Statistical Analysis Of The Characteristics Of Type ? Radio Bursts And Their Associated Solar Energetic Particle Events

Solar flares and coronal mass ejection(CME)are the two main forms of solar violent eruptions,which are accompanied by many types of radio bursts.Among them,the type ? radio burst signal can be used to determine whether there is a shock wave in the eruption activity.Solar energetic particles(SEP)are formed by super hot particles accelerated by coronal shock.Therefore,the study of the relationship between type ? radio bursts and SEP events is very important for understanding the correlation between SEP and flares,CME and the formation mechanism of SEP events.Through a more detailed classification of type ? radio bursts,this paper explores the relationship between different types of type ? radio bursts and SEP events,and then studies the shock conditions in the process of SEP generation.Based on the observation data of SOHO,wind/waves,stereo-A(B)satellites and Learmonth,culgoora and other ground stations,273 type ? radio burst events during the 24 th solar cycle from January 2010 to March 2018 are selected.According to the starting-ending frequencies,the type ? radio burst events are divided into five types: M ?s only,M-DH ?s,DH ?s only,DH-KM ?s,M-DH-KM ?s.According to the radio spectrum and CME height evolution curve,the formation and ending heights of shocks in the corresponding events are calculated,and the differences of observation characteristics of various types of type ? radio bursts and the correlation and variation rules between CME and solar energetic particle events are statistically analyzed.In addition,the statistical characteristics of seven failed eruption associated with type ? radio bursts and their associated SEP are preliminarily studied.The results are shown as follow:(1)Comparative analysis of five types of events shows that,the proportion of type ? radio burst starting from the metric band is higher than that starting from the DH band.Multi-band type ? radio bursts are more likely to generate SEP events than single band events.Among them,M-DH-KM ?s have the highest proportion of SEP events(73%),and DH ?s only have the lowest proportion of SEP events(19%).(2)Compared with the events without SEP,the type ? radio bursts accompanied by SEP events usually have higher starting frequency,lower ending frequency and longer duration,and the corresponding CME parameters(angular width,speed,mass and kinetic energy)are generally higher,but they have no obvious relationship with CME acceleration.The results show that there is a strong negative correlation between the duration and the ending frequency of type ? radio bursts(CC =-0.93),in which the proportion of SEP events increases with the increase of the duration of type ? radio bursts and decreases with the increase of the ending frequency.(3)Among the five types of events,type ? radio bursts accompanied by SEP events have lower starting height and higher ending height;through the analysis of shock sustained height,it shows that the the proportion of SEP events increases with the increase of sustained height.Among them,in M-DH-KM ?s events,the shock starts from < 3Rs and can sustain to a very high height(such as more than 30Rs)is the highest proportion(about 80%),which is significantly higher than other types of events,and the proportion of SEP events is also the largest.The results show that the CME driven shock starts to form at a low height(such as <3Rs)and sustains to a very high height(such as > 30Rs),which can fully accelerate the particles to produce SEP events,and the intensity of SEP events is also stronger.(4)Compared with successful burst events,the type ? radio bursts accompanied by the failed eruption events have slightly higher starting frequencies,higher ending frequencies and shorter duration.This shows that although the shock can start to form at a lower altitude in the failed eruption,due to the short duration and low ending height,the shock cannot last to a high enough altitude,and the particles will not experience long-term effective acceleration,so the obvious SEP events can not be observed in these eventsIn summary,whether there are SEP events depends more on the angular width,velocity,mass and kinetic energy of CME,as well as the frequency spanning and duration of type ? radio bursts.Among them,M-DH-KM ?s has the largest band spanning,the longest duration,the largest corresponding CME parameters and the largest proportion of SEP events.CME can effectively accelerate the particles to generate SEP events,which requires that the shock wave has a lower formation height and a higher ending height to generate SEP events,so that the shock wave has a long enough particle acceleration time and can sweep more seed particles(particles to be accelerated)in a larger space,and accelerate the particles to a higher energy more efficiently,which is more conducive to the generation of SEP events.The results of this paper are helpful for us to better understand the process and key conditions of SEP events generated by CME shock acceleration,and for the space weather modeling,forecasting and early warning of SEP events.