scholarly journals Relating magnetic reconnection to coronal heating

2015 ◽  
Vol 373 (2042) ◽  
pp. 20140263 ◽  
Author(s):  
D. W. Longcope ◽  
L. A. Tarr
Keyword(s):  
Energy Dissipation ◽  
Magnetic Fields ◽  
Solar Corona ◽  
Magnetic Reconnection ◽  
Active Regions ◽  
Coronal Heating ◽  
Flux Emergence ◽  
Coronal Magnetic Fields ◽  
Field Lines ◽  
A Current

It is clear that the solar corona is being heated and that coronal magnetic fields undergo reconnection all the time. Here we attempt to show that these two facts are related—i.e. coronal reconnection generates heat. This attempt must address the fact that topological change of field lines does not automatically generate heat. We present one case of flux emergence where we have measured the rate of coronal magnetic reconnection and the rate of energy dissipation in the corona. The ratio of these two, , is a current comparable to the amount of current expected to flow along the boundary separating the emerged flux from the pre-existing flux overlying it. We can generalize this relation to the overall corona in quiet Sun or in active regions. Doing so yields estimates for the contribution to coronal heating from magnetic reconnection. These estimated rates are comparable to the amount required to maintain the corona at its observed temperature.

scholarly journals Statistical Properties of Magnetic Separators in Model Active Regions

2000 ◽  
Vol 195 ◽  
pp. 443-444
Author(s):  
B. T. Welsch ◽  
D. W. Longcope
Keyword(s):  
Active Region ◽  
Solar Corona ◽  
Magnetic Reconnection ◽  
First Principles ◽  
Magnetic Charge ◽  
Active Regions ◽  
Heating Rates ◽  
X Ray ◽  
Field Lines ◽  
Charge Topology

“Transient brightenings” (or “microflares”) regularly deposit 1027 ergs of energy in the solar corona, and account for perhaps 20% of the active corona's power (Shimizu 1995). We assume these events correspond to episodes of magnetic reconnection along magnetic separators in the solar corona. Using the techniques of magnetic charge topology, we model active region fields as arising from normally distributed collections of “magnetic charges”, point-like sources/sinks of flux (or field lines). Here, we present statistically determined separator (X-ray loop) lengths, derived from first principles. We are in the process of statistical calculations of heating rates due to reconnection events along many separators.

scholarly journals Coronal Heating Mechanism in the Presence of a Flow: A Numerical Approach

1998 ◽  
Vol 185 ◽  
pp. 469-470
Author(s):  
S. Parhi ◽  
T. Tanaka
Keyword(s):  
Magnetic Fields ◽  
Solar Corona ◽  
Plasma Heating ◽  
Inhomogeneous Plasma ◽  
Resonant Absorption ◽  
Numerical Approach ◽  
Coronal Heating ◽  
Heating Mechanism ◽  
Driving Current ◽  
Field Lines

The solar corona is a hot, tenuous plasma permeated with the structured magnetic fields. A variety of waves is generated in the corona due to the convective upwelling motion in the photosphere. The excitation of MHD fluctuations is generated by the footpoint motion of the field lines in the photosphere. Resonant absorption of the Alfvén waves in an inhomogeneous plasma has been suggested as a means of driving current and plasma heating in the corona (Sakurai et al., 1991). We study this problem in the presence of flow.

Calculated Coronal Magnetic Fields and Their Comparison with the Coronal Structures as Observed during Five Solar Eclipses

1994 ◽  
Vol 144 ◽  
pp. 559-564
Author(s):  
P. Ambrož ◽  
J. Sýkora
Keyword(s):  
Magnetic Field ◽  
Solar Cycle ◽  
Magnetic Fields ◽  
Solar Corona ◽  
Coronal Magnetic Field ◽  
Coronal Magnetic Fields ◽  
Solar Eclipses ◽  
Coronal Structures

AbstractWe were successful in observing the solar corona during five solar eclipses (1973-1991). For the eclipse days the coronal magnetic field was calculated by extrapolation from the photosphere. Comparison of the observed and calculated coronal structures is carried out and some peculiarities of this comparison, related to the different phases of the solar cycle, are presented.

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.

scholarly journals Stellar Coronae

1980 ◽  
Vol 5 ◽  
pp. 419-428 ◽  
Author(s):  
G. S. Vaiana
Keyword(s):  
Magnetic Fields ◽  
Solar Corona ◽  
Main Sequence ◽  
High Energy ◽  
Coronal Heating ◽  
Standard Theory ◽  
Plasma Structure ◽  
X Ray ◽  
Spatially Resolved ◽  
Surface Convection

The standard theory of stellar coronae requires the presence of vigorous surface convection. In consequence, the expectation of such a theory is that stellar x-ray emission — if due to a corona — should be limited to a subset of stars (principally those of main sequence spectral types F and G), and therefore should be relatively rare. This theory also makes detailed predictions about coronal heating, which are subject to test if spatially resolved coronal data are available. We are now in a position to subject the standard coronal scenarios to observational scrutiny on both counts: Skylab and later observations have supplied us with spatially resolved data of the solar corona, while the succession of high-energy x-ray astronomy satellites, culminating with EINSTEIN, now gives us a long-awaited glimpse of stellar x-ray emission throughout the K-R diagram.I will maintain that these new data imply that coronal x-ray emission dominantly derives from plasma structure confined by stellar surface magnetic fields; that coronal heating is likely to be non-acoustic in character and involves the confining magnetic fields; that stellar x-ray emission is not well correlated with the level of surface convection activity. These results of course cast serious doubt upon the viability of the standard theory of stellar coronal formation. In the following, I will try to very briefly summarize the solar and stellar data, to present the context in which they were initially obtained, and very briefly sketch the new coronal picture we are pursuing. The results presented here are excerpted from lectures presented by R. Rosner and myself recently at Erice, Italy (viz. Vaiana 1979) and from the preliminary results of the EINSTEIN Stellar Survey (Vaiana et al. 1979). The latter, part of a larger effort in x-ray astronomy led by R. Giacconi, involves the work of many people, including F.R. Harnden, L. Golub, P. Gorenstein, R. Rosner, F. Seward, K. Topika at CFA, as well as a number of EINSTEIN guest investigators.

scholarly journals The Evolution of Unstable 'Beta-Gamma' Magnetic Fields of Active Region AR 2222

2015 ◽  
Vol 48 ◽  
pp. 95-102
Author(s):  
Zety Sharizat Hamidi ◽  
S.N.U. Sabri ◽  
N.N.M. Shariff ◽  
C. Monstein
Keyword(s):  
Active Region ◽  
Magnetic Fields ◽  
Solar Corona ◽  
Solar Flares ◽  
Active Regions ◽  
Group Type ◽  
Solar Burst ◽  
Type Iv ◽  
Fine Structures ◽  
Using Data

This event allows us to investigate how plasma–magnetic field interactions in the solar corona can produce suprathermal electron populations over periods from tens of minutes to several hours, and the interactions of wave-particle and wave-wave lead to characteristic fine structures of the emission. An intense and broad solar radio burst type IV was recorded by CALLISTO spectrometer from 240-360 MHz. Using data from a the KRIM observatory, we aim to provide a comprehensive description of the synopsis formation and dynamics of a a single solar burst type IV event due to active region AR2222. For five minutes, the event exhibited strong pulsations on various time scales and “broad patterns” with a formation of a group type III solar burst. AR 2222 remained the most active region, producing a number of minor C-Class solar flares. The speed of the solar wind also exceeds 370.8 km/second with 10.2 g/cm3 density of proton in the solar corona. The radio flux also shows 171 SFU. Besides, there are 3 active regions, AR2217, AR2219 and AR2222 potentially pose a threat for M-class solar flares. Active region AR2222 have unstable 'beta-gamma' magnetic fields that harbor energy for M-class flares. As a conclusion, we believed that Sun’s activities more active in order to achieve solar maximum cycle at the end of 2014.

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