Physics of the inner heliosphere: Mechanisms, models and observational signatures

The physics of the solar wind acceleration phenomena (e.g. effect of transient momentum deposition on the temporal and spatial variation of the temperature, density and flow speed of the solar wind, formation of shocks, etc.) and the resultant effects on observational signatures, particularly spectroscopic signature are studied. Phenomena under study include: (1) wave motions, particularly spectroscopic signatures are studied. Phenomena under study include:(1) wave motions, particularly Alfven and fast mode waves, (2) the formation of standing shocks in the inner heliosphere as a result of momentum and/or heat addition to the wind and (3) coronal transient phenomena where momentum and/or heat are deposited in the corona to produce transient plasma heating and/or mass ejections. Also included are the theoretical investigation of spectroscopic plasma diagnostics for the inner heliosphere and the analysis of existing Skylab and other relevant data

Corona and solar wind

The Pinhole/Occulter Facility is a powerful tool for studying the physics of the extended corona and origins of the solar wind. Spectroscopic data acquired by the P/OF coronal instruments can greatly expand empirical information about temperatures, densities, flow velocities, magnetic fields, and chemical abundances in the corona out to r or approx. 10 solar radii. Such information is needed to provide tight empirical constraints on critical physical processes involved in the transport and dissipation of energy and momentum, the heating and acceleration of plasma, and the acceleration of energetic particles. Because of its high sensitivity, high spatial and temporal resolutions, and powerful capabilities for plasma diagnostics, P/OF can significantly increase our empirical knowledge about coronal streamers and transients and thereby advance the understanding of the physics of these phenomena. P/OF observations can be used to establish the role in solar wind generation, if any, of small-scale dynamical phenomena, such as spicules, macrospicules and coronal bullets, and the role of the fine-scale structures, such as polar plumes. Finally, simultaneous measurements by the P/OF coronal and hard X-ray instruments can provide critical empirical information concerning nonthermal energy releases and acceleration of energetic particles in the corona

Solar EUV, XUV and soft X-ray telescope facilities

Facility class, high resolution instrumentation can enable maximum spatial, spectral and temporal resolutions and provide understanding of the complex physical conditions in the outer solar atmosphere and the mechanisms responsible for these conditions. The scientific rationale for facility class instruments operating in the EUV, XUV, and soft X ray spectral ranges are discussed. Possible configurations for these facilities and priorities for their development are considered

Effects of coronal disturbances on the ionization state of the solar wind

A theoretical investigation of the relationship between physical conditions in coronal disturbances and the ionization states of the resulting perturbed solar wind was conducted. Available measurements of active solar wind associated with solar flares often show an enhanced degree of ionization (e.g., Fe(+17)), implying that the measured solar wind material is flare-heated at its coronal source. In contrast, other active solar wind flows sometimes show anomalously low degrees of ionization (e.g., He(+)), implying that some solar material is expelled from the corona without ever reaching coronal temperatures. The effects of impulsive heat and/or momentum addition in the corona on the hydrodynamics and ionization state of the corona and solar wind were studied. One of the primary objectives of the current grant was the development of a software package suitable for: (1) generating models for the effects of impulsive heat and/or momentum deposition on plasma temperatures, densities and flow velocities; and (2) calculating the ionization state of the solar wind as a function of the location, duration and magnitude of heat and/or momentum deposition

Spectroscopic measurements of solar wind generation

Spectroscopically observable quantities are described which are sensitive to the primary plasma parameters of the solar wind's source region. The method is discussed in which those observable quantities are used as constraints in the construction of empirical models of various coronal structures. Simulated observations are used to examine the fractional contributions to observed spectral intensities from coronal structures of interest which co-exist with other coronal structures along simulated lines-of-sight. The sensitivity of spectroscopic observables to the physical parameters within each of those structures is discussed

The photospheric abundance of iron

Photospheric abundance of iro

Solar XUV limb brightening observations and interpretation

Solar XUV limb brightening observations and interpretation of lithium like ion

Extreme ultraviolet observations of active regions in the chromosphere and the corona

Extreme ultraviolet observations of active regions in chromosphere and corona from OSO-4 spectroheliomete

The effect of temperature anisotropy on observations of Doppler dimming and pumping in the inner corona

Recent observations of the spectral line profiles and intensity ratio of the O VI 1032 {\AA} and 1037.6 {\AA} doublet by the Ultraviolet Coronagraph Spectrometer (UVCS) on the Solar and Heliospheric Observatory (SOHO), made in coronal holes below 3.5 $R_s$, provide evidence for Doppler dimming of the O VI 1037.6 {\AA} line and pumping by the chromospheric C II 1037.0182 {\AA} line. Evidence for a significant kinetic temperature anisotropy of O$^{5+}$ ions was also derived from these observations. We show in this Letter how the component of the kinetic temperature in the direction perpendicular to the magnetic field, for both isotropic and anisotropic temperature distributions, affects both the amount of Doppler dimming and pumping. Taking this component into account, we further show that the observation that the O VI doublet intensity ratio is less than unity can be accounted for only if pumping by C II 1036.3367 {\AA} in addition to C II 1037.0182 {\AA} is in effect. The inclusion of the C II 1036.3367 {\AA} pumping implies that the speed of the O$^{5+}$ ions can reach 400 km/s around 3 $R_s$ which is significantly higher than the reported UVCS values for atomic hydrogen in polar coronal holes. These results imply that oxygen ions flow much faster than protons at that heliocentric distance.Comment: 9 pages, 3 figure

Ultraviolet spectroscopy of narrow coronal mass ejections

We present Ultraviolet Coronagraph Spectrometer (UVCS) observations of 5 narrow coronal mass ejections (CMEs) that were among 15 narrow CMEs originally selected by Gilbert et al. (2001). Two events (1999 March 27, April 15) were "structured", i.e. in white light data they exhibited well defined interior features, and three (1999 May 9, May 21, June 3) were "unstructured", i.e. appeared featureless. In UVCS data the events were seen as 4-13 deg wide enhancements of the strongest coronal lines HI Ly-alpha and OVI (1032,1037 A). We derived electron densities for several of the events from the Large Angle Spectrometric Coronagraph (LASCO) C2 white light observations. They are comparable to or smaller than densities inferred for other CMEs. We modeled the observable properties of examples of the structured (1999 April 15) and unstructured (1999 May 9) narrow CMEs at different heights in the corona between 1.5 and 2 R(Sun). The derived electron temperatures, densities and outflow speeds are similar for those two types of ejections. They were compared with properties of polar coronal jets and other CMEs. We discuss different scenarios of narrow CME formation either as a jet formed by reconnection onto open field lines or CME ejected by expansion of closed field structures. Overall, we conclude that the existing observations do not definitively place the narrow CMEs into the jet or the CME picture, but the acceleration of the 1999 April 15 event resembles acceleration seen in many CMEs, rather than constant speeds or deceleration observed in jets.Comment: AASTeX, 22 pages, incl. 3 figures (2 color) and 3 tables. Accepted for publication in Ap.