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... 8038 DURENG 10-13 MAY 1997 Rajmal Jam Nirav Mehta Han Om Vats MR Deshpande Shibu. ... intensity variation during 04:50 - 06:18 UT which enables us to confirm the existence of predominant 3 mm modes in Ha flare intensity discovered... more
... 8038 DURENG 10-13 MAY 1997 Rajmal Jam Nirav Mehta Han Om Vats MR Deshpande Shibu. ... intensity variation during 04:50 - 06:18 UT which enables us to confirm the existence of predominant 3 mm modes in Ha flare intensity discovered earlier by Jam and Tripathy (1997 ...
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Horizontal drift measurements of the ionospheric E-region irregularities, using spaced receiver technique at Tiruchirapalli during the period 1973–75 are presented. There is a marked day to day variability in the magnitude of the drift... more
Horizontal drift measurements of the ionospheric E-region irregularities, using spaced receiver technique at Tiruchirapalli during the period 1973–75 are presented. There is a marked day to day variability in the magnitude of the drift speed which is well correlated with the electrojet strength. Counter-electrojet events are maximum during J-solstices and minimum during equinoxes. Drift speeds are also shown to decrease linearly with increasing K index and with increasing southward component of the interplanetary magnetic field. Small changes due to lunar tidal effects are also isolated.
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Equatorial spread-F and Equatorial Ionization Anomaly EIA are very important geophysical phenomena These two important processes are very much associated with the geomagnetic disturbances geomagnetic storms of varying magnitude Equatorial... more
Equatorial spread-F and Equatorial Ionization Anomaly EIA are very important geophysical phenomena These two important processes are very much associated with the geomagnetic disturbances geomagnetic storms of varying magnitude Equatorial belt of strong spread-F extends right through the Appleton anomaly crest latitudes during high sunspot years Intense scintillations do occur in presence of the plasma density irregularities that are associated
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Title: Total electron content studies during 16 February 1980 solar eclipse by differential Doppler method. Authors: Deshpande, MR; Chandra, H.; Banshidhar; Vats, HO; Sethia, G.; Vadher, NM; Jain, CL; Sivaraman, MR; Kothari, SK; Goyal,... more
Title: Total electron content studies during 16 February 1980 solar eclipse by differential Doppler method. Authors: Deshpande, MR; Chandra, H.; Banshidhar; Vats, HO; Sethia, G.; Vadher, NM; Jain, CL; Sivaraman, MR; Kothari, SK; Goyal, SS. Publication: Proc. Indian Natl. Sci. ...
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ABSTRACT. - Amplitude scmtzllatlOns of latzo beacons aboard ATS-6 satellite on 40 MHz. 140 MHz and 360 MHz recorded during the ATS-6 phase II at an equatonal KttltlOn Ootacamund (dip 4° N) and the wnogramlI at a nearby statzon Kodalkanal... more
ABSTRACT. - Amplitude scmtzllatlOns of latzo beacons aboard ATS-6 satellite on 40 MHz. 140 MHz and 360 MHz recorded during the ATS-6 phase II at an equatonal KttltlOn Ootacamund (dip 4° N) and the wnogramlI at a nearby statzon Kodalkanal (dzp 3 5U N) (lfe /!XIllmned ...
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Bull. Astr. Soc. India (1993) 21, 615-617 Terrestrial effects of PSR 0950 + 08 (Paper II) Han Urn Vats, Harish Chandra, MR Deshpande, P. Janardhan and GD Vyas Physical Research Laboratory, Navrangpura, Ahmedabad 380 009 Abstract. This... more
Bull. Astr. Soc. India (1993) 21, 615-617 Terrestrial effects of PSR 0950 + 08 (Paper II) Han Urn Vats, Harish Chandra, MR Deshpande, P. Janardhan and GD Vyas Physical Research Laboratory, Navrangpura, Ahmedabad 380 009 Abstract. This article presents indirect ...
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... Thanks are also due to Mrs. Manisha S Pandya and Mrs. Bharti K Bhatt for scaling the ionograms. ... Terrest. Phys., 43, 437452, 1981. Rastogi RG and Kulkarni PP, SpreadF echoes over Ahmedabad over a solar cycle, Ann. Geophys., 25,... more
... Thanks are also due to Mrs. Manisha S Pandya and Mrs. Bharti K Bhatt for scaling the ionograms. ... Terrest. Phys., 43, 437452, 1981. Rastogi RG and Kulkarni PP, SpreadF echoes over Ahmedabad over a solar cycle, Ann. Geophys., 25, 577587, 1969. ...
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A Nd-YAG laser based Rayleigh Lidar was set up at Guru Shikhar, Mt. Abu (24.5o N, 72.7o E, altitude 1.7 km) to study the temperature structure in the altitude region of 30-75 km at tropical latitudes. Temperature profiles are derived from... more
A Nd-YAG laser based Rayleigh Lidar was set up at Guru Shikhar, Mt. Abu (24.5o N, 72.7o E, altitude 1.7 km) to study the temperature structure in the altitude region of 30-75 km at tropical latitudes. Temperature profiles are derived from the density measurements, using the method described by Hauchecorne and Channin (1980). Photon counts are averaged over 2 hours
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Details of the coordinated rocket and MST radar campaign for mesospheric turbulence studies carried out during July 19-27 2004 are presented One RH-300 MK II rocket instrumented with a Langmuir probe and spherical probe was launched from... more
Details of the coordinated rocket and MST radar campaign for mesospheric turbulence studies carried out during July 19-27 2004 are presented One RH-300 MK II rocket instrumented with a Langmuir probe and spherical probe was launched from SHAR 13 7 N 80 2 E at 1142 h IST on July 23 2004 when strong mesospheric echoes were observed by the
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Rayleigh lidars at Gadanki (13.5° N, 79.2° E), a tropical site, and at Mt. Abu (24.5° N, 72.7° E), a subtropical site, in India were operated simultaneously during the months of March, April, and May 2004. Significant differences are... more
Rayleigh lidars at Gadanki (13.5° N, 79.2° E), a tropical site, and at Mt. Abu (24.5° N, 72.7° E), a subtropical site, in India were operated simultaneously during the months of March, April, and May 2004. Significant differences are found in the temperatures over both the locations. Higher temperature, ~10–20 K, in the altitude region of 40–65 km is found during March 2004 over Mt. Abu. The mean stratopause temperature during March 2004 is found ~284 K at an altitude of 48 km over Mt. Abu, which is 18 K higher than the observed stratopause temperature of ~266 K over Gadanki. During April and May 2004, the temperatures over Mt. Abu are higher in the entire altitude range of 30–70 km than over Gadanki. Lidar-observed temperatures, over both the locations, are compared with the temperatures observed by SABER (Sounding of the Atmosphere using Broadband Emission Radiometry; onboard TIMED (Thermosphere Ionosphere Mesosphere Energetics and Dynamics)) and HALOE (Halogen Occultation Experim...
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ABSTRACT
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A number of radio experiments were conducted at Ahmedabad (23°N, 73°E) with the aim of studying the ionospheric effects of the total solar eclipse of 11 August 1999. Rapid radio soundings from the ionosonde were made on the eclipse day... more
A number of radio experiments were conducted at Ahmedabad (23°N, 73°E) with the aim of studying the ionospheric effects of the total solar eclipse of 11 August 1999. Rapid radio soundings from the ionosonde were made on the eclipse day and on control days. A riometer was operating at 30 MHz, and field strength measurements along the three oblique incidence paths of Colombo-Ahmedabad (11905 kHz), Bombay-Ahmedabad (558 kHz) and Rajkot-Ahmedabad (810 kHz) were also made. A reduction of about 20% was observed in the minimum frequency of reflection from the ionosonde (fmin), which indicates a reduction in D-region ionization. The critical frequency of the E-layer was not measurable beyond 1600 h IST on eclipse day due to the strong blanketing sporadic-E, but there is a 20% decrease in the critical frequency of the F1-layer. Although there was no change in the minimum virtual height of the F-layer on eclipse day, there appears to have been a decrease in the height of maximum ionization (h...
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The paper compares the scintillations of VHF radio waves at a tropical latitude station with the spread-F records at a nearby ionospheric sounding station. The scintillations are very strong (amplitude exceeding 10 dB peak to peak) and... more
The paper compares the scintillations of VHF radio waves at a tropical latitude station with the spread-F records at a nearby ionospheric sounding station. The scintillations are very strong (amplitude exceeding 10 dB peak to peak) and fast during the periods when the spread-F is characterized by a series of discrete multiple layers parallel to the first order (p-prime)-f trace over the entire frequency range. The scintillations become slow and weak when spread-F is characterized by overlapping series of (p-prime)-f curves on frequencies close to the critical frequency which occur generally during the postmidnight hours, when the ambient ionization is low. On a number of occasions, scintillations are observed in patches with brief periods of no scintillation activity. This patchy nature of scintillations closely corresponds with the pattern of spread-F appearance and disappearance for brief periods at Ahmedabad.
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This letter presents, to our knowledge for the first time, two cases of scintillations of the 244MHz satellite beacon signal recorded from the geostationary satellite FLEETSATCOM (FSC) (Long: 73°E) at the Haringhata Field Station (HFS)... more
This letter presents, to our knowledge for the first time, two cases of scintillations of the 244MHz satellite beacon signal recorded from the geostationary satellite FLEETSATCOM (FSC) (Long: 73°E) at the Haringhata Field Station (HFS) (Lat: 22.97°N Long: 88.50°E Dip: 32°N) of the University of Calcutta on the night of November 16/17, 1998, which corresponds to the peak period of
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... Nair, KN , Rastogi, RG , and Sarabhai, VA , Nature, 226, 740 (1970). Chandra, H. , and Rastogi, RG , J.-Atmosph. Terr. Phys., 32, 1309 (1970). Chapman, JH , Canad. ... Terr. Phys., 33, 128 (1971).Kavanagh, LD , Freeman, JW , and Chen,... more
... Nair, KN , Rastogi, RG , and Sarabhai, VA , Nature, 226, 740 (1970). Chandra, H. , and Rastogi, RG , J.-Atmosph. Terr. Phys., 32, 1309 (1970). Chapman, JH , Canad. ... Terr. Phys., 33, 128 (1971).Kavanagh, LD , Freeman, JW , and Chen, AJ , J. Geophys. Res., 73, 5511 (1968). ...
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Features of the equatorial electrojet are studied at Sao Luiz (2.6°S, 44.2°W, inclination −0.25°) in eastern Brazil and Sikasso (11.3°N, 5.7°W, inclination 0.1°) in the western African sector. The stations are situated on either side of... more
Features of the equatorial electrojet are studied at Sao Luiz (2.6°S, 44.2°W, inclination −0.25°) in eastern Brazil and Sikasso (11.3°N, 5.7°W, inclination 0.1°) in the western African sector. The stations are situated on either side of the lowest magnetic field intensity in the region of rapid changes in the declination. The daily variations of ΔX at the two stations are
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... AcknowledgementsThe authors are grateful to the staff of the Vikram Sarabhai Space Centre (VSSC) and of the Shri Harikota Range (SHAR) for providing all the facilities related to the rocket launch and ground support. Thanks ...
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Total electron content data at Ootacamund (dip 6 deg N) during the second phase of the ATS-6 program are analyzed for solar and lunar variations. Both the lunar semimonthly and lunar semidiurnal tides at Ootacamund are smaller in... more
Total electron content data at Ootacamund (dip 6 deg N) during the second phase of the ATS-6 program are analyzed for solar and lunar variations. Both the lunar semimonthly and lunar semidiurnal tides at Ootacamund are smaller in magnitude than at stations near the Appleton anomaly crest. The phases of the lunar oscillations however are almost the same as that
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The repositioning of the ATS-6 satellite at 34 deg E enabled the scientific community of India to use the satellite's radio beacon for ionospheric studies. Two scientific projects were undertaken. The objective of the first project... more
The repositioning of the ATS-6 satellite at 34 deg E enabled the scientific community of India to use the satellite's radio beacon for ionospheric studies. Two scientific projects were undertaken. The objective of the first project was to map ionospheric electron content, range rate errors, traveling ionospheric phenomena, solar flare effect, and magnetic phenomena. The second project was aimed at
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This paper describes the morphology of the equatorial electrojet (EEJ) along 45°W longitude in east Brazil, where the ground magnetic (dip) equator is associated with the largest declination in the world. Daily range of the horizontal... more
This paper describes the morphology of the equatorial electrojet (EEJ) along 45°W longitude in east Brazil, where the ground magnetic (dip) equator is associated with the largest declination in the world. Daily range of the horizontal field (ΔH), as expected, was largest at the station in the chain closest to the dip equator, Sao Luiz (inclination −0.25°S). ΔZ was largest
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Study of the electron density distributions over Thumba for two solar epoch years - 1965, a year of low solar activity, and 1967, a year of high solar activity. Standard profiles were obtained for quiet days, and the effect of magnetic... more
Study of the electron density distributions over Thumba for two solar epoch years - 1965, a year of low solar activity, and 1967, a year of high solar activity. Standard profiles were obtained for quiet days, and the effect of magnetic disturbance is studied by comparing various ionospheric parameters for quiet and disturbed days. Data suggest that ionization which is normally transported away around midday from the equator to the crest regions on quiet days remains at the equator itself on disturbed days. It is suggested that this may be due to the equatorial electric fields weakening during disturbed conditions, resulting in a reduction of the vertical E x B uplift of equatorial ionization.