Magnetic flux ropes, often observed during intervals of interplanetary coronal mass ejections, have long been recognized to be critical in space weather. In this work, we focus on magnetic flux rope structure but on a much smaller scale, and not necessarily related to interplanetary coronal mass ejections. Using near-Earth solar wind advanced composition explorer (ACE) observations from 1998 to 2016, we identified a total of 309 small-scale magnetic flux ropes (SMFRs). We compared the characteristics of identified SMFR events with those of normal magnetic cloud (MC) events available from the existing literature. First, most of the MCs and SMFRs have similar values of accompanying solar wind speed and proton densities. However, the average magnetic field intensity of SMFRs is weaker (~7.4 nT) than that of MCs (~10.6 nT). Also, the average duration time and expansion speed of SMFRs are ~2.5 hr and 2.6 km/s, respectively, both of which are smaller by a factor of ~10 than those of MCs. In addition, we examined the geoeffectiveness of SMFR events by checking their correlation with magnetic storms and substorms. Based on the criteria Sym-H < -50 nT (for identification of storm occurrence) and AL < -200 nT (for identification of substorm occurrence), we found that for 88 SMFR events (corresponding to 28.5 % of the total SMFR events), substorms occurred after the impact of SMFRs, implying a possible triggering of substorms by SMFRs. In contrast, we found only two SMFRs that triggered storms. We emphasize that, based on a much larger database than used in previous studies, all these previously known features are now firmly confirmed by the current work. Accordingly, the results emphasize the significance of SMFRs from the viewpoint of possible triggering of substorms.

1. INTRODUCTION
 2. METHODOLOGY
 3. STATISTICAL PROPERTIES OF SMFR EVENTS
 4. GEOEFFECTIVENESS OF SMFRS
 5. SUMMARY AND CONCLUSIONS
 ACKNOWLEDGMENTS
 REFERENCES

• Myeong Joon Kim(Department of Astronomy and Space Science, Chungbuk National University)
• Kyung Sun Park(Department of Astronomy and Space Science, Chungbuk National University)
• Dae-Young Lee(Department of Astronomy and Space Science, Chungbuk National University) Corresponding Author
• Cheong-Rim Choi(Department of Astronomy and Space Science, Chungbuk National University)
• Rok Soon Kim(Korea Astronomy and Space Science Institute, University of Science and Technology)
• Kyungsuk Cho(Korea Astronomy and Space Science Institute, University of Science and Technology)
• Kyu-Cheol Choi(SELab, Inc., Seoul 06049, Korea)
• Jaehun Kim(The Korean Space Weather Center of National Radio Research Agency)