International Advanced School on Space Weather (2-19 May, 2006), ICTP, Trieste, Italy AN INVESTIGATION INTO THE L-BAND IONOSPHERIC SCINTILLATION NEAR THE CREST OF THE EQUATORIAL ANOMALY AND TOWARDS DEVELOPING A SCINTILLATION MODEL FOR INDIAN SECTOR Debrup Hui 2, Sarbani Ray 2, Aditi Das 2, Ashik Paul 1, Ashish DasGupta 1,2 1.Institute of Radiophysics and Electronics, University of Calcutta, Kolkata. India 2.S.K. Mitra Center for Research in Space Environment, University of Calcutta, Kolkata, India.

International Advanced School on Space Weather (2-19 May, 2006), ICTP, Trieste, Italy (From Prof H. Lundstedt’s lecture)

International Advanced School on Space Weather (2-19 May, 2006), ICTP, Trieste, Italy T h e p h y s i c a l p r o c e s s...

International Advanced School on Space Weather (2-19 May, 2006), ICTP, Trieste, Italy SCINTILLATIONS Integrated electron density deviation ∫ ∆ Ndl Irregularity amplitude ∆N/N Background electron density and it distribution in the Ionosphere N Undergoes drastic change with sunspot cycle (Basu et al, 1988)

International Advanced School on Space Weather (2-19 May, 2006), ICTP, Trieste, Italy Equatorial F layer Appleton Anomaly (From M. Mendillo’s lecture) Irregular electron distribution

International Advanced School on Space Weather (2-19 May, 2006), ICTP, Trieste, Italy Equatorial Electric Field Pre-reversal enhancement (Fejer, 1991) seasonal solar Fountain effect F layer goes up- where recombination is negligible and condition favorable for the irregularity generation (Haerendel, 1974; Woodman and La Hoz, 1976) Plasma bubbles are formed which goes to the topside with velocity > F-layer plasma velocity. (Anderson and Harendel, 1979) Rayleigh-Taylor mechanisms Steep gradients in the edges help generate small scale irregularities (Haerendel, 1974; Costa and Kelly, 1978)

International Advanced School on Space Weather (2-19 May, 2006), ICTP, Trieste, Italy L-band Scintillation timeline: 1972: Craft and Westerlund -discovered GHz scintillations 1976: Basu and Basu – High ambient ionization could cause GHz scintillations 1981: Aarons et al – hypothesis that the dominant factor for L-band scintillation is propagation though anomaly region 1984: Maruyama and Matuura – Global distribution of spread F Occurrence Statistics of L-band scintillations (Mostly reported from American longitudinal sector) 1980: Basu Su. et al., Livingston, ; 1981: Aarons et al.; Basu and Basu; 1983: Aarons et al.; 1985: Basu Su. and Basu; 1988: Basu et al.; 1997: Groves et al.; 2002: Basu et al.; no such statistics have been reported from other longitudes.

International Advanced School on Space Weather (2-19 May, 2006), ICTP, Trieste, Italy m o d e l s...

International Advanced School on Space Weather (2-19 May, 2006), ICTP, Trieste, Italy A robust climatological model of scintillations WBMOD, which is useful for planning purposes, is now available (Secan et al., 1995, 1997). BUT… Scintillation is a phenomenon exhibiting extreme variability in space and time. THUS… Climatological models are unsuitable for supporting space-based communication and navigation systems and weather models, which can provide real-time specification and forecasting, are required.

International Advanced School on Space Weather (2-19 May, 2006), ICTP, Trieste, Italy Such a system, known as Scintillation Network Decision Aid (SCINDA) has been developed for the American sector (Groves et al., 1997). The DMSP data has been incorporated in the SCINDA system to provide actual forecast of scintillation to be observed one hour later at the longitude of DMSP transit on the same day (Basu et al., 2002). To specify and forecast scintillations, the Communication Navigation Outage Forecasting System (C/NOFS) Satellite is being launched

International Advanced School on Space Weather (2-19 May, 2006), ICTP, Trieste, Italy o u r m o d e l...

International Advanced School on Space Weather (2-19 May, 2006), ICTP, Trieste, Italy We are trying to develop a L-band scintillation model based on the data recorded over a solar cycle ( ) for the region near the crest of the equatorial anomaly in India…

International Advanced School on Space Weather (2-19 May, 2006), ICTP, Trieste, Italy LOCATION KOLKATA ( earlier CALCUTTA) ( N, E, 32 0 magnetic dip) Placed virtually under the northern crest of Equatorial anomaly, is very suitable for studying worst case scenario. Is one of the very few stations having record of L-band scintillation data for over a solar cycle (from 1990 till date) Most of the statistics still now are reported from American longitudinal sectors. Thus the data can very well contribute towards developing a global climatological or weather forecasting model.

International Advanced School on Space Weather (2-19 May, 2006), ICTP, Trieste, Italy DATA  From INMARSAT (64 0 E)  At MHz frequency  With ICOM Wideband Communication Receivers  Recorded on a PC-based Data Acquisition System and a strip chart recorder simultaneously

International Advanced School on Space Weather (2-19 May, 2006), ICTP, Trieste, Italy DATA (cont…)  The receivers are calibrated once a week by a HP Signal Generator (model: HP8648C) following Basu and Basu (1989)  The SI (dB) has been computed at 15 min. interval using the third peak method of Whitney et al. (1969).

International Advanced School on Space Weather (2-19 May, 2006), ICTP, Trieste, Italy 350km subionospheric points of INMARSAT and FSC Location of Kolkata provides an excellent platform for worst case scintillation study

International Advanced School on Space Weather (2-19 May, 2006), ICTP, Trieste, Italy FSC 244 MHz INMARSAT 1.5 GHz SAMPLE SCINTILLATION RECORD ML dB ML dB

International Advanced School on Space Weather (2-19 May, 2006), ICTP, Trieste, Italy IST Hourly PERCENTAGE OCCURENCE contours of L-band ( MHz) for SI>10dB. The E-region sunrise and sunset lines are also shown IST = Indian Standard Time = GMT+5hr30m

International Advanced School on Space Weather (2-19 May, 2006), ICTP, Trieste, Italy Solar Activity Dependence of L-band Scintillations observed at Kolkata Year: (After A. DasGupta, ILWS, Goa,2006)

International Advanced School on Space Weather (2-19 May, 2006), ICTP, Trieste, Italy No of days of Scintillation Occurrence at Kolkata over the solar cycle

International Advanced School on Space Weather (2-19 May, 2006), ICTP, Trieste, Italy Magnetic Activity Dependence of L-band Scintillations Observed at Kolkata Year: (After A. DasGupta, ILWS, Goa,2006)

International Advanced School on Space Weather (2-19 May, 2006), ICTP, Trieste, Italy Towards developing a Model… To predict the occurrence of scintillations on the basis of: Local time Season Solar activity Longitude

International Advanced School on Space Weather (2-19 May, 2006), ICTP, Trieste, Italy Variation with Sunspot Number Hourly measurement: We found that p = a 0 + a 1 (s) + a 2 (s) 2 p = percentage occurrence s = sunspot number

International Advanced School on Space Weather (2-19 May, 2006), ICTP, Trieste, Italy

International Advanced School on Space Weather (2-19 May, 2006), ICTP, Trieste, Italy summing up  Scintillation is very detrimental to present day Communication and Navigation systems like GPS and SBAS and is in dearth need to be understood for reliable operation of these systems.  Equatorial scintillations are controlled mainly by the Sun’s 11year cycle unlike the higher latitude scintillations which are controlled by transient phenomena of the Sun like the solar wind, IMF components and geomagnetic storm  Severe scintillations at L-band are frequently observed at Kolkata, located under the northern crest of the equatorial anomaly, in the post-sunset hours of equinoctial months of high sunspot number years, predominantly in magnetically quiet conditions.

International Advanced School on Space Weather (2-19 May, 2006), ICTP, Trieste, Italy THANK YOU Suggestion(s) are welcome at