586 research outputs found
The hard X-ray burst spectrometer event listing 1980-1987
This event listing is a comprehensive reference for the Hard X-ray bursts detected with the Hard X-ray Burst Spectrometer on the Solar Maximum Mission from the time of launch 14 February 1980 to December 1987. Over 8600 X-ray events were detected in the energy range from 30 to approx. 600 keV with the vast majority being solar flares. The listing includes the start time, peak time, duration and peak rate of each event
Holding on to Both Ends of a Pole:Empowering Feminine Sexuality and Reclaiming Feminist Emancipation
\u3cem\u3eDENND5B\u3c/em\u3e Regulates Intestinal Triglyceride Absorption and Body Mass
Regulation of lipid absorption by enterocytes can influence metabolic status in humans and contribute to obesity and related complications. The intracellular steps of chylomicron biogenesis and transport from the Endoplasmic Reticulum (ER) to the Golgi complex have been described, but the mechanisms for post-Golgi transport and secretion of chylomicrons have not been identified. Using a newly generated Dennd5b−/− mouse, we demonstrate an essential role for this gene in Golgi to plasma membrane transport of chylomicron secretory vesicles. In mice, loss of Dennd5b results in resistance to western diet induced obesity, changes in plasma lipids, and reduced aortic atherosclerosis. In humans, two independent exome sequencing studies reveal that a common DENND5B variant, p.(R52K), is correlated with body mass index. These studies establish an important role for DENND5B in post-Golgi chylomicron secretion and a subsequent influence on body composition and peripheral lipoprotein metabolism
Major Geomagnetic Storms (Dst less than or equal to -100 nT) Generated by Corotating Interaction Regions
Seventy-nine major geomagnetic storms (minimum Dst less than or equal to -100 nT) observed in 1996 to 2004 were the focus of a Living with a Star Coordinated Data-Analysis Workshop (CDAW) in March, 2005. In 9 cases, the storm driver appears to have been purely a corotating interaction region (CIR) without any contribution from coronal mass ejection-related material (interplanetary coronal mass ejections, ICMEs). These storms were generated by structures within CIRs located both before and/or after the stream interface that included persistently southward magnetic fields for intervals of several hours. We compare their geomagnetic effects with those of 159 CIRs observed during 1996 - 2005. The major storms form the extreme tail of a continuous distribution of CIR geoeffectiveness which peaks at Dst approx. -40 nT but is subject to a prominent seasonal variation of - 40 nT which is ordered by the spring and fall equinoxes and the solar wind magnetic field direction towards or away from the Sun. The O'Brien and McPherron [2000] equations, which estimate Dst by integrating the incident solar wind electric field and incorporating a ring current loss term, largely account for the variation in storm size. They tend to underestimate the size of the larger CIR-associated storms by Dst approx. 20 nT. This suggests that injection into the ring current may be more efficient than expected in such storms. Four of the nine major storms in 1996 - 2004 occurred during a period of less than three solar rotations in September - November, 2002, also the time of maximum mean IMF and solar magnetic field intensity during the current solar cycle. The maximum CIR-storm strength found in our sample of events, plus additional 23 probable CIR-associated Dst less than or equal to -100 nT storms in 1972 - 1995, is (Dst = -161 nT). This is consistent with the maximum storm strength (Dst approx. -180 nT) expected from the O'Brien and McPherron equations for the typical range of solar wind electric fields associated with CIRs. This suggests that CIRs alone are unlikely to generate geomagnetic storms that exceed these levels
Initiation and propagation of coronal mass ejections
This paper reviews recent progress in the research on the initiation and
propagation of CMEs. In the initiation part, several trigger mechanisms are
discussed; In the propagation part, the observations and modelings of EIT
waves/dimmings, as the EUV counterparts of CMEs, are described.Comment: 8 pages, 1 figure, an invited review, to appear in J. Astrophys.
Astro
Statistical Survey of Type III Radio Bursts at Long Wavelengths Observed by the Solar TErrestrial RElations Observatory (STEREO)/Waves Instruments: Radio Flux Density Variations with Frequency
We have performed a statistical study of Type III radio bursts observed
by Solar TErrestrial RElations Observatory (STEREO)/Waves between May 2007 and
February 2013. We have investigated the flux density between kHz and
MHz. Both high- and low-frequency cutoffs have been observed in of
events suggesting an important role of propagation. As already reported by
previous authors, we observed that the maximum flux density occurs at MHz on
both spacecraft. We have developed a simplified analytical model of the flux
density as a function of radial distance and compared it to the STEREO/Waves
data.Comment: published in Solar Physic
From Predicting Solar Activity to Forecasting Space Weather: Practical Examples of Research-to-Operations and Operations-to-Research
The successful transition of research to operations (R2O) and operations to
research (O2R) requires, above all, interaction between the two communities. We
explore the role that close interaction and ongoing communication played in the
successful fielding of three separate developments: an observation platform, a
numerical model, and a visualization and specification tool. Additionally, we
will examine how these three pieces came together to revolutionize
interplanetary coronal mass ejection (ICME) arrival forecasts. A discussion of
the importance of education and training in ensuring a positive outcome from
R2O activity follows. We describe efforts by the meteorological community to
make research results more accessible to forecasters and the applicability of
these efforts to the transfer of space-weather research.We end with a
forecaster "wish list" for R2O transitions. Ongoing, two-way communication
between the research and operations communities is the thread connecting it
all.Comment: 18 pages, 3 figures, Solar Physics in pres
The dependence of the EIT wave velocity on the magnetic field strength
"EIT waves" are a wavelike phenomenon propagating in the corona, which were
initially observed in the extreme ultraviolet (EUV) wavelength by the EUV
Imaging Telescope (EIT). Their nature is still elusive, with the debate between
fast-mode wave model and non-wave model. In order to distinguish between these
models, we investigate the relation between the EIT wave velocity and the local
magnetic field in the corona. It is found that the two parameters show
significant negative correlation in most of the EIT wave fronts, {\it i.e.},
EIT wave propagates more slowly in the regions of stronger magnetic field. Such
a result poses a big challenge to the fast-mode wave model, which would predict
a strong positive correlation between the two parameters. However, it is
demonstrated that such a result can be explained by the fieldline stretching
model, \emph{i.e.,} that "EIT waves" are apparently-propagating brightenings,
which are generated by successive stretching of closed magnetic field lines
pushed by the erupting flux rope during coronal mass ejections (CMEs).Comment: 11 pages, 8 figures, accepted for publication in Solar Phy
Coronal Shock Waves, EUV waves, and Their Relation to CMEs. I. Reconciliation of "EIT waves", Type II Radio Bursts, and Leading Edges of CMEs
We show examples of excitation of coronal waves by flare-related abrupt
eruptions of magnetic rope structures. The waves presumably rapidly steepened
into shocks and freely propagated afterwards like decelerating blast waves that
showed up as Moreton waves and EUV waves. We propose a simple quantitative
description for such shock waves to reconcile their observed propagation with
drift rates of metric type II bursts and kinematics of leading edges of coronal
mass ejections (CMEs). Taking account of different plasma density falloffs for
propagation of a wave up and along the solar surface, we demonstrate a close
correspondence between drift rates of type II bursts and speeds of EUV waves,
Moreton waves, and CMEs observed in a few known events.Comment: 30 pages, 15 figures. Solar Physics, published online. The final
publication is available at http://www.springerlink.co
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