A shock associated (SA) radio event and related phenomena observed from the base of the solar corona to 1 AU

Bougeret, Jean‐Louis; Zarka, Philippe; Caroubalos, C.; Karlický, M.; Leblanc, Y.; Maroulis, Dimitris; Hillaris, A.; Moussas, X.; Alissandrakis, C. E.; Dumas, G.; Perche, C.

doi:10.1029/98gl50563

Cited by 48 publications

(31 citation statements)

References 22 publications

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“…Lowfrequency type III bursts starting at tens of MHz and lower have been attributed to both flare and shock accelerations. Of particular importance are the complex type III bursts (see e.g., Bougeret et al 1998) because of their association with large SEP events (Cane et al 2002;MacDowall et al 2003;Cliver and Ling 2009;Gopalswamy and Mäkelä 2010). Type II radio bursts are caused by electrons accelerated at the shock front and hence provide the earliest evidence for the presence of shocks in eruptive events.…”

Section: Overview Of Cycle 23 Eventsmentioning

confidence: 99%

“…The electrons responsible for these type III bursts were initially thought to be shock-accelerated (SA) (Cane et al 1981). Cane and Stone (1984) changed "shock-accelerated" to "shockassociated" to allow for the possibility that the electrons responsible for the type III bursts may not physically originate from the associated shock (see Bougeret et al 1998 for a recent discussion on the terminology). With the recent finding that such type III bursts can occur with no accompanying shock, the term "SA event" is questionable (Gopalswamy and Mäkelä 2010).…”

Section: Low-frequency Type III Bursts Associated With Glesmentioning

confidence: 99%

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Properties of Ground Level Enhancement Events and the Associated Solar Eruptions During Solar Cycle 23

et al. 2012

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Solar cycle 23 witnessed the most complete set of observations of coronal mass ejections (CMEs) associated with the Ground Level Enhancement (GLE) events. We present an overview of the observed properties of the GLEs and those of the two associated phenomena, viz., flares and CMEs, both being potential sources of particle acceleration. Although we do not find a striking correlation between the GLE intensity and the parameters of flares and CMEs, the solar eruptions are very intense involving X-class flares and extreme CME speeds (average ∼2000 km/s). An M7.1 flare and a 1200 km/s CME are the weakest events in the list of 16 GLE events. Most (80 %) of the CMEs are full halos with the three nonhalos having widths in the range 167 to 212 degrees. The active regions in which the GLE events originate are generally large: 1290 msh (median 1010 msh) compared to 934 msh (median: 790 msh) for SEP-producing active regions. For accurate estimation of the CME height at the time of metric type II onset and GLE particle release, we estimated the initial acceleration of the CMEs using flare and CME observations. The initial acceleration of GLE-associated CMEs is much larger (by a factor of 2) than that of ordinary CMEs (2.3 km/s 2 vs. 1 km/s 2 ). We confirmed the initial acceleration for two events for which CME measurements are available in the inner corona. The GLE particle release is delayed with respect to the onset of all electromagnetic signatures of the eruptions: type II bursts, low frequency type III bursts, soft X-ray flares and CMEs. The presence of metric type II radio bursts some 17 min (median: 16 min; range: 3 to 48 min) before the GLE onset indicates shock formation well before the particle release. The release of GLE particles occurs when the CMEs reach an average height of ∼3.09 R s (median: 3.18 R s ; range: 1.71 to 4.01 R s ) for well-connected events (source longitude in the range W20-W90). events, the average CME height at GLE particle release is ∼66 % larger (mean: 5.18 R s ; median: 4.61 R s ; range: 2.75-8.49 R s ). The longitudinal dependence is consistent with shock accelerations because the shocks from poorly connected events need to expand more to cross the field lines connecting to an Earth observer. On the other hand, the CME height at metric type II burst onset has no longitudinal dependence because electromagnetic signals do not require magnetic connectivity to the observer. For several events, the GLE particle release is very close to the time of first appearance of the CME in the coronagraphic field of view, so we independently confirmed the CME height at particle release. The CME height at metric type II burst onset is in the narrow range 1.29 to 1.8 R s , with mean and median values of 1.53 and 1.47 R s . The CME heights at metric type II burst onset and GLE particle release correspond to the minimum and maximum in the Alfvén speed profile. The increase in CME speed between these two heights suggests an increase in Alfvénic Mach number from 2 to 3. The CME heights at GLE particle r...

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Section: Overview Of Cycle 23 Eventsmentioning

confidence: 99%

Section: Low-frequency Type III Bursts Associated With Glesmentioning

confidence: 99%

Properties of Ground Level Enhancement Events and the Associated Solar Eruptions During Solar Cycle 23

et al. 2012

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“…So-called herringbone (HB) bursts (e.g. Cairns & Robinson 1987) and shock accelerated (SA) type III bursts (Cane 1981;Bougeret et al 1998) show clear evidence of shock accelerated electrons at energies ≤30 keV. The HB represent rapidly drifting (type III-like) fine structures emanating from type II lanes towards higher and lower frequencies.…”

Section: Introductionmentioning

confidence: 99%

“…The SA type III bursts also start from a type II, but contrary to HB the SA bursts extend into the IP medium and can be measured in situ by spaceborne radio receivers and electron detectors (e.g. Bougeret et al 1998;Dulk et al 2000). Both HB and SA bursts are usually interpreted as plasma emission arising from fast electron beams accelerated by shock waves (Roberts 1959).…”

Section: Introductionmentioning

confidence: 99%

Solar energetic electron events and coronal shocks

Klassen

Bothmer

Mann

et al. 2002

A&A

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Abstract. Mildly relativistic electrons appear during the solar energetic particle events. A detailed investigation on the origin of such electrons is presented for four particlular solar events. The mildly relativistic electrons have been detected at energies of 0.25-0.7 MeV by COSTEP/SOHO and below 0.392 MeV by Wind 3-DP experiments. Coronal shocks associated with these electron events are identified from the metric-to-decametric solar type II radio bursts. All selected events were associated with solar activity at western longitudes, so that the magnetic footpoints connecting the spacecraft with the Sun were close to the flare/shock/CME site. The associated type II bursts were accompanied by so-called shock accelerated (SA) type III bursts appearing to be emerging from the type II emission site. We found: (1) that all of the 0.25-0.7 MeV electron events were released during or after, but never simultaneously with the onset of type II bursts and CMEs. The time delay between the type II burst onset and the release of the mildly relativistic electrons is in the range of 11.5−45 min; (2) that the mildly relativistic electrons were released rather at the end of SA type III bursts or somewhat later; (3) that the mildly relativistic electrons were released when the associated type II burst and the CME reached a certain height (h ∼ 1-4 Rs) above the photosphere. For the four events studied, it is concluded that mildly relativistic electrons at 0.25-0.7 MeV energies measured in the interplanetary medium from solar energetic particle events are accelerated by coronal shock waves, commonly in association with white-light CMEs.

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“…This phenomenon seems to imply both related and distinct generation processes for QS bursts and MS or FS patterns. Although we do not yet have any theoretical explanation for it, we can simply notice that emergence of fine substructures from a broader emission pattern is known for solar Type II radio bursts, the emerging or forking structures being called "herringbones" (Bougeret et al 1998). In that case, accelerated electrons are thought to be produced in both directions from a shock moving away from the Sun through the solar corona and wind.…”

Section: Conclusion and Discussionmentioning

confidence: 99%

Fast and slow frequency-drifting millisecond bursts in Jovian decametric radio emissions

Ryabov

Zarka

Hess

et al. 2014

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We present an analysis of several Jovian Io-related decametric radio storms recorded in 2004−2012 at the Ukrainian array UTR-2 using the new generation of baseband digital receivers. Continuous baseband sampling within sessions lasting for several hours enabled us to study the evolution of multiscale spectral patterns during the whole storm at varying time and frequency resolutions and trace the temporal transformation of burst structures in unprecedented detail. In addition to the well-known frequency drifting millisecond patterns known as S bursts we detected two other classes of events that often look like S bursts at low resolution but reveal a more complicated structure in high resolution dynamic spectra. The emissions of the first type (LS bursts, superposition of L and S type emissions) have a much lower frequency drift rate than the usual quasi linearly drifting S bursts (QS) and often occur within a frequency band where L emission is simultaneously present, suggesting that both LS and at least part of L emissions may come from the same source. The bursts of the second type (modulated S bursts called MS) are formed by a wideband frequency-modulated envelope that can mimic S bursts with very steep negative (or even positive) drift rates. Observed with insufficient time-frequency resolution, MS look like S bursts with complex shapes and varying drifts; MS patterns often occur in association with (i) narrowband emission; (ii) S burst trains; or (iii) sequences of fast drift shadow events. We propose a phenomenological description for various types of S emissions, that should include at least three components: high-and low-frequency limitation of the overall frequency band of the emission, fast frequency modulation of emission structures within this band, and emergence of elementary S burst substructures, that we call "forking" structures. All together, these three components can produce most of the observed spectral structures, including S bursts with apparently very complex time-frequency structures.

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A shock associated (SA) radio event and related phenomena observed from the base of the solar corona to 1 AU

Cited by 48 publications

References 22 publications

Properties of Ground Level Enhancement Events and the Associated Solar Eruptions During Solar Cycle 23

Properties of Ground Level Enhancement Events and the Associated Solar Eruptions During Solar Cycle 23

Solar energetic electron events and coronal shocks

Fast and slow frequency-drifting millisecond bursts in Jovian decametric radio emissions

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