Characteristics of events with metric-to-decahectometric type II radio bursts associated with CMEs and flares in relation to SEP events

Prakash, Om; Li, Feng; Michałek, G.; Gan, Weiqun; Lu, Ling; Shanmugaraju, A.; Umapathy, Siva

doi:10.1007/s10509-017-3034-y

Cited by 11 publications

(11 citation statements)

References 73 publications

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“…The average height of Category 1 events is in fairly good agreement with the average shock formation heights found by Gopalswamy et al (2013) for 32 CMEs associated with metric type II bursts. On the other hand, the shock formation heights of Category 1 and 2 events are slightly lower than those reported by Prakash et al (2017) for metric type II bursts (1.58 R ) and for DH type II bursts (3.54 R ) associated with SEP events. Prakash et al (2017) determined the shock formation heights by back extrapolation of the CME heights assuming a constant CME speed.…”

Section: Proton Release Heightscontrasting

confidence: 65%

“…On the other hand, the shock formation heights of Category 1 and 2 events are slightly lower than those reported by Prakash et al (2017) for metric type II bursts (1.58 R ) and for DH type II bursts (3.54 R ) associated with SEP events. Prakash et al (2017) determined the shock formation heights by back extrapolation of the CME heights assuming a constant CME speed. Figure 8a showed a clear dependence of the proton intensity rise rate on the difference between the proton release time and type III onset time.…”

Section: Proton Release Heightscontrasting

confidence: 65%

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Properties of High-Energy Solar Particle Events Associated with Solar Radio Emissions

2019

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We have analysed 58 high-energy proton events and 36 temporally related nearrelativistic electron events from the years 1997 -2015 for which the velocity dispersion analysis of the first-arriving particles gave the apparent path lengths between 1 and 3 AU. We investigated the dependence of the characteristics of the proton events on the associations of type II, III, and IV radio bursts. We also examined the properties of the soft X-ray flares and coronal mass ejections associated with these events. All proton events were associated with decametric type III radio bursts, while type IV emission was observed only in the meter wavelengths in some of the events (32/58). Almost all proton events (56/58) were associated with radio type II bursts: 11 with metric (m) type II only, 11 with decametrichectometric (DH) only, and 34 with type II radio bursts at both wavelength ranges. By examining several characteristics of the proton events, we discovered that the proton events can be divided into two categories. The characteristics of events belonging to the same category were similar, while they significantly differed between events in different categories. The distinctive factors between the categories were the wavelength range of the associated type II radio emission and the temporal relation of the proton release with respect to the type II onset. In Category 1 are the events which were associated with only metric type II emission or both m and DH type II and the release time of protons was before the DH type II onset (18/56 events). Category 2 consists of the events which were associated with only DH type II emission or both m and DH type II and the protons were released at or after the DH type II onset (31/56 events). For seven of the 56 events we were not able to determine a definite category due to timing uncertainties. The events in Category 1 had significantly higher intensity rise rates, shorter rise times, lower release heights, and harder energy spectra than B D. Ameri dahame@utu.fi E. ValtonenCategory 2 events. Category 1 events also originated from magnetically well-connected regions and had only small time differences between the proton release times and the type III onsets. The soft X-ray flares for these events had significantly shorter rise times and durations than for Category 2 events. We found 36 electron events temporally related to the proton events, which fulfilled the same path length criterion as the proton events. We compared the release times of protons and electrons at the Sun, and discovered that in 19 of the 36 events protons were released almost simultaneously (within ± 7 minutes) with the electrons, in 16 events protons were released later than the electrons, and in one event electrons were released after the protons. The simultaneous proton and electron events and the delayed proton events did not unambiguously fall in the two categories of proton events, although most of the events in which the protons were released after the electrons belonged to Category 2. We conclude that acceleration ...

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Section: Proton Release Heightscontrasting

confidence: 65%

Section: Proton Release Heightscontrasting

confidence: 65%

Properties of High-Energy Solar Particle Events Associated with Solar Radio Emissions

2019

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“…This corresponds to a plasma frequency in the low corona of 1.6 GHz, and second harmonic of 3.2 GHz. However, most solar CMEs do not form shocks low in the corona, accelerating with height as Alfvén speed declines with height, enabling them to form shocks at heights of ∼ 1.3−2R * Prakash et al 2017). For now, to estimate plausible start frequencies for stellar Type II bursts, we consider the case where a shock forms at r = 2R * .…”

Section: Choice Of Frequency Bandsmentioning

confidence: 99%

Ultra-wideband Detection of 22 Coherent Radio Bursts on M Dwarfs

Villadsen

Hallinan

2019

ApJ

103

106

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Coherent radio bursts detected from M dwarfs have some analogy with solar radio bursts, but reach orders of magnitude higher luminosities. These events trace particle acceleration, powered by magnetic reconnection, shock fronts (such as formed by coronal mass ejections, CMEs), and magnetospheric currents, in some cases offering the only window into these processes in stellar atmospheres. We conducted a 58-hour, ultra-wideband survey for coherent radio bursts on 5 active M dwarfs. We used the Karl G. Jansky Very Large Array (VLA) to observe simultaneously in three frequency bands covering a subset of 224-482 MHz and 1-6 GHz, achieving the widest fractional bandwidth to date for any observations of stellar radio bursts. We detected 22 bursts across 13 epochs, providing the first large sample of wideband dynamic spectra of stellar coherent radio bursts. The observed bursts have diverse morphology, with durations ranging from seconds to hours, but all share strong (40-100%) circular polarization. No events resemble solar Type II bursts (often associated with CMEs), but we cannot rule out the occurrence of radio-quiet stellar CMEs. The hours-long bursts are all polarized in the sense of the x-mode of the star's large-scale magnetic field, suggesting they are cyclotron maser emission from electrons accelerated in the large-scale field, analogous to auroral processes on ultracool dwarfs. The duty cycle of luminous coherent bursts peaks at 25% at 1-1.4 GHz, declining at lower and higher frequencies, indicating source regions in the low corona. At these frequencies, active M dwarfs should be the most common galactic transient source.

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“…Scattering of data points in this plot indicated the involvement of other factors in the particle acceleration [38] [25] [13] [53]. Later many authors found that the peak intensity of SEPs correlated with both speed and width of the associated CMEs [36] [66] [25] [59] [15] [63]. Significant number of authors pointed out that duration of the solar flares is important parameter to predict the space weather events [9] [40] [69].…”

Section: Introductionmentioning

confidence: 99%

Statistical Characteristics on SEPs, Radio-Loud CMEs, Low Frequency Type II and Type III Radio Bursts Associated with Impulsive and Gradual Flares

Kalaivani¹,

Shanmugaraju²,

Prakash

et al. 2020

Earth Moon Planets

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We have statistically analyzed a set of 115 low frequency (Deca-Hectometer wavelengths range) type II and type III bursts associated with major Solar Energetic Particle (SEP: E p > 10 MeV) events and their solar causes such as solar flares and coronal mass ejections (CMEs) observed from 1997 to 2014. We classified them into two sets of events based on the duration of the associated solar flares:75 impulsive flares (duration < 60 min) and 40 gradual flares (duration > 60 min).On an average, the peak flux (integrated flux) of impulsive flares X2.9 (0.32 J m −2) is stronger than that of gradual flares M6.8 (0.24 J m −2). We found that impulsive flare-associated CMEs are highly decelerated with larger initial acceleration and they achieved their peak speed at lower heights (-27.66 m s −2 and 14.23 R o) than the gradual flare-associated CMEs (6.26 m s −2 and 15.30 R o), even though both sets of events have similar sky-plane speed (space speed) within LASCO field of view. The impulsive flare-associated SEP events (Rt = 989.23 min: 2.86 days) are

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Characteristics of events with metric-to-decahectometric type II radio bursts associated with CMEs and flares in relation to SEP events

Cited by 11 publications

References 73 publications

Properties of High-Energy Solar Particle Events Associated with Solar Radio Emissions

Properties of High-Energy Solar Particle Events Associated with Solar Radio Emissions

Ultra-wideband Detection of 22 Coherent Radio Bursts on M Dwarfs

Statistical Characteristics on SEPs, Radio-Loud CMEs, Low Frequency Type II and Type III Radio Bursts Associated with Impulsive and Gradual Flares

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