Iron Charge State Research Articles

OBSERVATIONS OF SEVERAL UNUSUAL PLASMA COMPOSITIONAL SIGNATURES WITHIN SMALL INTERPLANETARY MAGNETIC FLUX ROPES

Interplanetary coronal mass ejections (ICMEs) often show unusual plasma compositional signatures (high He/P ratio, high ratio, and high Fe charge states), and their enhanced charge states of oxygen and iron are caused by flare-related heating in the corona. We investigated the abnormal plasma composition of small interplanetary magnetic flux ropes (IMFRs) in terms of He/P ratio, ratio, and mean Fe charge state. We discover that 18 of the 24 small IMFRs showed high He/P ratios. In addition, 12 and 8 of the 24 events showed high Fe charge states and ratios, respectively. This observation implies that these small IMFRs and ICMEs may be caused by the same coronal eruptions.

OBSERVATION OF HIGH IRON CHARGE STATES AT LOW ENERGIES IN SOLAR ENERGETIC PARTICLE EVENTS

The ionic charge states of solar energetic particles (SEPs) provide direct information about the source plasma, the acceleration environment, and their transport. Recent studies report that both gradual and impulsive SEP events show mean iron charge states Q Fe ~ 10-14 at low energies E ≤ 0.1 MeV nuc–1, consistent with their origin from typical corona material at temperatures 1-2 MK. Observed increases of Q Fe up to 20 at energies 0.1-0.5 MeV nuc–1 in impulsive SEPs are attributed to stripping during acceleration. However, Q Fe > 16 is occasionally found in the solar wind, particularly coming from active regions, in contrast to the exclusively reported Q Fe ≤ 14 for low energy SEPs. Here we report results from a survey of all 89 SEP events observed with Advanced Composition Explorer Solar Energetic Particle Ionic Charge Analyzer (SEPICA) in 1998-2000 for iron charge states augmented at low energy with Solar and Heliospheric Observatory CELIAS suprathermal time-of-flight (STOF). Nine SEP events with Q Fe ≥ 14 throughout the entire SEPICA and STOF energy range have been identified. Four of the nine events are impulsive events identified through velocity dispersion that are consistent with source temperatures ≥2 MK up to ~4 MK. The other five events show evidence of interplanetary acceleration. Four of them involve re-acceleration of impulsive material, whose original energy dependent charge states appear re-distributed to varying extent bringing higher charge states to lower energy. One event, which shows flat but elevated Q Fe ~ 14.2 over the entire energy range, can be associated with interplanetary acceleration of high temperature material. This event may exemplify a rare situation when a second shock plows through high temperature coronal mass ejection material.

A Haldane-Anderson impurity model study for the spin- and charge-states of iron in heme proteins

To understand the spin and charge properties of iron(II) hemo-proteins like myoglobin, we formulated a Haldane-Anderson impurity model within the closed-shell DFT-hybrid-GGA approximation. We employed a mean-field approximation to solve a simple model of myoglobin active site, the iron porphyin-imidazol complex FeP(Im), which was found to reproduce some of the known spin-charge states of myoglobin. We also computed the spin-charge phase diagram of iron in FeP(Im) with and without O2 attached to the central iron, and found that the spin-charge states for FeP(Im) is much more sensitive to the local correlations than that for FeP(Im)(O2).

COMPOSITION STRUCTURE OF INTERPLANETARY CORONAL MASS EJECTIONS FROM MULTISPACECRAFT OBSERVATIONS, MODELING, AND COMPARISON WITH NUMERICAL SIMULATIONS

We present an analysis of the ionic composition of iron for two interplanetary coronal mass ejections observed in May 21-23 2007 by the ACE and STEREO spacecraft in the context of the magnetic structure of the ejecta flux rope, sheath region, and surrounding solar wind flow. This analysis is made possible due to recent advances in multispacecraft data interpolation, reconstruction, and visualization as well as results from recent modeling of ionic charge states in MHD simulations of magnetic breakout and flux cancellation CME initiation. We use these advances to interpret specific features of the ICME plasma composition resulting from the magnetic topology and evolution of the CME. We find that in both the data and our MHD simulations, the flux ropes centers are relatively cool, while charge state enhancements surround and trail the flux ropes. The magnetic orientation of the ICMEs are suggestive of magnetic breakout-like reconnection during the eruption process, which could explain the spatial location of the observed iron enhancements just outside the traditional flux rope magnetic signatures and between the two ICMEs. Detailed comparisons between the simulations and data were more complicated, but a sharp increase in high iron charge states in the ACE and STEREO-A data during the second flux rope corresponds well to similar features in the flux cancellation results. We discuss the prospects of this integrated in-situ data analysis and modeling approach to advancing our understanding of the unified CME-to-ICME evolution.

MEASUREMENT OF THE Fe VIII–Fe XVI 3–3 EMISSION IN THE EXTREME ULTRAVIOLET AND COMPARISON WITH CHIANTI

Laboratory measurements of the n = 3 to n = 3 emission from M-shell iron ions are presented and compared to synthetic spectra from the CHIANTI spectral model. The measurements cover the range 170-290 Angstrom-Sign and are made at an electron density of about 10{sup 11} cm{sup -3}. Emission from Fe VIII through Fe XVI has been identified. Excellent agreement with CHIANTI predictions is found for most lines. Twenty weaker features are noted in the laboratory data that are either absent in CHIANTI or have recently been added and correspond to lines that have not been verified by experimental measurements. A few of these lines may have already been observed (but not yet identified) in the Sun. The features are attributed to emission from various charge states of iron, notably Fe IX and Fe XIII, and two features have been identified as transitions in Fe VIII, i.e., the 3p{sup 6}3d {sup 2}D{sub 5/2}-3p {sup 5}3d{sup 2} {sup 2}P{sub 3/2} and the 3p {sup 6}3d {sup 2}D{sub 3/2}-3p {sup 5}3d{sup 2} {sup 2}P{sub 1/2} transitions at 225.25 {+-} 0.12 and 226.35 {+-} 0.10 Angstrom-Sign , respectively. Seven lines in Fe XI, Fe XII, and Fe XIII between 200 and 205 Angstrom-Signmore » are noted for which the wavelengths in the CHIANTI database disagree with those in the current database of the National Institute of Standards and Technology. Our measurements of five of these lines appear to agree with the assignments used in CHIANTI.« less

A GLOBAL TWO-TEMPERATURE CORONA AND INNER HELIOSPHERE MODEL: A COMPREHENSIVE VALIDATION STUDY

The recent solar minimum with very low activity provides us a unique opportunity for validating solar wind models. During CR2077 (2008 November 20 through December 17), the number of sunspots was near the absolute minimum of solar cycle 23. For this solar rotation, we perform a multi-spacecraft validation study for the recently developed three-dimensional, two-temperature, Alfven-wave-driven global solar wind model (a component within the Space Weather Modeling Framework). By using in situ observations from the Solar Terrestrial Relations Observatory (STEREO) A and B, Advanced Composition Explorer (ACE), and Venus Express, we compare the observed proton state (density, temperature, and velocity) and magnetic field of the heliosphere with that predicted by the model. Near the Sun, we validate the numerical model with the electron density obtained from the solar rotational tomography of Solar and Heliospheric Observatory/Large Angle and Spectrometric Coronagraph C2 data in the range of 2.4 to 6 solar radii. Electron temperature and density are determined from differential emission measure tomography (DEMT) of STEREO A and B Extreme Ultraviolet Imager data in the range of 1.035 to 1.225 solar radii. The electron density and temperature derived from the Hinode/Extreme Ultraviolet Imaging Spectrometer data are also used to compare with the DEMT as well as the model output. Moreover, for the first time, we compare ionic charge states of carbon, oxygen, silicon, and iron observed in situ with the ACE/Solar Wind Ion Composition Spectrometer with those predicted by our model. The validation results suggest that most of the model outputs for CR2077 can fit the observations very well. Based on this encouraging result, we therefore expect great improvement for the future modeling of coronal mass ejections (CMEs) and CME-driven shocks.

Cation vacancy order in the K0.8+xFe1.6−ySe2 system: Five-fold cell expansion accommodates 20% tetrahedral vacancies

Ordering of the tetrahedral site vacancies in two crystals of refined compositions K0.93(1)Fe1.52(1)Se2 and K0.862(3)Fe1.563(4)Se2 produces a fivefold expansion of the parent ThCr2Si2 unit cell in the ab plane which can accommodate 20% vacancies on a single site within the square FeSe layer. The iron charge state is maintained close to +2 by coupling of the level of alkali metal and iron vacancies, producing a potential doping mechanism which can operate at both average and local structure levels.

Solar wind ion trends and signatures: STEREO PLASTIC observations approaching solar minimum

Abstract. STEREO has now completed the first two years of its mission, moving from close proximity to Earth in 2006/2007 to more than 50 degrees longitudinal separation from Earth in 2009. During this time, several large-scale structures have been observed in situ. Given the prevailing solar minimum conditions, these structures have been predominantly coronal hole-associated solar wind, slow solar wind, their interfaces, and the occasional transient event. In this paper, we extend earlier solar wind composition studies into the current solar minimum using high-resolution (1-h) sampling times for the charge state analysis. We examine 2-year trends for iron charge states and solar wind proton speeds, and present a case study of Carrington Rotation 2064 (December 2007) which includes minor ion (He, Fe, O) kinetic and Fe composition parameters in comparison with proton and magnetic field signatures at large-scale structures observed during this interval.

Iron emission lines in solar and laboratory plasmas

We present a spectrum of the Sun taken by the Cosmic Hot Interstellar Plasma Spectrometer (CHIPS) covering 150 to 275 Å. This spectrum is dominated in the 200 Å region by emission lines from intermediate charge states of iron (Fe VIII - FeXVI). We also made laboratory measurements of iron emission at temperatures relevent to solar emission on the EBIT-II electron beam ion trap and the Large Helical Device stellerator. We used our laboratory measurements to identify lines and check the CHIANTI database and then used CHIANTI to validate line identifications in the CHIPS spectrum.

A Novel Technique to Infer Ionic Charge States of Solar Energetic Particles

In some large solar energetic particle (SEP) events, the intensities of higher energy SEPs decay more rapidly than at lower energies. This energy dependence varies with particle species, as would be expected if the decay timescale depended on a rigidity-dependent diffusion mean free path. By comparing the decay timescales of carbon, nitrogen, oxygen, neon, magnesium, silicon, sulfur, and iron, mean charge states are inferred for these (and other) elements in three SEP events between 1997 and 2002 at energies between 10 and 200 MeV nucleon−1. In a fourth event, upper limits for the charge states are inferred. The charge states of many different particle species are all consistent with a single source temperature; in two events in 1997 and 2002, the best-fit temperature is much higher than that of the corona, which could imply a contribution from solar flare material. However, comparison with lower energy iron charge states for the 1997 event implies that the observed high-energy charge state could also be understood as the result of stripping during shock acceleration in the corona.

Theory of chemical bonds in metalloenzymes XI: Full geometry optimization and vibration analysis of porphyrin iron‐oxo species

AbstractPhysiochemical properties of compound I and II intermediate states for heme enzymes (catalase, peroxidase, P450) and inorganic models are investigated by hybrid density functional theory. Used theoretical models are composed of an oxoferryl porphyrin and an axial ligand, which are cresol, methylimidazole, methylthiol, and chloride for catalase, peroxidase, P450, and inorganic models, respectively. The oxoferryl bonds are characterized in terms of bond lengths and vibration frequencies. It is found that the oxoferryl bond lengths (the stretching frequency) are shorter (higher) than those of the X‐ray crystal structures of enzymes, on the other hand for inorganic models, they are comparable with the experimental values. Spin density distributions showed that radical state at the compound I can be classified into two types: (1) porphyrin radical state and (2) axial ligand radical state. Peroxidase and inorganic model are in the former case and Catalase and P450 are in the later case at the present calculation models. Magnetic interactions between oxoferryl and ligand radical moieties are analyzed by the natural orbital analysis and it is showed that the effective exchange integral (J) values are strongly related to the radical spin density distributions: axial ligand radical tends to increase the antiferromagnetic interaction. Mössbauer shift parameters are also evaluated and it is shown that iron charge states are similar for these models. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008

Development of a Wide Band and Compact X-Ray Crystal Spectrometer for Iron Charge State Distribution Measurement on LHD

A wide band and compact X-ray spectrometer has been developed using a Johan-type crystal and a back-illuminated CCD detector for charge state distribution measurement of highly ionized iron in LHD. In order to observe all charge states of iron ions a curved crystal of LiF(220) with a curvature of 430 mm was selected for the spectrometer. A wide energy range of 6.4-7.0 keV could be observed with use of CCD detector in a size of 26.6 × 6.7 mm2 . An energy resolution of the spectrometer was 10 eV at full width at half maximum (FWHM). Time-developed Fe Kα spectra were thus measured with a time interval of 10 ms in the full binning mode of the CCD. The charge states from Fe ions of FeXXI to FeXXV were clearly observed, but FeXXVI has not been observed. In the next step, then, the charge state distribution measurement is focused on the measurement of FeXXI-XXV and a quartz(2023) curved crystal is selected to measure the energy range of 6.40-6.75 keV. The expected energy resolution is 4 eV at 6.7 keV for the quartz crystal, which is enough for further analysis of the iron charge state distribution.

Measurement of metastable lifetimes for transitions inFe9+,Fe10+, andFe13+

Radiative lifetimes are measured for metastable levels in the iron charge states ${\mathrm{Fe}}^{9+},{\mathrm{Fe}}^{10+}$, and ${\mathrm{Fe}}^{13+}$. The ions are generated in a 14 GHz electron cyclotron resonance ion source and trapped in a Kingdon ion trap. The Fe levels and their measured lifetimes are (a) $73.0\ifmmode\pm\else\textpm\fi{}0.8\phantom{\rule{0.3em}{0ex}}\mathrm{ms}$ for the $3{s}^{2}3{p}^{4}(^{3}P)3d$ $^{4}F_{7∕2}$ level in ${\mathrm{Fe}}^{9+}$, (b) $9.91\ifmmode\pm\else\textpm\fi{}0.5\phantom{\rule{0.3em}{0ex}}\mathrm{ms}$ for the $3{s}^{2}3{p}^{4}$ $^{1}D_{2}$ level in ${\mathrm{Fe}}^{10+}$, and (c) $17.0\ifmmode\pm\else\textpm\fi{}0.2\phantom{\rule{0.3em}{0ex}}\mathrm{ms}$ for the $3{s}^{2}3p$ $^{2}P^{o}_{3∕2}$ level in ${\mathrm{Fe}}^{13+}$. Comparisons are made to other measured results using a Kingdon trap, an ion storage, and an electron-beam ion trap (EBIT).

Two paramagnetic iron states at the Verwey phase transition in magnetite

At the Verwey phase transition (VPT) region a wide line of the ferromagnetic resonance (FMR) and a narrow EPR spectrum were observed. The EPR line at 125 K occurred and then disappeared below 85 K. This unexpected phenomenon is observed only if iron charge state transformation is present. Simulation of both FMR as well as EPR spectra has indicated the presence of two different iron clusters in the Fe 3O 4 structure. Best fit of both spectra yielded g eff = 2.4 and 4.1 for FMR, and g EPR = 2.8 and 3.4 for EPR. The presence of two-component (EPR, FMR) spectra at about T V is due to a frustration of charge distribution in the B-sublattice as a result of the orthorhombic Pmca pseudosymmetry constraints on the atomic positions in monoclinic symmetry cell P2/c. The paramagnetic (EPR) center observed is an admixtured Fe 2+ state in antiferromagnetically ordered A-sublattice ferromagnetically coupled with the B-lattice. Two paramagnetic defects observed (EPR) of localized spin states are evoked by two valency states of Fe 2.4 and Fe 2.6 below T v . They can originate from two types of Fe 4O 4 cubes: “electron-rich” and” electron-poor” at a ratio 3:1 [J.P. Wright, J.P. Attfield, P.G. Radaelli, Phys. Rev. Lett. 87 (2001) 266401; Phys. Rev. B 66 (2002) 214422] or from two types of bond dimerization (H. Seo, M. Ogata, H. Fukuyama, Phys. Rev. B65 (2002) 85107).

Identification of interplanetary coronal mass ejections at 1 AU using multiple solar wind plasma composition anomalies

We investigate the use of multiple simultaneous solar wind plasma compositional anomalies, relative to the composition of the ambient solar wind, for identifying interplanetary coronal mass ejection (ICME) plasma. We first summarize the characteristics of several solar wind plasma composition signatures (O7/O6, Mg/O, Ne/O, Fe charge states, He/p) observed by the ACE and Wind spacecraft within the ICMEs during 1996–2002 identified by Cane and Richardson [2003], hereafter CR03. We then develop a set of simple criteria that may be used to identify such compositional anomalies and hence potential ICMEs. To distinguish these anomalies from the normal variations seen in ambient solar wind composition, which depend on the wind speed, we compare observed compositional signatures with those “expected” in ambient solar wind with the same solar wind speed. This method identifies anomalies more effectively than the use of fixed thresholds. The occurrence rates of individual composition anomalies within ICMEs range from ∼70% for enhanced iron and oxygen charge states to ∼30% for enhanced He/p (>0.06) and Ne/O and are generally higher in magnetic clouds than other ICMEs. Intervals of multiple anomalies are usually associated with ICMEs and provide a basis for the identification of the majority of ICMEs. We estimate that CR03, who did not refer to composition data, probably identified ∼90% of the ICMEs present. However, around 10% of their ICMEs have weak compositional anomalies, suggesting that the presence of such signatures does not provide a necessary requirement for an ICME. We note a remarkably similar correlation between the Mg/O and O7/O6 ratios in hourly‐averaged data within both ICMEs and the ambient solar wind. This “universal” relationship suggests that similar processes produce the first‐ionization potential bias and enhanced ion freezing‐in temperatures in the source regions of both ICMEs and the ambient solar wind.

Nucleogenic iron charge states in CoO studied by Mössbauer spectroscopy

Single crystal of CoO was doped by about 40-at. ppm of 57Co. Mössbauer spectra were measured vs. sample orientation, temperature and under reduced oxygen pressure, i.e. for a low cobalt vacancy concentration. Distinctly different iron charge states coexist till about 866 K. A mixed-valent state is observed above this temperature. It evolves gradually towards the Fe 2+ state above 1255 K due to the decreasing mobility of holes, as compared to the mobility of the electrons. The ratio of the mobility of holes to the mobility of electrons increases with the increasing vacancy concentration, i.e. with the increasing oxygen pressure. Defects order into clusters below 866 K leaving behind almost perfect structure. A recoilless fraction exhibits some anharmonicity above 923 K.

Correction to “Iron charge state distributions as an indicator of hot ICMEs: Possible sources and temporal and spatial variations during solar maximum”

Correction to “Iron charge state distributions as an indicator of hot ICMEs: Possible sources and temporal and spatial variations during solar maximum”

Iron charge state distributions as an indicator of hot ICMEs: Possible sources and temporal and spatial variations during solar maximum

It has been shown that Fe charge states greater than and equal to 16 are often observed in the presence of interplanetary coronal mass ejections (ICMEs) at 1 AU. These elevated charge states, representative of hot source regions on the Sun, provide an identifier of ICMEs independent of expansion processes and heliocentric distance. Using this new identifier, we present a comparative study of Fe charge state distributions as a function of latitude and time. We compare Fe charge state data from the ACE spacecraft in the ecliptic plane with that from the Ulysses spacecraft along its orbit from low to high latitudes. We discuss the frequencies of high Fe charge state distributions through a range of latitudes on the approach toward solar maximum. Close to solar maximum, we find almost an order of magnitude fewer hot ICMEs at higher latitudes than in the ecliptic. We offer an explanation for the existence of high Fe charge states in hot ICMEs as a result of magnetic connectivity to flaring regions.

The use of iron charge state changes as a tracer for solar wind entry and energization within the magnetosphere

Abstract. The variation of the charge state of iron [Fe] ions is used to trace volume elements of plasma in the solar wind into the magnetosphere and to determine the time scales associated with the entry into and the action of the magnetospheric energization process working on these plasmas. On 2–3 May 1998 the Advanced Composition Explorer (ACE) spacecraft located at the L1 libration point observed a series of changes to the average charge state of the element Fe in the solar wind plasma reflecting variation in the coronal temperature of their original source. Over the period of these two days the average Fe charge state was observed to vary from + 15 to + 6 both at the Polar satellite in the high latitude dayside magnetosphere and at ACE. During a period of southward IMF the observations at Polar inside the magnetosphere of the same Fe charge state were simultaneous with those at ACE delayed by the measured convection speed of the solar wind to the subsolar magnetopause. Comparing the phase space density as a function of energy at both ACE and Polar has indicated that significant energization of the plasma occurred on very rapid time scales. Energization at constant phase space density by a factor of 5 to 10 was observed over a range of energy from a few keV to about 1 MeV. For a detector with a fixed energy threshold in the range from 10 keV to a few hundred keV this observed energization will appear as a factor of ~103 increase in its counting rate. Polar observations of very energetic O+ ions at the same time indicate that this energization process must be occurring in the high latitude cusp region inside the magnetosphere and that it is capable of energizing ionospheric ions at the same time.Key words. Magnetospheric physics (magnetopause, cusp, and boundary layers; magnetospheric configuration and dynamics; solar wind-magnetosphere interactions)

Internal structure of magnetic clouds: Plasma and composition

A comprehensive analysis of magnetic clouds observed by the Advanced Composition Explorer (ACE) spacecraft from February 1998 to July 2001 is presented. The magnetic field data from the MAG instrument is fit with the cylindrically symmetric, linear force‐free model and the fit parameter distributions are examined. This magnetic field model enables us to map plasma data from the SWEPAM and SWICS instruments to a position within the model cylinder. A superposed epoch analysis of all our magnetic cloud events is used to construct diameter cuts through an “average” cloud profile in any desired plasma, elemental composition, or charge state quantity. These diameter cuts are found to have nontrivial structure and there appears to be significant composition and structural differences between clouds of different speeds. The slow magnetic clouds (〈Vrad〉 < 500 km/s) have an almost constant proton density profile whereas the fast magnetic cloud (〈Vrad〉 ≥ 500 km/s) profile is depleted throughout with symmetric dips and a local maximum at the cloud center. The fast magnetic clouds have a slightly higher Nα/Np ratio than the slow clouds. Both the fast and slow events have enhanced oxygen and iron charge states compared to the slow solar wind. The fast events have a slightly increased O7+/O6+ average profile and a much stronger Fe≥16+/Fetotal profile than the slow events. We briefly discuss the implications for physical conditions at the Sun, the role these coronal mass ejections (CMEs) may play in transporting magnetic flux, and the application of our structure results to the current flux rope CME modeling effort.