On the relationship between coronal mass ejections and magnetic clouds

Gopalswamy, Ν.; Hanaoka, Yoichiro; Kosugi, T.; Lepping, R. P.; Steinberg, J. T.; Plunkett, S. P.; Howard, R. A.; Thompson, B. J.; Gurman, J. B.; Ho, G. C.; Nitta, N.; Hudson, H. S.

doi:10.1029/98gl50757

Cited by 87 publications

(66 citation statements)

References 13 publications

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“…(3) holds, even though it has been established that there is some acceleration or deceleration of ejecta generally (see, e.g. Gopalswamy, 2000), since this apparently occurs mainly near the Sun, and therefore does not negate the good approximation of Eq. (3).)…”

Section: The Scalar Derivation Of V Ementioning

confidence: 93%

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Estimates of magnetic cloud expansion at 1 AU

Lepping

Berdichevsky

et al. 2008

Ann. Geophys.

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Abstract.In this study we analyze 53 magnetic clouds (MCs) of standard profiles observed in WIND magnetic field and plasma data, in order to estimate the speed of MC expansion (V E ) at 1 AU, where the expansion is investigated only for the component perpendicular to the MCs' axes. A high percentage, 83%, of the good and acceptable quality cases of MCs (N(good)=64) were actually expanding, where "good quality" as used here refers to those MCs that had relatively well determined axial attitudes. Two different estimation methods are employed. The "scalar" method (where the estimation is denoted V E,S ) depends on the average speed of the MC from Sun-to-Earth (), the local MC's radius (R O ), the duration of spacecraft passage through the MC (at average local speed ), and the assumption that =. The second method, the "vector determination" (denoted V E,V ), depends on the decreasing value of the absolute value of the Z-component (in MC coordinates) of plasma velocity (|V Z |) across the MC, the closest approach distance (Y O ), and estimated R O ; the Z-component is related to spacecraft motion through the MC. Another estimate considered here, V E,V , is similar to V E,V in its formulation but depends on the decreasing |V Z | across part of the MC, that part between the maximum and minimum points of |V Z | which are usually close to (but not the same as) the boundaries points. The scalar means of estimating V E is almost independent of any MC parameter fitting model results, but the vector means slightly depends on quantities that are model dependent (e.g. |CA|≡|Y O |/R O ). The most probable values of V E from all three means, based on the full set of N=53 cases, are shown to be around 30 km/s, but V E has larger average values of =49 km/s, =36 km/s, and =44 km/s, with standard deviations of 27 km/s, 38 km/s, and 38 km/s, respectively. The linear correlation coefficient for V E,S vs. V E,V is 0.85 but isCorrespondence to: R. P. Lepping (ronald.p.lepping@nasa.gov) lower (0.76) for V E,S vs. V E,V , as expected. The individual values of V E from all three means are usually well below the local Alfvén velocities, which are on average (for the cases considered here) equal to 116 km/s around the inbound boundary, 137 km/s at closest approach, and 94 km/s around the outbound boundary. Hence, a shock upstream of a MC is not expected to be due to MC expansion. Estimates reveal that the errors on the "vector" method of estimating V E (typically about ±7 km/s, but can get as large as ±25 km/s) are expected to be markedly smaller than those for the scalar method (which is usually in the range ±(15⇔20) km/s, depending on MC speed). This is true, despite the fact that |CA| (on which the vector method depends) is not always well determined by our MC parameter fitting model , but the vector method only weakly depends on knowledge of |CA|.

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Section: The Scalar Derivation Of V Ementioning

confidence: 93%

“…Also it is believed that MCs are essentially the "core" of Interplanetary Coronal Mass Ejections (ICMEs); e.g. see Gopalswamy et al (1998), and also see early reviews by Gosling (1990Gosling ( , 1997 that compare CMEs to large magnetic flux ropes in the solar wind which are usually the essence of MCs.…”

Section: Introductionmentioning

confidence: 99%

Estimates of magnetic cloud expansion at 1 AU

Lepping

Berdichevsky

et al. 2008

Ann. Geophys.

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“…They are a subset of interplanetary CMEs that consist of plasma and magnetic field, expanding behind a shock wave into interplanetary space. Gopalswamy et al (1998) suggested that MCs originate from the structure overlying an eruptive prominence and its associated CME and include the coronal cavity and a bright frontal structure. A typical MC may carry a magnetic helicity of some 10 41 to 10 43 Mx 2 ).…”

Section: Helicity Dissipation and Helicity Transportmentioning

confidence: 99%

The magnetic field in the solar atmosphere

Wiegelmann

Thalmann

Solanki

2014

Astron Astrophys Rev

182

125

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This publication provides an overview of magnetic fields in the solar atmosphere with the focus lying on the corona. The solar magnetic field couples the solar interior with the visible surface of the Sun and with its atmosphere. It is also responsible for all solar activity in its numerous manifestations. Thus, dynamic phenomena such as coronal mass ejections and flares are magnetically driven. In addition, the field also plays a crucial role in heating the solar chromosphere and corona as well as in accelerating the solar wind. Our main emphasis is the magnetic field in the upper solar atmosphere so that photospheric and chromospheric magnetic structures are mainly discussed where relevant for higher solar layers. Also, the discussion of the solar atmosphere and activity is limited to those topics of direct relevance to the magnetic field. After giving a brief overview about the solar magnetic field in general and its global structure, we discuss in more detail the magnetic field in active regions, the quiet Sun and coronal holes.

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“…Many papers have discussed the relationship between the prominence material and magnetic cloud in consideration of the magnetic field helicity [Bothmer and Schwenn, 1998;Ruzmaikin et al, 2003] or plasma features, including the existence of He + [Gosling et al, 1980;Schwenn et al, 1980;Zwickl et al, 1983], though it appeared rarely in the in situ data , the higher charge state of ions at 1 AU [Rakowski et al, 2007], and the high abundance of He 2+ [Hirshberg et al, 1972;Burlaga et al, 1998;Gopalswamy et al, 1998]. However, the previous work did not identify the prominence material by both the magnetic field and plasma features, nor did it investigate the property variation of prominence material inside 1 AU.…”

Section: Introductionmentioning

confidence: 99%

Identification of prominence ejecta by the proton distribution function and magnetic fine structure in interplanetary coronal mass ejections in the inner heliosphere

Yao

Marsch

et al. 2010

J. Geophys. Res.

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[1] This work presents in situ solar wind observations of three magnetic clouds (MCs) that contain cold high-density material when Helios 2 was located at 0.3 AU on 9 May 1979, 0.5 AU on 30 March 1976, and 0.7 AU on 24 December 1978. In the cold high-density regions embedded in the interplanetary coronal mass ejections we find (1) that the number density of protons is higher than in other regions inside the magnetic cloud, (2) the possible existence of He + , (3) that the thermal velocity distribution functions are more isotropic and appear to be colder than in the other regions of the MC, and the proton temperature is lower than that of the ambient plasma, and (4) that the associated magnetic field configuration can for all three MC events be identified as a flux rope. This cold high-density region is located at the polarity inversion line in the center of the bipolar structure of the MC magnetic field (consistent with previous solar observation work that found that a prominence lies over the neutral line of the related bipolar solar magnetic field). Specifically, for the first magnetic cloud event on 8 May 1979, a coronal mass ejection (CME) was related to an eruptive prominence previously reported as a result of the observation of Solwind (P78-1). Therefore, we identify the cold and dense region in the MC as the prominence material. It is the first time that prominence ejecta were identified by both the plasma and magnetic field features inside 1 AU, and it is also the first time that the thermal ion velocity distribution functions were used to investigate the microstate of the prominence material. Moreover, from our three cases, we also found that this material tended to fall behind the magnetic cloud and become smaller as it propagated farther away from the Sun, which confirms speculations in previous work. Overall, our in situ observations are consistent with three-part CME models.Citation: Yao, S., E. Marsch, C.-Y. Tu, and R. Schwenn (2010), Identification of prominence ejecta by the proton distribution function and magnetic fine structure in interplanetary coronal mass ejections in the inner heliosphere,

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On the relationship between coronal mass ejections and magnetic clouds

Cited by 87 publications

References 13 publications

Estimates of magnetic cloud expansion at 1 AU

Estimates of magnetic cloud expansion at 1 AU

The magnetic field in the solar atmosphere

Identification of prominence ejecta by the proton distribution function and magnetic fine structure in interplanetary coronal mass ejections in the inner heliosphere

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