A new approach to the maser emission in the solar corona

Régnier, Stéphane

doi:10.1051/0004-6361/201425346

Cited by 23 publications

(24 citation statements)

References 22 publications

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“…ECM emission is a possible emission mechanism in the solar corona, but only at heights below 1.1 R in the active region studied. These results agree with Régnier et al [2015], where estimates of the ω p /Ω e ratio showed that ECM is possible at heights up to 1.2 R based on a sample of four active regions.…”

Section: The Location Of the Active Region Noaa 11785 On The Limb (supporting

confidence: 90%

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Characteristics of type III radio bursts and solar S bursts

Morosan¹,

Gallagher²

2018

Planetary Radio Emissions Viii

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The Sun is an active source of radio emission which is often associated with the acceleration of electrons arising from processes such as solar flares and coronal mass ejections (CMEs). At low radio frequencies (<100 MHz), numerous solar S bursts (where S stands for short) and storms of type III radio bursts have been observed, that are not directly relates to flares and CMEs. Here, we expand our understanding on the spectral characteristic of these two different types of radio bursts based on observations from the Low Frequency Array (LOFAR). On 9 July 2013, over 3000 solar S bursts accompanied by over 800 type III radio bursts were observed over a time period of ∼8 hours. The characteristics of type III radio bursts presented here are consistent with previous studies. S bursts are shown to be different compared to type III bursts: they show narrow bandwidths, short durations and drift rates of about 1/2 the drift rate of type III bursts. Both type III bursts and solar S bursts occur in a region in the corona where plasma emission is the dominant emission mechanism as determined by data constrained density and magnetic field models.

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Section: The Location Of the Active Region Noaa 11785 On The Limb (supporting

confidence: 90%

“…Each beam produces a high time and frequency resolution dynamic spectrum (∼10 ms; 12.5 kHz) at a unique spatial location as shown in Figure 1b and 1c. The dynamic spectra can be used to produce tied-array images of radio bursts that can give an approximate position of radio sources (for more details see Morosan et al [2014;2015]). …”

Section: Observationsmentioning

confidence: 99%

Characteristics of type III radio bursts and solar S bursts

Morosan¹,

Gallagher²

2018

Planetary Radio Emissions Viii

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“…The moving Type IV burst presented here starts its outward movement at 1.15 R , higher than the heights predicted by Régnier (2015) and Morosan et al (2016). Stupp (2000) proposed that the ratio ω p /Ω e can be as high as 2 for o-and x-mode emission, in which case it is possible for ECM to occur at greater heights in the corona.…”

Section: Second Component Of the Type IV Burstmentioning

confidence: 48%

Variable emission mechanism of a Type IV radio burst

Morosan

Kilpua

Carley

et al. 2019

A&A

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Context. The Sun is an active star and the source of the largest explosions in the solar system, such as flares and coronal mass ejections (CMEs). Flares and CMEs are powerful particle accelerators that can generate radio emission through various emission mechanisms. Aims. CMEs are often accompanied by Type IV radio bursts that are observed as continuum emission in dynamic spectra at decimetric and metric wavelengths, but their emission mechanism can vary from event to event. Here, we aim to determine the emission mechanism of a complex Type IV burst that accompanied the flare and CME on 22 September 2011.Methods. We used radio imaging from the Nançay Radioheliograph, spectroscopic data from the e-Callisto network, ARTEMIS, Ondrejov, and Phoenix3 spectrometers combined with extreme-ultraviolet observations from NASA's Solar Dynamic Observatory to analyse the Type IV radio burst and determine its emission mechanism. Results. We show that the emission mechanism of the Type IV radio burst changes over time. We identified two components in the Type IV radio burst: an earlier stationary Type IV showing gyro-synchrotron behaviour, and a later moving Type IV burst covering the same frequency band. This second component has a coherent emission mechanism. Fundamental plasma emission and the electroncyclotron maser emission are further investigated as possible emission mechanisms for the generation of the moving Type IV burst. Conclusions. Type IV bursts are therefore complex radio bursts, where multiple emission mechanisms can contribute to the generation of the wide-band continuum observed in dynamic spectra. Imaging spectroscopy over a wide frequency band is necessary to determine the emission mechanisms of Type IV bursts that are observed in dynamic spectra.

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“…They found that the LOmode dominates as harmonic modes are approached, resulting in emission angles corresponding to maximum growth, θ max < 15 • , that are therefore nearly aligned with the magnetic field. Régnier (2015) simulated the plasma emission properties of the solar corona above active regions using force-free models of the magnetic field together with hydrostatic models of the plasma. Similarly, he found that while the RX-mode dominates for ω p /Ω ≤ 0.35, LO-mode dominates for 0.35 ≤ ω p /Ω ≤ 1.…”

Section: J0607+24 Orientation Considerationsmentioning

confidence: 99%

Is WISEP J060738.65+242953.4 Really a Magnetically Active, Pole-on L Dwarf?

Route

2017

ApJ

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The interplay of rotation and manifested magnetic activity on ultracool dwarfs (UCDs) is of key importance for gathering clues as to the operation of the dynamos within these objects. A number of magnetized UCDs host kG-strength magnetic fields. It was recently reported that the L8 dwarf WISEP J060738.65+242953.4 is a radio-emitting UCD that is likely observed pole-on, due to its lack of photometric variability and narrow spectral lines. Follow-up radio observations at Arecibo Observatory, together with careful analysis of previously published details, however, suggest that the scientific and statistical significance of the radio and spectroscopic data have been overstated. If the UCD is observed along its aligned spin/magnetic axis, the absence of observed Hα activity may present challenges to the auroral model of UCD magnetism, although short or long-term cyclic magnetic activity may explain this behavior. Monte Carlo simulations presented here suggest that the source probably rotates with v sin i=6-12 km s −1 , indicating that its inclination angle and rotational velocity are unexceptional and that its angular momentum has evolved as expected for brown dwarfs observed in ∼1 Myr-old clusters. The discovery and verification of the most rapidly and slowest rotating brown dwarfs place valuable constraints on the angular momentum evolution and magnetic activity history of these objects.

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A new approach to the maser emission in the solar corona

Cited by 23 publications

References 22 publications

Characteristics of type III radio bursts and solar S bursts

Characteristics of type III radio bursts and solar S bursts

Variable emission mechanism of a Type IV radio burst

Is WISEP J060738.65+242953.4 Really a Magnetically Active, Pole-on L Dwarf?

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