Analysis of EUV, Microwave, and Magnetic Field Observations of Solar Plage

AbstractWe obtained simultaneous images of solar plage on 7 May 1991 with Goddard Space Flight Center’s Solar EUV Rocket Telescope and Spectrograph (SERTS), the Very Large Array (VLA), and the NASA/NSO spectromagnetograph at Kitt Peak. Using intensity ratios of Fe XVI to Fe XV emission lines, we find that the coronal plasma temperature is 2.5 ± 0.3 ×lO6 K throughout the region. The column emission measure ranges from 2.6 × 1027 to 1.3 × 1028 cm−5. The calculated structure and intensity of the 20 cm wavelength thermal bremsstrahlung emission from the hot plasma observed by SERTS is quite similar to the observed structure and intensity of the 20 cm microwave emission observed by the VLA. Using the revised coronal iron abundance of Meyer (1991, 1992), we find no evidence for either cool absorbing plasma or for contributions from thermal gyroemission. Combining the observed microwave polarization and the SERTS plasma parameters, we calculate a map of the coronal longitudinal magnetic field. The resulting values, ~ 30 – 60 Gauss, are comparable to extrapolated values of the potential field at heights of 5,000 and 10,000 km.

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X-Ray Flares and Outflows Driven by Magnetic Interaction Between a Protostar and its Surrounding Disk

International Astronomical Union Colloquium ◽

10.1017/s0252921100043608 ◽

1997 ◽

Vol 163 ◽

pp. 717-718

Author(s):

Mitsuru Hayashi ◽

Kazunari Shibata ◽

Ryoji Matsumoto

Keyword(s):

Magnetic Field ◽

Current Sheet ◽

Plasma Temperature ◽

Magnetic Interaction ◽

Central Star ◽

X Ray ◽

Mhd Simulations ◽

Flare Loops ◽

Hot Plasma ◽

Dipole Magnetic Field

AbstractHere we present a model of hard X-ray flares and hot plasma outflows (optical jets) observed in protostars. Assuming that the dipole magnetic field of a protostar threads the protostellar disk, we carried out 2.5-dimensional magnetohydrodynamic (MHD) simulations of the diskstar interaction. The closed magnetic loops connecting the central star and the disk are twisted by the rotation of the disk. In the presence of resistivity, magnetic reconnection takes place in the current sheet formed inside the expanding loops. Hot, outgoing plasmoid and post flare loops are formed as a result of the reconnection. Numerical results are consistent with the observed plasma temperature (107 – 108K), the length of the flaring loop (1011 – 1012cm), and the speed of optical jets (200 – 400 km s−1 ).

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Estimation of Plasma Properties and Magnetic Field in a Prominence-like Structure as Observed by SDO/AIA

Proceedings of the International Astronomical Union ◽

10.1017/s1743921313011290 ◽

2013 ◽

Vol 8 (S300) ◽

pp. 405-407

Author(s):

B. N. Dwivedi ◽

A. K. Srivastava ◽

Anita Mohan

Keyword(s):

Magnetic Field ◽

Flux Tube ◽

Emission Measure ◽

Solar Dynamics Observatory ◽

Plasma Parameters ◽

Plasma Properties ◽

Plasma Dynamics ◽

Cool Plasma ◽

Kink Waves ◽

Solar Dynamics

AbstractWe analyze a prominence-like cool plasma structure as observed by Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO). We perform the Differential Emission Measure (DEM) analysis using various filters of AIA, and also deduce the temperature and density structure in and around the observed flux-tube. In addition to deducing plasma parameters, we also find an evidence of multiple harmonics of fast magnetoacoustic kink waves in the observed prominence-like magnetic structure. Making use of estimated plasma parameters and observed wave parameters, under the baseline of MHD seismology, we deduce magnetic field in the flux-tube. The wave period ratio P1/P2 = 2.18 is also observed in the flux-tube, which carries the signature of magnetic field divergence where we estimate the tube expansion factor as 1.27. We discuss constraints in the estimation of plasma and magnetic field properties in such a structure in the current observational perspective, which may shed new light on the localized plasma dynamics and heating scenario in the solar atmosphere.

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Instabilität der positiven Säule endlicher Länge im magnetischen Feld / Instability of the Positive Column of Finite Length in a Magnetic Field

Zeitschrift für Naturforschung A ◽

10.1515/zna-1970-0702 ◽

1970 ◽

Vol 25 (7) ◽

pp. 992-1006

Author(s):

G. Janzen ◽

F. Moser ◽

E. Räuchle

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Frequency Spectrum ◽

Satisfactory Agreement ◽

Finite Length ◽

Positive Column ◽

Longitudinal Magnetic Field ◽

Gas Discharge ◽

Plasma Parameters ◽

Theory And Experiments

The instability of a diffusion-dominated positive column of a gas discharge in a longitudinal magnetic field is investigated both experimentally and theoretically. Dispersion relations are derived for the case of an m = l helical instability considering the finite length of the column. Regions of instability are calculated for various wavelengths of the instability.Experiments were carried out in a positive column of variable length, ranging from 8.5 to 40 cm. at varying pressures of about 0.1 Torr of Neon. There is a satisfactory agreement between theory and experiments. The main results are: a) in long tubes instability occurs at a distinct magnetic field, calculated first by Kadomtsev and Nedospasov. Stable intermediate regions are possible at higher fields depending on the relations between the plasma-parameters; b) in short tubes the column is stable again for higher magnetic fields; c) in very short tubes there is no instability of this kind. The observed frequency spectrum agrees with the theoretical values

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Global MHD Modeling of the Solar Corona and Inner Heliosphere for the Whole Heliosphere Interval

Proceedings of the International Astronomical Union ◽

10.1017/s1743921310010367 ◽

2009 ◽

Vol 5 (H15) ◽

pp. 491-493 ◽

Cited By ~ 2

Author(s):

Pete Riley ◽

Jon A. Linker ◽

Zoran Mikic

Keyword(s):

Magnetic Field ◽

Solar Corona ◽

Extreme Ultraviolet ◽

Plasma Temperature ◽

Transport Processes ◽

Coronal Heating ◽

Dimensional Structure ◽

Plasma Parameters ◽

Whole Heliosphere Interval ◽

Inner Heliosphere

AbstractWith the goal of understanding the three-dimensional structure of the solar corona and inner heliosphere during the “Whole Heliosphere Interval” (WHI), we have developed a global MHD solution for Carrington rotation (CR) 2068. Our model, which includes energy transport processes, such as coronal heating, conduction of heat parallel to the magnetic field, radiative losses, and the effects of Alfvén waves, is capable of producing significantly better estimates of the plasma temperature and density in the corona than have been possible in the past. With such a model, we can compute emission in extreme ultraviolet (EUV) and X-ray wavelengths, as well as scattering in polarized white light. Additionally, from our heliospheric solutions, we can deduce magnetic field and plasma parameters along specific spacecraft trajectories. We have made detailed comparisons of both remote solar and in situ observations with the model results, allowing us to: (1) Connect these disparate sets of observations; (2) Infer the global structure of the inner heliosphere; and (3) Provide support for (or against) assumptions in the MHD model, such as the empirically-based coronal heating profiles.

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Investigation of the Cyclotron Harmonic Radiation from a Plasma in a Magnetic Field

Zeitschrift für Naturforschung A ◽

10.1515/zna-1966-0403 ◽

1966 ◽

Vol 21 (4) ◽

pp. 383-390

Author(s):

Eberhard Räuchle ◽

Walther Hess

Keyword(s):

Magnetic Field ◽

Radiation Intensity ◽

Pressure Range ◽

Positive Column ◽

Longitudinal Magnetic Field ◽

Microwave Emission ◽

Harmonic Radiation ◽

Pressure Discharge ◽

Cyclotron Harmonic ◽

Theory And Experiment

The microwave emission of the positive column of a low pressure discharge in a magnetic field is investigated by means of a 10 000 Mc/sec radiometer. The radiation intensity as a function of the longitudinal magnetic field shows a number of peaks near the electron cyclotron harmonic frequencies. The measurements are performed for noble gases in the pressure range from 10 to 10-2 Torr at electron densities varying from 109 to 1013 cm-3. In order to compare the experimental results with a theoretical investigation performed by one of the authors12, the emission of harmonics was observed in dependence on the electron density. A satisfactory agreement between theory and experiment is shown.

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