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

Abstract

The physical properties of eruptive prominences are unknown at large distances from the Sun. They are rarely, if ever, measured by in situ spacecraft and until recently our ability to measure them beyond the fields of view of solar imagers has been severely limited. The data quality of heliospheric imaging has reached a point where some quantitative measurements of prominences are now possible. I present the first such measurements of a bright prominence continually out to distances of around 1 AU from the Sun. This work follows on from the preparatory work presented in an accompanying paper, which showed that that the brightness of a prominence can be safely assumed to arise entirely from Thomson scattering in the STEREO/HI fields of view. Measurements of distance, speed, and mass are provided along with those from its accompanying coronal mass ejection (CME) to demonstrate their geometric, kinematic, and mass relationships. I find that the prominence travels with a slower speed than that of the CME, but its location relative to the CME structure does not conform to the expected location for basic geometric expansion. Further, the mass of the prominence was found to decrease by around an order of magnitude while that of the CME increased by an order of magnitude across the same distance.

Challenging Some Contemporary Views of Coronal Mass Ejections. Ii. The Case for Absent Filaments

“…They found that filaments are not necessarily tied to the magnetic properties of their accompanying CME and that the geometry of the filaments remained intact out to many tens of R e . The two filaments studied by Howard (2015aHoward ( , 2015b and Wood et al (2016) were clear cases of CME cores that were actual filaments that originated at the Sun and propagated through the heliosphere. Although additional such filaments were sought by Wood et al (2016) they found only those two in the STEREO/ HI-2 data sets for the entire duration of the STEREO mission.…”

“…Of those, only two have so far been confirmed to contain eruptive filaments that have been tracked to large distances from the Sun. These were associated with CMEs that departed the Sun on 2011 June 07 and 2012 August 31 and the large-distance evolution of both have been investigated by Howard (2015aHoward ( , 2015b and Wood et al (2016). A summary of these works is provided in Section 1.1.…”

Validation of Coronal Mass Ejection Arrival-Time Forecasts by Magnetohydrodynamic Simulations based on Interplanetary Scintillation Observations

“…Some CME parameters assumed in this study can be derived from LASCO white-light images by tting the CME geometry using models such as the graduated cylindrical shell model (e.g., Thernisien et al 2006). CMEs propagating in interplanetary space can be derived from the Heliospheric Imager onboard STEREO satellites (Möstl et al 2014;Howard 2015). White-light coronagraph data can also be estimated from our MHD simulations by calculating the Thomson scattering along the line of sight.…”

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.…”

“…4.2) they concluded that the light was due to Ha emission, as photospheric Ha is known to have an unusually low polarization due to Lyb absorption . The author has recently published two papers that explore a filament measured at large distances from the Sun (Howard 2015a(Howard , 2015b. …”