Long-duration magnetic clouds: a comparison of analyses using torus- and cylinder-shaped flux rope models

International audienceWe identified 17 magnetic clouds (MCs) with durations longer than 30 h, surveying the solar wind data obtained by the WIND and ACE spacecraft during 10 years from 1995 through 2004. Then, the magnetic field structures of these 17 MCs were analyzed by the technique of the least-squares fitting to force-free flux rope models. The analysis was made with both the cylinder and torus models when possible, and the results from the two models are compared. The torus model was used in order to approximate the curved portion of the MCs near the flanks of the MC loops. As a result, we classified the 17 MCs into 4 groups. They are (1) 5 MC events exhibiting magnetic field rotations through angles substantially larger than 180° which can be interpreted only by the torus model; (2) 3 other MC events that can be interpreted only by the torus model as well, though the rotation angles of magnetic fields are less than 180°; (3) 3 MC events for which similar geometries are obtained from both the torus and cylinder models; and (4) 6 MC events for which the resultant geometries obtained from both models are substantially different from each other, even though the observed magnetic field variations can be interpreted by either of the torus model or the cylinder model. It is concluded that the MC events in the first and second groups correspond to those cases where the spacecraft traversed the MCs near the flanks of the MC loops, the difference between the two being attributed to the difference in distance between the torus axis and the spacecraft trajectory. The MC events in the third group are interpreted as the cases where the spacecraft traversed near the apexes of the MC loops. For the MC events in the fourth group, the real geometry cannot be determined from the model fitting technique alone. Though an attempt was made to determine which model is more plausible for each of the MCs in this group by comparing the characteristics of associated bidirectional electron heat flows, the results were not very definitive. It was also found that the radii of the flux ropes obtained from the torus fitting tend to be generally smaller than those obtained from the cylinder fitting. This result raises a possible problem in estimating the magnetic flux and helicity carried away from the Sun by the MCs

STEREO and Wind observations of a fast ICME flank triggering a prolonged geomagnetic storm on 5-7 April 2010

On 5 April 2010 an interplanetary (IP) shock was detected by the Wind spacecraft ahead of Earth, followed by a fast (average speed 650 km/s) IP coronal mass ejection (ICME). During the subsequent moderate geomagnetic storm (minimum Dst = -72 nT, maximum Kp=8-), communication with the Galaxy 15 satellite was lost. We link images from STEREO/SECCHI to the near-Earth in situ observations and show that the ICME did not decelerate much between Sun and Earth. The ICME flank was responsible for a long storm growth phase. This type of glancing collision was for the first time directly observed with the STEREO Heliospheric Imagers. The magnetic cloud (MC) inside the ICME cannot be modeled with approaches assuming an invariant direction. These observations confirm the hypotheses that parts of ICMEs classified as (1) long-duration MCs or (2) magnetic-cloud-like (MCL) structures can be a consequence of a spacecraft trajectory through the ICME flank.Comment: Geophysical Research Letters (accepted); 3 Figure

The Grad-Shafranov Reconstruction of Toroidal Magnetic Flux Ropes: Method Development and Benchmark Studies

We develop an approach of Grad-Shafranov (GS) reconstruction for toroidal structures in space plasmas, based on in-situ spacecraft measurements. The underlying theory is the GS equation that describes two-dimensional magnetohydrostatic equilibrium as widely applied in fusion plasmas. The geometry is such that the arbitrary cross section of the torus has rotational symmetry about the rotation axis $Z$, with a major radius $r_0$. The magnetic field configuration is thus determined by a scalar flux function $\Psi$ and a functional $F$ that is a single-variable function of $\Psi$. The algorithm is implemented through a two-step approach: i) a trial-and-error process by minimizing the residue of the functional $F(\Psi)$ to determine an optimal $Z$ axis orientation, and ii) for the chosen $Z$, a $\chi^2$ minimization process resulting in the range of $r_0$. Benchmark studies of known analytic solutions to the toroidal GS equation with noise additions are presented to illustrate the two-step procedures and to demonstrate the performance of the numerical GS solver, separately. For the cases presented, the errors in $Z$ and $r_0$ are 9$^\circ$ and 22\%, respectively, and the relative percent error in the numerical GS solutions is less than 10\%. We also make public the computer codes for these implementations and benchmark studies.Comment: submitted to Sol. Phys. late Dec 2016; under review; code will be made public once review is ove

Magnetic Flux of EUV Arcade and Dimming Regions as a Relevant Parameter for Early Diagnostics of Solar Eruptions - Sources of Non-Recurrent Geomagnetic Storms and Forbush Decreases

This study aims at the early diagnostics of geoeffectiveness of coronal mass ejections (CMEs) from quantitative parameters of the accompanying EUV dimming and arcade events. We study events of the 23th solar cycle, in which major non-recurrent geomagnetic storms (GMS) with Dst <-100 nT are sufficiently reliably identified with their solar sources in the central part of the disk. Using the SOHO/EIT 195 A images and MDI magnetograms, we select significant dimming and arcade areas and calculate summarized unsigned magnetic fluxes in these regions at the photospheric level. The high relevance of this eruption parameter is displayed by its pronounced correlation with the Forbush decrease (FD) magnitude, which, unlike GMSs, does not depend on the sign of the Bz component but is determined by global characteristics of ICMEs. Correlations with the same magnetic flux in the solar source region are found for the GMS intensity (at the first step, without taking into account factors determining the Bz component near the Earth), as well as for the temporal intervals between the solar eruptions and the GMS onset and peak times. The larger the magnetic flux, the stronger the FD and GMS intensities are and the shorter the ICME transit time is. The revealed correlations indicate that the main quantitative characteristics of major non-recurrent space weather disturbances are largely determined by measurable parameters of solar eruptions, in particular, by the magnetic flux in dimming areas and arcades, and can be tentatively estimated in advance with a lead time from 1 to 4 days. For GMS intensity, the revealed dependencies allow one to estimate a possible value, which can be expected if the Bz component is negative.Comment: 27 pages, 5 figures. Accepted for publication in Solar Physic

Operative blood loss and use of blood products after full robotic and conventional low anterior resection with total mesorectal excision for treatment of rectal cancer

To date, no studies have investigated the estimated blood loss (EBL) after full robotic low anterior resection (R-LAR) in a case-matched model, comparing it with the conventional open approach (O-LAR). Forty-nine patients in the R-LAR and 105 in the O-LAR group were matched for age, gender, BMI (body mass index), ASA (American Society of Anesthesiology) class, tumor–node–metastasis (TNM) classification and UICC (Union for International Cancer Control) stage, distance of the lower edge of the tumor from the anal verge, presence of comorbidities, and preoperative hemoglobin (Hb). EBL was significantly higher in the O-LAR group (P < 0.001); twelve units of packed red blood cells were globally transfused in the O-LAR group, compared to one unit only in the R-LAR (P = 0.051). A significantly higher postoperative Hb drop (3.0 vs. 2.4 g/dL, P = 0.015) was registered in the O-LAR patients. The length of hospital stay was much lower for the R-LAR group (8.4 vs. 12.4 days, P < 0.001). The number of harvested lymph nodes (17.4 vs. 13.5, P = 0.006) and extent of distal margin (2.9 vs. 1.9 cm, P < 0.001) were significantly higher in the R-LAR group. Open surgery was confirmed as the sole variable significantly associated (P < 0.001) with blood loss (odds ratio = 4.41, 95% CI 2.06–9.43). It was a confirmed prognosticator of blood loss (P = 0.006) when a preoperative clinical predictive model was built, using multivariate analysis (odds ratio = 3.95, 95% CI 1.47–10.6). In conclusion, R-LAR produced less operative blood loss and less drop in postoperative hemoglobin when compared to O-LAR. Other clinically relevant outcomes were similar or superior to O-LAR

Identification of Nicotiana tabacum Linkage Group Corresponding to the Q Chromosome Gene(s) Involved in Hybrid Lethality

BACKGROUND: A linkage map consisting of 24 linkage groups has been constructed using simple sequence repeat (SSR) markers in Nicotiana tabacum. However, chromosomal assignments of all linkage groups have not yet been made. The Q chromosome in N. tabacum encodes a gene or genes triggering hybrid lethality, a phenomenon that causes death of hybrids derived from some crosses. METHODOLOGY/PRINCIPAL FINDINGS: We identified a linkage group corresponding to the Q chromosome using an interspecific cross between an N. tabacum monosomic line lacking the Q chromosome and N. africana. N. ingulba yielded inviable hybrids after crossing with N. tabacum. SSR markers on the identified linkage group were used to analyze hybrid lethality in this cross. The results implied that one or more genes on the Q chromosome are responsible for hybrid lethality in this cross. Furthermore, the gene(s) responsible for hybrid lethality in the cross N. tabacum × N. africana appear to be on the region of the Q chromosome to which SSR markers PT30342 and PT30365 map. CONCLUSIONS/SIGNIFICANCE: Linkage group 11 corresponded to the Q chromosome. We propose a new method to correlate linkage groups with chromosomes in N. tabacum