Conditions for electron-cyclotron maser emission in the solar corona

Morosan, Diana; Zucca, Pietro; Bloomfield, D. Shaun; Gallagher, Peter T.

doi:10.1051/0004-6361/201628392

Cited by 43 publications

(48 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The J-burst components observed by LOFAR (F1, F2 and H2) at frequencies below 90 MHz were imaged using LOFAR tied-array imaging described in Morosan et al (2014Morosan et al ( , 2015. The higher frequency components (>140 MHz) of the J-burst were imaged using the NRH.…”

Section: J-burst Characteristicsmentioning

confidence: 99%

The association of aJ-burst with a solar jet

Morosan

Gallagher

Fallows

et al. 2017

A&A

Self Cite

View full text Add to dashboard Cite

Context. The Sun is an active star that produces large-scale energetic events such as solar flares and coronal mass ejections and numerous smaller-scale events such as solar jets. These events are often associated with accelerated particles that can cause emission at radio wavelengths. The reconfiguration of the solar magnetic field in the corona is believed to be the cause of the majority of solar energetic events and accelerated particles. Aims. Here, we investigate a bright J-burst that was associated with a solar jet and the possible emission mechanism causing these two phenomena. Methods. We used data from the Solar Dynamics Observatory (SDO) to observe a solar jet, and radio data from the Low Frequency Array (LOFAR) and the Nançay Radioheliograph (NRH) to observe a J-burst over a broad frequency range (33-173 MHz) on 9 July 2013 at ∼11:06 UT. Results. The J-burst showed fundamental and harmonic components and it was associated with a solar jet observed at extreme ultraviolet wavelengths with SDO. The solar jet occurred at a time and location coincident with the radio burst, in the northern hemisphere, and not inside a group of complex active regions in the southern hemisphere. The jet occurred in the negative polarity region of an area of bipolar plage. Newly emerged positive flux in this region appeared to be the trigger of the jet. Conclusions. Magnetic reconnection between the overlying coronal field lines and the newly emerged positive field lines is most likely the cause of the solar jet. Radio imaging provides a clear association between the jet and the J-burst which shows the path of the accelerated electrons. These electrons travelled from a region in the vicinity of the solar jet along closed magnetic field lines up to the top of a closed magnetic loop at a height of ∼360 Mm. Such small-scale complex eruptive events arising due to magnetic reconnection could facilitate accelerated electrons continuously to produce the large numbers of Type III bursts observed at low frequencies, in a similar way to the J-burst analysed here.

show abstract

Section: J-burst Characteristicsmentioning

confidence: 99%

The association of aJ-burst with a solar jet

Morosan

Gallagher

Fallows

et al. 2017

A&A

Self Cite

View full text Add to dashboard Cite

show abstract

“…Moreover, Zhao et al (2013) have developed a theory to explain the Type I radio burst with the ECM mechanism, which is also a long-duration continuum. In addition, Morosan et al (2016) showed that close to active regions, the ECM emission mechanism might dominate the plasma emission. This supports our conclusion.…”

Section: Conclusion and Discussionmentioning

confidence: 99%

A Solar Stationary Type IV Radio Burst and Its Radiation Mechanism

et al. 2018

View full text Add to dashboard Cite

A stationary Type IV (IVs) radio burst was observed on September 24, 2011. Observations from the Nançay RadioHeliograph (NRH) show that the brightness temperature (T B ) of this burst is extremely high, over 10 11 K at 150 MHz and over 10 8 K in general. The degree of circular polarization (q) is between −60% ∼ −100%, which means that it is highly left-handed circularly polarized. The flux-frequency spectrum follows a power-law distribution, and the spectral index is considered to be roughly −3 ∼ −4 throughout the IVs. Radio sources of this event are located in the wake of the coronal mass ejection and are spatially dispersed. They line up to present a formation in which lower-frequency sources are higher. Based on these observations, it is suggested that the IVs was generated through electron cyclotron maser emission.

show abstract

“…This active region group was shown to be associated with the occurrence of solar S bursts [Morosan et al, 2016]…”

Section: Figure 3: Drift Rate As a Function Of Frequency For Solar S mentioning

confidence: 97%

“…We constructed a map of the electron densities to determine ω p (Equation (2)) and a map of the magnetic field strength to determine Ω e (Equation (3)) above this active region in order to determine if ECM emission was likely to occur instead of plasma emission [Morosan et al, 2016]. We used the method of Zucca et al [2014] to calculate the off-limb electron densities in the corona up to a height of 2.5 solar radii (R ), where 1 R is 695 Mm (see Zucca et al [2014] for further details).…”

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

confidence: 99%

“…We used the PFSS solution from 4 July 2013 when the active region was not as close to the limb to extract the longitudinal slice through the active region that is equivalent to the Earthviewed plane-of-sky on 1 July 2013 [Morosan et al, 2016]. This was necessary as the photospheric magnetic field is only accurately represented in the PFSS bottom boundary when the active region is not located close to the east limb (owing to the transition from the flux-transported surface field on the unobserved hemisphere to the observed field on the Earth-facing hemisphere).…”

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

confidence: 99%

See 1 more Smart Citation

Characteristics of type III radio bursts and solar S bursts

Morosan¹,

Gallagher²

2018

Planetary Radio Emissions Viii

View full text Add to dashboard Cite

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.

show abstract

Conditions for electron-cyclotron maser emission in the solar corona

Cited by 43 publications

References 23 publications

The association of aJ-burst with a solar jet

The association of aJ-burst with a solar jet

A Solar Stationary Type IV Radio Burst and Its Radiation Mechanism

Characteristics of type III radio bursts and solar S bursts

Contact Info

Product

Resources

About