Are CME-Related Dimmings Always a Simple Signature of Interplanetary Magnetic Cloud Footpoints?

Mandrini, C. H.; Nakwacki, M. S.; Attrill, G. D. R.; Driel-Gesztelyi, L. van; Démoulin, P.; Dasso, S.; Elliott, H. A.

doi:10.1007/s11207-007-9020-8

Cited by 86 publications

(100 citation statements)

References 64 publications

(57 reference statements)

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“…Although such large-scale disturbances may play a role in the detection of SEPs with quick onsets from poorly-connected regions such as GLE 65 (whose associated global dimming is discussed by Mandrini et al (2007)), examples such as GLEs 55 and 69 are well-connected events, in which the acceleration region or shock does not have to move large distances before particles are injected. Therefore, we fail to establish the possible importance of coronal or EIT waves in GLEs.…”

Section: Large-scale Coronal Disturbancesmentioning

confidence: 99%

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: Large-scale Coronal Disturbancesmentioning

confidence: 99%

What Are Special About Ground-Level Events?

et al. 2012

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“…Another goal is to correct the effect of mixing spatialvariation/time-evolution in the one-point observations to obtain a better determination of the MC field configuration. The expansion of several magnetic clouds has been analyzed previously by fitting different velocity models to the data Shimazu & Vandas 2002;Berdichevsky et al 2003;Vandas et al 2005;Yurchyshyn et al 2006;Dasso et al 2007;Mandrini et al 2007;Démoulin et al 2008).…”

Section: Introductionmentioning

confidence: 99%

Global and local expansion of magnetic clouds in the inner heliosphere

Gulisano

Démoulin²,

Dasso

et al. 2009

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Context. Observations of magnetic clouds (MCs) are consistent with the presence of flux ropes detected in the solar wind (SW) a few days after their expulsion from the Sun as coronal mass ejections (CMEs). Aims. Both the in situ observations of plasma velocity profiles and the increase of their size with solar distance show that MCs are typically expanding structures. The aim of this work is to derive the expansion properties of MCs in the inner heliosphere from 0.3 to 1 AU. Methods. We analyze MCs observed by the two Helios spacecraft using in situ magnetic field and velocity measurements. We split the sample in two subsets: those MCs with a velocity profile that is significantly perturbed from the expected linear profile and those that are not. From the slope of the in situ measured bulk velocity along the Sun-Earth direction, we compute an expansion speed with respect to the cloud center for each of the analyzed MCs. Results. We analyze how the expansion speed depends on the MC size, the translation velocity, and the heliocentric distance, finding that all MCs in the subset of non-perturbed MCs expand with almost the same non-dimensional expansion rate (ζ). We find departures from this general rule for ζ only for perturbed MCs, and we interpret the departures as the consequence of a local and strong SW perturbation by SW fast streams, affecting the MC even inside its interior, in addition to the direct interaction region between the SW and the MC. We also compute the dependence of the mean total SW pressure on the solar distance and we confirm that the decrease of the total SW pressure with distance is the main origin of the observed MC expansion rate. We found that ζ was 0.91 ± 0.23 for non-perturbed MCs while ζ was 0.48 ± 0.79 for perturbed MCs, the larger spread in the last ones being due to the influence of the solar wind local environment conditions on the expansion.

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“…A.2.2). The GLE 66 occurs inside a magnetic cloud (previously studied by Mandrini et al 2007). We remark that this magnetic cloud is related to the CME ejected from the Sun on Oct. 28, 2003 at 11:30 UT during the solar eruption that produced the GLE 65.…”

Section: Icme Magnetic Cloud or Back Regionmentioning

confidence: 99%

The interplanetary magnetic structure that guides solar relativistic particles

Masson

Démoulin

Dasso

et al. 2012

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Context. Relating in-situ measurements of relativistic solar particles to their parent activity in the corona requires understanding the magnetic structures that guide them from their acceleration site to the Earth. Relativistic particle events are observed at times of high solar activity, when transient magnetic structures such as interplanetary coronal mass ejections (ICMEs) often shape the interplanetary magnetic field (IMF). They may introduce interplanetary paths that are longer than nominal, and magnetic connections rooted far from the nominal Parker spiral. Aims. We present a detailed study of the IMF configurations during ten relativistic solar particle events of the 23rd activity cycle to elucidate the actual IMF configuration that guides the particles to the Earth, where they are measured by neutron monitors. Methods. We used magnetic field (MAG) and plasma parameter measurements (SWEPAM) from the ACE spacecraft and determined the interplanetary path lengths of energetic particles through a modified version of the velocity dispersion analysis based on energetic particle measurements with SoHO/ERNE. Results. We find that the majority (7/10) of the events is detected in the vicinity of an ICME. Their interplanetary path lengths are found to be longer (1.5-2.6 AU) than those of the two events propagating in the slow solar wind (1.3 AU). The longest apparent path length is found in an event within the fast solar wind, probably caused by enhanced pitch angle scattering. The derived path lengths imply that the first energetic and relativistic protons are released at the Sun at the same time as electron beam emitting type III radio bursts. Conclusions. The timing of the first high-energy particle arrival on Earth is mainly determined by the type of IMF in which the particles propagate. Initial arrival times are as expected from Parker's model in the slow solar wind, and significantly longer in or near transient structures such as ICMEs.

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Are CME-Related Dimmings Always a Simple Signature of Interplanetary Magnetic Cloud Footpoints?

Cited by 86 publications

References 64 publications

What Are Special About Ground-Level Events?

What Are Special About Ground-Level Events?

Global and local expansion of magnetic clouds in the inner heliosphere

The interplanetary magnetic structure that guides solar relativistic particles

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