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5,681 results on '"Coronal loop"'

1. Solution to the Problem of the Evolution of a Weak Perturbation Induced at the Boundary of a Hot Coronal Loop in a Strong Magnetic Field.

Author

Frolova, A. S., Zavershinskii, D. I., and Molevich, N. E.

Abstract

Magnetoacoustic waves are actively used as a means of diagnosing plasma parameters and processes occurring in it. In this paper, we study the problem of the evolution of a weak perturbation specified at the base of a coronal loop. The analysis is carried out under the assumption that the plasma is in a strong magnetic field, such that the evolution of slow magnetoacoustic and entropy modes can be described within the framework of gas dynamics equations with a high degree of accuracy. The spectrum of the waves in question is assumed to be such that the main source of dispersion and dissipation of the waves is the thermal conduction of the medium. Within the framework of the specified approximations, an exact solution to the boundary value problem for the linear evolution equation is found using the Fourier method and Duhamel's principle. The obtained exact analytical solution can be used to interpret the observation results, as well as numerical modeling of slow magnetoacoustic and entropy waves in the solar corona. [ABSTRACT FROM AUTHOR]

Published
2024
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2. Three-Dimensional Reconstruction of Coronal Features: A Python Tool for Geometric Triangulation.

Author

Nisticò, Giuseppe

Subjects
*HELIOSEISMOLOGY, *SOLAR corona, *PRINCIPAL components analysis, *SOLAR atmosphere, *MAGNETIC structure, *TRIANGULATION, *OBSERVATORIES, *SEISMOLOGY
Abstract

The determination of the three-dimensional (3D) geometry of coronal features is important for understanding the magnetic structuring of the solar atmosphere. In this context, the length of a coronal loop, which is subject to standing transverse oscillations, is a crucial parameter in coronal seismology for the correct estimation of the phase speed of the wave and, consequently, of the Alfvén speed and coronal magnetic-field strength. Simultaneous space-based observations of the solar corona from different vantage points, e.g. one from the Solar Dynamics Observatory (SDO) and the second from the Solar TErrestrial RElations Observatory (STEREO), have permitted the reconstruction of the geometry of coronal loops. Nisticò, Verwichte, and Nakariakov (Entropy15, 4520, 2013) proposed a method based on principal component analysis for fitting an ensemble of 3D points that sample a coronal loop. This method was shown to retrieve easily the main geometric parameters that define a loop, such as the loop axes and the loop plane. In this article, an extension of that work is presented that includes a Python tool for performing geometric triangulation of coronal features seen by two different observers. [ABSTRACT FROM AUTHOR]

Published
2023
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3. Geomagnetically induced currents (GICs) during strong geomagnetic activity (storms, substorms, and magnetic pulsations) on 23–24 April 2023.

Author

Despirak, Irina, Setsko, Pavel, Lubchich, Andris, Hajra, Rajkumar, Sakharov, Yaroslav, Lakhina, Gurbax, Selivanov, Vasiliy, and Tsurutani, Bruce Tsatnam

Subjects
*SOLAR wind, *INTERPLANETARY magnetic fields, *MAGNETIC storms, *GEOMAGNETISM, *SPACE environment, *CORONAL mass ejections, *ELECTRIC lines
Abstract

We analyzed intense geomagnetically induced currents (GICs) recorded during a complex space weather event observed on 23–24 April 2023. Two geomagnetic storms characterized by SYM/H intensities of −179 nT and −233 nT were caused by southward interplanetary magnetic field (IMF) Bz component of −25 nT in the sheath fields, and −33 nT in the magnetic cloud (MC) fields, respectively. GIC observations were divided into two local time sectors: nighttime (1700–2400 UT on 23 April) GICs observed during the interplanetary sheath magnetic storm, and morning sector (0200–0700 UT on 24 April) GICs observed during the MC magnetic storm. By using the direct measurements of GICs on several substations of Karelian-Kola power line (located in the north-west portion of Russia) and gas pipeline station near Mäntsälä (south of Finland), we managed to trace the meridional profile of GIC increases at different latitudes. It was shown that the night sector GIC intensifications (∼18–42 A) occurred in accordance with poleward expansion of the westward electrojet during a substorm. On the other hand, the intense morning sector GICs (∼12–46 A) were caused by Ps 6 magnetic pulsations. In addition, a strong local morning GIC (∼44 A) was associated with a local substorm-like disturbance caused by a high-density solar wind structure, possibly a coronal loop portion of an interplanetary coronal mass ejection. • Intense GICs (∼12–46A) detected during two magnetic storms on 23–24 April 2023. • Night sector GIC bursts occurred in accordance with substorm expansion. • GIC bursts in the morning sector were caused by Ps6 magnetic pulsations. • Maximal GIC was associated with the local substorm-like intensification caused by coronal loop portion of an ICME. • This is the first time that a coronal loop has been shown to be geoeffective. [ABSTRACT FROM AUTHOR]

Published
2024
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10. MHD Turbulence

Author

Chiuderi, Claudio, Velli, Marco, Cini, Michele, Series editor, Ferrari, Attilio, Series editor, Forte, Stefano, Series editor, Inguscio, Massimo, Series editor, Montagna, Guido, Series editor, Nicrosini, Oreste, Series editor, Peliti, Luca, Series editor, Rotondi, Alberto, Series editor, Chiuderi, Claudio, and Velli, Marco

Published
2015
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12. Preface

Author

Mansour, Nagi N., Kosovichev, Alexander G., Komm, Rudolf, Longcope, Dana, Leibacher, John W., Mansour, Nagi N., editor, Kosovichev, Alexander G., editor, Komm, Rudolf, editor, and Longcope, Dana, editor

Published
2014
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13. Waves in the Sun

Author

Narayanan, A. Satya, Börner, G., Series editor, Burkert, A., Series editor, Burton, W. B., Series editor, Dopita, M. A., Series editor, Eckart, A., Series editor, Grebel, E. K., Series editor, Leibundgut, B., Series editor, Maeder, A., Series editor, Trimble, V., Series editor, and Narayanan, A. Satya

Published
2013
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19. Coronal Heating

Author

Hood, Alan William, Garcia, Paulo Jorge Valente, editor, and Ferreira, Joao Miguel, editor

Published
2010
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22. Our Violent Sun

Author

Lang, Kenneth R., Börner, G., editor, Burkert, A., editor, Burton, W. B., editor, Dopita, M. A., editor, Eckart, A., editor, Encrenaz, T., editor, Grebel, E. K., editor, Leibundgut, B., editor, Lequeux, J., editor, Maeder, A., editor, Trimble, V., editor, and Lang, Kenneth R.

Published
2009
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23. Instruments for a Revolution

Author

Lang, Kenneth R., Börner, G., editor, Burkert, A., editor, Burton, W. B., editor, Dopita, M. A., editor, Eckart, A., editor, Encrenaz, T., editor, Grebel, E. K., editor, Leibundgut, B., editor, Lequeux, J., editor, Maeder, A., editor, Trimble, V., editor, and Lang, Kenneth R.

Published
2009
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25. Pulsating Solar Radio Emission

Author

Nindos, Alexander, Aurass, Henry, Beig, R., editor, Beiglböck, W., editor, Domcke, W., editor, Englert, B.-G., editor, Frisch, U., editor, Hänggi, P., editor, Hasinger, G., editor, Hepp, K., editor, Hillebrandt, W., editor, Imboden, D., editor, Jaffe, R. L., editor, Lipowsky, R., editor, Löhneysen, H.v., editor, Ojima, I., editor, Sornette, D., editor, Theisen, S., editor, Weise, W., editor, Wess, J., editor, Zittartz, J., editor, Klein, Karl-Ludwig, editor, and MacKinnon, Alexander L., editor

Published
2007
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26. Quasi-periodic Pulsations as a Diagnostic Tool for Coronal Plasma Parameters

Author

Nakariakov, V. M., Stepanov, A. V, Beig, R., editor, Beiglböck, W., editor, Domcke, W., editor, Englert, B.-G., editor, Frisch, U., editor, Hänggi, P., editor, Hasinger, G., editor, Hepp, K., editor, Hillebrandt, W., editor, Imboden, D., editor, Jaffe, R. L., editor, Lipowsky, R., editor, Löhneysen, H.v., editor, Ojima, I., editor, Sornette, D., editor, Theisen, S., editor, Weise, W., editor, Wess, J., editor, Zittartz, J., editor, Klein, Karl-Ludwig, editor, and MacKinnon, Alexander L., editor

Published
2007
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28. OUR MAGNETIC SUN

Author

Priest, E.R., Del Toro Iniesta, J.C., editor, Alfaro, E.J., editor, Gorgas, J.G., editor, Salvador-Solé, E., editor, and Butcher, H., editor

Published
2006
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30. Physics of 'Hot' Plasmas

Author

Zohm, H., Beig, R., editor, Beiglböck, W., editor, Domcke, W., editor, Englert, B.-G., editor, Frisch, U., editor, Hänggi, P., editor, Hasinger, G., editor, Hepp, K., editor, Hillebrandt, W., editor, Imboden, D., editor, Jaffe, R. L., editor, Lipowsky, R., editor, Löhneysen, H. v., editor, Ojima, I., editor, Sornette, D., editor, Theisen, S., editor, Weise, W., editor, Wess, J., editor, Zittartz, J., editor, Dinklage, Andreas, editor, Klinger, Thomas, editor, Marx, Gerrit, editor, and Schweikhard, Lutz, editor

Published
2005
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43. The Solar Corona

Author

Dwivedi, B. N., Beig, R., editor, Englert, B. -G., editor, Frisch, U., editor, Hänggi, P., editor, Hepp, K., editor, Hillebrandt, W., editor, Imboden, D., editor, Jaffe, R. L., editor, Lipowsky, R., editor, v. Löhneysen, H., editor, Ojima, I., editor, Sornette, D., editor, Theisen, S., editor, Weise, W., editor, Wess, J., editor, Zittartz, J., editor, Antia, H. M., editor, Bhatnagar, Arvind, editor, and Ulmschneider, Peter, editor

Published
2003
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44. Coronal Heating and Reduced MHD

Author

Oughton, Sean, Dmitruk, Pablo, Matthaeus, William H., Beig, R., editor, Englert, B. -G., editor, Frisch, U., editor, Hänggi, P., editor, Hepp, K., editor, Hillebrandt, W., editor, Imboden, D., editor, Jaffe, R. L., editor, Lipowsky, R., editor, Löhneysen, H. v., editor, Ojima, I., editor, Sornette, D., editor, Theisen, S., editor, Weise, W., editor, Wess, J., editor, Zittartz, J., editor, Falgarone, Edith, editor, and Passot, Thierry, editor

Published
2003
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45. Analytical Model of a Magnetopause in a Multicomponent Collisionless Plasma with a Kappa Energy Distribution of Particles

Author

Vitaly V. Kocharovsky, A. A. Nechaev, and Vl. V. Kocharovsky

Subjects
Physics, Gyroradius, Computational Mechanics, General Physics and Astronomy, 02 engineering and technology, Coronal loop, Plasma, Electron, 01 natural sciences, 010305 fluids & plasmas, Computational physics, Magnetic field, Solar wind, Current sheet, 020303 mechanical engineering & transports, 0203 mechanical engineering, Physics::Plasma Physics, Mechanics of Materials, Physics::Space Physics, 0103 physical sciences, Magnetopause
Abstract

We propose an analytical model for a distributed current sheet with a variable profile that separates two regions of anisotropic collisionless plasma with different magnetic fields and different effective temperatures of the kappa energy distributions of electrons and ions. The model also admits the presence of several ion components with different effective temperatures and spatially separated localized countercurrents of each of these components. We demonstrate the change in the characteristics of the current sheet when going from a Maxwellian to a kappa distribution, which takes into account the presence of a power-law spectrum of energetic particles typical of a nonequilibrium magnetoactive plasma. The theory developed allows us to carry out for the first time analytical modeling of such current configurations in both laboratory and cosmic plasmas, e.g., in planetary magnetopauses, coronal loops, and stellar wind with magnetic clouds.

Published
2021

46. The dynamic magnetosphere of Swift J1818.0–1607

Author

Fernando Camilo, Simon Johnston, Matthew Bailes, Marcus E. Lower, and Ryan Shannon

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Physics, education.field_of_study, 010308 nuclear & particles physics, Linear polarization, Astrophysics::High Energy Astrophysical Phenomena, Population, FOS: Physical sciences, Magnetosphere, Astronomy and Astrophysics, Astrophysics, Coronal loop, Position angle, Magnetar, 01 natural sciences, Magnetic field, Pulsar, Space and Planetary Science, 0103 physical sciences, Astrophysics - High Energy Astrophysical Phenomena, education, 010303 astronomy & astrophysics
Abstract

Radio-loud magnetars display a wide variety of radio-pulse phenomenology seldom seen among the population of rotation-powered pulsars. Spectropolarimetry of the radio pulses from these objects has the potential to place constraints on their magnetic topology and unveil clues about the magnetar radio emission mechanism. Here we report on eight observations of the magnetar Swift J1818.0$-$1607 taken with the Parkes Ultra-Wideband Low receiver covering a wide frequency range from 0.7 to 4 GHz over a period of 5 months. The magnetar exhibits significant temporal profile evolution over this period, including the emergence of a new profile component with an inverted spectrum, two distinct types of radio emission mode switching, detected during two separate observations, and the appearance and disappearance of multiple polarization modes. These various phenomena are likely a result of ongoing reconfiguration of the plasma content and electric currents within the magnetosphere. Geometric fits to the linearly polarized position angle indicate we are viewing the magnetar at an angle of $\sim$99$^{\circ}$ from the spin axis, and its magnetic and rotation axes are misaligned by $\sim$112$^{\circ}$. While conducting these fits, we found the position angle swing had reversed direction on MJD 59062 compared to observations taken 15 days earlier and 12 days later. We speculate this phenomena may be evidence the radio emission from this magnetar originates from magnetic field lines associated with two co-located magnetic poles that are connected by a coronal loop., Comment: 13 pages, 10 figures, 4 tables. Accepted to MNRAS

Published
2020

47. Coronal Loops and Optical Radiation from Flaring Stars

Author

Z. S. Akhtemov, Yu. T. Tsap, Yu. G. Kopylova, V. M. Malashchuk, and Alexander V. Stepanov

Subjects
Physics, 010504 meteorology & atmospheric sciences, Astrophysics::High Energy Astrophysical Phenomena, Continuum (design consultancy), Astrophysics, Coronal loop, 01 natural sciences, Standard Model, law.invention, Atmosphere, Stars, Geophysics, Space and Planetary Science, law, Physics::Space Physics, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Optical radiation, Astrophysics::Earth and Planetary Astrophysics, Irradiation, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences, Flare
Abstract

The possibility that large-scale coronal loops of solar-type stars and M dwarfs make a significant contribution to the white-light continuum emission is considered. It is shown that that the existence of high-density (>1012 cm–3) coronal loops contradicts the standard model of solar and stellar flares. As a result, the optical flare emission cannot be determined by free–free or free–bound processes within loops. The contribution from the lower atmosphere, which is heated beneath the loops due to the irradiation of soft X-ray emission, should be also negligible. The possible alternative scenarios are discussed.

Published
2020

48. Kink Oscillations of Coronal Loops with a Longitudinal Electric Current

Author

S. B. Derteev, B. B. Mikhalyaev, N. K. Shividov, and Lyudmila Naranovna Dzhimbeeva

Subjects
Physics, 010504 meteorology & atmospheric sciences, Shell (structure), Coronal loop, 01 natural sciences, Magnetic tube, Loop (topology), Geophysics, Space and Planetary Science, Quantum electrodynamics, 0103 physical sciences, Tube (fluid conveyance), Electric current, Dispersion (water waves), 010303 astronomy & astrophysics, Energy (signal processing), 0105 earth and related environmental sciences
Abstract

Oscillations of coronal loops with electric currents from one base to another are studied. The energy of longitudinal currents can be a source of energy for loop flares (Alfven and Carlqvist, 1967). A simplified model of a loop in the form of a composite cylindrical magnetic tube containing a shell with a potential azimuthal magnetic field is considered for the theoretical study of oscillations of loops with longitudinal currents. The dispersion features of the tube natural kink oscillations are considered based on numerical calculations.

Published
2020

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