Correction to “Solar and interplanetary sources of major geomagnetic storms (Dst ≤ −100 nT) during 1996–2005”

Abstract

We present the results of an investigation of the sequence of events from the Sun to the Earth that ultimately led to the 88 major geomagnetic storms (defined by minimum Dst À100 nT) that occurred during 1996-2005. The results are achieved through cooperative efforts that originated at the Living with a Star (LWS) Coordinated Data-Analysis Workshop (CDAW) held at George Mason University in March 2005. On the basis of careful examination of the complete array of solar and in situ solar wind observations, we have identified and characterized, for each major geomagnetic storm, the overall solar-interplanetary (solar-IP) source type, the time, velocity, and angular width of the source coronal mass ejection (CME), the type and heliographic location of the solar source region, the structure of the transient solar wind flow with the storm-driving component specified, the arrival time of shock/disturbance, and the start and ending times of the corresponding IP CME (ICME). The storm-driving component, which possesses a prolonged and enhanced southward magnetic field (B s), may be an ICME, the sheath of shocked plasma (SH) upstream of an ICME, a corotating interaction region (CIR), or a combination of these structures. We classify the Solar-IP sources into three broad types: (1) S-type, in which the storm is associated with a single ICME and a single CME at the Sun; (2) M-type, in which the storm is associated with a complex solar wind flow produced by multiple interacting ICMEs arising from multiple halo CMEs launched from the Sun in a short period; (3) C-type, in which the storm is associated with a CIR formed at the leading edge of a high-speed stream originating from a solar coronal hole (CH). For the 88 major storms, the S-type, M-type, and C-type events number 53 (60%), 24 (27%), and 11 (13%), respectively. For the 85 events for which the surface source regions could be investigated, 54 (63%) of the storms originated in solar active regions, 11 (13%) in quiet Sun regions associated with quiescent filaments or filament channels, and 11 (13%) were associated with coronal holes. Remarkably, nine (11%) CME-driven events showed no sign of eruptive features on the surface or in the low corona (e.g., no flare, no coronal dimming, and no loop arcade, etc.), even though all the available solar observations in a suitable time period were carefully examined. Thus while it is generally true that a major geomagnetic storm is more likely to be driven by a frontside fast halo CME associated with a major flare, our study indicates a broad distribution of source properties. The implications of the results for space weather forecasting are briefly discussed.

Association of radiation belt electron enhancements with earthward penetration of Pc5 ULF waves: a case study of intense 2001 magnetic storms

“…Hence, the electron flux dropout should represent a true loss of particles due to irreversible (non-adiabatic) processes. On the basis of solar wind plasma and magnetic field signatures, the structure in the near-Earth solar wind leading to the magnetic storm of 17 August 2001 was identified as a magnetic cloud (see Zhang et al, 2007, for details), similar to the previous case studies. Nonetheless, a significantly shorter interval (from 15:00 to 19:50 UT) of southward IMF B z reaching values as low as −22 nT depressed the Dst index to just below −100 nT.…”

“…The interplanetary driver of the main phase of each storm did not differ significantly among the three magnetic storms of March and April 2001 (see Zhang et al, 2007, for details). The solar wind structure associated with the intense and sus- tained geomagnetic activity was in three well-separated interplanetary coronal mass elections (ICMEs) with a sheath of shocked plasma (SH) upstream.…”

“…As a measure of storm intensity, we use the 1 h resolution final Dst index, provided by the World Data Center (WDC) for Geomagnetism of the Kyoto University, which was lower than −100 nT. A similar threshold for intense storms has been used by other authors as well (Gonzalez et al, 2007;Zhang et al, 2007). These were not preceded by any other magnetic storm within a period of 3 days before the Dst reached its minimum value and were not followed by any magnetic storm in the next 5 days.…”

“…Geospace magnetic storms are associated with either coronal mass ejections (CMEs) or highspeed solar streams (Gonzalez et al, 2007). Nonetheless, major magnetic storms have been found to be mainly caused by CMEs (Zhang et al, 2007), and these involve acceleration of charged particles in the Earth's radiation belts and intensification of electric current systems with characteristic signatures on the geomagnetic field (Daglis et al, 1999;Daglis, 2004).…”

Solar activity impact on the Earth’s upper atmosphere

“…This is an event thought to be due to a single solar source (Zhang et al 2007) and with quiet geomagnetic conditions that prevailed before and after the storm. Hence, its geomagnetic and ionospheric effects could be gauged very accurately.…”