The CME-ICME Connection and Interplanetary Structure During Solar Minimum

Details The CME-ICME Connection and Interplanetary Structure During Solar Minimum The CME-ICME Connection and Interplanetary Structure During Solar Minimum

Dec 2008

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008agufmsh13b1542l&link_type=abstract

American Geophysical Union, Fall Meeting 2008, abstract #SH13B-1542

Physics

2101 Coronal Mass Ejections (7513), 2111 Ejecta, Driver Gases, And Magnetic Clouds, 2162 Solar Cycle Variations (7536), 7511 Coronal Holes, 7524 Magnetic Fields

Scientific paper

When an interplanetary transient (ICME) exhibits a large angle and smooth rotation in the IMF vector, it is classified as a magnetic cloud (MC) and commonly interpreted as the signature of a magnetic flux rope. On the average bout a third of ICME ejecta are MCs, although the fraction seems to be larger during the quiet phase of the solar cycle. Non-flux rope ICMEs are likely (1) distorted during the transit through heliosphere, (2) observed at an unfavorable crossing angle if the ICME structure has spatial variation, (3) or are simply have a more complex internal structure. Five Magnetic Clouds (MC) have been found from a total of nine ICMEs observed during 2007 January 01 to 2008 August 31, when the separation of STEREO A (STA) and B (STB) spacecraft varied between 0.05 to 70.35 degrees heliolongitude. We investigate the four best MCs using observations from three spacecraft (STA, STB and ACE). The first MC seems to have been detected by all three spacecraft (STA and STB 40.4 degrees apart), while the latter three were detected by only one of the STEREO spacecraft and sometimes by ACE. From the inferred flux rope orientation at each crossing and the spatial variation of the ICME properties, we interpret how each MC flux rope was situated relative to the spacecraft, and its connection to the Sun from corresponding coronal and heliospheric modeling results. Each of the MCs can be associated at low confidence (in contrary to expectations for solar minimum time) with a CME observed by coronagraphs on board STEREO and/or SOHO. All potential parent CMEs were very slow in the 200 km/s range (plane-of-sky), but the speeds of the MCs were between ~390 and ~480 km/s, indicating acceleration in the heliosphere. Solar disk activities are minor around the four CMEs, with no GOES x-ray flares, and two possibly associated filament eruptions. Some CME structures appear to form in the coronagraph field of view rather than rising from below. Several low/mid- latitude coronal holes and a highly warped coronal streamer arcade and source surface neutral line dominate the coronal structure during the period of the study. Previous studies have shown that the MC fluxrope orientation may be aligned with the large-scale coronal streamer arcades. Estimated MC orientations are discussed and compared with events during the previous solar minimum, which exhibited a more dipolar coronal structure. This work was supported, in part, by NASA NNG06GE51G, NNX08AJ04G, and NAS5-03131.

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