The Earth's Response to the Interplanetary Small-scale Magnetic Flux Ropes

We analyze interplanetary small-scale magnetic flux ropes (ISMFRs) observed by multi-satellites propagating from 1 AU to the Earth to understand their geomagnetic effectiveness. We use ACE, WIND, GEOTAIL, CLUSTER, THEMIS, and several geosynchronous spacecraft. Using published criteria for identification of ISMFR, we selected 15 events during 2007-2008. The duration of these events average about 90 mins. We analyzed each event using both in situ and ground data and found that significant perturbations in the inner magnetosphere, like substorms and enhanced ULF wave activity, are often triggered by ISMFR. Combined with the ISMFR database (1995-2005) from previous work, 97 ISMFRs are identified. Of these 49 ISMFR have signatures of magnetic reconnection (MR) at one or two of their boundaries based on the 3-s WIND data. Furthermore, based on the 1-min AE/AL indices and time-shifted IMF data from OMNI website, substorms were triggered during more than half of these flux ropes. The superposed epoch analysis shows that the solar wind electric field (Ey) is the most correlated parameter of the flux ropes with the Earth's geomagnetic activity. It also indicates that the geomagnetic field responds differently to the events with different polarity sequences (i.e., ISMFR with north then south turning compared to south then north turning).