An Analytical Diffusion–Expansion Model for Forbush Decreases Caused by Flux Ropes

Dumbović, Mateja; Heber, Bernd; Vršnak, Bojan; Temmer, Manuela; Kirin, Anamarija

doi:10.3847/1538-4357/aac2de

Cited by 52 publications

(55 citation statements)

References 76 publications

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“…force-free flux tube fitting results are inconclusive due to the low magnetic field strength in the magnetic ejecta), we assume that the observational path is a reasonable estimate of the FR radius but we also have to consider that the uncertainties are large. Using a power-law equation for the increase of FR size with heliospheric distance given by Dumbović et al (2018) adapted from a more general expression by Démoulin et al (2008) and constrained by the derived GCS and in situ results we estimate the power-law index n A , i.e. the expansion factor to n A = 0.51 −0.13 +0.14 .…”

Section: Flux Rope Evolution Using Gcs Resultsmentioning

confidence: 99%

CME–HSS Interaction and Characteristics Tracked from Sun to Earth

et al. 2019

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In a thorough study, we investigate the origin of a remarkable plasma and magnetic field configuration observed in situ on June 22, 2011, near L1, which appears to be a magnetic ejecta (ME) and a shock signature engulfed by a solar wind high-speed stream (HSS). We identify the signatures as an Earth-directed coronal mass ejection (CME), associated with a C7.7 flare on June 21, 2011, and its interaction with a HSS, which emanates from a coronal hole (CH) close to the launch site of the CME. The results indicate that the major interaction between the CME and the HSS starts at a height of 1.3 R up to 3 R . Over that distance range, the CME undergoes a strong north-eastward deflection of at least 30 • due to the open magnetic field configuration of the CH. We perform a comprehensive analysis for the CME-HSS event using multi-viewpoint data (from the Solar TErrestrial RElations Observatories, the Solar and Heliospheric Observatory and the Solar Dynamics Observatory), and combined modeling efforts (nonlinear force-free field modeling, Graduated Cylindrical Shell CME modeling, and the Forecasting a CME's Altered Trajectory -ForeCAT model).

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Section: Flux Rope Evolution Using Gcs Resultsmentioning

confidence: 99%

CME–HSS Interaction and Characteristics Tracked from Sun to Earth

et al. 2019

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“…We find to be 1.5, which represents a very fast expanding CME as for nonperturbed MCs, typical ≈ 0.8 (Gulisano et al, 2010) with the typical spread being ±0.19 (Démoulin, 2010). According to them, the magnetic field in the ejecta falloff as ∼ r (see also Dumbović et al, 2018) where ≈ −2 . According to them, the magnetic field in the ejecta falloff as ∼ r (see also Dumbović et al, 2018) where ≈ −2 .…”

Section: Expansion Speed and Expansion Of The Magnetic Ejectamentioning

confidence: 99%

“…The maximum magnetic field strength in the sheath falls off as ∼ r H (see Dumbović et al, 2018 for a discussion of logarithmic decrease of magnetic field and increase in size of CMEs and their relation) where is −1.7 ± 0.21. In the case of the ejecta, the maximum magnetic field strength falls off as ∼ r H where is −1.91±0.25, which is in reasonable agreement with previous theoretical considerations (Démoulin & Dasso, 2009) and empirical fits (Farrugia et al, 2005;Leitner et al, 2007;Wang et al, 2005;Winslow et al, 2015).…”

Section: Magnetic Field Intensitymentioning

confidence: 99%

Radial Evolution of Coronal Mass Ejections Between MESSENGER, Venus Express, STEREO, and L1: Catalog and Analysis

2020

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Our knowledge of the properties of coronal mass ejections (CMEs) in the inner heliosphere is constrained by the relative lack of plasma observations between the Sun and 1 AU. In this work, we present a comprehensive catalog of 47 CMEs measured in situ measurements by two or more radially aligned spacecraft (MESSENGER, Venus Express, STEREO, Wind/ACE). We estimate the CME impact speeds at Mercury and Venus using a drag-based model and present an average propagation profile of CMEs (speed and deceleration/acceleration) in the inner heliosphere. We find that CME deceleration continues past Mercury's orbit but most of the deceleration occurs between the Sun and Mercury. We examine the exponential decrease of the maximum magnetic field strength in the CME with heliocentric distance using two approaches: a modified statistical method and analysis from individual conjunction events. Findings from both the approaches are on average consistent with previous studies but show significant event-to-event variability. We also find the expansion of the CME sheath to be well fit by a linear function. However, we observe the average sheath duration and its increase to be fairly independent of the initial CME speed, contradicting commonly held knowledge that slower CMEs drive larger sheaths. We also present an analysis of the 3 November 2011 CME observed in longitudinal conjunction between MESSENGER, Venus Express, and STEREO-B focusing on the expansion of the CME and its correlation with the exponential falloff of the maximum magnetic field strength in the ejecta.

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“…CME expansion has been investigated using theoretical and statistical studies by Schwenn (1998), Liu et al (2005), Démoulin andDasso (2009), Gulisano et al (2010), and for specific examples following the pioneer work of Farrugia et al (1993). Recently, Dumbović et al (2018) discussed the relation between heliospheric and in situ expansion as well as expansion in the size and magnetic field strength of the ME. Recently, Dumbović et al (2018) discussed the relation between heliospheric and in situ expansion as well as expansion in the size and magnetic field strength of the ME.…”

Section: Introductionmentioning

confidence: 99%

Evolution of a Long‐Duration Coronal Mass Ejection and Its Sheath Region Between Mercury and Earth on 9–14 July 2013

2020

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Using in situ measurements and remote-sensing observations, we study a coronal mass ejection (CME) that left the Sun on 9 July 2013 and impacted both Mercury and Earth while the planets were in radial alignment (within 3 • ). The CME had an initial speed as measured by coronagraphs of 580 ± 20 km/s, an inferred speed at Mercury of 580 ± 30 km/s, and a measured maximum speed at Earth of 530 km/s, indicating that it did not decelerate substantially in the inner heliosphere. The magnetic field measurements made by MESSENGER and Wind reveal a very similar magnetic ejecta at both planets. We consider the CME expansion as measured by the ejecta duration and the decrease of the magnetic field strength between Mercury and Earth and the velocity profile measured in situ by Wind. The long-duration magnetic ejecta (20 and 42 hr at Mercury and Earth, respectively) is found to be associated with a relatively slowly expanding ejecta at 1 AU, revealing that the large size of the ejecta is due to the CME itself or its expansion in the corona or innermost heliosphere and not due to a rapid expansion between Mercury at 0.45 AU and Earth at 1 AU. We also find evidence that the CME sheath is composed of compressed material accumulated before the shock formed, as well as more recently shocked material.

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An Analytical Diffusion–Expansion Model for Forbush Decreases Caused by Flux Ropes

Cited by 52 publications

References 76 publications

CME–HSS Interaction and Characteristics Tracked from Sun to Earth

CME–HSS Interaction and Characteristics Tracked from Sun to Earth

Radial Evolution of Coronal Mass Ejections Between MESSENGER, Venus Express, STEREO, and L1: Catalog and Analysis

Evolution of a Long‐Duration Coronal Mass Ejection and Its Sheath Region Between Mercury and Earth on 9–14 July 2013

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