Astrophys Space Sci (2014) 350:33–45 DOI 10.1007/s10509-013-1728-3 ORIGINAL ARTICLE Geoeffectiveness and flare properties of radio-loud CMEs O. Prakash · A. Shanmugaraju · G. Michalek · S. Umapathy Received: 14 August 2013 / Accepted: 1 December 2013 / Published online: 11 December 2013 © Springer Science+Business Media Dordrecht 2013 Abstract A detailed investigation on geoeffective CMEs associated with meter to Deca-Hectometer (herein after m- and DH-type-II) wavelengths range type-II radio bursts observed during the period 1997–2005 is presented. The study consists of three steps: i ) the characteristics of m- and DH-type-II bursts associated with flares and geoeffec- tive CMEs; ii) characteristics of geo and non-geoeffective radio-loud and quiet CMEs, iii) the relationships between the geoeffective CMEs and flares properties. Interestingly, we found that 92 % of DH-type-II bursts are extension of m-type-II burst which are associated with faster and wider geoeffective DH-CMEs and also associated with longer/stronger flares. The geoeffective CME-associated m- type-II bursts have higher starting frequency, lower end- ing frequency and larger bandwidth compared to the gen- eral population of m-type-II bursts. The geoeffective CME- associated DH-type-II bursts have longer duration (P ≪ 1 %), lower ending frequency (P = 2 %) and lower drift rates (P = 2 %) than that of DH-type-IIs associated with non-geoeffective CMEs. The differences in mean speed of O. Prakash (B ) Department of Physics, Vaigai College of Engineering, Madurai - 625122, Tamil Nadu, India e-mail: prakash18941@gmail.com A. Shanmugaraju Department of Physics, Arul Anandar College, Karumathur, Madurai 625514, Tamil Nadu, India G. Michalek Astronomical Observatory of Jagiellonian University, Krakow, Poland S. Umapathy School of Physics, Madurai Kamaraj University, Madurai - 625021, Tamil Nadu, India geoeffective DH-CMEs and non-geoeffective DH-CMEs (1327 km s −1 and 1191 km s −1 , respectively) is statisti- cally insignificant (P = 20 %).However, the mean differ- ence in width (339 ◦ and 251 ◦ , respectively) is high sta- tistical significant (P = 0.8 %). The geo-effective general populations of LASCO CMEs speeds (545 km s −1 and 450 km s −1 , respectively) and widths (252 ◦ and 60 ◦ , respec- tively) is higher than the non geo-effective general popu- lations of LASCO CMEs (P = 3 % and P = 0.02 %, re- spectively). The geoeffective CMEs associated flares have longer duration, and strong flares than non-geoeffective DH- CMEs associated flares (P = 0.8 % and P = 1 %, respec- tively). We have found a good correlation between the geo- effective flare and DH-CMEs properties: i ) CMEs speed— acceleration (R =−0.78, where R is a linear correlation coefficient), ii) acceleration—flare peak flux (R =−0.73) and, iii) acceleration—Dst index intensity (R = 0.75). The radio-rich CMEs (DH-CMEs) produced more energetic storm than the radio-quiet CMEs (general populations of LASCO CMEs). The above results indicate that the DH- type-II bursts tend to be related with flares and geoeffective CMEs, although there is no physical explanation for the re- sult. If the DH-type-II burst is a continuation of m-type-II burst, it could be a good indicator of geoeffective storms, which has important implications for space weather studies. Keywords Coronal mass ejections · Type-II bursts, geoeffective radio-loud CMEs 1 Introduction The type-II radio bursts are the earliest evidence of shocks near the Sun and in the interplanetary medium (Gopalswamy et al. 2008a; 2008b). The meter wavelengths type-II radio