Shanmugaraju A.,Arul Anandar College |
Prasanna Subramanian S.,Mk University College |
Vrsnak B.,Hvar Observatory |
Ibrahim M.S.,Arul Anandar College
Solar Physics | Year: 2014
We report a detailed analysis of an interaction between two coronal mass ejections (CMEs) that were observed on 14 - 15 February 2011 and the corresponding radio enhancement, which was similar to the "CME cannibalism" reported by Gopalswamy et al. (Astrophys. J.548, L91, 2001). A primary CME, with a mean field-of-view velocity of 669 km s-1 in the Solar and Heliospheric Observatory (SOHO)/Large Angle Spectrometric Coronagraph (LASCO), was more than as twice as fast as the slow CME preceding it (326 km s-1), which indicates that the two CMEs interacted. A radio-enhancement signature (in the frequency range 1 MHz - 400 kHz) due to the CME interaction was analyzed and interpreted using the CME data from LASCO and from the Solar Terrestrial Relations Observatory (STEREO) HI-1, radio data from Wind/Radio and Plasma Wave Experiment (WAVES), and employing known electron-density models and kinematic modeling. The following results are obtained: i) The CME interaction occurred around 05:00 - 10:00 UT in a height range 20 - 25 R⊙. An unusual radio signature is observed during the time of interaction in the Wind/WAVES dynamic radio spectrum. ii) The enhancement duration shows that the interaction segment might be wider than 5 R⊙. iii) The shock height estimated using density models for the radio enhancement region is 10 - 30 R⊙. iv) Using kinematic modeling and assuming a completely inelastic collision, the decrease of kinetic energy based on speeds from LASCO data is determined to be 0.77×1023 J, and 3.67×1023 J if speeds from STEREO data are considered. vi) The acceleration, momentum, and force are found to be a=-168 m s-2, I=6.1×1018 kg m s-1, and F=1.7×1015 N, respectively, using STEREO data. © 2014 Springer Science+Business Media Dordrecht.
Subramanian S.P.,Mk University College |
Shanmugaraju A.,Arul Anandar College
Astrophysics and Space Science | Year: 2016
We present a statistical study and comparison on the properties of intensive solar flares (>M5.0 X-ray flare), decameter–hectometric (DH) wavelength [frequency, 1–14 MHz] type II radio bursts and solar energetic particle (SEP) events during the rising phase of solar cycles 23 and 24. The period of study is May 1996–November 2000 for solar cycle 23 and December 2008–June 2013 for solar cycle 24. Apart from reported weakness of solar cycle 24 compared to the cycle 23, we noted the following differences between the two cycles on the properties of these activities associated with intensive flares: (i) The reduction in the number of intensive flares (>M5.0 class) in cycle 24 is ∼34 %, similar to the reduction in sunspot number reported by Gopalswamy et al. (2014a); (ii) The slightly higher mean starting-frequency (4.15 MHz) and lower ending frequency (0.58 MHz) in cycle 24 compared to those of cycle 23 (2.63 and 0.89 MHz, respectively) indicate that the radio emission of this cycle started closer to the Sun and the CME-shock travelled farther away from the Sun in cycle 24; (iv) Cycle 23 produced a nearly equal number of SEP events as cycle 24 during the rising phase. The correlation between SEP intensity and CME speed is more prominent in cycle 23 (CC=0.7) than in cycle 24 (CC=0.3). © 2016, Springer Science+Business Media Dordrecht.
Shanmugaraju A.,Arul Anandar College |
Prasanna Subramanian S.,Mk University College
Astrophysics and Space Science | Year: 2014
We have analyzed a set of 25 interacting events which are associated with the DH type II bursts. These events are selected from the Coronal Mass Ejections (CMEs) observed during the period 1997-2010 in SOHO/LASCO and DH type IIs observed in Wind/WAVES. Their pre and primary CMEs from nearby active regions are identified using SOHO/LASCO and EIT images and their height-time diagrams. Their interacting time and height are obtained, and their associated activities, such as, flares and Solar Energetic Particles (>10 pfu) are also investigated. Results from the analysis are: primary CMEs are much faster than the pre-CMEs, their X-ray flares are also stronger (X- and M-class) compared to the flares (C- and M-class) of pre-CMEs. Most of the events (22/25) occurred during the period 2000-2006. From the observed width and speed of pre and primary CMEs, it is found that the pre-CMEs are found to be less energetic than the primary CMEs. While the primary CMEs are tracked up to the end of LASCO field of view (30 Rs), most of the pre-CMEs can be tracked up to <26 Rs. The SEP intensity is found to be related with the integrated flux of X-ray flares associated with the primary CMEs for nine events originating from the western region. © 2014 Springer Science+Business Media Dordrecht.