![]() The source of diurnal and semiannual variations in geomagnetic activity. DOI.ĭanilov, A.A., Krymskii, G.F., Makarov, G.A.: 2013, Geomagnetic activity as a reflection of processes in the magnetospheric tail: 1. DOI.ĭaglis, I.A., Thorne, R.M., Baumjohann, W., Orsini, S.: 1999, The terrestrial ring current: origin, formation, and decay. DOI.Ĭortie, A.L.S.J.: 1912, Sun-spots and terrestrial magnetic phenomena, 1898 – 1911: the cause of the annual variation in magnetic disturbances. DOI.Ĭliver, E.W., Kamide, Y., Ling, A.G.: 2000, Mountains versus valleys: semiannual variation of geomagnetic activity. DOI.Ĭhi, Y., Shen, C., Luo, B., Wang, Y., Xu, M.: 2018, Geoeffectiveness of stream interaction regions from 1995 to 2016. DOI.īurlaga, L.F., Klein, L.W., Lepping, R.P., Behannon, K.W.: 1984, Large-scale interplanetary magnetic fields: Voyager 1 and 2 observations between 1 AU and 9.5 AU. 18, 401.īurlaga, L.F., Behannon, K.W., Hansen, S.F., Pneuman, G.W., Feldman, W.C.: 1978, Sources of magnetic fields in recurrent interplanetary streams. DOI.īroun, J.A.: 1848, Observations in magnetism and meteorology made at Makerstoun in Scotland. DOI.īoller, B.R., Stolov, H.L.: 1970, Kelvin-Helmholtz instability and the semiannual variation of geomagnetic activity. Jr.: 1971, Large-amplitude Alfvén waves in the interplanetary medium, 2. DOI.īaker, D.N., Kanekal, S.G., Pulkkinen, T.I., Blake, J.B.: 1999, Equinoctial and solstitial averages of magnetospheric relativistic electrons: a strong semiannual modulation. DOI.Īlves, M.V., Echer, E., Gonzalez, W.D.: 2006, Geoeffectiveness of corotating interaction regions as measured by Dst index. DOI.Īllen, R.C., Ho, G.C., Mason, G.M., Li, G., Jian, L.K., Vines, S.K., Schwadron, N.A., Joyce, C.J., Bale, S.D., Bonnell, J.W., Case, A.W., Christian, E.R., Cohen, C.M.S., Desai, M.I., Filwett, R., Goetz, K., Harvey, P.R., Hill, M.E., Kasper, J.C., Korreck, K.E., Lario, D., Larson, D., Livi, R., MacDowall, R.J., Malaspina, D.M., McComas, D.J., McNutt, R., Mitchell, D.G., Paulson, K.W., Pulupa, M., Raouafi, N., Stevens, M.L., Whittlesey, P.L., Wiedenbeck, M.: 2021, Radial evolution of a CIR: observations from a nearly radially aligned event between Parker Solar Probe and STEREO-A. On average, SYM-H is strongly associated with the CIR plasma characteristic parameters (anti-correlation coefficient \(r=-0.65\) to −0.89), while the association is weaker for the AE-index ( \(r=0.41\) to 0.67).Īllen, R.C., Lario, D., Odstrcil, D., Ho, G.C., Jian, L.K., Cohen, C.M.S., Badman, S.T., Jones, S.I., Arge, C.N., Mays, M.L., Mason, G.M., Bale, S.D., Bonnell, J.W., Case, A.W., Christian, E.R., Dudok de Wit, T., Goetz, K., Harvey, P.R., Henney, C.J., Hill, M.E., Kasper, J.C., Korreck, K.E., Larson, D., Livi, R., MacDowall, R.J., Malaspina, D.M., McComas, D.J., McNutt, R., Mitchell, D.G., Pulupa, M., Raouafi, N., Schwadron, N., Stevens, M.L., Whittlesey, P.L., Wiedenbeck, M.: 2020, Solar wind streams and stream interaction regions observed by the Parker Solar Probe with corresponding observations at 1 au. CIRs during equinoxes are found to be more geoeffective compared to those during solstices. The geoeffectiveness is found to decrease with the decreasing solar flux. About 30% of the CIRs are found to be geoeffective, causing geomagnetic storms with the peak SYM-H \(\leq -50\) nT 25% caused moderate storms (−50 nT ≥ SYM-H \(>-100\) nT), and 5% caused intense storms (SYM-H \(\leq -100\) nT). The CIR characteristic features exhibit no clear solar-cycle phase dependence. CIRs are characterized by average (median) plasma density of \(\approx 29\) cm −3 ( \(\approx 26\) cm −3), ram pressure of \(\approx 11\) nPa ( \(\approx 9\) nPa), temperature of \(\approx 5\times 10^\) K), and magnetic-field magnitude of \(\approx 15\) nT ( \(\approx 14\) nT). ![]() At 1 AU, CIRs are found to be large-scale interplanetary structures with an average (median) duration of \(\approx 26\) hours ( \(\approx 24\) hours) and radial extent of \(\approx 0.31\) AU ( \(\approx 0.27\) AU). The occurrence rate is the maximum during the solar-cycle descending phase ( \(\approx 33\) year −1), followed by occurrences during solar minimum ( \(\approx 24\) year −1), the ascending phase ( \(\approx 22\) year −1), and solar maximum ( \(\approx 11\) year −1). Using solar-wind measurements upstream of Earth, we identified 290 CIRs encountered by Earth during January 2008 through December 2019 (Solar Cycle 24). Corotating interaction regions (CIRs) form in the interaction region between the solar-wind high-speed streams and slow streams, leading to compressed plasma and magnetic fields.
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