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

Abstract

[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,

The Physical Processes of CME/ICME Evolution

“…Given its relatively cool temperatures, filament material in the corona is dominated by heavy ion charge states such as C 2−3+ , O 2−4+ and Fe 4−6+ , which have been directly observed with SOHO/UVCS (e.g., Lee and Raymond 2012). Filament material can be ejected into interplanetary space where it can be distinguished by these ionization states (Schwenn et al 1980;Burlaga et al 1998;Skoug et al 1999;Yao et al 2010). Gopalswamy et al (1998) provides a clear example of the identification of low charge state filament material in the 07-11 February 1997 CME/ICME event.…”

Measuring an Eruptive Prominence at Large Distances From the Sun. Ii. Approaching 1 Au

“…While prominences of the latter variety have been studied for as long as solar imagery has been available, little is known of the former category beyond distances of a few solar radii from the Sun. Coronal mass ejections (CMEs), many of which contain eruptive prominences when they are observed close to the Sun by coronagraphs, are commonly observed in situ (see, e.g., Cane & Richardson 2003), but they are very rarely (if ever) accompanied by signatures of prominences (e.g., Gosling et al 1980;Schwenn et al 1980;Cane et al 1986;Yao et al 2010). Likewise, studies of prominences using coronagraphs are rare when they are beyond a few solar radii (e.g., , and I am aware of only one paper that has presented measurements of one using a heliospheric imager (Jackson et al 2006, using SMEI).…”

Regarding the detectability and measurement of coronal mass ejections

“…Under this narrative, the shock and sheath in-situ components correspond to the bright leading edge in the coronagraph three-part CME, but the fate of the underlying filament component observed in coronagraphs remains open to debate. Little evidence exists of filament signatures at large distances from the Sun (Howard 2015b), and although periods of high-density cold plasma have been observed in-situ (e.g., Cane et al 1986;Yao et al 2010) it remains an open question as to whether these features are actually filaments and therefore how commonplace they are within CMEs at distances near 1 AU.…”