The FIP and Inverse FIP Effects in Solar and Stellar Coronae

Abstract

We review our state of knowledge of coronal element abundance anomalies in the Sun and stars. We concentrate on the first ionization potential (FIP) effect observed in the solar corona and slow-speed wind, and in the coronae of solar-like dwarf stars, and the "inverse FIP" effect seen in the corona of stars of later spectral type; specifically M dwarfs. These effects relate to the enhancement or depletion, respectively, in coronal abundance with respect to photospheric values of elements with FIP below about 10~eV. They are interpreted in terms of the ponderomotive force due to the propagation and/or reflection of magnetohydrodynamic waves in the chromosphere. This acts on chromospheric ions, but not neutrals, and so can lead to ion-neutral fractionation. A detailed description of the model applied to closed magnetic loops, and to open field regions is given, accounting for the observed difference in solar FIP fractionation between the slow and fast wind. It is shown that such a model can also account for the observed depletion of helium in the solar wind. The helium depletion is sensitive to the chromospheric altitude where ion-neutral separation occurs, and the behavior of the helium abundance in the closed magnetic loop strongly suggests that the waves have a coronal origin. This, and other similar inferences may be expected to have a strong bearing on theories of solar coronal heating. Chromospheric waves originating from below as acoustic waves mode convert, mainly to fast mode waves, can also give rise to ion-neutral separation. Depending on the geometry of the magnetic field, this can result in FIP or Inverse FIP effects. We argue that such configurations are more likely to occur in later-type stars (known to have stronger field in any case), and that this explains the occurrence of the Inverse FIP effect in M dwarfs.Comment: Review paper submitted to Living Reviews in Solar Physics. 74 pages. Some material revised and updated from astro-ph/0405230, arXiv:0901.3350, arXiv:1110.435

Coronal mass ejections and their sheath regions in interplanetary space

“…For example, the O +7 /O +6 ratio > 1.0 (e.g., Henke et al 2001), and average iron charge states > 12 (e.g., Lepri et al 2001) are good signatures of the ICME-plasma. On the other hand, the elemental ratios depend, in a complex way, on chromospheric temperatures, the magnetic field configuration at the origin of the plasma, and the plasma confinement time before the release (e.g., Laming (2015), and references therein). In ICMEs, increased amounts of high charge states of elements such as Fe, Ne, Si, Mg are often observed suggesting extended confinement times (e.g., Lepri et al 2001;Zurbuchen et al 2016).…”

On-Disc Observations of Flux Rope Formation Prior to Its Eruption

“…FIP biases of the order 1.0 are representative of photospheric plasma, whereas FIP biases of the order of 2 -3 correspond to coronal plasma composition (for a review of the FIP effect including the interpretation of FIP biases, see Laming, 2015). Therefore, these values both suggest plasma that is coronal in composition rather than photospheric.…”

Density diagnostics derived from the O iv and S iv intercombination lines observed by IRIS

“…It has long been observed that some solar TR and coronal features show variations in the chemical abundances, which are correlated with the first ionization potential (FIP) of the element (see, e.g., Laming 2015). The low-FIP (≤ 10 eV) elements are more abundant than the high-FIP ones, relative to the photospheric values (the FIP bias).…”