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Mujiber Rahman A.,Madurai Kamaraj University | Umapathy S.,Madurai Kamaraj University | Shanmugaraju A.,Arul Anandhar College | Moon Y.-J.,Kyung Hee University
Advances in Space Research | Year: 2012

We have analyzed 101 CMEs, and their associated ICMEs and interplanetary (IP) shocks observed during the period 1997-2005. The main aim of the present work is to study the interplanetary characteristics of metric and DH type II associated CMEs such as, shock strength, IP shock speed, ICME speed, stand off distance and transit time. Among these 101 CMEs, 38 events show both metric and DH type II bursts characteristics. There are no metric and DH type II association for 52 events. While DH type II alone is found in 7 cases, metric type II alone is found in 4 events. It is found that the mean speeds of CMEs increase progressively from CMEs without type II events to CMEs associated with metric and DH type IIs as suggested by Gopalswamy et al. (2005). In addition, we found that the speeds of ICMEs and IP shocks progressively increase in the following order: events without metric and DH type IIs, events with metric alone, events with DH alone and events with both metric and DH type IIs. Similarly the Mach number is found to increase in the same order. While there is not much change in the stand-off distance among these cases, it is minimum (∼18 R ȯ) for CMEs with speed greater than 2200 km/s. The above results confirm that more energetic CMEs can produce both metric and DH type IIs for which the interplanetary parameters such as mean values of ICME speed and IP shock speed and Mach number are found to be higher. © 2012 COSPAR. Published by Elsevier Ltd. All rights reserved.

Mujiber Rahman A.,Madurai Kamaraj University | Shanmugaraju A.,Arul Anandhar College | Umapathy S.,Madurai Kamaraj University | Moon Y.-J.,Kyung Hee University
Journal of Atmospheric and Solar-Terrestrial Physics | Year: 2013

We have analyzed the stand-off distance values of 101 interplanetary CMEs (ICMEs) observed during the period 1997-2005. Main aim of the present work is to study the stand-off distance and its dependence on various parameters of CMEs, ICMEs and IP shocks, Alfvenic Mach numbers and transit time. From the distribution, the stand-off time and stand-off distance values of many of the events are found to be in the range between ~2-20h and ~1-40R⊙ (R⊙=Solar radius). From the correlation between speed of CMEs and stand-off distance, we noted smaller stand-off distance for energetic CMEs, which indicated that the driver CME (CME which is generating the shock) and its shock travel closely together. From the correlation plot between CME acceleration and stand-off distance, we found that the highly decelerated events and highly accelerated events have lower stand-off distance range (i.e., 10-40R⊙) than the other events. The events with longer travel time to reach 1AU (>70h) show stand-off times ≤20h and for those faster events (VCME>2200km/s) with smaller travel time (≤40h), stand-off time is extremely low (≤10h). A wide range of stand-off distance is seen for a particular value of CME and ICME parameters. The poor correlations of stand-off distance with all the above parameters confirm that the stand-off distance does not strongly depend on CME, ICME and IP shock parameters, but depends on a combination of all these parameters. On the other hand, the faster CMEs having lower stand-off distance and/or stand-off time imply that as long as the CMEs are energetic, the CMEs and shocks travel closely together. Also, it can be noted that the stand-off distance is not only dependent on gamma, but it is related to other parameters. © 2013 Elsevier Ltd.

Shanmugaraju A.,Arul Anandhar College | Syed Ibrahim M.,Arul Anandhar College | Moon Y.-J.,Kyung Hee University | Kasro Lourdhina K.,Arul Anandhar College | Dharanya M.,Arul Anandhar College
Astrophysics and Space Science | Year: 2015

The Coronal Mass Ejection (CME) is an eruptive event in which magnetic plasma is ejected from the Sun into space through the solar corona. We considered a set of 51 Interplanetary Coronal Mass Ejections (ICMEs) listed by Kim et al. (Solar Phys. 184:77, 2013) from Coordinated Data Analysis Workshop (CDAW, Gopalswamy et al. in Astrophys. J. 710:1111, 2010). Among the 51 events, 22 events are classified as Magnetic Clouds (MC) and 29 events are classified as Ejecta (EJ) where the MC and EJ are subsets of ICMEs. We have analyzed the physical properties of CMEs and ICMEs associated with MC and EJ, and correlated them with the CME’s transit time/arrival time from the Sun to the Earth. Main aims of the present study are to examine (a) dependence of transit time on the properties of CMEs and ICMEs, and (b) differences between MC and EJ. It is found that CME’s initial speed decides the transit time which is in support of the known results in literature. Apart from this, some important results from the present study are: (i) transit time predicted using an empirical relation obtained in the present work is found comparable with the observations (correlation coefficient=0.70). (ii) The transit time of MC and EJ-associated CMEs ranges from 20 to 120 hours and IP acceleration lies between −10 m/s2 to 5 m/s2. (iii) There are certain differences between MC and EJ such as: (a) Ejecta takes slightly more time to travel and only 30 % of them are accelerated in the interplanetary medium. Whereas, MC takes less time to travel and nearly 50 % of them are accelerated, (b) The correlations of IP acceleration and speed with transit time are higher for MC than that of EJ, (c) A weak relationship between the deflection and transit time is found for MC, but it is absent in the case of EJ and (d) Only EJ-type CMEs have wider range of direction parameter and acceleration. Further, we checked the solar wind speed as another parameter has any influence on CME acceleration and it shows that there is no clear dependence between the two parameters. While it is observed that the average acceleration of MC-associated CME is larger for lower direction parameter values (<0.2), it is larger for EJ-associated CME for higher direction parameter values (>0.6). © 2015, Springer Science+Business Media Dordrecht.

Shanmugaraju A.,Arul Anandhar College | Syed Ibrahim M.,Arul Anandhar College | Moon Y.-J.,Kyung Hee University | Mujiber Rahman A.,Hajee Karutha Rowther Howdia College | Umapathy S.,Madurai Kamaraj University
Solar Physics | Year: 2015

We analyzed the physical characteristics of 40 halo coronal mass ejections (CMEs) and their geo-effective parameters observed during the period 2011 to 2013 in the rising phase of Solar Cycle 24. Out of all halo CMEs observed by SOHO/LASCO, we selected 40 halo CMEs and investigated their geomagnetic effects. In particular, we estimated the CME direction parameter (DP) from coronagraph observations, and we obtained the geomagnetic storm disturbance index (Dst) value corresponding to each event by following certain criteria. We studied the correlation between near-Sun parameters of CMEs such as speed and DP with Dst. For this new set of events in the current solar cycle, the relations are found to be consistent with those of previous studies. When the direction parameter increases, the Dst value also increases for symmetrical halo CME ejections. If DP>0.6, these events produce high Dst values. In addition, the intensity of geomagnetic storm calculated using an empirical model with the near-Sun parameters is nearly equal to the observed values. More importantly, we find that the geo-effectiveness in the rising phase of Solar Cycle 24 is much weaker than that in Cycle 23. © 2015, Springer Science+Business Media Dordrecht.

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