%0 Journal Article
%4 sid.inpe.br/mtc-m19@80/2010/
%2 sid.inpe.br/mtc-m19@80/2010/
%@issn 1364-6826
%T The properties of two solar wind high speed streams and related geomagnetic activity during the declining phase of solar cycle 23
%D 2011
%8 Jan.
%A Tsurutani, Bruce T.,
%A Echer, Ezequiel,
%A Guarnieri, Fernando L.,
%A Gonzalez Alarcon, Walter Demétrio,
%@affiliation CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA
%@affiliation Instituto Nacional de Pesquisas Espaciais (INPE)
%@affiliation Universidade do Vale do Paraiba (UNIVAP)
%@affiliation Instituto Nacional de Pesquisas Espaciais (INPE)
%B Journal of Atmospheric and Solar-Terrestrial Physics
%V 73
%N 1
%P 164-177
%K High speed solar wind streams, Interplanetary Alfvenicity, Geomagnetic activity, HILDCAAs.
%X Two high speed stream (HSS) solar wind intervals (days 283¨C294 and 314¨C318, 2003, hereafter called Events 1 and 2) during the declining phase of solar cycle 23 have been examined in detail for their interplanetary characteristics and their resultant geomagnetic activity. Event 1 had an associated storm initial phase with peak Dst=+9 nT. This was caused by a high plasma density heliospheric plasma sheet (HPS) which impacted the magnetosphere. The southward component of IMF Bz fluctuations in the corotating interaction regions (CIRs) of both Events 1 and 2 led to peak storm main phases of Dst=−85 and −62 nT, respectively. The extended storm ¡°recovery¡± phases were associated with ¦¤B/Bo 1¨C2 Alfv¨¦nic fluctuations in the HSS proper. High-intensity, long-duration, continuous AE (HILDCAA) intervals were present, presumably due to the southward component of the Alfv¨¦n waves. The IMF Bx¨CVx 4-h cross-correlation values were >0.8 in Event 2, and lower, >0.6, in Event 1. The difference in Alfv¨¦nicity between the two HSS events is not understood at present. The IMF Bz 10-min to 3-h variances and are highest during the CIRs. The normalized variances during the HSS proper are approximately the same as those for the CIRs. For Event 1, the 1-h IMF and are 5.0 nT2 and 1.1¡Á10−1, respectively. The IMF Bz-AE cross-correlation (c.c.) coefficients during the storm main phase of Event 1 and for 24-h of the HSS of Event 2 give similar results. For the Event 1, a peak c.c. of −0.4 occurred with a lag of 103 min, and for Event 2 a peak c.c of −0.38 with a lag of 67 min was obtained. Both c.c. results were sharply peaked. The decay-portion of a HSS prior to Event 1 was characterized by low Np, low Bo and low Alfv¨¦n wave amplitudes. The 1-h IMF and were 0.84 nT2 and 2.9¡Á10−2, respectively. This quiet interplanetary interval led to a quiet geomagnetic activity period (AE<100 nT, Dst +5 nT). On the other hand, what is quite surprising is that this region was the most purely ¡°Alfv¨¦nic¡± interval studied (c.c. of Bx-Vx=0.95).The ¦Å parameter was calculated using both GSE and GSM coordinates. It was found that ¦Å is 30% larger for GSM coordinates. Thus, the major cause of geomagnetic activity during HSSs is the large amplitude Alfv¨¦n waves but not coordinate transformations. Sector polarities (IMF By values) may be a secondary factor. However, other models, like the tilted solar dipole, should be considered as well.
%@language en
%3 the properties of two solar.pdf