THE NANOFLARE ORIGINS OF THE FIRST IONIZATION POTENTIAL EFFECT

Abstract:

The First Ionization Potential (FIP) Effect is the by now well known abundance anomaly in the solar corona
and slow speed solar wind. Elements which are predominantly ionized in the chromosphere, i.e. those with FIP less than about 10 eV, are enhanced in abundance in the corona by a factor of about 3-4, while elements that are predominantly neutral are essentially unchanged (although He and Ne can be further depleted). A compelling explanation for this phenomenon invokes the ponderomotive force associated with Alfven or fast mode waves propagating through or reflecting from the chromosphere. The usual solar FIP effect, and most of its variations, are best modeled by waves resonant with the coronal loop on which they propagate, and therefore most plausibly have a coronal origin.
We report on 3D compressible MHD simulations of coronal loop heating with the HYPERION code. A ponderomotive force of the correct sign and magnitude is produced naturally as a by-product of coronal heating processes that also produce a 1-3 MK corona loop, reinforcing our conjecture above. We argue that coronal element abundance anomalies, and the waves that produce them, offer a novel but hitherto largely untried approach to the problem of coronal heating.