MHD Avalanches: Self-Consistent Heating in Model Active Regions

2021 ◽  
Author(s):  
Jack Reid ◽  
James Threlfall ◽  
Alan Hood ◽  
Craig Johnston
Keyword(s):  
Active Regions ◽  
Self Consistent

scholarly journals A New Explanation for Flares on dMe Stars

1989 ◽  
Vol 104 (2) ◽  
pp. 357-360
Author(s):  
G.M. Simnett
Keyword(s):  
Magnetic Field ◽  
Energy Transfer ◽  
Solar Corona ◽  
Solar Flares ◽  
Active Regions ◽  
Strong Fields ◽  
Stellar Flares ◽  
Self Consistent ◽  
The Magnetic Field

AbstractIt has been proposed that non-thermal ions dominate the energy transfer at the onset of solar flares. Here we examine this hypothesis in the context of flares on dMe stars. If the magnetic field in the stellar corona is significantly larger than that in the solar corona, and if strong fields in the photosphere, analagous to active regions, are absent, then a self-consistent explanation of stellar flares may be formulated.

Sensitivity of a VCSEL threshold performance to inaccuracies in its manufacturing

2010 ◽  
Vol 18 (2) ◽  
Author(s):  
M. Żujewski ◽  
W. Nakwaski
Keyword(s):  
Room Temperature ◽  
Continuous Wave ◽  
Diode Lasers ◽  
Active Regions ◽  
Lasing Threshold ◽  
Bragg Reflectors ◽  
Distributed Bragg Reflectors ◽  
Self Consistent ◽  
Uncontrolled Variation ◽  
Threshold Increase

AbstractThe paper describes an impact of various possible inaccuracies in manufacturing of verticalcavity surface-emitting diode lasers (VCSELs), like thicknesses and compositions of their layers different from assumed ones, on VCSEL room-temperature (RT) continuous-wave (CW) threshold performance. To this end, the fully self-consistent comprehensive optical-electrical-thermal-recombination VCSEL model has been applied. While the analysis has been carried out for the 1.3-μm oxide-confined intra-cavity contacted GaInNAs/GaAs VCSEL, its conclusions are believed to be more general and concern most of modern VCSEL designs. As expected, the VCSEL active region has been found to require the most scrupulous care in its fabrication, any uncontrolled variation in compositions and/or thicknesses of its layers is followed by unaccepted RT CW lasing threshold increase. Also spacer thicknesses should be manufactured with care to ensure a proper overlapping of the optical standing wave and both the gain and lossy areas within the cavity. On the contrary, less than 5% thickness changes in distributed-Bragg-reflectors are followed by nearly insignificant changes in VCSEL RT CW threshold. However, exceeding the above limit causes a rapid increase in lasing thresholds. As expected, in all the above cases, VCSELs equipped with larger active regions have been confirmed to require more careful technology. The above results should enable easier organization of VCSEL manufacturing.

The Effect of Temperature on the Efficiency of Nitride-based Multi-quantum well Light-emitting Diodes

2009 ◽  
Vol 1229 ◽  
Author(s):  
Oskari Heikkilä ◽  
Jani Oksanen ◽  
Jukka Tulkki
Keyword(s):  
Quantum Well ◽  
Light Emitting Diode ◽  
Active Regions ◽  
Effect Of Temperature ◽  
Current Transport ◽  
Internal Heating ◽  
Light Emitting ◽  
Self Consistent ◽  
Multi Quantum Well ◽  
Present Simulation

AbstractWe have recently developed a self consistent light-emitting diode (LED) model that accounts for the current transport and internal heating in AlGaAs-GaAs LEDs. In this paper we extend the model to describe multi-quantum well (MQW) active regions and III-N materials, within the limits of the currently known values and temperature dependencies of the recombination parameters in these materials. The MQW description accounts for the effect of the reduced wave function overlap to the recombination. We present simulation results obtained for an InGaN MQW LED with 4 wells at selected temperatures and discuss the factors limiting the efficiency and luminescent output of LEDs.

Synoptic Charts of the Solar Eclipses of 1990 and 1991

1994 ◽  
Vol 144 ◽  
pp. 517-521
Author(s):  
Z. Mouradian ◽  
G. Buchholtz ◽  
G. Zlicaric
Keyword(s):  
Solar Limb ◽  
Active Regions ◽  
Solar Eclipses ◽  
Coronal Structures

AbstractThe synoptic charts of solar rotations 1831 and 1844 have been drawn up, corresponding to the eclipses of 22 July 1990 and 11 July 1991. These charts contain the active regions and the filaments, and show the position of the solar limb, at the time of the eclipse. They are for use in studying the coronal structures observed during these eclipses. The variation of these structures is given in the table. The last section of the article contains a formula for identifying the structures out of the limb.

Solar Corona Investigation by the Coronal Line Photometer at Lomnický Peak

1994 ◽  
Vol 144 ◽  
pp. 431-434
Author(s):  
M. Minarovjech ◽  
M. Rybanský
Keyword(s):  
Solar Corona ◽  
Time Resolution ◽  
Active Regions ◽  
High Time ◽  
High Time Resolution ◽  
List Type ◽  
Type Number ◽  
Coronal Line ◽  
Global Cycle

AbstractThis paper deals with a possibility to use the ground-based method of observation in order to solve basic problems connected with the solar corona research. Namely:1.heating of the solar corona2.course of the global cycle in the corona3.rotation of the solar corona and development of active regions.There is stressed a possibility of high-time resolution of the coronal line photometer at Lomnický Peak coronal station, and use of the latter to obtain crucial observations.

The evolution of the Kuiper belt during the formation of the outer planets

1999 ◽  
Vol 173 ◽  
pp. 37-44
Author(s):  
M.D. Melita ◽  
A. Brunini
Keyword(s):  
Kuiper Belt ◽  
Outer Planets ◽  
Self Consistent ◽  
Planetary Bodies ◽  
Mass Depletion

AbstractA self-consistent study of the formation of planetary bodies beyond the orbit of Saturn and the evolution of Kuiper disks is carried out by means of an N-body code where accretion and gravitational encounters are considered. This investigation is focused on the aggregation of massive bodies in the outer planetary region and on the consequences of such process in the corresponding cometary belt. We study the link between the bombardment of massive bodies and mass depletion and eccentricity excitation.

Radio Measurements of Coronal Magnetic Fields

1994 ◽  
Vol 144 ◽  
pp. 21-28 ◽  
Author(s):  
G. B. Gelfreikh
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Solar Corona ◽  
Active Regions ◽  
High Sensitivity ◽  
Coronal Magnetic Field ◽  
Transverse Magnetic ◽  
Radio Sources ◽  
Radio Waves ◽  
Solar Active Regions

AbstractA review of methods of measuring magnetic fields in the solar corona using spectral-polarization observations at microwaves with high spatial resolution is presented. The methods are based on the theory of thermal bremsstrahlung, thermal cyclotron emission, propagation of radio waves in quasi-transverse magnetic field and Faraday rotation of the plane of polarization. The most explicit program of measurements of magnetic fields in the atmosphere of solar active regions has been carried out using radio observations performed on the large reflector radio telescope of the Russian Academy of Sciences — RATAN-600. This proved possible due to good wavelength coverage, multichannel spectrographs observations and high sensitivity to polarization of the instrument. Besides direct measurements of the strength of the magnetic fields in some cases the peculiar parameters of radio sources, such as very steep spectra and high brightness temperatures provide some information on a very complicated local structure of the coronal magnetic field. Of special interest are the results found from combined RATAN-600 and large antennas of aperture synthesis (VLA and WSRT), the latter giving more detailed information on twodimensional structure of radio sources. The bulk of the data obtained allows us to investigate themagnetospheresof the solar active regions as the space in the solar corona where the structures and physical processes are controlled both by the photospheric/underphotospheric currents and surrounding “quiet” corona.

Interpretation of the Filament Depression at Millimetric and Centimetric Wavelengths

1979 ◽  
Vol 44 ◽  
pp. 131-134
Author(s):  
A. Raoult ◽  
P. Lantos ◽  
E. Fürst
Keyword(s):  
Radio Telescope ◽  
Active Regions ◽  
Simple Shape ◽  
Quiet Sun ◽  
Unstable Process

The depressions at centimetric and millimetric wavelengths associated with the filaments are studied using already published maps as well as unpublished observations from the Effelsberg 100 m radio telescope of the M.P.I., Bonn. The study has been restricted to large Ha quiescent prominences of relatively simple shape, situated far from the limb and from active regions. The data has been reduced employing one method whose main characteristics are choice of a local quiet sun definition and avoidance of the unstable process of deconvolution.

The Hemispheric Sign Rule of Current Helicity during the Rising Phase of Cycle 23

2000 ◽  
Vol 179 ◽  
pp. 303-306
Author(s):  
S. D. Bao ◽  
G. X. Ai ◽  
H. Q. Zhang
Keyword(s):  
Solar Cycle ◽  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Active Regions ◽  
Hemispheric Preference ◽  
Current Helicity

AbstractWe compute the signs of two different current helicity parameters (i.e., αbestandHc) for 87 active regions during the rise of cycle 23. The results indicate that 59% of the active regions in the northern hemisphere have negative αbestand 65% in the southern hemisphere have positive. This is consistent with that of the cycle 22. However, the helicity parameterHcshows a weaker opposite hemispheric preference in the new solar cycle. Possible reasons are discussed.

Sign in / Sign up

Export Citation Format

Share Document