[1] We report first results from a spatiotemporal statistical analysis of ionospheric emissions as observed by the Ultraviolet Imager (UVI) onboard the POLAR spacecraft during 4 months of 1997 and 1998. Approximately 12,300 individual emission events near local midnight with durations exceeding the sampling time of the image sequences are investigated. The probability distributions of these events over the lifetime T, maximum area A, integrated area S, maximum power W, and integrated energy output are shown to obey distinct power law relationsover a wide range of scales. The observed behavior is consistent with the behavior of statistical-physical avalanche models near a stationary critical state. These results support the hypothesis of self-organized critical dynamics of the magnetosphere and suggest an important role for cross-scale coupling effects in the development of geomagnetic disturbances.

[1] Statistical results for the ionospheric outflows indicate that the ionosphere is an important source of plasma to the magnetosphere. However, the exact consequences on the dynamics of the magnetosphere from this ionospheric outflow have yet to be determined. This issue is taken up in multifluid modeling of the 24-25 September 1998 magnetic cloud event for which strong heavy ionospheric outflows have been previously reported. It is demonstrated that one of the key influences of heavy ionospheric outflows is to lower the cross-polar cap potential due to the mass loading it produces on the magnetosphere; i.e., the heavy ions provide a major sink for momentum that is transferred from the solar wind to the magnetosphere. The derived values for the cross-polar cap potential are shown to converge to that attained by assimilated mapping of ionospheric electrodynamics (AMIE) as the O + concentration at the ionospheric boundary is increased to $50% of the H

mission designed to orbit as close as 7 million km (9.86 solar radii) from Sun center. WISPR employs a 95 • radial by 58 • transverse field of view to image the fine-scale structure of the solar corona, derive the 3D structure of the large-scale corona, and determine whether a dust-free zone exists near the Sun. WISPR is the smallest heliospheric imager to date yet it comprises two nested wide-field telescopes with large-format (2 K × 2 K) APS CMOS detectors to optimize the performance for their respective fields of view and to minimize the risk of dust damage, which may be considerable close to the Sun. The WISPR electronics are very flexible allowing the collection of individual images at cadences up to 1 second at perihelion or the summing of multiple images to increase the signal-to-noise when the spacecraft is further from the Sun. The dependency of the Thomson scattering emission of the corona on the imaging geometry dictates that WISPR will be very sensitive to the emission from plasma close to the spacecraft in contrast to the situation for imaging from Earth orbit. WISPR will be the first 'local' imager providing a crucial link between the large-scale corona and the in-situ measurements.

We examine the different element abundances exhibited by the closed loop solar corona and the slow speed solar wind. Both are subject to the First Ionization Potential (FIP) Effect, the enhancement in coronal abundance of elements with FIP below 10 eV (e.g. Mg, Si, Fe) with respect to high FIP elements (e.g. O, Ne, Ar), but with subtle differences. Intermediate elements, S, P, and C, with FIP just above 10 eV, behave as high FIP elements in closed loops, but are fractionated more like low FIP elements in the solar wind. On the basis of FIP fractionation by the ponderomotive force in the chromosphere, we discuss fractionation scenarios where this difference might originate. Fractionation low in the chromosphere where hydrogen is neutral enhances the S, P and C abundances. This arises with nonresonant waves, which are ubiquitous in open field regions, and is also stronger with torsional Alfvén waves, as opposed to shear (i.e. planar) waves. We discuss the bearing these findings have on models of interchange reconnection as the source of the slow speed solar wind. The outflowing solar wind must ultimately be a mixture of the plasma in the originally open and closed fields, and the proportions and degree of mixing should depend on details of the reconnection process. We also describe novel diagnostics in ultraviolet and extreme ultraviolet spectroscopy now available with these new insights, with the prospect of investigating slow speed solar wind origins and the contribution of interchange reconnection by remote sensing.