Catalogue of &gt; 55 ${&gt;}\,55$ MeV Wide-longitude Solar Proton Events Observed by SOHO, ACE, and the STEREOs at ≈ 1 ${\approx}\,1$ AU During 2009 – 2016

Paassilta, Miikka; Papaioannou, Athanasios; Dresing, Nina; Vainio, R.; Валтонен, Э.; Heber, B.

doi:10.1007/s11207-018-1284-7

Cited by 37 publications

(21 citation statements)

References 41 publications

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“…For our analysis we use the SEP event list given in Table 3 of Paassilta et al (2018), which consists of 46 SEP events with energies greater than 50 MeV that occurred from 2009 to 2016. This catalog is based on measurements of energetic protons by the Energetic and Relativistic Nuclei and Electron experiment (ERNE; Torsti et al 1995) on board the Solar and Heliospheric Observatory (SOHO) and the High Energy Telescope (HET; von Rosenvinge et al 2008) on board STEREO.…”

Section: Selection Of Sep Eventsmentioning

confidence: 99%

“…We further examine the relative time difference between the estimated release time of the S/C-specific SEP events and the time when the shock waves reach the well-connected field lines for each S/C. We use Tables 4 and 5 of Paassilta et al (2018), which include the SEP release times for the events in our list. Those times were inferred from the application of either the velocity dispersion analysis (VDA) or the time-shifting analysis (TSA) to the SEPs' onset times.…”

Section: Relating the Shock Wave Evolution To Sep Release Timesmentioning

confidence: 99%

“…In the top panel of Figure 10 we show the distributions of the computed time difference, T D , between the SEP release time and the time when the shock becomes supercritical. We have rejected the cases in Paassilta et al (2018) when the release times have an uncertainty greater than 60 minutes. From the timing distributions of the top panel, we find a maximum at -15 minutes for both VDA and TSA and a median around −11 minutes from VDA and −23 minutes from TSA, i.e., the SEP release occurs on average later than the time when the well-connected shock waves become supercritical along specific lines.…”

Section: Relating the Shock Wave Evolution To Sep Release Timesmentioning

confidence: 99%

“…This time difference must to a large extent be attributed to the time for the particles to be accelerated to high energy by the shock. The scatter of timings around the distribution maximum/mean values arises mainly from two likely sources: (1) the uncertainty in the methods used to estimate SEP release time (mean errors of ∼30 minutes; see Paassilta et al 2018), and (2) the inherent uncertainty from the selection of the critical Mach number threshold. Additionally, there are cases for which release times cannot be explained from the evolution of the shock wave parameters only.…”

Section: Relating the Shock Wave Evolution To Sep Release Timesmentioning

confidence: 99%

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Connecting the Properties of Coronal Shock Waves with Those of Solar Energetic Particles

Kouloumvakos

Rouillard

et al. 2019

ApJ

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We develop and exploit a new catalog of coronal pressure waves modeled in 3D to study the potential role of these waves in accelerating solar energetic particles (SEPs) measured in situ. Our sample comprises modeled shocks and SEP events detected during solar cycle 24 observed over a broad range of longitudes. From the 3D reconstruction of shock waves using coronagraphic observations we derived the 3D velocity along the entire front as a function of time. Combining new reconstruction techniques with global models of the solar corona, we derive the 3D distribution of basic shock parameters such as Mach numbers, compression ratios, and shock geometry. We then model in a time-dependent manner how the shock wave connects magnetically with spacecraft making in situ measurements of SEPs. This allows us to compare modeled shock parameters deduced at the magnetically wellconnected regions, with different key parameters of SEPs such as their maximum intensity. This approach accounts for projection effects associated with remote-sensing observations and constitutes the most extensive study to date of shock waves in the corona and their relation to SEPs. We find a high correlation between the maximum flux of SEPs and the strength of coronal shock waves quantified, for instance, by the Mach number. We discuss the implications of that work for understanding particle acceleration in the corona.

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Section: Selection Of Sep Eventsmentioning

confidence: 99%

Section: Relating the Shock Wave Evolution To Sep Release Timesmentioning

confidence: 99%

Section: Relating the Shock Wave Evolution To Sep Release Timesmentioning

confidence: 99%

Section: Relating the Shock Wave Evolution To Sep Release Timesmentioning

confidence: 99%

See 2 more Smart Citations

Connecting the Properties of Coronal Shock Waves with Those of Solar Energetic Particles

Kouloumvakos

Rouillard

et al. 2019

ApJ

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“…Strongly disturbed interplanetary conditions and wide-spread coronal shocks can, however, dissolve a simple dependence on the connection angle. In their study of wide-spread SEP events, Paassilta et al (2018) concluded that there is no simple relation between the connection angle and the rise time or release delay of protons. Our events cover the longitude range from 23E to 90W and a number of events beyond the west limb of the Sun, but with a large majority of events in the western solar hemisphere.…”

Section: Does Connection Angle Explain the Differences Between Categomentioning

confidence: 99%

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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Helium Suppression in Impulsive Solar Energetic-Particle Events

Reames

2019

Sol Phys

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We have studied the element abundances and energy spectra of the small "Hepoor" impulsive solar energetic-particle (SEP) events, comparing them with other impulsive SEP events with more-normal abundances of He. He-poor events can have abundances as low as He/O ≈ 2, while both impulsive and gradual SEP events usually have source abundances of 30 ≤ He/O ≤ 100 with mean values of ≈ 50 -60. He/C ratios are not only low, but often decrease with energy in He-poor events. Abundance enhancement patterns of other elements with atomic numbers 6 ≤ Z ≤ 56, and likely values of their mass-to-charge ratios A/Q, are generally unaltered in He-poor events, as are the probable source-plasma temperatures of 2.5 -3.2 MK for all impulsive SEP events. One He-poor event is also an example of a rarer C-poor event with C/O = 0.08 ± 0.04, suppressed by a factor over 5 from the mean. We discuss suggestions of a possible A/Q threshold during acceleration and of the sluggish ionization of He entering the corona, because of its uniquely high first ionization potential (FIP), but the suppression of He and the decline of He/C with energy is difficult to explain if both He and C are fully ionized with A/Q = 2 as expected at 2.5 -3.2 MK. Although less dramatic, a possible excess enhancement of Ne in some impulsive SEP events is also considered. Possible causes of the large ≈30% spectral and abundance variations in impulsive events are also discussed.However, the physics of the He-poor events remains a mystery.

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Catalogue of > 55 ${>}\,55$ MeV Wide-longitude Solar Proton Events Observed by SOHO, ACE, and the STEREOs at ≈ 1 ${\approx}\,1$ AU During 2009 – 2016

Cited by 37 publications

References 41 publications

Connecting the Properties of Coronal Shock Waves with Those of Solar Energetic Particles

Connecting the Properties of Coronal Shock Waves with Those of Solar Energetic Particles

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

Helium Suppression in Impulsive Solar Energetic-Particle Events

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