Type II bursts in Meter and Decameter – Hectometer Wavelength Ranges and Their Relation to Flares and CMEs

Michałek

et al. 2017

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A gradual solar energetic particle (SEP) event is thought to happen when particles are accelerated at a shock due to a fast coronal mass ejection (CME). To quantify what kind of solar eruptions can result in such SEP events, we have conducted detailed investigations on the characteristics of CMEs, solar flares and metric-to-decahectometric wavelength type II radio bursts (herein after m-to-DH type II bursts) for SEP-associated and non-SEP-associated events, observed during the period of 1997-2012. Interestingly, 65% of m-to-DH type II bursts associated with CMEs and flares produced SEP events. The SEP-associated CMEs have higher sky-plane mean speed, projection corrected speed, and sky-plane peak speed than those of non-SEP-associated CMEs respectively by 30%, 39%, and 25%, even though the two sets of CMEs achieved their sky-plane peak speeds at nearly similar heights within LASCO field of view. We found Pearsons correlation coefficients between the speeds of CMEs (skyplane speed and corrected speed) and logarithmic peak intensity of SEP events are cc = 0.62 and cc = 0.58, respectively. We also found that the SEP-associated CMEs are on average of three times more decelerated (-21.52 m s −2 ) than the non-SEP-associated CMEs (-5.63 m s −2 ). The SEP-associated flares have a mean peak flux (1.85 × 10 −4 W m −2 ) three times larger than that of non-SEP-associated flares, even though the flare duration (rise time) of both sets of events is similar. The SEP-associated m type II bursts have higher frequency drift rate and associated shock speed than those of the non-SEP-associated events by 70% and 25% respectively. The average formation heights of m and DH type II radio bursts for SEP-associated events (1.31 R • and 3.54 R • , respectively) are lower than for non-SEPassociated events (1.61 R • and 3.91 R • , respectively). 93% of SEP-associated events originate from the western hemisphere and 65% of SEP-associated events are associated with interacting CMEs. The obtained results indicate that, at least for the set of CMEs associated with m-to-DH type II bursts, SEP-associated CMEs are more energetic than those not associated with SEPs, thus suggesting that they are effective particle accelerators.

Section: Characteristics Of Sep-associated and Non-sep-associated Flaresmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Characteristics of events with metric-to-decahectometric type II radio bursts associated with CMEs and flares in relation to SEP events

Michałek

et al. 2017

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“…The flare rise-time (interval Fig. 3 Distribution of: (a) flare rise-times; (b) flare decay-times, for DH CMEs following and preceding the associated flares (left and right respectively) from flare start to flare peak) is the most important parameter in analyzing the relationship between flares and CMEs (Shanmugaraju et al 2003;Subramanian et al 2003;Zhang et al 2004;Prakash et al 2009). As seen from Fig.…”

Section: The Flare Rise-time and Decay-timementioning

confidence: 99%

Distinctions between the characteristics of before and after DH CMEs associated flares

Umapathy

Shanmugaraju

2012

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A detailed analysis of characteristics of coronal mass ejections and flares associated with deca-hectometer wavelength type-II radio bursts (DH-CMEs and DH-flares) observed in the period 1997-2008 is presented. A sample of 62 limb events is divided into two populations known as after-flare CMEs (AF-CMEs) and before-flare CMEs (BFCMEs) based on the relative timing of the flare and CME onsets. On average, AF-CMEs (1589 km s −1 ) have more speed than the BF-CMEs (1226 km s −1 ) and the difference between mean values are highly significant (P ∼ 2%). The average CME nose height at the time of type-II start is at larger distance for AF-CMEs than the BF-CMEs (4.89 and 3.84 R o , respectively). We found a good anti-correlation for accelerating (R a = −0.89) and decelerating (R d = −0.78) AF-CMEs. In the case of decelerating BF-CMEs, the correlation seems to be similar to that for decelerating AF-CMEs (R d = −0.83). The number of decelerating AF-CMEs is 51% only; where as, the number of decelerating BF-CMEs is 83%. The flares associated with BF-CMEs have shorter rise and decay times than flares related to AF-CMEs. We found statistically significant differences between the two sets of associated DH-type-II bursts characteristics: starting frequency (P ∼ 4%), drift rate (P ∼ 1%), and ending frequency (P ∼ 6%). The delay time analysis of DH-type-II start and flare onset times shows that the time lags are longer in AF-CME events than in BF-CME events (P 1%). From the above results, the AF-CMEs which are associated O. Prakash ( ) · S. Umapathy

“…Flare rise time (the interval from the flare start to flare peak) is the most important parameter in analyzing the relationship between flares and type-II bursts. Shanmugaraju et al (2003) and Prakash et al (2009) studied the relation between the flare-CMEs-metric type-II radio bursts. They found that the coronal shock is formed between the start and peak of the X-ray flare.…”

Section: Properties Of Flares and Cmes Of Group I Ii And Iii Eventsmentioning

confidence: 99%

Characteristics of DH type II bursts, CMEs and flares with respect to the acceleration of CMEs

Umapathy

Shanmugaraju³

et al. 2011

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A detailed investigation on DH-type-II radio bursts recorded in Deca-Hectometer (hereinafter DH-type-II) wavelength range and their associated CMEs observed during the year 1997-2008 is presented. The sample of 212 DH-type-II associated with CMEs are classified into three populations: (i) Group I (43 events): DH-type-II associated CMEs are accelerating in the LASCO field view (a > 15 m s −2 ); (ii) Group II (99 events): approximately constant velocity CMEs (−15 < a < 15 m s −2 ) and (iii) Group III (70 events): represents decelerating CMEs (a < −15 m s −2 ). Our study consists of three steps: (i) statistical properties of DH-type-II bursts of Group I, II and III events; (ii) analysis of time lags between onsets of flares and CMEs associated with DH-type-II bursts and (iii) statistical properties of flares and CMEs of Group I, II and III events. We found statistically significant differences between the properties of DH-type-II bursts of Group I, II and III events. The significance (P a ) is found using the one-way ANOVA-test to examine the differences between means of groups. For example, there is significant difference in the duration (P a = 5%), ending frequency (P a = 4%) and band-O. Prakash ( ) · S. Umapathy width (P a = 4%). The accelerating and decelerating CMEs have more kinetic energy than the constant speed CMEs. There is a significant difference between the nose height of CMEs at the end time of DH-type-IIs (P a 1%). From the time delay analysis, we found: (i) there is no significant difference in the delay (flare start-DH-type-II start and flare peak-DH-type-II start); (ii) small differences in the time delay between the CME onset and DH-type-II start, delay between the flare start and CME onset times. However, there are high significant differences in: flare duration (P a = 1%), flare rise time (P a = 0.5%), flare decay time (P a = 5%) and CMEs speed (P a 1%) of Group I, II and III events. The general LASCO CMEs have lower width and speeds when compared to the DH CMEs. It seems there is a strong relation between the kinetic energy of CMEs and DH-type-II properties.