Hard X-Rays Associated with Type III Radio Bursts

Coronal jets represent important manifestations of ubiquitous solar transients, which may be the source of significant mass and energy input to the upper solar atmosphere and the solar wind. While the energy involved in a jet-like event is smaller than that of "nominal" solar flares and coronal mass ejections (CMEs), jets share many common properties with these phenomena, in particular, the explosive magnetically driven dynamics. Studies of jets could, therefore, provide critical insight for understanding the larger, more complex drivers of the solar activity. On the other side of the size-spectrum, the study of jets could also supply important clues on the physics of transients close or at the limit of the current spatial resolution such as spicules. Furthermore, jet phenomena may hint to basic process for heating the corona and accelerating the solar wind; consequently their study gives us the opportunity to attack a broad range of solar-heliospheric problems.Comment: 53 pages, 24 figure

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“…6), which is suggestive of the important role of magnetic reconnection in generating both phenomena. Christe et al (2008).…”

Section: Rhessi Observationsmentioning

confidence: 99%

Solar Coronal Jets: Observations, Theory, and Modeling

et al. 2016

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“…The very low energies of impulsive event electrons (typically ∼1 keV but sometimes reaching ∼0.1 keV) suggests that the acceleration may be occurring high in the corona (Lin et al 1995), thus these events are often referred to as "coronal flares" (Lin 1985). RHESSI (with attenuators out) has detected very weak 3-15 keV X-ray bursts in coincidence with type-III radio bursts (Christe et al 2008), suggesting a coronal explosion. Associations with jets observed in EUV that occur close to a coronal hole boundary (Wang et al 2006), and with fast (≥600 km s −1 ) narrow (≤20 • ) CMEs (Kahler et al 2001;Haggerty and Roelof 2002;Wang et al 2011) have also been reported.…”

Section: Flares and Impulsive Sepsmentioning

confidence: 99%

Energy Release and Particle Acceleration in Flares: Summary and Future Prospects

Lin

2011

Space Sci Rev

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RHESSI measurements relevant to the fundamental processes of energy release and particle acceleration in flares are summarized. RHESSI's precise measurements of hard X-ray continuum spectra enable model-independent deconvolution to obtain the parent electron spectrum. Taking into account the effects of albedo, these show that the low energy cut-off to the electron power-law spectrum is typically tens of keV, confirming that the accelerated electrons contain a large fraction of the energy released in flares. RHESSI has detected a high coronal hard X-ray source that is filled with accelerated electrons whose energy density is comparable to the magnetic-field energy density. This suggests an efficient conversion of energy, previously stored in the magnetic field, into the bulk acceleration of electrons. A new, collisionless (Hall) magnetic reconnection process has been identified through theory and simulations, and directly observed in space and in the laboratory; it should occur in the solar corona as well, with a reconnection rate fast enough for the energy release in flares. The reconnection process could result in the formation of multiple elongated magnetic islands, that then collapse to bulk-accelerate the electrons, rapidly enough to produce the observed hard X-ray emissions. RHESSI's pioneering γ -ray line imaging of energetic ions, revealing footpoints straddling a flare loop arcade, has provided strong evidence that ion acceleration is also related to magnetic reconnection. Flare particle acceleration is shown to have a close relationship to impulsive Solar Energetic Particle (SEP) events observed in the interplanetary medium, and also to both fast coronal mass ejections and gradual SEP events. New instrumentation to provide the high sensitivity and wide dynamic range hard X-ray and γ -ray measurements, plus energetic neutral atom (ENA) imaging of SEPs above ∼2 R , will enable the next great leap forward in understanding particle acceleration and energy release is large solar eruptions-solar flares and associated fast coronal mass ejections (CMEs).

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“…Observations show that in active regions during flares the temperature T h is greater than ∼10 MK and can reach up to ∼50 MK [ Lin , 1974; Benz , 1993; Aschwanden et al , 1995; Feldman et al , 1996; Christe et al , 2008]. We investigate here the effects of varying T h on remote type III emission.…”

Section: Effects Of Varying Electron Heating Parametersmentioning

confidence: 99%

Simulations of coronal type III solar radio bursts: 3. Effects of beam and coronal parameters

Cairns

Robinson

2009

J. Geophys. Res.

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[1] A recently developed simulation model is used to investigate the effects of varying the coronal and electron heating conditions on the dynamic spectra of coronal type III bursts (70-370 MHz) observed at Earth. The flux of 2f p emission is significantly higher than that of f p emission, which is unlikely to be observable except under very favorable propagation conditions. Moreover, the 2f p emission is unlikely to continue into the solar wind, although some bursts are very strong and will extend into the upper corona with lower frequencies than simulated, consistent qualitatively with observations. The flux and brightness temperature of 2f p emission are affected significantly by variations in the parameters, while the frequency drift rate and half-power duration are affected only weakly. Further, the simulations confirm the standard interpretation of the drift rate of 2f p emission in terms of the plasma density profile and a characteristic beam speed that agrees quantitatively with the simulated beam dynamics for wide ranges of coronal and heating conditions. For weak heating events or events with high coronal electron temperature, the remote radiation shows characteristics that agree quantitatively with microbursts. When the heating is even weaker and/or the electron temperature is even higher, the heating events are radio quiet, consistent qualitatively with hard X-ray observations. For similar heating originating in similar frequency ranges, different density models yield quantitatively similar results except for the drift rate. Variations of the levels of a given density profile, corresponding to background corona or coronal streamers, can also cause significant changes in spectral characteristics.

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Hard X-Rays Associated with Type III Radio Bursts

Cited by 28 publications

References 28 publications

Solar Coronal Jets: Observations, Theory, and Modeling

Solar Coronal Jets: Observations, Theory, and Modeling

Energy Release and Particle Acceleration in Flares: Summary and Future Prospects

Simulations of coronal type III solar radio bursts: 3. Effects of beam and coronal parameters

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