STUDY OF IONOSPHERIC ABSORPTION OF
COSMIC NOISE AT HIGH LATITUDES DURING
CMEs USING IMAGING RIOMETER TECHNIQUE
Ashok Kumar Sharma and Rajiv Shrikant Vhatkar
Space Science Laboratory, Department of Physics, Shivaji University, Kolhapur- 416004, M.
S., India (sharma_ashokkumar@yahoo.com)
The study of ionospheric opacity to cosmic radio noise at high latitudes due to major
geoeffective Solar Proton Events (SPE) related to the Coronal Mass Ejections (CMEs)
during years 2000, 2001 and 2003 is done by using imaging riometer technique at
Kilpisjarvi (69.05 degree North; 20.79 degree West), Northern Finland. This tech-
nique is also used to quantify the intensity, time of occurrence and location of the
CMEs. This data is compared with that of the data available from insitu e.g. from
SOHO and GOES and from ground based magnetometer. This observation and data
analysis is done with an aim to study the effects of CMEs and their tracking from their
origin at the Sun to Earth’s ionosphere. From the analysis and interpretation of the
above mentioned data, it is found that extremely high energetic protons accelerated
during CME spiral down to the Earth’s ionosphere where they produces significant
ionization in the D-region at high latitudes, which causes Polar Cap Absorption. The
equal spatial distribution of PCA was observed. In some events a sharp increase in
the absorption was observed due to the CME related sudden impulse. It is observed
that for all solar proton events responsible for PCA are associated with halo CMEs
and which originated from west of 30 degree east and between ± 30 degree of solar
equator.
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