NOPR Collection:

GNSS positioning accuracy over Nigeria during geomagnetic storm of 24-27 October 2011 and 7-10 October 2012

2016-07-20T06:07:12Z

Title: GNSS positioning accuracy over Nigeria during geomagnetic storm of 24-27 October 2011 and 7-10 October 2012 Authors: Joseph, Omojola; Johnson, Abimbola Oladiran Abstract: The present work investigates the positioning error of five Nigeria GNSS network stations during the geomagnetic storm of 24-27 October 2011, a sudden storm commencement (SSC) with disturbance storm time (Dst) minimum of -134 nT; and 7-10 October 2012, a gradual storm commencement (GSC) with Dst minimum -105 nT. Satellite data were obtained from Nigeria GNSS network stations and Dst values were obtained from World Data Center (WDC) for Geomagnetism Kyoto, Japan while the quiet period was selected with Ap index of zero (0) and one (1) for the two storms, respectively from the same World Data Center. RTKLIB (version 2.4.2), a GNSS analysis software, was used to determine the positioning of the stations during the selected storm period and quiet period and the results were analyzed using MATLAB. This investigation revealed that during the selected storm period, the positioning error of the stations increase; though the two storms do not show the same characteristics on GNSS positioning. The GSC of 7-10 October 2012 showed a latitudinal effect, which may be as a result of local variation in the electron density and enhancement of ionospheric irregularity during the storm. This was not clearly depicted in the SSC of 24–27 October 2011. Page(s): 138-146

Electrical conductivity of the stratosphere over Hyderabad, India: Results from Balloon borne measurements

2016-07-20T06:06:21Z

Title: Electrical conductivity of the stratosphere over Hyderabad, India: Results from Balloon borne measurements Authors: Gupta, S P; Thampi, Smitha V Abstract: The stratospheric conductivity is an important parameter of the global electric circuit. In this paper, the stratospheric conductivity measurements are presented, which were made using high altitude balloon flights from Hyderabad (geographic 17.5°N, 78.5°E; magnetic lat 8.5°N), India as a part of the IMAP (1982-1994) program of India. The vertical profiles of ion conductivity were measured from Hyderabad during periods with different solar activity levels and during different seasons using different techniques. It was observed that conductivity values in stratosphere are larger in high solar activity period as compared to low solar activity period. This is similar in nature to the observations from mid-latitudes. The observed positive correlation with solar activity is discussed in terms of composition changes due to the change in intensity of the UV (200-300 nm) radiation with solar activity. It was found that the dissociation of heavy cluster ions to lighter ions, as conjectured by Gupta [Solar cycle variation of stratospheric conductivity over low latitude, Adv Space Res (UK), 26 (2000.) pp 1225–1229] is the main reason for the observed positive correlation of stratospheric conductivity with solar activity. No significant seasonal effect was noticed. In addition, conductivity profile obtained from Hyderabad is compared to that obtained from Cachoeira Paulista, Brazil. Page(s): 132-137

Climatic variance and its effects on decametric Jovian signal reception at a high altitude station Darjeeling

2016-07-20T06:05:20Z

Title: Climatic variance and its effects on decametric Jovian signal reception at a high altitude station Darjeeling Authors: Mondal, S; Bhattacharya, A B Abstract: In this paper precipitation, firing related to extraterrestrial bodies and other ionospheric effects on decametric Jovian radio signal reception at high altitude has been discussed. Jovian signal is observed at 20.1 MHz in the observatory installed at Darjeeling. As Jovian signal is studied under light of Jupiter-Io coupling, it is found that rainfall, out of different atmospheric components, has highest potential to influence reception of Jovian non-Io emission. The observations show that rainfall density plays crucial role in screening extra-terrestrial signal reception from Earth based observatories. The primitive study also suggests that cumulonimbus cloud may have effect on radio signal reception at high altitude. Some interesting findings regarding climatic influence on Jovian signal reception are reported in this paper. Page(s): 126-131

Solar cycle variation of coronal green line index

2016-07-20T06:04:09Z

Title: Solar cycle variation of coronal green line index Authors: Kane, R P Abstract: During 1966-2008 (solar cycles 20-23), the evolutions of sunspots (Rz) and solar flare index (SF) show similar evolution, i.e. a rising phase, a broad maximum and a declining phase in each cycle. On the other hand, coronal holes are more frequent in the declining phase of each cycle. Hence, the coronal green line index (CG), which represents coronal heating, is expected to be similar to sunspots and solar flare index during the rising and maximum phases of solar cycle but dissimilar in the declining phase. Observations show that this was true, but the excess of CG in the declining phase is small compared to the CG intensities at solar maximum. Thus, the contribution of coronal hole could not be unique or even major one for the large coronal heating. There are many solar parameters which evolve differently from the sunspot numbers. But in the present paper, it is assumed that comparison with sunspot numbers may be a reasonable one. Page(s): 122-125