Statistical properties and geoeffectiveness of southward interplanetary magnetic field with emphasis on weakly southward Bz events

被引:3
作者
Choi, Kyung-Eun [1 ]
Lee, Dae-Young [1 ]
Choi, Kyu-Cheol [2 ]
Kim, Jaehun [3 ]
机构
[1] Chungbuk Natl Univ, Dept Astron & Space Sci, Cheongju, South Korea
[2] SELab Inc, Res Inst, Seoul, South Korea
[3] Natl Radio Res Agcy, Korean Space Weather Ctr, Jeju, South Korea
基金
新加坡国家研究基金会;
关键词
IMF B-z; southward B-z; CORONAL MASS EJECTIONS; SOLAR-WIND; ALFVEN WAVES; LONG-DURATION; GEOMAGNETIC STORMS; LARGE-AMPLITUDE; CLOUDS; BEHAVIOR; MAGNETOSPHERE; INTENSITY;
D O I
10.1002/2016JA023836
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
In this work we analyze the statistical properties and geoeffectiveness of southward interplanetary magnetic field (IMF) B-z (B-s) events measured near the Earth from 1996 to 2015. We classify the B-s events into six contrasting classes according to the duration and intensity of B-s: two subclasses of long-lasting major intensity, two subclasses of long-lasting weak intensity, and two subclasses of short-lasting weak intensity. We find the following results. (1) The occurrence rate of B-s events is lowest for the long-lasting major-intensity B-s classes and increases toward shorter-lasting and weaker-intensity B-s classes. (2) Many of the B-s events in nearly all classes are associated with regions other than interplanetary coronal mass ejections and coronal hole high-speed streams. (3) Alfven waves account for a significant fraction of the B-s events (e.g., similar to 60% for the short-lasting and weak-intensity B-s classes). (4) There are clear differences in solar cycle dependence of B-s events among the different B-s classes. (5) Even either the long-lasting or short-lasting weak-intensity class B-s events can often be geoeffective by triggering substorms of weak-to-medium intensity and by enhancing geosynchronous relativistic electron fluxes. In conclusion, we emphasize that even the weakly (in terms of either intensity or duration) southward IMF B-z should be considered significant from the viewpoint of their high occurrence rate and their geoeffectiveness compared to those of long-lasting major intensity.
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页码:4921 / 4934
页数:14
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