( 2009) based on statistics of cross-polar cap potential.
#OMNIWEB REVIEW PC#
( 1988) using PC index and by Grocott et al.
#OMNIWEB REVIEW DRIVER#
In the following, we adopt the approximation for the driver to be in the form E KL = V SW B sin 2 ( θ/2), first suggested by Kan and Lee ( 1979) and thereafter confirmed, for example, by Troshichev et al. In fact, on short time scale (a few hours or less) the driver variations described by these formulas are predominantly controlled by the variation of IMF B Z magnetic field component, and the above mentioned combinations highly correlate to each other. Whereas many different combinations of SW and IMF parameters have been tested and proposed to represent best the driver of magnetospheric activity, most of them contain a combination of magnetic field and flow parameters in the form V α B β sin γ ( θ/2) (with α, β, and γ power law coefficients, see, e.g., a summary in Newell et al., 2007). In the following, we pay the main attention to the variations of the SW magnetic field (IMF) whose variations basically control the changes of the dayside reconnection process. ( 1998, 2000), Richardson and Paularena ( 2001), Weimer and King ( 2009), Case and Wild ( 2012), and Jackel et al. The accuracy of the propagated SW data and a number of related questions have been addressed in many studies, which compared the parameters measured at 2 points in the SW, particularly by correlating the observations made at around the L1 point, for example, ISEE-3, ACE, WIND, and DSCOVR, to the observations of the near-Earth monitor (such as ISEE-1, IMP-8, Geotail, and Cluster)-see, for example, Crooker et al. This suggests that the SW measured at 230 R E may miss the magnetosphere. The size of that SW flow tube that directly interacts with the dayside magnetosphere during the reconnection process is known to be as small as ~4R E (Burke et al., 1999). The quality of that research depends on how accurately these data correspond to the actual SW that reaches the magnetosphere and drives magnetospheric dynamics. After estimating the SW phase front orientations and propagation to the Earth's bow shock subsolar point (roughly at 14 R E), these recomputed continuous SW data are widely available to the community for the research and application purposes in the highly popular OMNI database (see King & Papitashvili, 2005, and website at ). During the last two decades, the monitoring of SW at the L1 Lagrange point, located approximately 230 R E upstream, has provided a continuous data stream of the IMF and SW plasma parameters. Magnetospheric activity is controlled largely by the solar wind (SW) and its interplanetary magnetic field (IMF). We also discovered that the OMNI data are generally of a good quality when the PC index of geomagnetic activity correlates well with the solar wind-magnetosphere coupling factor suggested by Kan and Lee (1979, ). The remaining data set includes 42% of very good data ( CC ≥ 0.8), 33% of relatively good data (0.5 ≤ CC < 0.8 and PE ≥ 0), 10% of data having correct variability but wrong absolute values (0.5 ≤ CC < 0.8 and PE < 0), and 15% of poor data ( CC < 0.5). In roughly 20% of the analyzed data, low CC and PE values were the consequence of low IMF variability (a low signal-to-noise ratio). Confirming previous studies, we found that the prediction quality of actual IMF degrades continuously with increasing distance of OMNI spacecraft from the Sun-Earth line, with the amounts of poor and good predictions become nearly equal for R YZ ≥ 65 R E (they constitute ~12% of the entire database).
We used two metrics: Pearson correlation coefficient ( CC) and prediction efficiency ( PE). To test the quality of the OMNI database, we cross-correlate the 2-hr intervals of 1-min interplanetary magnetic field (IMF) data provided mostly by ACE and WIND spacecraft with Geotail measurements in front of the bow shock (10,409 cases in 1997–2016). The OMNI database is formed by propagating the solar wind measured at around Lagrange point L1, whose result may differ from the actual solar wind in the vicinity of the bow shock nose.
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