An assessment of potentially space weather causing CMEs through analysis of associated interplanetary type II solar radio bursts and solar energetic particle events

Abstract

This study investigates the space weather implications of coronal mass ejections (CMEs) by analyzing 39 metric type II solar radio bursts with decametric–hectometric (DH) counterparts during a segment of Solar Cycle 24. To minimize projection effects, only limb CMEs originating far from the solar disk center (central meridian distances between $\mathrm{60}°$ and $\mathrm{90}°$) were considered. The events were categorized into three groups: (i) all metric type II bursts with DH counterparts (m-DH), (ii) those accompanied by solar energetic particle (SEP) events (m-DH-SEP), and (iii) those without SEP events (m-DH-NonSEP). Analysis of CME parameters revealed that m-DH-SEP events are associated with faster (average speed of 1203 km/s) and wider CMEs compared to m-DH-NonSEP events (average speed of 333 km/s). Additionally, the fraction of halo CMEs increased across the groups: m-DH-NonSEP (62.5%), m-DH (74.3%), and m-DH-SEP (93%). A strong positive correlation (Pearson’s CC = 0.76; ${\mathrm{SE}}_{\mathrm{cc}}=\mathrm{0.18}$) was found between CME speeds and the logarithmic peak intensity of SEP events. Notably, 87% of m-DH-SEP events originated from the western hemisphere in StonyHurst coordinates, consistent with favorable magnetic connectivity to Earth. Further analysis indicated that 62.5% of western hemisphere metric type II bursts with DH counterparts were followed by SEPs at Earth, compared to only 13% without DH counterparts. These findings confirm that fast and wide CMEs associated with DH type II bursts are effective in accelerating energetic particles, underscoring the significance of DH type II bursts as indicators of SEP events and their relevance in space weather forecasting.