Collective radio-emission from plasmas

Papadopoulos, K.; Freund, H. P.

doi:10.1007/bf00172213

Cited by 20 publications

(7 citation statements)

References 35 publications

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“…Previous theoretical works have shown that localized electrostatic wave packets can emit electromagnetic radiation much like a transmitting antenna [ Papadopoulos and Freund , 1979; Pottelette et al , 1992]. Eigenmode modulated Langmuir waves therefore possess a potential mechanism for generating radiation at the local plasma frequency and its harmonics.…”

Section: Discussionmentioning

confidence: 99%

“…[39] Previous theoretical works have shown that localized electrostatic wave packets can emit electromagnetic radiation much like a transmitting antenna [Papadopoulos and Freund, 1979;Pottelette et al, 1992]. Eigenmode modulated Langmuir waves therefore possess a potential Figure 1d (Langmuir wave observed on 22 January 2007 13:07:23.424 UT rotated into a magnetic field-aligned coordinate system) into planes parallel and perpendicular to the magnetic field in the same format as Figures 2b-2d.…”

Section: Discussionmentioning

confidence: 99%

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Observations of three‐dimensional Langmuir wave structure

Malaspina

Ergun

2008

J. Geophys. Res.

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[1] Measurements of the three-dimensional structure of solar wind Langmuir waves made by the STEREO spacecraft are presented. Langmuir wave structure is studied using hodograms classified as one-, two-, or three-dimensional. Multi-dimensional Langmuir waves are both less-often observed than one-dimensional events and clustered in time. These observations show that a minority of Langmuir waves have electric fields transverse to the local magnetic field direction. We present a new explanation for this transverse structure based on an interpretation of Langmuir waves as eigenmodes of solar wind density cavities. These new observations are compared with previous theories for transverse wave structure and the eigenmode interpretation is found to be consistent with STEREO observations.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Observations of three‐dimensional Langmuir wave structure

Malaspina

Ergun

2008

J. Geophys. Res.

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“…Efficient conversion of electrostatic (es) plasma waves to electromagnetic (em) near the plasma frequency is a basic plasma physics problem with relevance to astrophysics [1,2]. The conversion is due either to breakdown of geometric optics in the presence of a sharp index of refraction gradients, especially near boundaries, or due to nonlinear interaction of electrostatic plasma waves with ion or electron density fluctuations.…”

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confidence: 99%

“…The conversion is due either to breakdown of geometric optics in the presence of a sharp index of refraction gradients, especially near boundaries, or due to nonlinear interaction of electrostatic plasma waves with ion or electron density fluctuations. As discussed in several reviews [1,2], the conversion efficiency of these processes is very small. An often quoted process, by which em wave frequencies can be up-shifted, relies on reflection of an em wave ͑v o , k o ͒ incident upon an over-dense ͑v o ø v e ͒ plasma front moving with relativistic speed U.…”

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confidence: 99%

Conversion of Electrostatic to Electromagnetic Waves by Superluminous Ionization Fronts

2001

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The conversion of static electric fields to electromagnetic radiation by the incidence of a superluminous ionization front on plasma is investigated. For extremely superluminous fronts, the radiation is close to the plasma frequency and is converted with efficiency of order unity. A proof-of-principle experiment was conducted using semiconductor plasma containing an alternately charged capacitor array. The process has important implications in astrophysical plasmas, such as supernova emission, and to laboratory development of compact, coherent, tunable radiation sources in the THz range.

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“…The electric field associated with the skin current in the loop can Papadopoulos et al 1977;Haber et al 1978). Electrons with velocity ν < ν < v.. will precipitate but without any hard X-ray signature, since the hard X-ray flux is below the sensitivity of all current instruments.…”

Section: Runaway Electrons and Their Dynamic Evolutionmentioning

confidence: 99%

Plasma Properties and Radiation Signatures of Current Driven Active Region Loops on the Sun

Βλαχοσ¹

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Our present understanding of the various phenomena taking place in the Sun's atmosphere has radically changed over the past few years.Recent observations, primarily from Skylab, have confirmed the existence of small scale structures which in turn have put severe constraints on the homogeneous plain parallel models of the Sun's atmosphere traditionally used to analyze the observations. It is now generally accepted that the small scale magnetic fields are responsible for these structures. Generally speaking, three types of regions can be identified on the Sun depending on the dominant magnetic field structure, i.e. the coronal holes, where the magnetic field lines are open; the "quiet sun" regions where the magnetic field lines are diffuse, irregular and weak; and the active regions, which are characterized by strong closed magnetic field structures.We usually identify as loops the magnetic field structures connecting opposite magnetic polarities in the photosphere. The average plasma density in the coronal part of the loop is higher than in its surroundings but the ratio of the plasma kinetic pressure to magnetic pressure is less than one. These loop-like magnetic field lines may act as the energy transport lines from the internal layers of the Sun's photosphere to the chromosphere and the corona where the energy is stored and suddenly released or slowly dissipated.We focus our studies at the photospheric disturbances which are associated with steady currents along the potential magnetic field lines. CHAPTER I: ACTIVE REGION OVERVIEW 1 1. Introduction 2 2. The Origin and Role of the Small Scale Magnetic Fields on the Sun 9 3. Photospheric Motions and Current Generation Mechanisms in Closed Loops 4. A Magnetic Model for Complex Active Region

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Collective radio-emission from plasmas

Cited by 20 publications

References 35 publications

Observations of three‐dimensional Langmuir wave structure

Observations of three‐dimensional Langmuir wave structure

Conversion of Electrostatic to Electromagnetic Waves by Superluminous Ionization Fronts

Plasma Properties and Radiation Signatures of Current Driven Active Region Loops on the Sun

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