Solar energetic particle (SEP) events, driven by solar flares and coronal mass ejections (CMEs), are occasionally accompanied by ground level enhancements (GLEs), detected by neutron monitors. While GLEs represent only a subset of SEP events, their occurrence may provide insight into the acceleration and propagation mechanisms of SEPs. In this study, we conducted a statistical analysis of 122 SEP events from 1997 to 2023, including 16 events associated with GLE and 106 without, using elemental composition data from the ACE/SIS instrument and X-ray fluence data from GOES/XRS. The results show that SEP events with GLE exhibit significantly higher fluences of SIS elements (He, C, N, O, Ne, Mg, Si) than those without, particularly at high energy channels. Notably, the fluences of carbon and oxygen were particularly enhanced in SEP events associated with GLE, suggesting a potential role for these elements in the generation of GLEs. A strong correlation (average r ≈ 0.75) was observed between the X-ray fluence of associated solar flares and the elemental fluences in SEP events with GLE, whereas a weaker correlation (average r ≈ 0.32–0.40) was found for SEP events without GLE. These findings imply that the presence of a GLE is linked to distinct acceleration conditions and enhanced ion production, particularly of light ions with large charge-to-mass ratios. This study contributes to a better understanding of SEP composition, GLE-associated mechanisms, and their relevance to space weather forecasting and radiation hazard assessments.

We present optical observations of a nearby Type Ia supernova (SN Ia) 2018kp on January 24 2018, +1.4 days after the estimated first light time. Its host galaxy, NGC 3367, has been under high-cadence monitoring (≲1 day) with the purpose of providing valuable early light curves of supernovae as a primary target of the Intensive Monitoring Survey of Nearby Galaxies (IMSNG; Im et al. 2019). SN 2018kp exhibits the characteristics of a normal SN Ia, with a peak luminosity of MB = −19.0 ± 0.4 mag and Δm15(B) = 1.19 ± 0.03 mag, derived from our long-term light curve analysis. We estimate the host extinction to be high [E(B − V )host = 0.697 ± 0.028 mag], contrasting with its sibling, SN 1986A. We estimate the mass of 56Ni synthesized in the explosion to beMNi = 0.55±0.14M⊙. A single power-law model (tα) describes the rising behavior of the early light curve well, with little evidence of the shock-heated cooling emission. We place upper limits on the radii of the progenitor (Rp ≤ 1.8 R⊙) and the companion star (Rc ≤ 1.9 R⊙ at the optimal or Rc ≤ 19.2 R⊙ at the common viewing angle, respectively) ruling out a large companion such as a red giant. Based on our data, we derive a distance to the host galaxy of 41.38 ± 2.20 Mpc assuming that SN 2018kp follows the Phillips relation.

The Sun-Earth Lagrange point L4, which is called a parking space of space, is considered one of the unique places where solar activity and the heliospheric environment can be observed continuously and comprehensively. The L4 mission affords a clear and wide-angle view of the Sun-Earth line for the study of Sun-Earth connections from remote-sensing observations. The L4 mission will significantly contribute to advancing heliophysics science, improving space weather forecasting capability, extending space weather studies far beyond near-Earth space, and reducing risk from solar radiation hazards on human missions to the Moon and Mars. Our paper outlines the importance of L4 observations by using remote-sensing instruments and advocates comprehensive and coordinated observations of the heliosphere at multi-points including other planned L1 and L5 missions. We mainly discuss scientific perspectives on three topics in view of remote sensing observations: (1) solar magnetic field structure and evolution, (2) source regions of geoeffective solar energetic particles (SEPs), and (3) stereoscopic views of solar corona and coronal mass ejections (CMEs).