Observable Effects of Interplanetary Coronal Mass Ejections on Ground Level Neutron Monitor Count Rates
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In this work, non-recurrent Forbush decreases (FDs) triggered by the passage of shock-driving interplanetary coronal mass ejections (ICMEs) have been analyzed. Fifty-nine ICMEs have been studied, but only 25 % of them were associated to a FD. We find that shock-driving magnetic clouds (MCs) produce deeper FDs than shock-driving ejecta. This fact can be explained regarding the observed growing trends between decreases in neutron monitor (NM) count rate and MC/ejecta speed and its associated rigidity. MCs are faster and have higher associated rigidities than ejecta. Also the deceleration of ICMEs seems to be a cause for producing FDs, as can be inferred from the decreasing trend between NM count rate and deceleration. This probably implies that the interaction between the ICME traveling from the corona to the Earth and the solar wind can play an important role in producing deeper FDs. Finally, we conclude that ejecta without flux rope topology are the ones less effective in unchaining FDs.
KeywordsICME Magnetic cloud Ejecta Forbush decrease
We acknowledge the NMDB database ( www.nmdb.eu ), founded under the European Union’s FP7 programme (contract no. 213007) for providing data, especially to Oulu neutron monitor station and the Sodankyla Geophysical Observatory of the University of Oulu for the operation of the monitor, also to the MFI and SWE instruments on board Wind and Mag and SWEPAM on board ACE and Coordinated Data Analysis Web (CDAWeb) for the use of data. This work has been supported under the grants: JCCM PPII10-0150-6529 and AYA2011-29727-C02-01. The authors in particular wish to thank the Parque Científico y Tecnológico de Guadalajara (Guadalab) team.
- Burlaga, L.F., Sittler, E., Mariani, F., Schwenn, R.: 1981, J. Geophys. Res. 86, 6. Google Scholar
- Hidalgo, M.A., Nieves-Chinchilla, T., Blanco, J.J.: 2013, Solar Phys., in this issue. doi: 10.1007/s11207-012-0191-6.
- Kananen, H., Tanskanen, P.J., Gentile, L.C., Shea, M.A., Smart, D.F.: 1991, In: Proc. 22nd ICRC 3, 145. Google Scholar
- Mavromichalaki, H., Papaioannou, A., Plainaki, C., Sarlanis, C., Souvatzoglou, G., Gerontidou, M., Papailiou, M., Eroshenko, E., Belov, A.A., Yanke, V., Fluckiger, E.O., Butikofer, R., Parisi, M., Storini, M., Klein, K.-L., Fuller, N., Steigies, C.T., Rother, O.M., Heber, B., Wimmer-Schweingruber, R.F., Kudela, K., Strharsky, I., Langer, R., Usoskin, I., Ibragimov, A., Chilingaryan, A., Hovsepyan, G.A., Reymers, A., Yeghikyan, A., Kryakunova, O., Dryn, E., Nikolayevskiy, M., Dorman, L., Pustilnik, L.: 2011, Adv. Space Res. 47, 2210. ADSCrossRefGoogle Scholar
- Ogilvie, K.W., Chorney, D.J., Fitzenreiter, R.J., Hunsaker, F., Keller, J., Lobell, J., Miller, G., Scudder, J.D., Sittler, E.C. Jr., Torbert, R.B., Bodet, D., Needell, G., Lazarus, A.J., Steinberg, J.T., Tappan, J.H., Mavretic, A., Gergin, E.: 1995, Space Sci. Rev. 71, 55. ADSCrossRefGoogle Scholar