Great geomagnetic storm of 9 November 1991: Association with a disappearing solar filament
TL;DR: In this paper, the authors attributed the great geomagnetic storm on 8 and 10 November 1991 to a large-scale eruption that encompassed the disappearance of a ∼25° solar filament in the southern solar hemisphere.
Abstract: [1] We attribute the great geomagnetic storm on 8–10 November 1991 to a large-scale eruption that encompassed the disappearance of a ∼25° solar filament in the southern solar hemisphere. The resultant soft X-ray arcade spanned ∼90° of solar longitude. The rapid growth of an active region lying at one end of the X-ray arcade appears to have triggered the eruption. This is the largest geomagnetic storm yet associated with the eruption of a quiescent filament. The minimum hourly Dst value of −354 nT on 9 November 1991 compares with a minimum Dst value of −161 nT for the largest 27-day recurrent (coronal hole) storm observed from 1972 to 2005 and the minimum −559 nT value observed during the flare-associated storm of 14 March 1989, the greatest magnetic storm recorded during the space age. Overall, the November 1991 storm ranks 15th on a list of Dst storms from 1905 to 2004, surpassing in intensity such well-known storms as 14 July 1982 (−310 nT) and 15 July 2000 (−317 nT). We used the Cliver et al. and Gopalswamy et al. empirical models of coronal mass ejection propagation in the solar wind to provide consistency checks on the eruption/storm association.
Citations
More filters
TL;DR: The most recent estimates of the flare soft X-ray (SXR) peak intensity and D st magnetic storm index for this event are: SXR class = X45 (± 5) (vs. X35 (±5) for the 4 November 2003 flare) and minimum D st = −900 nT (+50, −150) nT for the great storm of May 1921.
Abstract: The solar flare on 1 September 1859 and its associated geomagnetic storm remain the standard for an extreme solar-terrestrial event. The most recent estimates of the flare soft X-ray (SXR) peak intensity and D st magnetic storm index for this event are: SXR class = X45 (±5) (vs. X35 (±5) for the 4 November 2003 flare) and minimum D st = −900 (+50, −150) nT (vs. −825 to −900 nT for the great storm of May 1921). We have no direct evidence of an associated solar energetic proton (SEP) event but a correlation between >30 MeV SEP fluence (F30 ) and flare size based on modern data yields a best guess F30 value of ~1.1 × 1010 pr cm−2 (with the ±1σ uncertainty spanning a range from ~109 –1011 pr cm−2 ) for a composite (multi-flare plus shock) 1859 event. This value is approximately twice that of estimates/measurements – ranging from ~5–7 × 109 pr cm−2 – for the largest SEP episodes (July 1959, November 1960, August 1972) in the modern era.
238 citations
53 citations
TL;DR: Vennerstrom et al. as discussed by the authors presented an analysis of historical Sun-Earth connection events in the context of the most extreme space weather events of the last ∼150$ years, focusing on associating and characterizing the active regions (sunspot groups) that are most likely linked to these major geomagnetic storms.
Abstract: An analysis of historical Sun–Earth connection events in the context of the most extreme space weather events of the last $\sim150$
years is presented. To identify the key factors leading to these extreme events, a sample of the most important geomagnetic storms was selected based mainly on the well-known aa index and on geomagnetic parameters described in the accompanying paper (Vennerstrom et al., Solar Phys. in this issue, 2016, hereafter Paper I). This part of the analysis focuses on associating and characterizing the active regions (sunspot groups) that are most likely linked to these major geomagnetic storms. For this purpose, we used detailed sunspot catalogs as well as solar images and drawings from 1868 to 2010. We have systematically collected the most pertinent sunspot parameters back to 1868, gathering and digitizing solar drawings from different sources such as the Greenwich archives, and extracting the missing sunspot parameters. We present a detailed statistical analysis of the active region parameters (sunspots, flares) relative to the geomagnetic parameters developed in Paper I. In accordance with previous studies, but focusing on a much larger statistical sample, we find that the level of the geomagnetic storm is highly correlated to the size of the active regions at the time of the flare and correlated with the size of the flare itself. We also show that the origin at the Sun is most often a complex active region that is also most of the time close to the central meridian when the event is identified at the Sun. Because we are dealing with extremely severe storms, and not the usual severe storm sample, there is also a strong correlation between the size of the linked active region, the estimated transit speed, and the level of the geomagnetic event. In addition, we confirm that the geomagnetic events studied here and the associated events at the Sun present a low probability of occurring at low sunspot number value and are associated mainly with the maximum and descending part of the solar cycle.
48 citations
29 citations
TL;DR: In this paper, the solar wind conditions of an extreme geomagnetic storm were examined using magnetic field observations obtained from geosynchronous satellites and the disturbance storm-time (Dst) index; these data were then used to estimate the IMF and solar wind speed.
Abstract: The solar wind conditions of an extreme geomagnetic storm were examined using magnetic field observations obtained from geosynchronous satellites and the disturbance storm-time (Dst) index. During geosynchronous magnetopause crossings (GMCs), magnetic field variations at the magnetosheath, which is the modulated interplanetary magnetic field (IMF), were observed by geosynchronous satellite. The dawn to dusk solar wind electric field (VBS) was estimated from the Dst index by using an empirical formula for Dst prediction; these data were then used to estimate the IMF and solar wind speed. This method was applied in the analysis of an extreme geomagnetic storm event that occurred on March 13–14, 1989, for which no direct solar wind information was available. A long duration of the GMC was observed after the second storm sudden commencement (SSC) of this event. The solar flare possibly associated with the second SSC of this storm event was identified as the March 12 M7.3/2B flare. The IMF B
z was estimated to be about −50 nT with a solar wind speed of about 960 km/s during the 5 h in which the main phase of the storm rapidly developed, assuming an Alfven Mach number (M
A) during this period of more than 2.
23 citations
Cites background from "Great geomagnetic storm of 9 Novemb..."
...geomagnetic variations or indices (e.g., Li et al. 2006; Cliver et al. 2009)....
[...]
...Other papers have reconstructed solar wind parameters during large storms by using geomagnetic variations or indices (e.g., Li et al. 2006; Cliver et al. 2009)....
[...]
References
More filters
[...]
TL;DR: In this paper, the authors outline a different paradigm of cause and effect that removes solar flares from their central position in the chain of events leading from the Sun to near-Earth space.
Abstract: Many years of research have demonstrated that large, nonrecurrent geomagnetic storms, shock wave disturbances in the solar wind, and energetic particle events in interplanetary space often occur in close association with large solar flares. This result has led to a pradigm of cause and effect - that large solar flares are the fundamental cause of these events in the near-Earth space environmemt. This paradigm, which I call 'the solar flare myth,' dominates the popular perception of the relationship between solar activity and interplanetary and geomagnetic events and has provided much of the pragmatic rationale for the study of the solar flare phenomenon. Yet there is good evidence that this paradigm is wrong and that flares do not generally play a central role in producing major transient disturbances in the near-Earth space environment. In this paper I outline a different paradigm of cause and effect that removes solar flares from their central position in the chain of events leading from the Sun to near-Earth space. Instead, this central role is given to events known as coronal mass ejections.
877 citations
"Great geomagnetic storm of 9 Novemb..." refers background in this paper
...…[1964] as a precursor of the general recognition, which came nearly 30 years later, that certain CMEs, rather than the major flares with which they were characteristically, but not always, associated, were the essential element for producing great sporadic storms [Kahler, 1992; Gosling, 1993]....
[...]
...CMEs, rather than the major flares with which they were characteristically, but not always, associated, were the essential element for producing great sporadic storms [Kahler, 1992; Gosling, 1993]....
[...]
802 citations
"Great geomagnetic storm of 9 Novemb..." refers background or methods in this paper
...Because the widely used am and Dst geomagnetic indices [Mayaud, 1980] have different dependencies on these parameters, we can use them to fill data gaps in the following manner: (1) on the basis of experience and intuition, assume solar wind speed and magnetic field data for periods of missing…...
[...]
...[2] Following Newton [1943], and prior to Joselyn and McIntosh [1981], solar flares were widely considered to be the sole source of great sporadic geomagnetic storms....
[...]
...Because the widely used am and Dst geomagnetic indices [Mayaud, 1980] have different dependencies on these parameters, we can use them to fill data gaps in the following manner: (1) on the basis of experience and intuition, assume solar wind speed and magnetic field data for periods of missing data; (2) use these composite profiles (consisting of actual and assumed values) to derive one of the indices (in our case am, via Svalgaard [1977]); (3) adjust the assumed, gap-filling, solar wind parameters as necessary until the observed am is faithfully reproduced by the model; (4) use the various continuous solar wind parameter series obtained by this method (i....
[...]
...Because the widely used am and Dst geomagnetic indices [Mayaud, 1980] have different dependencies on these parameters, we can use them to fill data gaps in the following manner: (1) on the basis of experience and intuition, assume solar wind speed and magnetic field data for periods of missing data; (2) use these composite profiles (consisting of actual and assumed values) to derive one of the indices (in our case am, via Svalgaard [1977]); (3) adjust the assumed, gap-filling, solar wind parameters as necessary until the observed am is faithfully reproduced by the model; (4) use the various continuous solar wind parameter series obtained by this method (i.e., V, BX, BY, BZ, and n (density); with V and BZ shown in Figure 7) to calculate the other index (Dst, via Temerin and Li [2002]) as a test of the method....
[...]
TL;DR: In this paper, X-ray images of the solar corona showed a magnetically open structure in the low corona which extended from N20W20 to the south pole.
Abstract: X-ray images of the solar corona showed a magnetically open structure in the low corona which extended from N20W20 to the south pole. Analysis of the measured X-ray intensities shows the density scale heights within the structure to be typically a factor of two less than that in the surrounding large scale magnetically closed regions. The structure is identified as a coronal hole. Wind measurements for the appropriate period were traced back to the sun by the method of instantaneous ideal spirals. A striking agreement was found between the Carrington longitude of the solar source of a recurrent high velocity solar wind stream and the position of the hole.
716 citations
George Mason University1, University of Maryland, College Park2, Goddard Space Flight Center3, Boston College4, University of California, Berkeley5, Massachusetts Institute of Technology6, University of Alabama in Huntsville7, The Catholic University of America8, Royal Observatory of Belgium9, Moscow State University10
TL;DR: In this article, the authors presented 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 �� 100 nT) that occurred during 1996-2005.
Abstract: [1] 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 �� 100 nT) that occurred during 1996–2005. The results are achieved through cooperative efforts that originated at the Living with a Star (LWS) Coordinated DataAnalysis 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 (Bs), 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.
540 citations
TL;DR: In this paper, the formation and maintenance of filaments are reviewed in the light of recent findings on their structure, chirality, inferred magnetic topology, and mass flows, and evidence is put forth for three additional conditions associated with fully developed filaments: (A) field-aligned mass flows parallel with their fine structure (B) a multi-polar background source of small-scale magnetic fields necessary for the formation of the filament barbs and (C) a handedness property known as chiral which requires them to be either of two types, dextral
Abstract: Observational conditions for the formation and maintenance of filaments are reviewed since 1989 in the light of recent findings on their structure, chirality, inferred magnetic topology, and mass flows. Recent observations confirm the necessary conditions previously cited: (1) their location at a boundary between opposite-polarity magnetic fields (2) a system of overlying coronal loops, (3) a magnetically-defined channel beneath, (4) the convergence of the opposite-polarity network magnetic fields towards their common boundary within the channel and (5) cancellation of magnetic flux at the common polarity boundary. Evidence is put forth for three additional conditions associated with fully developed filaments: (A) field-aligned mass flows parallel with their fine structure (B) a multi-polar background source of small-scale magnetic fields necessary for the formation of the filament barbs and (C) a handedness property known as chirality which requires them to be either of two types, dextral or sinistral. One-to-one relationships have been established between the chirality of filaments and the chirality of their filament channels and overlying coronal arcades. These findings reinforce earlier evidence that every filament magnetic field is separate from the magnetic field of the overlying arcade but both are parts of a larger magnetic field system. The larger system has at least quadrupolar footprints in the photosphere and includes the filament channel and subphotospheric magnetic fields, This ‘systems’ view of filaments and their environment enables new perspectives on why arcades and channels are invariable conditions for their existence.
532 citations
"Great geomagnetic storm of 9 Novemb..." refers background in this paper
...The 17 April event represents an extreme example of a problem storm in that the long segment of chromospheric neutral line over which the eruption occurred was marked only by filament channels (FC) [Martin, 1998] and small and faint filaments....
[...]