%0 Journal Article
%T Studies on Longer Wavelength Type II Radio Bursts Associated with Flares and CMEs during the Rise and Decay Phase of 23rd Solar Cycle
%A V. Vasanth
%A S. Umapathy
%J Journal of Astrophysics
%D 2014
%R 10.1155/2014/168718
%X A statistical study on the properties of CMEs and flares associated with DH-type II bursts in the 23rd solar cycle during the period 1997¨C2008 is carried out. A sample of 229 events from our recent work is used for the present study (Vasanth and Umapathy, 2013). The collected events are divided into two groups as (i) solar cycle rise phase events and (ii) solar cycle decay phase events. The properties of CMEs in the two groups were compared and the results are presented. It is noted that there is no difference in the properties of type II burst like start frequency and end frequency between the solar cycle rise phase events and decay phase events. The mean CME speed of solar cycle decay phase events (1373£¿km£¿s£¿1) is slightly higher than the solar cycle rise phase events (1058£¿km£¿s£¿1). The mean CME acceleration of solar cycle decay phase events (£¿15.18£¿m£¿s£¿2) is found to be higher than that of the solar cycle rise phase events (£¿1.32£¿m£¿s£¿2). There exists good correlation between (i) CME speed and width and (ii) CME speed and acceleration for solar cycle decay phase events ( , ) compared to solar cycle rise phase events ( , ). These results indicate that the type II bursts parameters do not depend upon the time of appearance in the solar cycle. 1. Introduction Coronal mass ejections (CMEs) are the large eruption of magnetized plasma from sun into heliosphere and are important cause for geomagnetic storms if they are directed towards earth. The shocks driven by the CMEs accelerate electrons and produce type II bursts in the corona and interplanetary medium (IP) [1]. Type II bursts are the longest known signatures of shock wave [2]. In the dynamic spectrum they are observed as slowly drifting (from high to low frequency) emission bands. The first identification of type II bursts was made by Payne-Scott et al. [3] and later Wild and McCready [2] classified them as type II bursts to differentiate them from fast drifting type III bursts. The first observation of type II bursts in the IP medium was made by IMP-6 [4] and Voyager [5] spacecraft missions. Many IP type II bursts are observed by ISEE-3 spacecraft in the frequency range of 2£¿MHz to 30£¿kHz [6, 7]. The data on DH-type II bursts are provided by radio and plasma wave (WAVES) experiment on board wind spacecraft launched in 1994 [8]. The wind spacecraft observes the type II/IV radio bursts in the frequency range between 14£¿MHz and 20£¿kHz by RAD1 and RAD2 due to ionospheric cut-off frequency [9¨C11]. The frequency range in the decameter hectometric (DH) wavelength domain corresponds to the heights of 2¨C10£¿
%U http://www.hindawi.com/journals/jas/2014/168718/