@Article{SzajkoCrisMandDalL:2013:VeInGe,
author = "Szajko, N. S. and Cristiani, G. and Mandrini, C. H. and Dal Lago,
Alisson",
affiliation = "Instituto de Astronom{\'{\i}}a y F{\'{\i}}sica del Espacio,
CONICET-UBA, Buenos Aires and Instituto de Astronom{\'{\i}}a y
F{\'{\i}}sica del Espacio, CONICET-UBA,Buenos Aires and
Instituto de Astronom{\'{\i}}a y F{\'{\i}}sica del Espacio,
CONICET-UBA, 428 Buenos Aires and {Instituto Nacional de Pesquisas
Espaciais (INPE)}",
title = "Very intense geomagnetic storms and their relation to
interplanetary and solar active phenomena",
journal = "Advances in Space Research",
year = "2013",
volume = "51",
number = "10",
pages = "1842--1856",
month = "May",
keywords = "Very intense geomagnetic storms, Solar activity, CMEs/ICMEs.",
abstract = "We revisit previous studies in which the characteristics of the
solar and interplanetary sources of intense geomagnetic storms
have been discussed. In this particular analysis, using the Dst
time series, we consider the very intense geomagnetic storms that
occurred during Solar Cycle 23 by setting a value of as threshold.
After carefully examining the set of available solar and in situ
observations from instruments aboard the Solar and Heliospheric
Observatory (SOHO) and the Advanced Composition Explorer (ACE),
complemented with data from the ground, we have identified and
characterized the solar and interplanetary sources of each storm.
That is to say, we determine the time, angular width,
plane-of-the-sky, lateral expansion, and radial velocities of the
source coronal mass ejection (CME), the type and heliographic
location of the CME solar source region (including the
characteristics of the sunspot groups), and the time duration of
the associated flare. After this, we investigate the overall
characteristics of the interplanetary (IP) main-phase storm
driver, including the time arrival of the shock/disturbance at 1
AU, the type of associated IP structure/ejecta, the origin of a
prolonged and enhanced southward component (Bs) of the IP field,
and other characteristics related to the energy injected into the
magnetosphere during the storm (i.e. the solar wind maximum
convected electric field, Ey). The analyzed set consists of 20
events, some of these are complex and present two or more Dst
minima that are, in general, due to consecutive solar events. The
20 storms are distributed along Solar Cycle 23 (which is a
double-peak cycle) in such a way that 15% occurs during the rising
phase of the cycle, 45% during both cycle maxima, and,
surprisingly, 40% during the cycle descending phase. This latter
set includes half of the superstorms and the only cycle extreme
event. 85% of the storms are associated to full halo CMEs and 10%
to partial halo events. One of the storms occurred at the time
contact with SOHO was lost. The CME solar sources of all analyzed
storms, but one, are active regions (ARs). The source of the
remaining CME is a bipolar low-field region where a long and
curved filament erupts. The ARs where the CMEs originate show, in
general, high magnetic complexity; ¦{\"A} spots are present in
74% of the ARs, 10% are formed by several bipolar sunspot groups,
and only 16% present a single bipolar sunspot group. All CMEs are
associated to long duration events (LDEs), exceeding 3 h in all
cases, with around 75% lasting more than 5 h. The associated
flares are, in general, intense events, classified as M or X in
soft X-rays; only 3 of them fall in the C class, with the one
happening in the bipolar low field region hardly reaching the C
level. We calculate the lateral expansion velocity for most of the
CMEs. The values found exceed in all cases but one the fast solar
wind speed (¡{\"O}750 km s\−1). The average lateral
expansion velocity is 2400 km s\−1. The spatial
distribution of the solar CME sources on the solar disk shows an
evident asymmetry; while there are no sources located more
eastward than 12¡{\~a} in longitude, there are 7 events more
westward than12¡{\~a}. Nevertheless, the bulk of the solar
sources are located near Sun center, i.e. at less than 20¡{\~a}
in longitude or latitude. Considering the IP structures
responsible for a long and enhanced Bs, we find that 35%
correspond to magnetic clouds (MCs) or ICME fields, 30% to sheath
fields, and 30% to combined sheath and MC or ICME fields. For only
one storm the origin of Bs is related to the back compression of
an ICME by a high speed stream coming from a coronal hole in the
neighborhood of the corresponding CME source region. We have also
found that for this particular set of storms the linear relation
between Ey and the storm intensity holds (with a correlation
coefficient of 0.73). These results complement and extend those of
other works in the literature.",
doi = "10.1016/j.asr.2012.03.006",
url = "http://dx.doi.org/10.1016/j.asr.2012.03.006",
issn = "0273-1177",
urlaccessdate = "16 jun. 2024"
}