Observable Effects of Interplanetary Coronal Mass Ejections on Ground Level Neutron Monitor Count Rates

Blanco, J. J.; Catalán, Edwin; Hidalgo, M. A.; Medina, J.; García, O. Boente; Rodrı́guez-Pacheco, J.

doi:10.1007/s11207-013-0256-1

Cited by 28 publications

(26 citation statements)

References 31 publications

(45 reference statements)

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“…This discrepancy arises because Jordan et al (2011) analysed a set of ICMEs both with and without an MC inside an ICME, while in this work we focus on MCs. The comparison is an even poorer match for the 25% obtained by Blanco et al (2013) from a pool of 59 shock-driving ICMEs from January 1997 to September 2006. Still, in this list only 24 MCs were detected and eight of them (33%) produced an observable FD at ground-level neutron monitors.…”

Section: Discussionmentioning

confidence: 77%

“…Still, in this list only 24 MCs were detected and eight of them (33%) produced an observable FD at ground-level neutron monitors. All events in Blanco et al (2013) were recorded at 1 AU while the events presented in this work were detected at heliocentric distances below 1 AU. This clear difference could be explained if the MC location plays a role for the FD depth, which deeper when the MC is closer to Sun.…”

Section: Discussionmentioning

confidence: 97%

“…They concluded that the clear differences in the FD shape and depth could be explained by assuming that spacecraft followed different paths through the ejecta and one of the spacecraft traversed the ejecta partially. Blanco et al (2013) analysed a pool of FDs detected by neutron monitors and produced by ICMEs with MCs and ICMEs with flux ropes. These authors showed that MCs are more effective than flux ropes in producing deeper FDs.…”

Section: Forbush Decreases and MC Propertiesmentioning

confidence: 99%

“…The shape of the FD is determined by the shock, the ICME, the MC, and small magnetic structures. Also, as pointed out by Blanco et al (2013), it is determined by the region of the ICME, which sweeps the Earth, and the ICME's deceleration from Sun to Earth. These decreases are also observed by instruments onboard the spacecraft.…”

Section: Introductionmentioning

confidence: 99%

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Energetic-particle-flux decreases related to magnetic cloud passages as observed by the Helios 1 and 2 spacecraft

Blanco

Hidalgo

Gómez-Herrero

et al. 2013

A&A

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It has been observed that a magnetic cloud (MC) can affect the propagation conditions of solar energetic particles and low-energy cosmic rays. This effect is commonly observed as a decrease in the energetic-particle fluxes, which are partially excluded from the interior of the cloud. The twin spacecraft Helios 1 and Helios 2 explored the inner heliosphere between 0.29 AU and 1 AU from the mid 1970s to early 1980s. The E6 Experiment onboard Helios is the energetic-particle detector able to measure electrons, protons and alphas in the range of 300 keV/n to >50 MeV/n. It has been shown previously that, in absence of strong solar-particle events, the single detector rates of the E6 anti-coincidence and saphire Cherenkov detectors are sensitive to cosmic rays with rigidities above GV. Because their statistical precision is in the order of hundreds of counts per second, both detectors are very well suited for studying the short-term decreases observed in their count rates during magnetic cloud passages. A total of 35 magnetic clouds have been identified at the Helios locations. Nineteen of them were free of solar energetic-particle contamination. This subset led us to investigate the effect of magnetic clouds on the galactic cosmic ray (GCR) flux. The depth of the decreases are studied in terms of the solar wind and magnetic field properties of the magnetic cloud. We found dependences with the MC magnetic field strength, magnetic rigidity and with the MC time of flight, with the latter supporting the idea of magnetically closed MCs, i.e. with the two legs rooted in the Sun. We also studied MC properties and found evidence of MC expansion during its journey through the inner heliosphere.

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Section: Discussionmentioning

confidence: 77%

Section: Discussionmentioning

confidence: 97%

Section: Forbush Decreases and MC Propertiesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Energetic-particle-flux decreases related to magnetic cloud passages as observed by the Helios 1 and 2 spacecraft

Blanco

Hidalgo

Gómez-Herrero

et al. 2013

A&A

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“…On the other hand, other studies (e.g., Badruddin et al 1986;Sanderson et al 1990;Kuwabara et al 2009) have concluded that magnetic clouds can make an important contribution to FDs. There have been recent conclusive associations of FDs with Earth-directed CMEs (Blanco et al 2013;Oh & Yi 2012). Cane (2000) introduced the concept of a two-step FD, where the first step of the decrease is due to the shock and the second step is due to the ICME.…”

Section: Introductionmentioning

confidence: 99%

High-rigidity Forbush decreases: due to CMEs or shocks?

Arunbabu

Antia

Dugad

et al. 2013

A&A

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Aims. We seek to identify the primary agents causing Forbush decreases (FDs) in high-rigidity cosmic rays observed from the Earth. In particular, we ask if these FDs are caused mainly by coronal mass ejections (CMEs) from the Sun that are directed towards the Earth, or by their associated shocks. Methods. We used the muon data at cutoff rigidities ranging from 14 to 24 GV from the GRAPES-3 tracking muon telescope to identify FD events. We selected those FD events that have a reasonably clean profile, and can be reasonably well associated with an Earth-directed CME and its associated shock. We employed two models: one that considers the CME as the sole cause of the FD (the CME-only model) and one that considers the shock as the only agent causing the FD (the shock-only model). We used an extensive set of observationally determined parameters for both models. The only free parameter in these models is the level of MHD turbulence in the sheath region, which mediates cosmic ray diffusion (into the CME for the CME-only model, and across the shock sheath for the shock-only model). Results. We find that good fits to the GRAPES-3 multi-rigidity data using the CME-only model require turbulence levels in the CME sheath region that are only slightly higher than those estimated for the quiescent solar wind. On the other hand, reasonable model fits with the shock-only model require turbulence levels in the sheath region that are an order of magnitude higher than those in the quiet solar wind. Conclusions. This observation naturally leads to the conclusion that the Earth-directed CMEs are the primary contributors to FDs observed in high-rigidity cosmic rays.

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Interplanetary coronal mass ejection observed at STEREO‐A, Mars, comet 67P/Churyumov‐Gerasimenko, Saturn, and New Horizons en route to Pluto: Comparison of its Forbush decreases at 1.4, 3.1, and 9.9 AU

et al. 2017

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We discuss observations of the journey throughout the Solar System of a large interplanetary coronal mass ejection (ICME) that was ejected at the Sun on 14 October 2014. The ICME hit Mars on 17 October, as observed by the Mars Express, Mars Atmosphere and Volatile EvolutioN Mission (MAVEN), Mars Odyssey, and Mars Science Laboratory (MSL) missions, 44 h before the encounter of the planet with the Siding‐Spring comet, for which the space weather context is provided. It reached comet 67P/Churyumov‐Gerasimenko, which was perfectly aligned with the Sun and Mars at 3.1 AU, as observed by Rosetta on 22 October. The ICME was also detected by STEREO‐A on 16 October at 1 AU, and by Cassini in the solar wind around Saturn on the 12 November at 9.9 AU. Fortuitously, the New Horizons spacecraft was also aligned with the direction of the ICME at 31.6 AU. We investigate whether this ICME has a nonambiguous signature at New Horizons. A potential detection of this ICME by Voyager 2 at 110–111 AU is also discussed. The multispacecraft observations allow the derivation of certain properties of the ICME, such as its large angular extension of at least 116°, its speed as a function of distance, and its magnetic field structure at four locations from 1 to 10 AU. Observations of the speed data allow two different solar wind propagation models to be validated. Finally, we compare the Forbush decreases (transient decreases followed by gradual recoveries in the galactic cosmic ray intensity) due to the passage of this ICME at Mars, comet 67P, and Saturn.

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Observable Effects of Interplanetary Coronal Mass Ejections on Ground Level Neutron Monitor Count Rates

Cited by 28 publications

References 31 publications

Energetic-particle-flux decreases related to magnetic cloud passages as observed by the Helios 1 and 2 spacecraft

Energetic-particle-flux decreases related to magnetic cloud passages as observed by the Helios 1 and 2 spacecraft

High-rigidity Forbush decreases: due to CMEs or shocks?

Interplanetary coronal mass ejection observed at STEREO‐A, Mars, comet 67P/Churyumov‐Gerasimenko, Saturn, and New Horizons en route to Pluto: Comparison of its Forbush decreases at 1.4, 3.1, and 9.9 AU

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