Articles written in Journal of Earth System Science
Volume 99 Issue 3 September 1990 pp 413-423
The equatorial wave campaign-II which formed a part of the Indian Middle Atmosphere Programme (IMAP), was conducted from SHAR (13.7°N, 80.2°E) from 15 January to 28 February 1986. Winds were measured from ground to 60 km by means of high altitude balloon and a meteorological rocket (RH-200), once everyday, for 45 days. The frequencies of the oscillations in the deviations of the east-west component of the winds from its mean at each height with one kilometer interval were obtained by the maximum entropy (ME) method and phases/amplitudes of these frequencies were determined by the least squares technique on the wind variation time series. The ME method has the inherent advantage of providing periodicities up to 1.5 times the data length.
The height structure of the long period waves of > 23 day periodicities that have larger amplitudes nearly by a factor of 2 as compared to the medium (9 to 22 day) or shorter period (4 to 8 day) ones, reveal two height regions of enhanced amplitudes, one in the troposphere and another in the upper stratosphere/lower mesosphere, that too, mostly in the regions of positive (westerly increasing or easterly decreasing with height) wind shears. The waves are seen to be inhibited in the negative wind shear regions. From the abrupt changes in the altitude variation of phase, the possible source region has been identified. The vertical wavelengths have been estimated to be 34 km and 19 km in the troposphere and lower stratosphere respectively and 8 km in the upper stratosphere and lower mesosphere. Around 56 km the wave amplitude is reduced to 1/4 of its value below, while the vertical shear strength in the mean wind doubled up. The tropospheric waves are suggested to be Rossby waves of extratropical origin penetrating to tropical latitudes. The stratospheric/mesospheric waves however appear to emanate from a source around the stratopause.
Volume 107 Issue 3 September 1998 pp 203-211
The first optical signatures of plasmapause associated processes were gleaned from the daytime auroral emissions monitored from Maitri, the Indian station in Antarctica, using the newly built, ground-based, Multiwavelength Daytime Photometer (MWDPM). The plasmapause boundary inferred from these measurements conforms well with the known empirical relationship with the geomagnetic index
Volume 114 Issue 6 December 2005 pp 749-760
This paper reports on the Sub-keV Atom Reflecting Analyzer (SARA) experiment that will be flown on the first Indian lunar mission Chandrayaan-1. The SARA is a low energy neutral atom (LENA) imaging mass spectrometer, which will perform remote sensing of the lunar surface via detection of neutral atoms in the energy range from 10 eV to 3 keV from a 100km polar orbit. In this report we present the basic design of the SARA experiment and discuss various scientific issues that will be addressed. The SARA instrument consists of three major subsystems: a LENA sensor (CENA), a solar wind monitor (SWIM), and a digital processing unit (DPU). SARA will be used to image the solar wind-surface interaction to study primarily the surface composition and surface magnetic anomalies and associated mini-magnetospheres. Studies of lunar exosphere sources and space weathering on the Moon will also be attempted. SARA is the first LENA imaging mass spectrometer of its kind to be flown on a space mission. A replica of SARA is planned to fly to Mercury onboard the BepiColombo mission.