| Summary: | Cosmic noise absorption (CNA) measurred by imaging riometer, is an excellent tool to passively study the high latitude D-region ionospheric conditions and dynamics. An imaging riometer has been installed at Indian Antarctic station Maitri (geographic 70.75°S, 11.75°E; corrected geomagnetic 63.11°S, 53.59°E) in February 2010. This is the first paper using the imaging riometer data from Maitri. The present paper introduces the details of this facility, including its instrumentation, related CNA theory and its applications. Sidereal shift of around 2 hours in the diurnal pattern validates the data obtained from the newly installed instrument. Moreover, the strength of cosmic noise signal on quiet days also varies with months. This is apparently due to solar ionization of D-region ionosphere causing enhanced electron density where collision frequency is already high. The main objective of installing the imaging riometer at Maitri is to study magneotspheric–ionospheric coupling during substorm processes. In the current study, we present two typical examples of disturbed time CNA associated with storm-time and non-storm time substorm. Results reveal that CNA is more pronounced during storm-time substorm as compared to non-storm time substorm. The level of CNA strongly depends upon the strengthening of convectional electric field and the duration of southward turning of interplanetary magnetic field before the substorm onset.
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