We study the X17 eruptive flare on 2003 October 28 using Michelson Doppler Imager observations of photospheric magnetic and velocity fields and TRACE 1600 A images of the flare in a three-dimensional ...model of energy buildup and release in NOAA 10486. The most dramatic feature of this active region is the 123? rotation of a large positive sunspot over 46 hr prior to the event. We apply a method for including such rotation in the framework of the minimum current corona model of the buildup of energy and helicity due to the observed motions. We distinguish between helicity and energy stored in the whole active region and that released in the flare itself. We find that while the rotation of a sunspot contributes significantly to the energy and helicity budgets of the whole active region, it makes only a minor contribution to that part of the region that flares. We conclude that in spite of the fast rotation, shearing motions alone store sufficient energy and helicity to account for the flare energetics and interplanetary coronal mass ejection helicity content within their observational uncertainties. Our analysis demonstrates that the relative importance of shearing and rotation in this flare depends critically on their location within the parent active region topology.
We study the relationship between magnetic reconnection and acceleration of filaments and coronal mass ejections (CMEs) in different magnetic configurations. They occur in either quiet-Sun or active ...regions of either bipolar or multi-polar magnetic fields, and are either or not accompanied by filament eruptions. The preliminary results of the case studies confirm the temporal correlation and magnitude scaling relationship between reconnection rate and acceleration in the early phase of eruptions. The results suggest no clear difference between events of different magnetic configurations. It is shown that the total reconnection flux, which is calculated to be
10
21
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22
Mx
, is proportional to the average velocities of CMEs, suggesting the important role of magnetic reconnection in the early stage of solar eruptions.
Abstract
In order to bridge the gap between heliospheric and solar observations of coronal mass ejections (CMEs), one of the key steps is to improve the understanding of their corresponding magnetic ...structures like the magnetic flux ropes (MFRs). But it remains a challenge to confirm the existence of a coherent MFR before or upon the CME eruption on the Sun and to quantitatively characterize the CME-MFR due to the lack of direct magnetic field measurements in the corona. In this study, we investigate MFR structures originating from two active regions (ARs), AR 11719 and AR 12158, and estimate their magnetic properties quantitatively. We perform nonlinear force-free field extrapolations with preprocessed photospheric vector magnetograms. In addition, remote-sensing observations are employed to find indirect evidence of MFRs on the Sun and to analyze the time evolution of magnetic reconnection flux associated with the flare ribbons during the eruption. A coherent “preexisting” MFR structure prior to the flare eruption is identified quantitatively for one event from the combined analysis of the extrapolation and observation. Then the characteristics of MFRs for two events on the Sun before and during the eruption forming the CME-MFR, including the axial magnetic flux, field line twist, and reconnection flux, are estimated and compared with the corresponding in situ modeling results. We find that the magnetic reconnection associated with the accompanying flares for both events injects a significant amount of flux into the erupted CME-MFRs.
Forbes & Lin derived simple equations to link the properties of magnetic reconnection in the corona to observed signatures of solar flares. We measured the photospheric magnetic fields and the flare ...ribbon separation speeds then applied these equations to derive two physical terms for the magnetic reconnection rates: the rate of magnetic flux change sub(rec) involved in magnetic reconnection in the low corona and the electric field E sub(rec) inside the reconnecting current sheet (RCS) that is generated during magnetic reconnection. The central interest in this work is to investigate and quantify the statistical correlation between the magnetic reconnection rate and the corresponding flux-rope acceleration. From a sample of 13 well-observed two-ribbon flares, which are associated with filament eruptions or coronal mass ejections (CMEs), the acceleration of erupting filaments is found mainly in the range of 0.05-0.4 km s super(-2), up to 3 km s super(-2). Correspondingly, the maximum E sub(rec) and sub(rec) mostly occur in the range of 0.2-5 V cm super(-1) and 0.5-6 x 10 super(18) Mx s super(-1), respectively. A positive and strong correlation is found with a cross-correlation coefficient of 0.94-0.97 between the magnetic reconnection rate and the acceleration of erupting filaments that represents the early stages of flux-rope eruptions in the low corona. However, the inferred reconnection rate is not correlated to the acceleration of CME fronts measured by the Large Angle and Spectrometric Coronagraph (LASCO) observations in the range of 2-30 solar radii (the correlation coefficient is less than 0.2). A reasonable correlation is found between the reconnection rate and the velocity of CMEs, which indicates the cumulative acceleration of CMEs from the low corona to the LASCO C2 field of view. The temporal correlation between the magnetic reconnection rate and the flare nonthermal emissions has also been verified in this paper.
We report on the detailed and systematic study of field line twist and length distributions within magnetic flux ropes embedded in interplanetary coronal mass ejections (ICMEs). The Grad‐Shafranov ...reconstruction method is utilized together with a constant‐twist nonlinear force‐free (Gold‐Hoyle) flux rope model to reveal the close relation between the field line twist and length in cylindrical flux ropes, based on in situ Wind spacecraft measurements. We show that the field line twist distributions within interplanetary flux ropes are inconsistent with the Lundquist model. In particular, we utilize the unique measurements of magnetic field line lengths within selected ICME events as provided by Kahler et al. () based on energetic electron burst observations at 1 AU and the associated type III radio emissions detected by the Wind spacecraft. These direct measurements are compared with our model calculations to help assess the flux rope interpretation of the embedded magnetic structures. By using the different flux rope models, we show that the in situ direct measurements of field line lengths are consistent with a flux rope structure with spiral field lines of constant and low twist, largely different from that of the Lundquist model, especially for relatively large‐scale flux ropes.
Key Points
Field line twist of MCs remains fairly constant
Field line lengths inside MCs are consistent with flux rope interpretations
Axial length of cylindrical flux ropes is within 1 and 2 AU
AIM： To investigate the association between nutrient intakes and high incidence rate of gastric cancer among residents in Zhoushan Islands.
METHODS： A frequency-matched design of case-control study ...was used during the survey on dietary factors and gastric cancer in Zhoushan Islands, China. A total of 103 cases of gastric cancer diagnosed in 2001 were included in the study and 133 controls were randomly selected from the residents in Zhoushan Islands. A food frequency questionnaire was specifically designed for the Chinese dietary pattern to collect information on dietary intake. A computerized database of the dietary and other relative information of each participant was completed. Total calories and 15 nutrients were calculated according to the food composition table and their adjusted odds ratios （ORs） and 95% confidence intervals （CIs） were estimated by gender using unconditional logistic regression models.
RESULTS： High intakes of protein, saturated fat, and cholesterol were observed with the increased risk of gastric cancer particularly among males （ORQ4 vs Q1 were 10.3, 3.24, 2.76 respectively）. While carbohydrate was a significant high-risk nutrient （ORQ4 vs Q1 = 14.8, Pfor linear trend = 0.024） among females. Regardless of their gender, the cases reported significantly higher daily intake of sodium mainly from salts. As to the nutrients of vitamins A and C, an inversed association with the risk of GC was found. Baseline characteristics of participants were brieflydescribed.
CONCLUSION： The findings from this study confirm the role of diet-related exposure in the etiology of gastric cancer from the point of view of epidemiology. An increased risk of gastric cancer is associated with high intakes of protein, saturated fat, cholesterol and sodium, while consumption of polyunsaturated fat, vitamin A and ascorbic acid may have a protective effect against gastriccancer.
We develop an optimization approach to model the magnetic field configuration of magnetic clouds, based on a linear force‐free formulation in three dimensions. Such a solution, dubbed the Freidberg ...solution, is kin to the axisymmetric Lundquist solution, but with more general “helical symmetry.” The merit of our approach is demonstrated via its application to two case studies of in situ measured magnetic clouds. Both yield results of reduced χ2 ≈ 1. Case 1 shows a winding flux rope configuration with one major polarity. Case 2 exhibits a double‐helix configuration with two flux bundles winding around each other and rooted on regions of mixed polarities. This study demonstrates the three‐dimensional complexity of the magnetic cloud structures.
Plain Language Summary
Magnetic clouds (MCs) are a type of magnetic field structures observed in space. They possess some well‐defined properties and have been well studied in the space age. The existing model for such a structure is a straight cylinder with no variation along its axis. They may impact Earth carrying significant amount of electromagnetic energy. They come in relatively large sizes. When encompassing the near‐Earth space environment, their impact can last for days. MCs originate from the Sun, directly born with the so‐called coronal mass ejections (CMEs) which can be seen as an ejection of large amount of solar material from telescopes aiming at the Sun. The CMEs are often accompanied by solar flares, the most energetic and explosive events in our solar system. When these happen, they release a wide range of radiations and disturbances that may adversely impact Earth with MCs being one major type of such disturbances. Therefore, studying the internal configuration of MCs is of importance to understanding their origin and impact. This study presents a more complex three‐dimensional MC model to better fit the in situ spacecraft measurements of such structures, which goes beyond the current model.
Key Points
First rigorous applications of a three‐dimensional (3D) model are carried out for in situ measurements of magnetic clouds (MCs)
Results via the optimal fitting approach yield reduced Chi2 values close to 1
Complexity of MC flux ropes is revealed by the model showing 3D winding magnetic flux bundles
Theoretically, coronal mass ejection (CME) kinematics are related to magnetic reconnection processes in the solar corona. However, the current quantitative understanding of this relationship is based ...on the analysis of only a handful of events. Here we report a statistical study of 60 CME-flare events from 2010 August to 2013 December. We investigate kinematic properties of CMEs and magnetic reconnection in the low corona during the early phase of the eruptions, by combining limb observations from STEREO with simultaneous on-disk views from SDO. For a subset of 42 events with reconnection rate evaluated by the magnetic fluxes swept by the flare ribbons on the solar disk observed from SDO, we find a strong correlation between the peak CME acceleration and the peak reconnection rate. Also, the maximum velocities of relatively fast CMEs ( 600 km s−1) are positively correlated with the reconnection flux, but no such correlation is found for slow CMEs. A time-lagged correlation analysis suggests that the distribution of the time lag of CME acceleration relative to reconnection rate exhibits three peaks, approximately 10 minutes apart, and on average, acceleration-led events have smaller reconnection rates. We further compare the CME total mechanical energy with the estimated energy in the current sheet. The comparison suggests that, for small-flare events, reconnection in the current sheet alone is insufficient to fuel CMEs. Results from this study suggest that flare reconnection may dominate the acceleration of fast CMEs, but for events of slow CMEs and weak reconnection, other mechanisms may be more important.
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