A Parametric Study of Erupting Flux Rope Rotation. Modeling the "Cartwheel CME" on 9 April 2008

The rotation of erupting filaments in the solar corona is addressed through a parametric simulation study of unstable, rotating flux ropes in bipolar force-free initial equilibrium. The Lorentz force due to the external shear field component and the relaxation of tension in the twisted field are the major contributors to the rotation in this model, while reconnection with the ambient field is of minor importance. Both major mechanisms writhe the flux rope axis, converting part of the initial twist helicity, and produce rotation profiles which, to a large part, are very similar in a range of shear-twist combinations. A difference lies in the tendency of twist-driven rotation to saturate at lower heights than shear-driven rotation. For parameters characteristic of the source regions of erupting filaments and coronal mass ejections, the shear field is found to be the dominant origin of rotations in the corona and to be required if the rotation reaches angles of order 90 degrees and higher; it dominates even if the twist exceeds the threshold of the helical kink instability. The contributions by shear and twist to the total rotation can be disentangled in the analysis of observations if the rotation and rise profiles are simultaneously compared with model calculations. The resulting twist estimate allows one to judge whether the helical kink instability occurred. This is demonstrated for the erupting prominence in the "Cartwheel CME" on 9 April 2008, which has shown a rotation of \approx 115 degrees up to a height of 1.5 R_sun above the photosphere. Out of a range of initial equilibria which include strongly kink-unstable (twist Phi=5pi), weakly kink-unstable (Phi=3.5pi), and kink-stable (Phi=2.5pi) configurations, only the evolution of the weakly kink-unstable flux rope matches the observations in their entirety.Comment: Solar Physics, submitte

Impact of chronic consumption of dairy products varying in fatty acid composition on postprandial lipid responses: preliminary insights from the RESET study

Impact of chronic consumption of dairy products varying in fatty acid composition on postprandial lipid responses: preliminary insights from the RESET stud

Temporal Correlation of Hard X-rays and Meter/Decimeter Radio Structures in Solar Flares

We investigate the relative timing between hard X-ray (HXR) peaks and structures in metric and decimetric radio emissions of solar flares using data from the RHESSI and Phoenix-2 instruments. The radio events under consideration are predominantly classified as type III bursts, decimetric pulsations and patches. The RHESSI data are demodulated using special techniques appropriate for a Phoenix-2 temporal resolution of 0.1s. The absolute timing accuracy of the two instruments is found to be about 170 ms, and much better on the average. It is found that type III radio groups often coincide with enhanced HXR emission, but only a relatively small fraction ($\sim$ 20%) of the groups show close correlation on time scales $<$ 1s. If structures correlate, the HXRs precede the type III emissions in a majority of cases, and by 0.69$\pm$0.19 s on the average. Reversed drift type III bursts are also delayed, but high-frequency and harmonic emission is retarded less. The decimetric pulsations and patches (DCIM) have a larger scatter of delays, but do not have a statistically significant sign or an average different from zero. The time delay does not show a center-to-limb variation excluding simple propagation effects. The delay by scattering near the source region is suggested to be the most efficient process on the average for delaying type III radio emission

Observation of An Evolving Magnetic Flux Rope Prior To and During A Solar Eruption

Explosive energy release is a common phenomenon occurring in magnetized plasma systems ranging from laboratories, Earth's magnetosphere, the solar corona and astrophysical environments. Its physical explanation is usually attributed to magnetic reconnection in a thin current sheet. Here we report the important role of magnetic flux rope structure, a volumetric current channel, in producing explosive events. The flux rope is observed as a hot channel prior to and during a solar eruption from the Atmospheric Imaging Assembly (AIA) telescope on board the Solar Dynamic Observatory (SDO). It initially appears as a twisted and writhed sigmoidal structure with a temperature as high as 10 MK and then transforms toward a semi-circular shape during a slow rise phase, which is followed by fast acceleration and onset of a flare. The observations suggest that the instability of the magnetic flux rope trigger the eruption, thus making a major addition to the traditional magnetic-reconnection paradigm.Comment: 13 pages, 3 figure

Survey on solar X-ray flares and associated coherent radio emissions

The radio emission during 201 X-ray selected solar flares was surveyed from 100 MHz to 4 GHz with the Phoenix-2 spectrometer of ETH Zurich. The selection includes all RHESSI flares larger than C5.0 jointly observed from launch until June 30, 2003. Detailed association rates of radio emission during X-ray flares are reported. In the decimeter wavelength range, type III bursts and the genuinely decimetric emissions (pulsations, continua, and narrowband spikes) were found equally frequently. Both occur predominantly in the peak phase of hard X-ray (HXR) emission, but are less in tune with HXRs than the high-frequency continuum exceeding 4 GHz, attributed to gyrosynchrotron radiation. In 10% of the HXR flares, an intense radiation of the above genuine decimetric types followed in the decay phase or later. Classic meter-wave type III bursts are associated in 33% of all HXR flares, but only in 4% they are the exclusive radio emission. Noise storms were the only radio emission in 5% of the HXR flares, some of them with extended duration. Despite the spatial association (same active region), the noise storm variations are found to be only loosely correlated in time with the X-ray flux. In a surprising 17% of the HXR flares, no coherent radio emission was found in the extremely broad band surveyed. The association but loose correlation between HXR and coherent radio emission is interpreted by multiple reconnection sites connected by common field lines.Comment: Solar Physics, in pres

High-sensitivity observations of solar flare decimeter radiation

A new acousto-optic radio spectrometer has observed the 1 - 2 GHz radio emission of solar flares with unprecedented sensitivity. The number of detected decimeter type III bursts is greatly enhanced compared to observations by conventional spectrometers observing only one frequency at the time. The observations indicate a large number of electron beams propagating in dense plasmas. For the first time, we report weak, reversed drifting type III bursts at frequencies above simultaneous narrowband decimeter spikes. The type III bursts are reliable signatures of electron beams propagating downward in the corona, apparently away from the source of the spikes. The observations contradict the most popular spike model that places the spike sources at the footpoints of loops. Conspicuous also was an apparent bidirectional type U burst forming a fish-like pattern. It occurs simultaneously with an intense U-burst at 600-370 MHz observed in Tremsdorf. We suggest that it intermodulated with strong terrestrial interference (cellular phones) causing a spurious symmetric pattern in the spectrogram at 1.4 GHz. Symmetric features in the 1 - 2 GHz range, some already reported in the literature, therefore must be considered with utmost caution.Comment: Astronomy and Astrophysics, in pres

Triggering an eruptive flare by emerging flux in a solar active-region complex

A flare and fast coronal mass ejection originated between solar active regions NOAA 11514 and 11515 on July 1, 2012 in response to flux emergence in front of the leading sunspot of the trailing region 11515. Analyzing the evolution of the photospheric magnetic flux and the coronal structure, we find that the flux emergence triggered the eruption by interaction with overlying flux in a non-standard way. The new flux neither had the opposite orientation nor a location near the polarity inversion line, which are favorable for strong reconnection with the arcade flux under which it emerged. Moreover, its flux content remained significantly smaller than that of the arcade (approximately 40 %). However, a loop system rooted in the trailing active region ran in part under the arcade between the active regions, passing over the site of flux emergence. The reconnection with the emerging flux, leading to a series of jet emissions into the loop system, caused a strong but confined rise of the loop system. This lifted the arcade between the two active regions, weakening its downward tension force and thus destabilizing the considerably sheared flux under the arcade. The complex event was also associated with supporting precursor activity in an enhanced network near the active regions, acting on the large-scale overlying flux, and with two simultaneous confined flares within the active regions.Comment: Accepted for publication in Topical Issue of Solar Physics: Solar and Stellar Flares. 25 pages, 12 figure

Plasma phospholipid fatty acid profile confirms compliance to a novel saturated fat-reduced, monounsaturated fat-enriched dairy product intervention in adults at moderate cardiovascular risk: a randomized controlled trial

$\textbf{Background:}$ Dairy products are a major contributor to dietary SFA. Partial replacement of milk SFA with unsaturated fatty acids (FAs) is possible through oleic-acid rich supplementation of the dairy cow diet. To assess adherence to the intervention of SFA-reduced, MUFA-enriched dairy product consumption in the RESET (REplacement of SaturatEd fat in dairy on Total cholesterol) study using 4-d weighed dietary records, in addition to plasma phospholipid FA (PL-FA) status. $\textbf{Methods:}$ In a randomised, controlled, crossover design, free-living UK participants identified as moderate risk for CVD (n = 54) were required to replace habitually consumed dairy foods (milk, cheese and butter), with study products with a FA profile typical of retail products (control) or SFA-reduced, MUFA-enriched profile (modified), for two 12-week periods, separated by an 8-week washout period. A flexible food-exchange model was used to implement each isoenergetic high-fat, high-dairy diet (38% of total energy intake (%TE) total fat): control (dietary target: 19%TE SFA; 11%TE MUFA) and modified (16%TE SFA; 14%TE MUFA). $\textbf{Results:}$ Following the modified diet, there was a smaller increase in SFA (17.2%TE vs. 19.1%TE; p < 0.001) and greater increase in MUFA intake (15.4%TE vs. 11.8%TE; p < 0.0001) when compared with the control. PL-FA analysis revealed lower total SFAs (p = 0.006), higher total cis-MUFAs and trans-MUFAs (both p < 0.0001) following the modified diet. $\textbf{Conclusion:}$ The food-exchange model was successfully used to achieve RESET dietary targets by partial replacement of SFAs with MUFAs in dairy products, a finding reflected in the PL-FA profile and indicative of objective dietary compliance. $\textbf{Trial registration:}$ ClinicalTrials.gov Identifier: NCT02089035 , date 05-01-2014.This work was supported by funding from the Medical Research Council (United Kingdom; Ref: MR/K020218/1)

Cold event in the South Atlantic Bight during summer of 2003 : model simulations and implications

Author Posting. © American Geophysical Union, 2007. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 112 (2007): C05022, doi:10.1029/2006JC003903.A set of model simulations are used to determine the principal forcing mechanisms that resulted in anomalously cold water in the South Atlantic Bight (SAB) in the summer of 2003. Updated mass field and elevation boundary conditions from basin-scale Hybrid Coordinate Ocean Model (HYCOM) simulations are compared to climatological forcing to provide offshore and upstream influences in a one-way nesting sense. Model skill is evaluated by comparing model results with observations of velocity, water level, and surface and bottom temperature. Inclusion of realistic atmospheric forcing, river discharge, and improved model dynamics produced good skill on the inner shelf and midshelf. The intrusion of cold water onto the shelf occurred predominantly along the shelf-break associated with onshore flow in the southern part of the domain north of Cape Canaveral (29° to 31.5°). The atmospheric forcing (anomalously strong and persistent upwelling-favorable winds) was the principal mechanism driving the cold event. Elevated river discharge increased the level of stratification across the inner shelf and midshelf and contributed to additional input of cold water into the shelf. The resulting pool of anomalously cold water constituted more than 50% of the water on the shelf in late July and early August. The excess nutrient flux onto the shelf associated with the upwelling was approximated using published nitrate-temperature proxies, suggesting increased primary production during the summer over most of the SAB shelf.The preparation of this paper was primarily supported by the Southeast Atlantic Coastal Ocean Observing System (SEACOOS) and the South Atlantic Bight Limited Area Model (SABLAM). SEACOOS is a collaborative, regional program sponsored by the Office of Naval Research under award N00014-02-1-0972 and managed by the University of North Carolina-General Administration. SABLAM was sponsored by the National Ocean Partnership Program (award NAG 13-00041). Data from ship surveys were collected and processed with the support from NSF grant OCE-0099167 (J. R. Nelson), NSF grant OCE-9982133 (J. O. Blanton, SkIO), NASA grant NAG-10557 (J. R. Nelson), and SEACOOS. NOAA NDBC buoy data and NOS coastal water level records were obtained through NOAA-supported data archives and web portals. Moored instrument data from the Carolina Coastal Ocean Observation and Prediction System (Caro-COOPS) were acquired from the system’s website (http://www.carocoops.org). Caro-COOPS is sponsored by NOAA grant NA16RP2543