Statistical Analysis of Solar Events Associated with Storm Sudden Commencements over One Year of Solar Maximum During Cycle 23: Propagation from the Sun to the Earth and Effects

Abstract

Taking the 32 storm sudden commencements (SSCs) listed by the International Service of Geomagnetic Indices (ISGI) of the Observatory de l'Ebre during 2002 (solar activity maximum in cycle 23) as a starting point, we performed a multi-criterion analysis based on observations (propagation time, velocity comparisons, sense of the magnetic field rotation, radio waves) to associate them with solar sources, identified their effects in the interplanetary medium, and looked at the response of the terrestrial ionized and neutral environment. We find that 28 SSCs can be related to 44 coronal mass ejections (CMEs), 15 with a unique CME and 13 with a series of multiple CMEs, among which 19 (68 %) involved halo CMEs. Twelve of the 19 fastest CMEs with speeds greater than 1000 km s −1 are halo CMEs. For the 44 CMEs, including 21 halo CMEs, the corresponding X-ray data classes are: 3 X-class, 19 M-class, and 22 C-class flares. The probability for an SSC to occur is 75 % if the CME is a halo CME. Among the 500, or even more, front-side, non-halo CMEs recorded in 2002, only 23 could be the source of an SSC, i.e. 5 %. The complex interactions between two (or more) CMEs and the modification of their trajectories have been examined using joint white-light and multiple-wavelength radio observations. The detection of long-lasting type IV bursts observed at metric-hectometric wavelengths is a very useful criterion for the CME-SSC events association. The events associated with the most depressed Dst values are also associated with type IV radio bursts. The four SSCs associated with a single shock at L1 correspond to four radio events exhibiting characteristics different from type IV radio bursts. The solar-wind structures at L1 after the 32 SSCs are 12 magnetic clouds (MCs), 6 interplanetary coronal mass ejections (ICMEs) without an MC structure, 4 miscellaneous structures, which cannot unambiguously be classified as ICMEs, 5 corotating or stream interaction regions (CIRs/SIRs), and 4 Shock events; note than one CIR caused two SSCs. The 11 MCs listed in 3 or more MC catalogs covering the year 2002 are associated with SSCs. For the three most intense geomagnetic storms (based on Dst minima) related to MCs, we note two sudden increases of the Dst, at the arrival of the sheath and the arrival of the MC itself. In terms of geoeffectiveness, the relation between the CME speed and the magnetic-storm intensity, as characterized using the Dst magnetic index, is very complex but generally, CMEs with velocities at the Sun larger than 1000 km s −1 have larger probabilities to trigger moderate or intense storms. The most geoeffective events are MCs, since 92 % of them trigger moderate or intense storms, followed by ICMEs (33 %). At best, CIRs/SIRs only cause weak storms. We show that these geoeffective events (ICMEs or MCs) trigger an increased and combined auroral kilometric radiation (AKR) and non-thermal continuum (NTC) wave activity in the magnetosphere, an enhanced convection in the ionosphere, and a stronger response in the thermosphere. Howe...

Shock deceleration in interplanetary coronal mass ejections (ICMEs) beyond Mercury’s orbit until one AU

“…IPs are related to ICMEs and we keep the two events in our study of the ICME shock deceleration. These events are important for space weather alerts as, at Earth and probably elsewhere, the sheath of the ICME can be more effective than the ICME itself (e.g., Kilpua et al, 2017;Bocchialini et al, 2018).…”

“…In these three cases, v SunMess might be underestimated because of a wrong CME-ICME association, thus making ICME acceleration questionable. Bocchialini et al (2018) discusses the difficulties of correctly associating CMEs with ICMEs. There is no definitive evidence of ICME shock acceleration beyond Mercury's orbit in these six events.…”

“…This makes CME/ICME association complex (Bocchialini et al, 2018) and wrong associations lead to wrong transit velocity estimations. CME channelling (Möstl et al, 2015) and CME-CME interaction (Gopalswamy et al, 2001b), identified by radio type II burst intense continuum-like emission, make the CME/ICME association more tricky.…”

Geoeffective events through solar cycles

“…Kepler satellite showed that a great number of high energetic flares occurred in stars having large sunspot areas some with similar class as the sun (Maehara et al 2012). Besides a recent study by Bocchialini et al (2018) studying all the Storm Sudden commencement (SSC) registered in Dst variations during 2002 showed that the 37 largest SSCs were mainly related to 44 CMEs. 52% CMEs have a velocity larger than 900 km/s, 75% are halo CMEs.…”

Editorial: Earth-affecting Solar Transients

“…Watari (2018) identified and studied two geomagnetic storms associated with coronal holes within the 19 intense geomagnetic storms that occurred in Cycle 24. Bocchialini et al (2018) selected 32 SSC events during 2002 as a starting point and performed a multidata analysis based on observations to associate them with their solar sources, identify their effects in the interplanetary medium, and analyzed the response of the terrestrial ionized and neutral environment.…”