5,486 research outputs found
A New Index for Predicting Catastrophes by Madhur Anand
A Review of Madhur Anand\u27s A New Index for Predicting Catastrophes
Abrupt Longitudinal Magnetic Field Changes and Ultraviolet Emissions Accompanying Solar Flares
We have used Transition Region and Coronal Explorer (TRACE) 1600 \AA images
and Global Oscillation Network Group (GONG) magnetograms to compare ultraviolet
(UV) emissions from the chromosphere to longitudinal magnetic field changes in
the photosphere during four X-class solar flares. An abrupt, significant, and
persistent change in the magnetic field occurred across more than ten pixels in
the GONG magnetograms for each flare. These magnetic changes lagged the GOES
flare start times in all cases, showing that they were consequences and not
causes of the flares. Ultraviolet emissions were spatially coincident with the
field changes. The UV emissions tended to lag the GOES start times for the
flares, and led the changes in the magnetic field in all pixels except one. The
UV emissions led the photospheric field changes by 4 minutes on average with
the longest lead being 9 minutes, however, the UV emissions continued for tens
of minutes, and more than an hour in some cases, after the field changes were
complete. The observations are consistent with the picture in which an
Alfv\'{e}n wave from the field reconnection site in the corona propagates field
changes outward in all directions near the onset of the impulsive phase,
including downwards through the chromosphere and into the photosphere, causing
the photospheric field changes, whereas the chromosphere emits in the UV in the
form of flare kernels, ribbons and sequential chromospheric brightenings during
all phases of the flare
Theoretical models of free-free microwave emission from solar magnetic loops
The free-free microwave emission is calculated from a series of model magnetic loops. The loops are surrounded by a cooler external plasma, as required by recent simultaneous X ray and microwave observations, and a narrow transition zone separating the loops from the external plasma. To be consistent with the observational results, upper limits on the density and temperature scale lengths in the transition zone are found to be 360 km and 250 km, respectively. The models which best produce agreement with X ray and microwave observations also yielded emission measure curves which agree well with observational emission measure curves for solar active regions
Recommended from our members
Malaria ecology, child mortality & fertility.
The broad determinants of fertility are thought to be reasonably well identified by demographers, though the detailed quantitative drivers of fertility levels and changes are less well understood. This paper uses a novel ecological index of malaria transmission to study the effect of child mortality on fertility. We find that temporal variation in the ecology of the disease is well-correlated to mortality, and pernicious malaria conditions lead to higher fertility rates. We then argue that most of this effect occurs through child mortality, and estimate the effect of child mortality changes on fertility. Our findings add to the literature on disease and fertility, and contribute to the suggestive evidence that child mortality reductions have a causal effect on fertility changes
Bangladesh Environmental Enteric Dysfunction (BEED) study: Protocol for a community-based intervention study to validate non-invasive biomarkers of environmental enteric dysfunction
The collisional relaxation of electrons in hot flaring plasma and inferring the properties of solar flare accelerated electrons from X-ray observations
X-ray observations are a direct diagnostic of fast electrons produced in
solar flares, energized during the energy release process and directed towards
the Sun. Since the properties of accelerated electrons can be substantially
changed during their transport and interaction with the background plasma, a
model must ultimately be applied to X-ray observations in order to understand
the mechanism responsible for their acceleration. A cold thick target model is
ubiquitously used for this task, since it provides a simple analytic
relationship between the accelerated electron spectrum and the emitting
electron spectrum in the X-ray source, with the latter quantity readily
obtained from X-ray observations. However, such a model is inappropriate for
the majority of solar flares in which the electrons propagate in a hot
megaKelvin plasma, because it does not take into account the physics of
thermalization of fast electrons. The use of a more realistic model, properly
accounting for the properties of the background plasma, and the collisional
diffusion and thermalization of electrons, can alleviate or even remove many of
the traditional problems associated with the cold thick target model and the
deduction of the accelerated electron spectrum from X-ray spectroscopy, such as
the number problem and the need to impose an ad hoc low energy cut-off.Comment: 6 pages, 14th Annual International Astrophysics Conference Tampa
proceeding
MOTOR VEHICLES AND TRAFFIC Registration and Licensing of Motor Vehicles: Allow Voluntary Cancellation and Re-Registration of Motor Vehicles; Require Satisfactory Proof of Insurance to Register a Vehicle with the DMV; Define Commercial and Fleet Policies; Add Reporting Requirements for Insurers to the Database; Allow Use of Cards as Proof of Insurance Through December 31, 2003
The Act updates the procedures motorists use for proving possession of insurance, making the Department of Motor Vehicles database an acceptable means of proving insurance coverage beginning January 1, 2004
Why Is There Corporate Taxation In a Small Open Economy? The Role of Transfer Pricing and Income Shifting
Several recent papers argue that corporate income taxes should not be used by small, open economies. With capital mobility, the burden of the tax falls on fixed factors (e.g., labor), and the tax system is more efficient if labor is taxed directly. However, corporate taxes not only exist but rates are roughly comparable with the top personal tax rates. Past models also forecast that multinationals should not invest in countries with low corporate tax rates, since the surtax they owe when profits are repatriated puts them at a competitive disadvantage. Yet such foreign direct investment is substantial. We suggest that the resolution of these puzzles may be found in the role of income shifting, both domestic (between the personal and corporate tax bases) and cross-border (through transfer pricing). Countries need cash-flow corporate taxes as a backstop to labor taxes to discourage individuals from converting their labor income into otherwise untaxed corporate income. We explore how these taxes can best be modified to deal as well with cross-border shifting.
- …