Solar wind ion trends and signatures: STEREO PLASTIC observations approaching solar minimum

Abstract

Abstract. STEREO has now completed the first two years of its mission, moving from close proximity to Earth in 2006/2007 to more than 50 degrees longitudinal separation from Earth in 2009. During this time, several large-scale structures have been observed in situ. Given the prevailing solar minimum conditions, these structures have been predominantly coronal hole-associated solar wind, slow solar wind, their interfaces, and the occasional transient event. In this paper, we extend earlier solar wind composition studies into the current solar minimum using high-resolution (1-h) sampling times for the charge state analysis. We examine 2-year trends for iron charge states and solar wind proton speeds, and present a case study of Carrington Rotation 2064 (December 2007) which includes minor ion (He, Fe, O) kinetic and Fe composition parameters in comparison with proton and magnetic field signatures at large-scale structures observed during this interval.

On lunar exospheric column densities and solar wind access beyond the terminator from ROSAT soft X-ray observations of solar wind charge exchange

“…By assuming that the heavy ions are a small enough fraction of the overall solar wind that their presence does not affect quasi‐neutrality (so that the proton density equals the electron density), the model can be expanded to include high charge heavy ions by invoking another fluid that must satisfy momentum and continuity in the presence of the electrostatic potential established by the protons and electrons. In the solar wind, the heavy ions have a mass to charge ratio of somewhere between about 2 and 10 [e.g., Von Steiger and Zurbuchen , ; Galvin et al , ] with O +8 a major contributor to soft X‐ray emission from SWCX because oxygen is fairly abundant in the solar wind [ Collier et al , ].…”

A multievent study of the coincidence of heliospheric current sheet and stream interface

“…Even though the ICME modified a part of the slow solar wind, it was separated from the compression region by several hours [ Farrugia et al ., ] and may contribute little to its formation. This SI has already been identified by several authors, using the same criteria [ Simunac et al ., ; Galvin et al ., ; Farrugia et al ., ]. The STEREO A observations were shown in Figure b, while we skip ACE/Wind observations since they have been well documented [ Farrugia et al ., ].…”

“…In this multievent study, we have used multispacecraft data (ACE, Wind, and STEREO A and B) from 2007 to 2010, which cover the extended solar minimum of solar cycle 23 [Galvin et al, 2009;Russell et al, 2010], when the solar wind is generally undisturbed by large solar eruptions [Wang et al, 2002;Kilpua et al, 2012;Y. D. Liu et al, 2014].…”

Suprathermal Fe in the Earth's Plasma Environment: Cluster RAPID Observations

“…The solar wind is known to be a source of Fe (Grevesse, ; von Steiger et al, ), so the rather high percentage of time in which Fe is observed is not surprising. Furthermore, it is reasonable to assume that most of the observed ions in this region are high charge state Fe (Galvin et al, ; Heidrich‐Meisner et al, ; von Steiger et al, ), and that a substantial part of their energy is a consequence of the high ram velocity in the solar wind and magnetosheath (Bochsler et al, ). Leakage of energetic ions from the magnetosphere into the magnetosheath (sometimes referred to as Asbridge, ; Sibeck et al, ) can not be excluded, but this population is obviously difficult to distinguish from solar wind ions in our measurements.…”