Tidal and gravity waves study from the airglow measurements at Kolhapur(India)

Simultaneous photometric measurements of the OI 557.7 nm and OH (7, 2) band from a low latitude station, Kolhapur (16.8° N, 74.2° E) during the period 2004-2007 are analyzed to study the dominant waves present in the 80-100 km altitude region of the atmosphere. The nocturnal intensity variations of different airglow emissions are observed using scanning temperature controlled filter photometers. Waves having period lying between 2 and 12 hours have been recorded. Some of these waves having subharmonic tidal oscillation periods 4, 6, 8 and 12 hours propagate upward with velocity lying in the range 1.6-11.3 m/s and the vertical wave length lying between 28.6 and 163 kms. The other waves may be the upward propagating gravity waves or waves resulting from the interaction of inter-mode tidal oscillations, interaction of tidal waves with planetary waves and gravity waves. Some times, the second harmonic wave has higher vertical velocity than the corresponding fundamental wave. Application of these waves in studying the thermal structure of the region is discussed

Solar wind-magnetosphere-ionosphere coupling: Pi2 observations

257-264There had been a number of studies using satellite and ground based observations on the interaction between the solar wind and the magnetosphere, which shows highly complex temporal and spatial interaction between the two. The magnetotail provides an important channel for the flow of energy from solar wind to the ionosphere and atmosphere. Solar wind drives reconnection under certain conditions on the dayside magnetopause, connecting the interplanetary and geomagnetic fields. As a result, the field lines are swept back to the magnetotail where magnetic energy is built up. This stored energy may be converted to plasma kinetic energy either in continuous mode or impulsive mode. In either case, this kinetic energy appears in the energization of the electrons and ions which stream along the magnetic field line in the plasma sheet boundary layer towards the Earth. This flow of energized charged particles results in the form of energy deposition in the high latitude ionosphere and high latitude atmosphere manifesting in terms of aurora. It has been shown from the results obtained from the analysis of ground based magnetic data that, the solar wind driven energy through the magnetotail makes global appearance in the night side of the Earth in the form of Pi2 pulsations. Compressional waves, following plasma sheet thinning due to reconnection, move Earthward and cause plasmasphere to oscillate at discrete frequencies. The present analysis reveals that Pi2 energy is having a global impact on the low latitude in transferring the energy and momentum from solar wind to ionosphere through tail region. During a geomagnetic quiet period (Kp= -3), the scrutiny of the magnetic records from a wide chain of magnetic observatories in the low and mid latitudes gave signatures of plasmaspheric cavity oscillations at dominant frequencies of 11.72 mHz and 23.44 mHz. It has been confirmed from various other parameters such as solar wind dynamic pressure, interplanetary magnetic field and AE-indices that the observed waves are Pi2 type pulsations and may be associated with substorm onset