All in-text references underlined in blue are linked to publications on ResearchGate, letting you... more All in-text references underlined in blue are linked to publications on ResearchGate, letting you access and read them immediately.
We have studied the behaviour of ionospheric Total Electron Content (TEC) at a mid latitude stati... more We have studied the behaviour of ionospheric Total Electron Content (TEC) at a mid latitude station Usuda (36.130N, 138.360E), Japan during intense geomagnetic storms which were observed during 23 solar cycle (1998-2006). For the present study we have selected 47 intense geomagnetic storms (Dst≤-100nT), for the given period, which were then categorised into four categories depending upon their solar and interplanetary sources like Magnetic Cloud (MC), Co-rotating Interaction Region (CIR), Sheath driven Interplanetary Coronal Mass Ejection (SH+ICME) and Sheath driven Magnetic cloud (SH+MC). From our study we found that the geomagnetic storms significantly affect the ionosphere having any of the solar origin. However the geomagnetic storms which are either caused by SH+MC or SH+ICME produced maximum effect in TEC.
Geomagnetic Storms are the disturbed magnetic conditions, influenced and induced by Interplanetar... more Geomagnetic Storms are the disturbed magnetic conditions, influenced and induced by Interplanetary Magnetic Field and the Charged Particle's motion around the Earth, respectively, in Geospace. As the ionosphere is woven by the earth's magnetic field it responds to the change in that. During the geomagnetic storms the filled-in plasma between the magnetic field lines, geomagnetic flux tubes, redistributes itself in effect of the magnetic field forcing. In the present study we have done the investigation of the morphology of the ionosphere over the mid and high latitude regions during intense Geomagnetic Storms. We got fairly convincing results; in three cases decrease of the critical frequency of F2 layer (foF2) and in one case enhancement of the critical frequency of F2 layer (foF2) at mid and high latitudes.
The equatorial ionospheric parameters, Kp and Dst indices characterized contribution of different... more The equatorial ionospheric parameters, Kp and Dst indices characterized contribution of different magnetospheric and ionospheric currents to the H-component of geomagnetic field are examined to test the geomagnetic activity effect on the generation of ionospheric irregularities producing scintillations. The Global Positioning System (GPS) provides an ideal way of measuring scintillation effects as the signals are continuously available and can be measured along many paths through the atmosphere simultaneously. A dual frequency GPS receiver utilizing the L1 (1575.42 MHz) and L2 (1227.60 MHz) signals were used to measure the amplitude variations during the geomagnetic storm condition for the year 2005. Data from GSV4004A GPS ionospheric Scintillation and TEe monitor (GISTM) has been chosen to study these effects at low latitude Station Bhopal (geog. lat. 23.2 N, geog. long. 77.6E). We found that the intense scintillations were associated with the main phases of the storms as well as recovery phases of the storms and were co-located with the enhancement of the equatorial ionization anomaly (EIA); the co-existence of large and small scale irregularities at daytime was also found.
Association rule mining was first introduced By Agarwalet al ([1], 1993; [3], 2000) which is the ... more Association rule mining was first introduced By Agarwalet al ([1], 1993; [3], 2000) which is the most important and well researched techniques ofdata mining, The Aimsof ARM to extract interesting correlations,repeated patterns, associations among sets of items in the transactiondatabases. Association rules are widely used in variousareas such as market,telecommunication networks,inventorycontrol and risk management etc. this paper leads the implementation of Apriori algorithm under the association rule mining technique of Data mining with using drought data. This algorithm is implemented with the help of Tangra([8], 2005) Data mining software.
When huge face database has to be searched for face detection time becomes the deciding factor fo... more When huge face database has to be searched for face detection time becomes the deciding factor for certain applications such as airport security checks where face detection within a short span of time is desirable. Genetic algorithm helps in close match in a very large face database based on heuristic search. PCA based features is a compulsion from the point of view of low dimension and space limitation. This paper proposes time bound adaptive genetic algorithm so as to reduce time for face detection application in shortest span of time. Integrated expert system will still reduce time for recognition.
... Copyright 2010 All rights reserved Integrated Publishing services Research article ISSN 0976 ... more ... Copyright 2010 All rights reserved Integrated Publishing services Research article ISSN 0976 4380 477 Effect of Geomagnetic Storms in the Equatorial Anomaly Region observed from ground based data Shweta Mukherjee 1 , Shivalika Sarkar 1 , PKPurohit 2 , AKGwal 1 ...
Drought is one of the major environmental disasters in many parts of the world. There are several... more Drought is one of the major environmental disasters in many parts of the world. There are several possibilities of drought monitoring based on ground measurements, hydrological, climatologically and Remote Sensing data. Drought indices that derived by meteorological data and Remote Sensing data have coarse spatial and temporal resolution. Because of the spatial and temporal variability and multiple impacts of droughts, we need to improve the tools and data available for mapping and monitoring this phenomenon on all scales. In this paper we present discovering knowledge by association rules from metrological and Remote Sensing data and we have also used descriptive modeling. For calculating drought taking metrological data which is extract from metrological department of Pune at Maharastra (India) and Remote Sensing data is extract from National Aeronautics and Space Administration (NASA).  so5l-�o� � es; mso-style-link:"Heading 7 Char"; mso-style-next:Normal; margi...
2021 International Conference on Advances in Technology, Management & Education (ICATME), 2021
The aperiodic fluctuations in the Solar Activities intensively affect ionospheric TEC (Total Elec... more The aperiodic fluctuations in the Solar Activities intensively affect ionospheric TEC (Total Electron Contents). These fluctuations are commonly studied with the help of Solar Activity Indices. For the present study, we have used three Solar Activity Indices [viz. Sunspot Number (Rz), Solar Extreme Ultraviolet Flux (EUV) and Coronal Mass Ejections (CME)]. These indices provide a wonderful opportunity to remotely observe the different Solar Phases. The aim of this study is to observe the relationship between the Solar Activity Indices and the Ionospheric TEC during Solar Maxima year 2012 and Solar Minima year 2017 at low latitude IGS station Pathum Wan, Thailand (Code-CUSV) at 13.74° N & 100.54° E. To perform this study, we have analyzed the diurnal variation of TEC during the solar Maxima and the Minima. We also analyzed the monthly as well as seasonal variation of the ionospheric TEC. We also investigated the relationship between Ionospheric TEC and solar activity indices.
All in-text references underlined in blue are linked to publications on ResearchGate, letting you... more All in-text references underlined in blue are linked to publications on ResearchGate, letting you access and read them immediately.
Solar and magnetic activity effects on VHF night-time ionospheric scintillations recorded during ... more Solar and magnetic activity effects on VHF night-time ionospheric scintillations recorded during three and half year at Bhopal, a station near the northern crest of the equatorial anomaly in the Indian region have been presented. The night time diurnal scintillation occurrence decreases with decrease in solar activity. Monthly mean scintillation occurrence changes according to solar activity during E- and D- months but not so during J-months. The magnetic activity shows seasonal effect on scintillations and, in general, inhibits the scintillation occurrence in pre-midnight period and enhances little in post-midnight period especially after 03h IST. For most of the severe magnetic storms in which Dst goes below −125 nT and recovery phase starts in post-midnight — dawn local time sector, strong post-midnight scintillations which sometimes extend for several hours beyond the local sunrise, are observed.
The solar activity hence the solar radiance follows a long term periodic variability with eleven ... more The solar activity hence the solar radiance follows a long term periodic variability with eleven years periodicity, known as solar cycle. This drives the long term variability of the ionosphere. In the present problem we investigate the long term behaviour of the ionosphere with the eleven year cyclic solar activity. Under the present study we characterize the ionospheric variability by Total Electron Content (TEC) using measurements made by Global Positioning System (GPS) and solar cycle variability by various solar activity indices. We make use of five solar activity indices viz. sunspot number (Rz), solar radio Flux (F10.7 cm), EUV Flux (26-34 nm), flare index and CME occurrences. The long term variability of these solar activity indices were then compared and correlated with the variability of ionospheric TEC, at a mid latitude station, Usuda (36.13N, 138.36E), of Japan, during the solar cycle 23 and ascending phase of cycle 24. From our study, we found that long term changes in the ionospheric TEC vary synchronously with corresponding changes in the solar activity indices. The correlation analysis shows that all the solar activity indices exhibit a very strong correlation with TEC (R =0.76 -0.99). Moreover the correlation between the two is stronger in the descending phase of the solar cycle. The correlation is found to be remarkably strongest during the deep minimum of the solar cycle 24 i.e. between 2007- 2009. Also we noticed a hysteresis effect exists with solar radio flux (F10.7 cm) and solar EUV flux (26-34 nm). This effect is absent with other parameters.
We investigate the effect of solar transients on the mid latitude ionosphere during the high sola... more We investigate the effect of solar transients on the mid latitude ionosphere during the high solar activity period of solar cycle 23 i.e 2003 and 2004. A mid latitude station, Guangzhou (23.1N, 113.4E) was selected to carry out the investigation. The ionospheric behaviour at the selected station is characterized by considering the critical frequency of F2 layer (foF2) obtained by using the ground based Ionosonde observations. Then we selected two types of solar transients viz. solar flares and Coronal Mass Ejections (CMEs). To quantify the effect of solar flares we have considered the X-ray flux (1-8 A) and EUV flux (26-34nm). Similarly to quantify the effect of CMEs, we have considered the geomagnetic storms, because during high solar activity the geomagnetic storms are caused by CMEs. From our analysis we conclude that during the geomagnetic storms the value of foF2 decreases as compared to quiet days thereby showing a negative effect. On the contrary we found that during solar flares there is sudden and intense increase in foF2. We also performed a correlation analysis to access the magnitude of association between changes in flux values and peak values of Dst during flares and storms with the corresponding changes and peak values of foF2. We found that a strong correlation exists between the enhancements/decrements in foF2 and enhancements in flux values and Dst. We conclude, while geomagnetic activity suppresses ionospheric activity the flares enhance the same.
The geomagnetic storm represents the most outstanding example of solar wind- magnetospheric inter... more The geomagnetic storm represents the most outstanding example of solar wind- magnetospheric interaction, which causes global disturbances in the geomagnetic field as well as triggers ionospheric disturbances. We study the behaviour of ionospheric Total Electron Content (TEC) during the geomagnetic storms. For this investigation we have selected 47 intense geomagnetic storms (Dst ≤ -100nT) that were observed during the solar cycle 23 i.e. during 1998- 2006. We then categorized these storms into four categories depending upon their solar sources like Magnetic Cloud (MC), Co-rotating Interaction Region (CIR), SH+ICME and SH+MC. We then studied the behaviour of ionospheric TEC at a mid latitude station Usuda (36.13N, 138.36E), Japan during these storm events produced by four different solar sources. During our study we found that the smooth variations in TEC are replaced by rapid fluctuations and the value of TEC is strongly enhanced during the time of these storms belonging to all the four categories. However, the greatest enhancements in TEC are produced during those geomagnetic storms which are either caused by Sheath driven Magnetic cloud (SH+MC) or Sheath driven ICME (SH+ICME). We also derived the correlation between the TEC enhancements produced during storms of each category with the minimum Dst. We found the strongest correlation exists for the SH+ICME category followed by SH+MC, MC and finally CIR. Since the most intense storms were either caused by SH+ICME or SH+MC while the least intense storms were caused by CIR, consequently the correlation was strongest with SH+ICME and SH+MC and least with CIR.
We have investigated the occurrence characteristics of ionospheric scintillations, using dual fre... more We have investigated the occurrence characteristics of ionospheric scintillations, using dual frequency GPS receiver, installed and operated at Indian scientific base station Maitri (71.45S and 11.45E) Antarctica, during December 2009 to December 2010. The scintillation morphology is described in terms of S4 Index. The scintillations are classified into four main categories as Weak (0.2<S4<0.4), Moderate (0.4<S4<0.6), Strong (0.6<S4<1.0) and Saturated (S4>1.0). From the analysis we found that the percentage of weak, moderate, strong and saturated scintillations were 96%, 80%, 58% and 7% respectively. The maximum percentage of all types of scintillation was observed in the summer season, followed by equinox and the least in winter season. As the year 2010 was a low solar activity period, consequently the maximum occurrences of scintillations were those of weak and moderate and only four cases of saturated scintillation were observed.
We have attempted to compare the behaviour of ionosphere during the deep minimum of solar cycle 2... more We have attempted to compare the behaviour of ionosphere during the deep minimum of solar cycle 23 and its peak. At the same time we have also studied the association of ionospheric behaviour with the solar radiation fluxes. We have selected a Japanese mid latitude station, Okinawa (26.3N, 127.8E) and taken the critical frequency of F2 layer (foF2) derived from ionosonde observations to compare the variability of ionosphere during deep minimum (2007) and peak (2003) of solar cycle 23. We found that the values of foF2 were low during 2007 and extremely high during 2003, showing that ionospheric activity has a direct relationship with the solar activity. We then took three solar proxies namely F10.7 cm, EUV flux (26-34nm) and X-ray flux (1-8Å) and probed the association of foF22003 and foF22007 with these solar proxies during the minimum and peak of cycle. We found that EUV flux and X-ray flux correlate with the foF22003 and foF22007 much better than F10.7cm, during both the phases of...
2013 IEEE International Conference on Space Science and Communication (IconSpace), 2013
ABSTRACT The ionospheric behavior is controlled by the solar output, therefore the ionospheric va... more ABSTRACT The ionospheric behavior is controlled by the solar output, therefore the ionospheric variability follows a synchronous variation with the solar activity. The solar activity follows a periodic long term variability, which therefore can be expected to be reflected in the ionospheric behavior. We investigated the variability of ionosphere by using the GPS derived Total Electron Content (TEC) at a mid latitude station Usuda (36.13N, 138.36E), Japan during the sunspot cycle 23 and 24. The solar activity is characterized by a number of activity indices, however for the present study we have used five solar activity indices relevant to the ionospheric studies namely, Sunspot Number (Rz), Solar radio Flux (F 10.7 cm), EUV Flux (26-34 nm), Flare Index and CME Occurrences. The long term variation of the solar activity indices were compared with the variability of ionospheric TEC, and it was found that ionospheric TEC and solar activity variations occur synchronously. The correlation analysis was performed to access the magnitude of correlation between the long term solar cycle variations and the ionospheric behavior. From the analysis we found that GPS derived TEC follows a strong correlation with the solar activity indices. The correlation was found to be remarkably strongest during the deep minimum of the cycle 24 i.e 2007-2008.
All in-text references underlined in blue are linked to publications on ResearchGate, letting you... more All in-text references underlined in blue are linked to publications on ResearchGate, letting you access and read them immediately.
We have studied the behaviour of ionospheric Total Electron Content (TEC) at a mid latitude stati... more We have studied the behaviour of ionospheric Total Electron Content (TEC) at a mid latitude station Usuda (36.130N, 138.360E), Japan during intense geomagnetic storms which were observed during 23 solar cycle (1998-2006). For the present study we have selected 47 intense geomagnetic storms (Dst≤-100nT), for the given period, which were then categorised into four categories depending upon their solar and interplanetary sources like Magnetic Cloud (MC), Co-rotating Interaction Region (CIR), Sheath driven Interplanetary Coronal Mass Ejection (SH+ICME) and Sheath driven Magnetic cloud (SH+MC). From our study we found that the geomagnetic storms significantly affect the ionosphere having any of the solar origin. However the geomagnetic storms which are either caused by SH+MC or SH+ICME produced maximum effect in TEC.
Geomagnetic Storms are the disturbed magnetic conditions, influenced and induced by Interplanetar... more Geomagnetic Storms are the disturbed magnetic conditions, influenced and induced by Interplanetary Magnetic Field and the Charged Particle's motion around the Earth, respectively, in Geospace. As the ionosphere is woven by the earth's magnetic field it responds to the change in that. During the geomagnetic storms the filled-in plasma between the magnetic field lines, geomagnetic flux tubes, redistributes itself in effect of the magnetic field forcing. In the present study we have done the investigation of the morphology of the ionosphere over the mid and high latitude regions during intense Geomagnetic Storms. We got fairly convincing results; in three cases decrease of the critical frequency of F2 layer (foF2) and in one case enhancement of the critical frequency of F2 layer (foF2) at mid and high latitudes.
The equatorial ionospheric parameters, Kp and Dst indices characterized contribution of different... more The equatorial ionospheric parameters, Kp and Dst indices characterized contribution of different magnetospheric and ionospheric currents to the H-component of geomagnetic field are examined to test the geomagnetic activity effect on the generation of ionospheric irregularities producing scintillations. The Global Positioning System (GPS) provides an ideal way of measuring scintillation effects as the signals are continuously available and can be measured along many paths through the atmosphere simultaneously. A dual frequency GPS receiver utilizing the L1 (1575.42 MHz) and L2 (1227.60 MHz) signals were used to measure the amplitude variations during the geomagnetic storm condition for the year 2005. Data from GSV4004A GPS ionospheric Scintillation and TEe monitor (GISTM) has been chosen to study these effects at low latitude Station Bhopal (geog. lat. 23.2 N, geog. long. 77.6E). We found that the intense scintillations were associated with the main phases of the storms as well as recovery phases of the storms and were co-located with the enhancement of the equatorial ionization anomaly (EIA); the co-existence of large and small scale irregularities at daytime was also found.
Association rule mining was first introduced By Agarwalet al ([1], 1993; [3], 2000) which is the ... more Association rule mining was first introduced By Agarwalet al ([1], 1993; [3], 2000) which is the most important and well researched techniques ofdata mining, The Aimsof ARM to extract interesting correlations,repeated patterns, associations among sets of items in the transactiondatabases. Association rules are widely used in variousareas such as market,telecommunication networks,inventorycontrol and risk management etc. this paper leads the implementation of Apriori algorithm under the association rule mining technique of Data mining with using drought data. This algorithm is implemented with the help of Tangra([8], 2005) Data mining software.
When huge face database has to be searched for face detection time becomes the deciding factor fo... more When huge face database has to be searched for face detection time becomes the deciding factor for certain applications such as airport security checks where face detection within a short span of time is desirable. Genetic algorithm helps in close match in a very large face database based on heuristic search. PCA based features is a compulsion from the point of view of low dimension and space limitation. This paper proposes time bound adaptive genetic algorithm so as to reduce time for face detection application in shortest span of time. Integrated expert system will still reduce time for recognition.
... Copyright 2010 All rights reserved Integrated Publishing services Research article ISSN 0976 ... more ... Copyright 2010 All rights reserved Integrated Publishing services Research article ISSN 0976 4380 477 Effect of Geomagnetic Storms in the Equatorial Anomaly Region observed from ground based data Shweta Mukherjee 1 , Shivalika Sarkar 1 , PKPurohit 2 , AKGwal 1 ...
Drought is one of the major environmental disasters in many parts of the world. There are several... more Drought is one of the major environmental disasters in many parts of the world. There are several possibilities of drought monitoring based on ground measurements, hydrological, climatologically and Remote Sensing data. Drought indices that derived by meteorological data and Remote Sensing data have coarse spatial and temporal resolution. Because of the spatial and temporal variability and multiple impacts of droughts, we need to improve the tools and data available for mapping and monitoring this phenomenon on all scales. In this paper we present discovering knowledge by association rules from metrological and Remote Sensing data and we have also used descriptive modeling. For calculating drought taking metrological data which is extract from metrological department of Pune at Maharastra (India) and Remote Sensing data is extract from National Aeronautics and Space Administration (NASA).  so5l-�o� � es; mso-style-link:"Heading 7 Char"; mso-style-next:Normal; margi...
2021 International Conference on Advances in Technology, Management & Education (ICATME), 2021
The aperiodic fluctuations in the Solar Activities intensively affect ionospheric TEC (Total Elec... more The aperiodic fluctuations in the Solar Activities intensively affect ionospheric TEC (Total Electron Contents). These fluctuations are commonly studied with the help of Solar Activity Indices. For the present study, we have used three Solar Activity Indices [viz. Sunspot Number (Rz), Solar Extreme Ultraviolet Flux (EUV) and Coronal Mass Ejections (CME)]. These indices provide a wonderful opportunity to remotely observe the different Solar Phases. The aim of this study is to observe the relationship between the Solar Activity Indices and the Ionospheric TEC during Solar Maxima year 2012 and Solar Minima year 2017 at low latitude IGS station Pathum Wan, Thailand (Code-CUSV) at 13.74° N & 100.54° E. To perform this study, we have analyzed the diurnal variation of TEC during the solar Maxima and the Minima. We also analyzed the monthly as well as seasonal variation of the ionospheric TEC. We also investigated the relationship between Ionospheric TEC and solar activity indices.
All in-text references underlined in blue are linked to publications on ResearchGate, letting you... more All in-text references underlined in blue are linked to publications on ResearchGate, letting you access and read them immediately.
Solar and magnetic activity effects on VHF night-time ionospheric scintillations recorded during ... more Solar and magnetic activity effects on VHF night-time ionospheric scintillations recorded during three and half year at Bhopal, a station near the northern crest of the equatorial anomaly in the Indian region have been presented. The night time diurnal scintillation occurrence decreases with decrease in solar activity. Monthly mean scintillation occurrence changes according to solar activity during E- and D- months but not so during J-months. The magnetic activity shows seasonal effect on scintillations and, in general, inhibits the scintillation occurrence in pre-midnight period and enhances little in post-midnight period especially after 03h IST. For most of the severe magnetic storms in which Dst goes below −125 nT and recovery phase starts in post-midnight — dawn local time sector, strong post-midnight scintillations which sometimes extend for several hours beyond the local sunrise, are observed.
The solar activity hence the solar radiance follows a long term periodic variability with eleven ... more The solar activity hence the solar radiance follows a long term periodic variability with eleven years periodicity, known as solar cycle. This drives the long term variability of the ionosphere. In the present problem we investigate the long term behaviour of the ionosphere with the eleven year cyclic solar activity. Under the present study we characterize the ionospheric variability by Total Electron Content (TEC) using measurements made by Global Positioning System (GPS) and solar cycle variability by various solar activity indices. We make use of five solar activity indices viz. sunspot number (Rz), solar radio Flux (F10.7 cm), EUV Flux (26-34 nm), flare index and CME occurrences. The long term variability of these solar activity indices were then compared and correlated with the variability of ionospheric TEC, at a mid latitude station, Usuda (36.13N, 138.36E), of Japan, during the solar cycle 23 and ascending phase of cycle 24. From our study, we found that long term changes in the ionospheric TEC vary synchronously with corresponding changes in the solar activity indices. The correlation analysis shows that all the solar activity indices exhibit a very strong correlation with TEC (R =0.76 -0.99). Moreover the correlation between the two is stronger in the descending phase of the solar cycle. The correlation is found to be remarkably strongest during the deep minimum of the solar cycle 24 i.e. between 2007- 2009. Also we noticed a hysteresis effect exists with solar radio flux (F10.7 cm) and solar EUV flux (26-34 nm). This effect is absent with other parameters.
We investigate the effect of solar transients on the mid latitude ionosphere during the high sola... more We investigate the effect of solar transients on the mid latitude ionosphere during the high solar activity period of solar cycle 23 i.e 2003 and 2004. A mid latitude station, Guangzhou (23.1N, 113.4E) was selected to carry out the investigation. The ionospheric behaviour at the selected station is characterized by considering the critical frequency of F2 layer (foF2) obtained by using the ground based Ionosonde observations. Then we selected two types of solar transients viz. solar flares and Coronal Mass Ejections (CMEs). To quantify the effect of solar flares we have considered the X-ray flux (1-8 A) and EUV flux (26-34nm). Similarly to quantify the effect of CMEs, we have considered the geomagnetic storms, because during high solar activity the geomagnetic storms are caused by CMEs. From our analysis we conclude that during the geomagnetic storms the value of foF2 decreases as compared to quiet days thereby showing a negative effect. On the contrary we found that during solar flares there is sudden and intense increase in foF2. We also performed a correlation analysis to access the magnitude of association between changes in flux values and peak values of Dst during flares and storms with the corresponding changes and peak values of foF2. We found that a strong correlation exists between the enhancements/decrements in foF2 and enhancements in flux values and Dst. We conclude, while geomagnetic activity suppresses ionospheric activity the flares enhance the same.
The geomagnetic storm represents the most outstanding example of solar wind- magnetospheric inter... more The geomagnetic storm represents the most outstanding example of solar wind- magnetospheric interaction, which causes global disturbances in the geomagnetic field as well as triggers ionospheric disturbances. We study the behaviour of ionospheric Total Electron Content (TEC) during the geomagnetic storms. For this investigation we have selected 47 intense geomagnetic storms (Dst ≤ -100nT) that were observed during the solar cycle 23 i.e. during 1998- 2006. We then categorized these storms into four categories depending upon their solar sources like Magnetic Cloud (MC), Co-rotating Interaction Region (CIR), SH+ICME and SH+MC. We then studied the behaviour of ionospheric TEC at a mid latitude station Usuda (36.13N, 138.36E), Japan during these storm events produced by four different solar sources. During our study we found that the smooth variations in TEC are replaced by rapid fluctuations and the value of TEC is strongly enhanced during the time of these storms belonging to all the four categories. However, the greatest enhancements in TEC are produced during those geomagnetic storms which are either caused by Sheath driven Magnetic cloud (SH+MC) or Sheath driven ICME (SH+ICME). We also derived the correlation between the TEC enhancements produced during storms of each category with the minimum Dst. We found the strongest correlation exists for the SH+ICME category followed by SH+MC, MC and finally CIR. Since the most intense storms were either caused by SH+ICME or SH+MC while the least intense storms were caused by CIR, consequently the correlation was strongest with SH+ICME and SH+MC and least with CIR.
We have investigated the occurrence characteristics of ionospheric scintillations, using dual fre... more We have investigated the occurrence characteristics of ionospheric scintillations, using dual frequency GPS receiver, installed and operated at Indian scientific base station Maitri (71.45S and 11.45E) Antarctica, during December 2009 to December 2010. The scintillation morphology is described in terms of S4 Index. The scintillations are classified into four main categories as Weak (0.2<S4<0.4), Moderate (0.4<S4<0.6), Strong (0.6<S4<1.0) and Saturated (S4>1.0). From the analysis we found that the percentage of weak, moderate, strong and saturated scintillations were 96%, 80%, 58% and 7% respectively. The maximum percentage of all types of scintillation was observed in the summer season, followed by equinox and the least in winter season. As the year 2010 was a low solar activity period, consequently the maximum occurrences of scintillations were those of weak and moderate and only four cases of saturated scintillation were observed.
We have attempted to compare the behaviour of ionosphere during the deep minimum of solar cycle 2... more We have attempted to compare the behaviour of ionosphere during the deep minimum of solar cycle 23 and its peak. At the same time we have also studied the association of ionospheric behaviour with the solar radiation fluxes. We have selected a Japanese mid latitude station, Okinawa (26.3N, 127.8E) and taken the critical frequency of F2 layer (foF2) derived from ionosonde observations to compare the variability of ionosphere during deep minimum (2007) and peak (2003) of solar cycle 23. We found that the values of foF2 were low during 2007 and extremely high during 2003, showing that ionospheric activity has a direct relationship with the solar activity. We then took three solar proxies namely F10.7 cm, EUV flux (26-34nm) and X-ray flux (1-8Å) and probed the association of foF22003 and foF22007 with these solar proxies during the minimum and peak of cycle. We found that EUV flux and X-ray flux correlate with the foF22003 and foF22007 much better than F10.7cm, during both the phases of...
2013 IEEE International Conference on Space Science and Communication (IconSpace), 2013
ABSTRACT The ionospheric behavior is controlled by the solar output, therefore the ionospheric va... more ABSTRACT The ionospheric behavior is controlled by the solar output, therefore the ionospheric variability follows a synchronous variation with the solar activity. The solar activity follows a periodic long term variability, which therefore can be expected to be reflected in the ionospheric behavior. We investigated the variability of ionosphere by using the GPS derived Total Electron Content (TEC) at a mid latitude station Usuda (36.13N, 138.36E), Japan during the sunspot cycle 23 and 24. The solar activity is characterized by a number of activity indices, however for the present study we have used five solar activity indices relevant to the ionospheric studies namely, Sunspot Number (Rz), Solar radio Flux (F 10.7 cm), EUV Flux (26-34 nm), Flare Index and CME Occurrences. The long term variation of the solar activity indices were compared with the variability of ionospheric TEC, and it was found that ionospheric TEC and solar activity variations occur synchronously. The correlation analysis was performed to access the magnitude of correlation between the long term solar cycle variations and the ionospheric behavior. From the analysis we found that GPS derived TEC follows a strong correlation with the solar activity indices. The correlation was found to be remarkably strongest during the deep minimum of the cycle 24 i.e 2007-2008.
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