Two components in major solar particle events

Cane, H. V.; Rosenvinge, T. T. von; Cohen, C. M. S.; Mewaldt, R. A.

doi:10.1029/2002gl016580

Cited by 167 publications

(176 citation statements)

References 20 publications

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“…However, the GLE onset time is not strongly correlated with how wellconnected the AR is. Furthermore, we may also anticipate more flare-accelerated particles from well-connected events as manifesting, for example, in elevated Fe/O ratios (Cane et al 2003(Cane et al , 2006. However, apart from a couple of well-connected GLEs with elevated Fe/O ratios, our study indicates that there is hardly a correlation of the Fe/O with magnetic connection.…”

Section: Discussioncontrasting

confidence: 42%

“…However, the time profiles of gradual SEP events depend on the source longitudes. For example, those from the western source ARs tend to rise more quickly to the peak than those from the eastern source regions (Cane et al 1988;Reames 1999;Cane et al 2003). This indicates that magnetic field connection of the source region and surrounding area may play a role in the SEP onset and peak times and possibly in other SEP properties, given that the western hemisphere is more likely connected to Earth in normal interplanetary conditions.…”

Section: Introductionmentioning

confidence: 92%

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What Are Special About Ground-Level Events?

et al. 2012

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Ground level events (GLEs) occupy the high-energy end of gradual solar energetic particle (SEP) events. They are associated with coronal mass ejections (CMEs) and solar flares, but we still do not clearly understand the special conditions that produce these rare events. During Solar Cycle 23, a total of 16 GLEs were registered, using ground-based neutron monitor data. We first ask if these GLEs are clearly distinguishable from other SEP events observed from space. Setting aside possible difficulties in identifying all GLEs consistently, we then try to find observables which may unmistakably isolate these GLEs by studying the basic properties of the associated eruptions and the active regions (ARs) that produced them. It is found that neither the magnitudes of the CMEs and flares nor the complexities of the ARs give sufficient conditions for GLEs. It is possible to find CMEs, flares or ARs that are not associated with GLEs but that have more extreme properties than those associated with GLEs. We also try to evaluate the importance of magnetic field connection of the AR with Earth on the detection of GLEs and their onset times. Using the potential field source surface (PFSS) model, a half of the GLEs are found to be well-connected. However, the GLE onset time with respect to the onset of the associated flare and CME does not strongly depend on how well-connected the AR is. The GLE onset behavior may be largely determined by when and where the CME-driven shock develops. We could not relate the shocks responsible for the onsets of past GLEs with features in solar images, but the combined data from the Solar TErrestrial RElations Observatory (STEREO) and the Solar Dynamics Observatory (SDO) have the potential to change this for GLEs that may occur in the rising phase of Solar Cycle 24.

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Section: Discussioncontrasting

confidence: 42%

Section: Introductionmentioning

confidence: 92%

What Are Special About Ground-Level Events?

et al. 2012

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“…Panel a shows an essentially constant Fe/O ratio once the CIR intensity increase is under way; this is the behavior for all events in the survey except for the case shown in (b), which shows a definite trend rise in Fe/O as the event progresses. The constancy of Fe/O during the events presumably reflects the nearly steady-state nature of CIRs, at least in comparison with SEP events that routinely show very strong Fe/O temporal variations (e.g., Mason et al 1983;Tylka et al 1999;Cane et al 2003). …”

Section: Spectral Forms and Temporal Variationsmentioning

confidence: 99%

Abundances and Energy Spectra of Corotating Interaction Region Heavy Ions Observed during Solar Cycle 23

Mason

Leske

Desai

et al. 2008

ApJ

102

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Using instruments on the ACE spacecraft, we surveyed the heavy-ion spectra and composition over the range HeFe for 41 corotating interaction regions (CIRs) during 1998-2007. Below $1 MeV nucleon À1 the spectra are power laws in kinetic energy nucleon À1 with an average spectral index of 2:51 AE 0:10, rolling over above $1 MeV nucleon À1 to power-law spectra with an average index of 4:47 AE 0:17. The spectral shapes for different species are similar, leading to relative abundances that are constant over our energy range, even though the intensities cover up to 8 orders of magnitude. Relative to oxygen, the measured abundances at 385 keV nucleon À1 for 4 He, C, N, Ne, Mg, Si, S, Ca, and Fe are 273 AE 72, 0:760 AE 0:023, 0:143 AE 0:005, 0:206 AE 0:009, 0:148 AE 0:006, 0:095 AE 0:005, 0:028 AE 0:002, 0:007 AE 0:001, and 0:088 AE 0:007, respectively. Except for an overabundance of 4 He and Ne, the abundances are quite close to that of the fast solar wind. We have found 3 He/ 4 He ratios to be enhanced over solar wind values in $40% of the CIRs. The Fe/O ratio in individual CIRs is observed to vary over a factor of $10 and is strongly correlated with the solar wind Fe/O ratio measured 2-4 days preceding each CIR. Taken together with previous studies showing the presence of pickup He + in CIRs, the observational data provide evidence that CIR energetic particles are accelerated out of a suprathermal ion pool that includes heated solar wind ions, pickup ions, and remnant suprathermals from impulsive solar energetic particle events.

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“…Observations in the 10-100 MeV nucl. −1 energy range suggest that flare material is present in most major SEP events (Cane et al 2003). As pointed out by Li & Zank (2005a), it may be possible to distinguish between different scenarios (DSA only, flare acceleration only, or DSA+flare), although the time-intensity profiles at high energies may be very similar in all scenarios.…”

Section: Discussionmentioning

confidence: 96%

Diffusive shock acceleration to relativistic energies in the solar corona

Sandroos

Vainio²

2009

A&A

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Aims. We study the effect of magnetic geometry on the efficiency of diffusive shock acceleration (DSA) of protons in the solar corona with emphasis on conditions that may lead to the formation of so-called ground level enhancements (GLEs) where the protons are accelerated into energies 1 GeV. Methods. We use Monte Carlo simulations of DSA in a semirealistic large scale coronal magnetic field near a bipolar active region. This active region is assumed to be the source region of a coronal mass ejection (CME) driving a shock wave in the corona. The shock geometry evolves in time, and the obliquity angle goes through a wide range of values from perpendicular to quasi-parallel. We consider the effect of the evolving magnetic geometry on the acceleration efficiency in five selected field lines. Results. In most of the considered field lines the maximum proton energies are of the order of 100 MeV, which is rather typical for gradual solar energetic particle (SEP) events. We find that the DSA can be more effective on field lines where the shock starts out by being oblique and gradually turns quasi-perpendicular than on field lines where the shock starts perpendicularly.

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Two components in major solar particle events

Cited by 167 publications

References 20 publications

What Are Special About Ground-Level Events?

What Are Special About Ground-Level Events?

Abundances and Energy Spectra of Corotating Interaction Region Heavy Ions Observed during Solar Cycle 23

Diffusive shock acceleration to relativistic energies in the solar corona

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