Relative occurrence rate and geoeffectiveness of large-scale types of the solar wind |
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Authors: | Yu I Yermolaev N S Nikolaeva I G Lodkina M Yu Yermolaev |
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Institution: | (1) Instituto Nacional Pesquisas Espaciais, São José dos Campos, São Paulo, Brazil;(2) Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, U.S.A |
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Abstract: | We investigate the relative occurrence rate for various types of the solar wind and their geoeffectiveness for magnetic storms
with Dst < —50 nT. Both integrated effect for the entire time 1976–2000 and variations during this period of 2.5 cycles of solar activity
are studied As raw data for the analysis we have used the catalog of large-scale types of the solar wind for the period 1976-2000
(see ftp://ftp.iki.rssi.ru/omni/) created by us with the use of the OMNI database (http://omni.web.gsgc.nasa.gov) 1] and
described in detail in 2]. The average annual numbers of different type of events are as follows: 124 ±81 for the heliospheric
current sheet (HCS), 8 ±6 for magnetic clouds (MC), 99 ±38 for Ejecta, 46 ±19 for Sheath before Ejecta, 6 ±5 for Sheath before
MC, and 63 ±15 for CIR. The measurements that allowed one to determine a source in the solar wind were available only for
58% of moderate and strong magnetic storms (with index Dst < —50 nT) during the period 1976–2000. Magnetic clouds (MC) are shown to be the most geoeffective (~61%). The CIR events and
Ejecta with Sheath region are three times less geoeffective (~20–21 %). Variations of occurrence rate and geoeffectiveness
of various types of the solar wind in the solar cycle are discussed. |
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