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D. J. Knipp

Publications and source records attributed to D. J. Knipp.

2 recordsLinked to original sources

FIP Bias Evolution in an Emerging Active Region as observed in SPICE Synoptic Observations

We investigate the time evolution of relative elemental abundances in the context of the first ionization potential effect focusing on an active region. Our aim is to characterize this evolution in different types of solar active region structures as well as in different atmospheric layers. We wish to assert how the measured changes relate to different magnetic topologies by computing abundance enhancement in different conditions using the ponderomotive force model. Leveraging spectroscopic observations from the Spectral Imaging of the Coronal Environment instrument on board Solar Orbiter, we use extreme ultraviolet lines from ions formed across a broad temperature range--from the upper chromosphere to the low corona--and we perform relative abundance ratios following differential emission measure analysis. This methodology yields relative abundance maps from low, intermediate, and high first ionization potential elements. We obtain the temporal evolution of a number of abundance ratios for different structures on the Sun. We compare these results with the outcomes of the ponderomotive force model. We find good correlation between the model and our results, suggesting an Alfvén-wave driven fractionation of the plasma. Fan loops, loop footpoints and active region boundaries exhibit coronal abundances, while the active region core shows more photospheric-like composition. A slow and steady increase in the magnesium to neon relative first ionization potential bias values is observed, starting around 1.5 and increasing by about 50\% after two days. The sulfur to oxygen evolution coupled with the model brings evidence of resonant waves fractionating the plasma in transition region structures.

astro-ph.SR

A large-scale view of Space Technology 5 magnetometer response to solar wind drivers

In this data report we discuss reprocessing of the Space Technology 5 (ST5) magnetometer database for inclusion in NASA's Coordinated Data Analysis Web (CDAWeb) virtual observatory. The mission consisted of three spacecraft flying in elliptical orbits, from 27 March to 27 June 2006. Reprocessing includes (1) transforming the data into the Modified Apex Coordinate System for projection to a common reference altitude of 110km, (2) correcting gain jumps, and (3) validating the results. We display the averaged magnetic perturbations as a keogram, which allows direct comparison of the full-mission data with the solar wind values and geomagnetic indices.With the data referenced to a common altitude, we find the following: (1) Magnetic perturbations that track the passage of corotating interaction regions and high-speed solar wind; (2) unexpectedly strong dayside perturbations during a solstice magnetospheric sawtooth oscillation interval characterized by a radial interplanetary magnetic field (IMF) component that may have enhanced the accompanying modest southward IMF; and (3) intervals of reduced magnetic perturbations or "calms," associated with periods of slow solar wind, interspersed among variable-length episodic enhancements. These calms aremost evidentwhen the IMF is northward or projectswith a northward component onto the geomagnetic dipole. The reprocessed ST5 data are in very good agreement with magnetic perturbations from the Defense Meteorological Satellite Program (DMSP) spacecraft, which we also map to 110km. We briefly discuss the methods used to remap the ST5 data and the means of validating the results against DMSP. Our methods form the basis for future intermission comparisons of space-based magnetometer data.

physics.space-ph