ISEE 3 observations of low‐energy proton bidirectional events and their relation to isolated interplanetary magnetic structures

Abstract

Bidirectional, field-aligned flows of low-energy particles in interplanetary space have been proposed as a possible signature of large-scale, looplike magnetic structures. We present the results of a survey of bidirectional anisotropy observations using data from the low-energy proton and magnetometer experiments on board ISEE 3 covering a 45-month period corresponding to the last solar maximum. During this period, 66 bidirectional flow (BDF) events have been identified, of which 48 could positively be associated with isolated magnetic field structures. We suggest that these structures are an interplanetary manifestation of coronal mass ejection (CME) events, and are able to group the BDF events into five classes according to the field signature of the related magnetic structure and the association or otherwise with an interplanetary shock. We conclude that the BDF events are an interplanetary signature not only of energetic, flare-associated transients but also low energy, nonflare CMEs. From a comparison of anisotropy signatures at 35 and 620 keV we conclude that our observations are most consistent with the transient magnetic structures being detached bubbles comprising closed loops or tightly wound cylindrical helices rather than extended tonguelike loops attached to the Sun at the time of observation. , 1984, 1986Schwenn, 1986]. In particular, the interplanetary signatures of energetic, flare-initiated CMEs have been widely studied, resulting in a general acceptance of the idea that most, if not all, interplanetary shock waves are produced by CME events. Evidence exists, however, that such energetic CME events are only a small fraction, perhaps 10% or less, of the total CME population [Gosling et al., 1974;Newkirk et al., 1981]. This idea is supported by the results of a study by Klein and Burlaga [1982] of so-called magnetic clouds, thought to be the magnetically contained ejecta from CMEs, in which they showed that only ca. one third of the 45 clouds identified had a positive shock association. Sime and Hundhausen [1987], in a study of looplike CMEs identified in SMM coronograph data, have analysed an event which they propose as a candidate for a coronal shock. They emphasize, however, that the event in question is atypical for the data set, and that the majority of SMM looplike CMEs cannot be identified with a shock front. In spite of the large body of correlative data linking CMEs observed close to the Sun to a range of interplanetary phenomena, detailed information is still lacking regarding the development of CMEs between the point at which they leave the field of view of space-borne coronagraphs and their detection in-situ by spacecraft in interplanetary space. Of particular importance in this respect is the magnetic field configurafion. The looplike topology seen in many coronagraph images of CMEs has been the basis for suggesting that at-tached, closed magnetic "bottles" could expand out to 1 AU and beyond in the manner proposed originally by Gold [1959]. On the other hand, as originally pointed out...

The Solar Energetic Particle Event of 14 December 2006

“…Bi-directional field-aligned energetic particle flows are often found in magnetic clouds and other ICMEs (e.g., Palmer, Allum, and Singer, 1978; Marsden et al, 1987;Richardson and Reames, 1993). Although the HET observations in only two viewing directions do not rule out the possibility that the detected protons may have developed bi-directional flows, the Wind anisotropy data suggest that only uni-directional or weak streaming occurred, at least at proton energies of ∼ 3 MeV.…”

Quantitative model for the generic 3D shape of ICMEs at 1 AU

“…Burlaga et al 1990), enhanced ion charge states (Lepri et al 2001;Lepri & Zurbuchen 2004), an increase of bidirectional fluxes of suprathermal particles (e.g. Marsden et al 1987;, etc. From the plasma parameters and the magnetic field reported in previous and recent ICME studies (and including the present one), a global picture for the structure of ICMEs has emerged.…”

Solar Energetic Particle Event Associated With the 2012 July 23 Extreme Solar Storm

“…In situ measurements of the solar wind plasma and magnetic field may provide a general context of the conditions through which SEPs propagate. Measurements of energetic particle anisotropy also provide important clues on the topology of the IMFs (e.g., Marsden et al 1987;Richardson et al 1991;Richardson 1994;Bieber et al 2002;Torsti et al 2004;Leske et al 2012;Tan et al 2012).…”