2,013 research outputs found
Automated Detection of Solar Eruptions
Observation of the solar atmosphere reveals a wide range of motions, from
small scale jets and spicules to global-scale coronal mass ejections.
Identifying and characterizing these motions are essential to advancing our
understanding the drivers of space weather. Both automated and visual
identifications are currently used in identifying CMEs. To date, eruptions near
the solar surface (which may be precursors to CMEs) have been identified
primarily by visual inspection. Here we report on EruptionPatrol (EP): a
software module that is designed to automatically identify eruptions from data
collected by SDO/AIA. We describe the method underlying the module and compare
its results to previous identifications found in the Heliophysics Event
Knowledgebase. EP identifies eruptions events that are consistent with those
found by human annotations, but in a significantly more consistent and
quantitative manner. Eruptions are found to be distributed within 15Mm of the
solar surface. They possess peak speeds ranging from 4 to 100 km/sec and
display a power-law probability distribution over that range. These
characteristics are consistent with previous observations of prominences.Comment: 6 pages, 4 figures, 7th Solar Information Processing Workshop, to
appear in Space Weather and Space Climat
The relative value of recall and recognition techniques for measuring precise knowledge of word meaning nouns, verbs, adjectives
Thesis (Ed.D.)--Boston University. This item was digitized by the Internet Archive
The importance of altimeter and scatterometer data for ocean prediction
The prediction of ocean circulation using satellite altimeter data is discussed. Three classes of oceanic response to atmospheric forcing are outlined and examined. Storms, surface waves, eddies, and ocean currents were evaluated in terms of forecasting time requirements. Scatterometer and radiometer applications to ocean prediction are briefly reviewed
A spectral optical flow method for determining velocities from digital imagery
We present a method for determining surface flows from solar images based
upon optical flow techniques. We apply the method to sets of images obtained by
a variety of solar imagers to assess its performance. The {\tt opflow3d}
procedure is shown to extract accurate velocity estimates when provided perfect
test data and quickly generates results consistent with completely distinct
methods when applied on global scales. We also validate it in detail by
comparing it to an established method when applied to high-resolution datasets
and find that it provides comparable results without the need to tune, filter
or otherwise preprocess the images before its application.Comment: 12 pages, 5 figures. Submitted to Earth Science Informatic
Effect of the radiative background flux in convection
Numerical simulations of turbulent stratified convection are used to study
models with approximately the same convective flux, but different radiative
fluxes. As the radiative flux is decreased, for constant convective flux: the
entropy jump at the top of the convection zone becomes steeper, the temperature
fluctuations increase and the velocity fluctuations decrease in magnitude, and
the distance that low entropy fluid from the surface can penetrate increases.
Velocity and temperature fluctuations follow mixing length scaling laws.Comment: 12 pages, 24 figures, accepted by Astron. Nach
Solar magnetoconvection
In recent years the study of how magnetic fields interact with thermal convection in the Sun has made significant advances. These are largely due to the rapidly increasing computer power and its application to more physically relevant parameters regimes and to more realistic physics and geometry in numerical models. Here we present a survey of recent results following one line of investigations and discuss and compare the results of these with observed phenomena
Nonaxisymmetric instabilities of convection around magnetic flux tubes
On the surface of the Sun, magnetic flux elements collect in regions of converging flow, grow in field strength and become pores, which have been observed to exhibit nonaxisymmetric structure over a range of scales. Around a fully developed sunspot, as well as the fine scale of the penumbra, the moat sometimes shows clearly observable spoke-like structure at low azimuthal wavenumbers. We investigate the formation of azimuthal structure by computing the linear stability properties of fully nonlinear axisymmetric magnetoconvection, which takes the form of a central flux tube surrounded by a convecting field-free region. We find
steady and oscillatory instabilities with a preferred azimuthal wavenumber. The unstable modes are concentrated in the convecting region close to the outer edge of the flux tube. The instability is driven by convection, and is not a magnetic fluting instability
Power, Responsibility, and Accountability: Re-Thinking the Legitimacy of Institutions for Climate Finance
Offers lessons from current mechanisms to finance climate mitigation and adaptation and considerations for legitimacy in new ones: the capacity to determine outcomes, the exercise of power as intended, and standards and systems to ensure accountability
- …