Ionization hole campaign—a coordinated rocket and ground-based study at the onset of equatorial spread-F: first results

• Published in: Journal of atmospheric and solar-terrestrial physics 1997-11, Vol.59 (16), p.2051-2067
• Main Authors: Sridharan, R., Chandra, H., Das, S.R., Sekar, R., Sinha, H.S.S., Raju, D.Pallam, Narayanan, R., Raizada, Shika, Misra, R.N., Raghavarao, R., Vyas, G.D., Rao, P.B., Ramarao, P.V.S., Somayajulu, V.V., Babu, V.V., Danilov, A.D.
• Format: Article
• Language: English
• ISSN: 1364-6826; 1879-1824
• DOI: 10.1016/S1364-6826(97)00031-X

A comprehensive multi-technique campaign involving the launch of two high altitude RH-560 rockets was carried out from Sriharikota (SHAR), India, a near-equatorial rocket launching station at the onset of equatorial spread-F, along with a host of ground-based complementary experiments at other locations spread over the country. The main objectives were to obtain the background ionospheric and thermospheric conditions at the onset of equatorial spread-F, and to be able to evaluate the relative importance of the various agencies, the neutral dynamics in particular. Multiple barium cloud releases, in situ plasma diagnostic measurements, along with complementary optical and radio probing experiments were carried out as a part of this campaign. The presence of large scale gradients in the ambient electric fields at ~185 km altitude and also of vertical winds of significant magnitudes at higher altitudes were found. The presence of large scale irregularities in the ion densities at heights above 250 km in a region of negative background density gradient is one of the significant new results. The details of the Ionization hole campaign along with the first results are presented and discussed in the context of the present knowledge of the phenomenon of equatorial spread-F.