Sun is an extremely dynamic star and strong changes take place on it on different time scales. Whatever changes take place on the sun, whether long term or short term, does not remain confined to the solar atmosphere only but also produce large scale disturbances in the interplanetary medium as well as planetary environments. The sun emits large fluxes of short wave length radiations. These radiations impinge on the top of atmosphere of earth and ionize the gasses present there and the density of ions and electrons are increased which significantly affects the propagation of electromagnetic waves and signals passing through it. Due to this satellite communication, navigational and surveillance applications are badly affected. In this book we have presented the response of geospace to solar eruptive processes on the magnetosphere and ionosphere of the earth.

Research paper thumbnail of Investigation of geo-effective properties of halo coronal mass ejections

Russian Journal of Earth Sciences

In the present paper, we have studied the geo-effective characteristics of halo coronal mass ejec... more In the present paper, we have studied the geo-effective characteristics of halo coronal mass ejections (CMEs) and examined their distribution over three kinds of geo-effective properties. To accomplish this study, we have selected the halo CMEs that were observed during the solar cycle 23, i.e. from 1996 to 2007. We selected three properties of CMEs viz. speed, acceleration and transit time and constructed several ranges of each type of property. From our analysis we have found that 60% of CMEs occur in the 500-1500 km s −1 category of CME speed. Similarly, 55% of CMEs are distributed over the range of 25-75 hours, of transit time while 60% of CMEs occur in the 0-20 m/s 2 category of positive acceleration and 78% of CMEs occur in the 0-20 m/s 2 category of negative acceleration. We also investigated the geomagnetic effects of the selected CMEs by considering the geomagnetic storms caused by them. The geomagnetic storms were divided into three categories on the basis of the peak value, as weak (> −50 nT), moderate (−100 nT < ≤ −50 nT) and intense (≤ −100 nT). The highest numbers of intense storms were registered in the intermediate ranges of CME properties. Moreover, it was also found that decelerating CMEs produced significantly larger number of intense storms. Hence, decelerating CMEs are more geo-effective than the accelerating CMEs.

Research paper thumbnail of Morphological Investigation of Disturbed Ionosphere during Intense Geomagnetic Storms

Journal of Physics: Conference Series, 2016

Research paper thumbnail of Evaluation of long term solar activity effects on GPS derived TEC

Journal of Physics: Conference Series, 2016

Research paper thumbnail of Solar Transients Disturbing the Mid Latitude Ionosphere during the High Solar Activity

Journal of Physics: Conference Series, 2016

Research paper thumbnail of Evaluation of geomagnetic storm effects on the GPS derived Total Electron Content (TEC)

Journal of Physics: Conference Series, 2015

Research paper thumbnail of The statistical investigation of amplitude Scintillations at Indian high latitude Station Maitri, Antarctica

Journal of Physics: Conference Series, 2015

Research paper thumbnail of Prakash Khatarkar

Research paper thumbnail of Geomagnetic disturbances and its impact on ionospheric critical frequency (foF2) at high, mid and low latitude region

A geomagnetic storm is a major disturbance of Earth's magnetosphere that occurs when there is a v... more A geomagnetic storm is a major disturbance of Earth's magnetosphere that occurs when there is a very efficient exchange of energy from the solar wind into the space environment surrounding Earth. During solar and geomagnetic activities, critical frequency of F2 layer (foF2) varies in a great extent. In this Study, our main aim is to examine the effect of solar and geomagnetic activities on the critical frequency (foF2) during January 2014 to April 2014 respectively. One magnetic intense storm occurred on 19 February with (Dst-112) and other moderate storm occurred on 12 April 2014 with (Dst-80). In our study, we have analyzed these effects on critical frequency of F2 layer for ionospheric monitoring. We have used ionospheric data at Low, mid and high latitude station. The absorption and ionization of the ionospheric medium depends on solar activity. The value of foF2 increased from their normal value at all the three latitudes. This is due to geomagnetic storms that occurred around the same time. A very interesting feature that can be seen in the figures is that the increase of foF2 at Low latitude is much more intense as compare to high and mid latitude. Comparison among all the latitudes shows that the values of foF2 at high latitude are quite less as compared to low and mid latitude. We have found that the effect of solar and geomagnetic storm disturbances is strongest at the low latitude and weakest at the high latitude during the geomagnetic storm time.

Research paper thumbnail of Variability of ionospheric TEC at low latitude station, Hyderabad during medium solar activity

Russian Journal of Earth Sciences, 2021

The successful operation of communicational and navigational applications requires knowledge of s... more The successful operation of communicational and navigational applications requires knowledge of state and behaviour of ionosphere as well as spatial and temporal changes taking place in it. With this view, we have studied the variability and changes in the low latitude ionosphere by considering a low latitude Indian station Hyderabad (17.41 ∘ N, 78.55 ∘ E). The variability is studied during the year 2014, by using the space borne Global Positioning System (GPS) observations. From GPS observations an important parameter; Total Electron Content (TEC) is obtained, which represents the integral electron density of the ionosphere and is widely used in studies concerning ionospheric variability. We have studied how the ionospheric conditions at Hyderabad change from hour to hour, day to day, month to month and season to season. We found that ionosphere over Hyderabad exhibits significant, interesting and regular variability. Although, the trends followed by the ionospheric changes are similar, but the magnitude of peak values differ on different time scales. Finally we have compared the variability of observed or actual values of TEC with the corresponding values predicted by International Reference Ionosphere (IRI) model-2016 and found good agreement between hourly values, while IRI model overestimates or underestimates the daily values.

Research paper thumbnail of Geomagnetic and Ionospheric Response to Solar Eruptive Phenomenon

The Sun is an extremely dynamic star and strong changes take place on it on different time scales... more The Sun is an extremely dynamic star and strong changes take place on it on different time scales. Whatever changes take place on the sun, whether long term or short term, does not remain confined to the solar atmosphere only but also produce large scale disturbances in the interplanetary medium as well as planetary environments. The sun emits large fluxes of short wave length radiations. These radiations impinge on the top of atmosphere of earth and ionize the gasses present there and the density of ions and electrons are increased which significantly affects the propagation of electromagnetic waves and signals passing through it. Due to this satellite communication, navigational and surveillance applications are badly affected. In this book we have presented the response of geospace to solar eruptive processes on the magnetosphere and ionosphere of the earth.

Research paper thumbnail of Investigation of geo-effective properties of halo coronal mass ejections

Russian Journal of Earth Sciences

In the present paper, we have studied the geo-effective characteristics of halo coronal mass ejec... more In the present paper, we have studied the geo-effective characteristics of halo coronal mass ejections (CMEs) and examined their distribution over three kinds of geo-effective properties. To accomplish this study, we have selected the halo CMEs that were observed during the solar cycle 23, i.e. from 1996 to 2007. We selected three properties of CMEs viz. speed, acceleration and transit time and constructed several ranges of each type of property. From our analysis we have found that 60% of CMEs occur in the 500-1500 km s −1 category of CME speed. Similarly, 55% of CMEs are distributed over the range of 25-75 hours, of transit time while 60% of CMEs occur in the 0-20 m/s 2 category of positive acceleration and 78% of CMEs occur in the 0-20 m/s 2 category of negative acceleration. We also investigated the geomagnetic effects of the selected CMEs by considering the geomagnetic storms caused by them. The geomagnetic storms were divided into three categories on the basis of the peak value, as weak (> −50 nT), moderate (−100 nT < ≤ −50 nT) and intense (≤ −100 nT). The highest numbers of intense storms were registered in the intermediate ranges of CME properties. Moreover, it was also found that decelerating CMEs produced significantly larger number of intense storms. Hence, decelerating CMEs are more geo-effective than the accelerating CMEs.

Research paper thumbnail of Morphological Investigation of Disturbed Ionosphere during Intense Geomagnetic Storms

Journal of Physics: Conference Series, 2016

Research paper thumbnail of Evaluation of long term solar activity effects on GPS derived TEC

Journal of Physics: Conference Series, 2016

Research paper thumbnail of Solar Transients Disturbing the Mid Latitude Ionosphere during the High Solar Activity

Journal of Physics: Conference Series, 2016

Research paper thumbnail of Evaluation of geomagnetic storm effects on the GPS derived Total Electron Content (TEC)

Journal of Physics: Conference Series, 2015

Research paper thumbnail of The statistical investigation of amplitude Scintillations at Indian high latitude Station Maitri, Antarctica

Journal of Physics: Conference Series, 2015

Research paper thumbnail of Prakash Khatarkar

Research paper thumbnail of Geomagnetic disturbances and its impact on ionospheric critical frequency (foF2) at high, mid and low latitude region

A geomagnetic storm is a major disturbance of Earth's magnetosphere that occurs when there is a v... more A geomagnetic storm is a major disturbance of Earth's magnetosphere that occurs when there is a very efficient exchange of energy from the solar wind into the space environment surrounding Earth. During solar and geomagnetic activities, critical frequency of F2 layer (foF2) varies in a great extent. In this Study, our main aim is to examine the effect of solar and geomagnetic activities on the critical frequency (foF2) during January 2014 to April 2014 respectively. One magnetic intense storm occurred on 19 February with (Dst-112) and other moderate storm occurred on 12 April 2014 with (Dst-80). In our study, we have analyzed these effects on critical frequency of F2 layer for ionospheric monitoring. We have used ionospheric data at Low, mid and high latitude station. The absorption and ionization of the ionospheric medium depends on solar activity. The value of foF2 increased from their normal value at all the three latitudes. This is due to geomagnetic storms that occurred around the same time. A very interesting feature that can be seen in the figures is that the increase of foF2 at Low latitude is much more intense as compare to high and mid latitude. Comparison among all the latitudes shows that the values of foF2 at high latitude are quite less as compared to low and mid latitude. We have found that the effect of solar and geomagnetic storm disturbances is strongest at the low latitude and weakest at the high latitude during the geomagnetic storm time.