Ion Charge States in the Fast Solar Wind: New Data Analysis and Theoretical Refinements

We present a further investigation into the increased ionization observed in element charge states in the fast solar wind compared to its coronal hole source regions. Once ions begin to be perpendicularly heated by ion cyclotron waves and execute large gyro-orbits, density gradients in the flow can excite lower hybrid waves that then damp by heating electrons in the parallel direction. We give further analysis of charge state data from polar coronal holes at solar minimum and maximum, and also from equatorial coronal holes. We also consider further the damping of lower hybrid waves by ions and the effect of non-Maxwellian electron distribution functions on the degree of increased ionization, both of which appear to be negligible for the solar wind case considered here. We also suggest that the density gradients required to heat electrons sufficiently to further ionize the solar wind can plausibly result from the turbulent cascade of MHD waves.Comment: 27 pages, accepted by Ap

Response of a delta-doped charge-coupled device to low energy protons and nitrogen ions

We present the results of a study of the response of a delta-doped charge-coupled device (CCD) exposed to ions with energies less than 10 keV10keV. The study of ions in the solar wind, the majority having energies in the 1–5 keV1–5keV range, has proven to be vital in understanding the solar atmosphere and the near Earth space environment. Delta-doped CCD technology has essentially removed the dead layer of the silicon detector. Using the delta-doped detector, we are able to detect H+H+ and N+N+ ions with energies ranging from 1 to 10 keV1to10keV in the laboratory. This is a remarkable improvement in the low energy detection threshold over conventional solid-state detectors, such as those used in space sensors, one example being the solar wind ion composition spectrometer (SWICS) on the Advanced Composition Explorer spacecraft, which can only detect ions with energies greater than 30 keV30keV because of the solid-state detector’s minimum energy threshold. Because this threshold is much higher than the average energy of the solar wind ions, the SWICS instrument employs a bulky high voltage postacceleration stage that accelerates ions above the 30 keV30keV detection threshold. This stage is massive, exposes the instrument to hazardous high voltages, and is therefore problematic both in terms of price and its impact on spacecraft resources. Adaptation of delta-doping technology in future space missions may be successful in reducing the need for heavy postacceleration stages allowing for miniaturization of space-borne ion detectors.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87896/2/053301_1.pd

Ion Charge States in Halo CMEs: What can we Learn about the Explosion?

We describe a new modeling approach to develop a more quantitative understanding of the charge state distributions of the ions of various elements detected in situ during halo Coronal Mass Ejection (CME) events by the Advanced Composition Explorer (ACE) satellite. Using a model CME hydrodynamic evolution based on observations of CMEs propagating in the plane of the sky and on theoretical models, we integrate time dependent equations for the ionization balance of various elements to compare with ACE data. We find that plasma in the CME ``core'' typically requires further heating following filament eruption, with thermal energy input similar to the kinetic energy input. This extra heating is presumably the result of post eruptive reconnection. Plasma corresponding to the CME ``cavity'' is usually not further ionized, since whether heated or not, the low density gives freeze-in close the the Sun. The current analysis is limited by ambiguities in the underlying model CME evolution. Such methods are likely to reach their full potential when applied to data to be acquired by STEREO when at optimum separation. CME evolution observed with one spacecraft may be used to interpret CME charge states detected by the other.Comment: 20 pages, accepted by Ap

New Solar Wind Diagnostic Using Both in Situ and Spectroscopic Measurements

We develop a new diagnostic technique that utilizes, at the same time, two completely different types of observations—in situ determinations of solar wind charge states and high-resolution spectroscopy of the inner solar corona—in order to study the temperature, density, and velocity of the solar wind as a function of height in the inner corona below the plasma freeze-in point. This technique relies on the ability to calculate the evolution of the ion charge composition as the solar wind escapes the Sun given the wind temperature, density, and velocity profiles as a function of distance. The resulting charge state composition can be used to predict frozen-in charge states as well as spectral line intensities. The predicted spectra and ion charge compositions can be compared with observations carried out when spectrometers and in situ instruments are in quadrature configuration to quantitatively test a set of assumptions regarding density, temperature, and velocity profiles in the low corona. Such a comparison can be used in two ways. If the input profiles are predicted by a theoretical solar wind model, this technique allows the benchmarking of the model. Otherwise, an empirical determination of the velocity, temperature, and density profiles can be achieved below the plasma freeze-in point applying a trial-and-error procedure to initial, user-specified profiles. To demonstrate this methodology, we have applied this technique to a state-of-the-art coronal hole and equatorial streamer model.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98555/1/0004-637X_750_2_159.pd

ON THE ORIGIN OF MID-LATITUDE FAST WIND: CHALLENGING THE TWO-STATE SOLAR WIND PARADIGM

The bimodal paradigm of solar wind describes a slow solar wind situated near the heliospheric current sheet while a fast wind overexpands from the poles to fill in the remainder of the heliosphere. In this paper, we challenge this paradigm and focus here on mid-latitude wind using three fast-latitude passes completed by the Ulysses spacecraft. Based on its composition and dynamic properties, we discuss how this wind differs from both the fast, polar coronal hole wind and the low latitude, streamer-associated slow solar wind. Using a detailed analysis of ionic and elemental abundances, as well as solar wind dynamic properties, we conclude that there is a third quasi-stationary solar wind state, called the boundary wind. This boundary wind is characterized by a charge-state distribution that is similar to slow wind, but with an elemental composition that is coronal hole like. Based on these data, we present arguments for the location of the origin of this wind. We conclude that the boundary wind is a subset of the fast wind emanating from regions close to the boundaries of coronal holes and is accelerated by a similar process

Constraints on Coronal Mass Ejection Evolution from in Situ Observations of Ionic Charge States

We present a novel procedure for deriving the physical properties of coronal mass ejections (CMEs) in the corona. Our methodology uses in situ measurements of ionic charge states of C, O, Si, and Fe in the heliosphere and interprets them in the context of a model for the early evolution of interplanetary CME (ICME) plasma, between 2 and 5 R _ . We find that the data are best fit by an evolution that consists of an initial heating of the plasma, followed by an expansion that ultimately results in cooling. The heating profile is consistent with a compression of coronal plasma due to flare reconnection jets and an expansion cooling due to the ejection, as expected from the standard CME/flare model. The observed frozen-in ionic charge states reflect this time history and, therefore, provide important constraints for the heating and expansion timescales, as well as the maximum temperature the CME plasma is heated to during its eruption. Furthermore, our analysis places severe limits on the possible density of CME plasma in the corona. We discuss the implications of our results for CME models and for future analysis of ICME plasma composition.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90747/1/0004-637X_730_2_103.pd

The Composition of Interplanetary Coronal Mass Ejections

Interplanetary coronal mass ejection (ICME) associated plasma can exhibit signatures in elemental, ionic and isotopic composition. These signatures occur in less than 50% of all ICMEs, but are very indicative of ICME plasma. We review these compositional anomalies and briefly discuss a physical scenario that could be responsible for these anomalies. © 2003 American Institute of PhysicsPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87653/2/604_1.pd

ON THE ORIGIN OF MID-LATITUDE FAST WIND: CHALLENGING THE TWO-STATE SOLAR WIND PARADIGM

The bimodal paradigm of solar wind describes a slow solar wind situated near the heliospheric current sheet while a fast wind overexpands from the poles to fill in the remainder of the heliosphere. In this paper, we challenge this paradigm and focus here on mid-latitude wind using three fast-latitude passes completed by the Ulysses spacecraft. Based on its composition and dynamic properties, we discuss how this wind differs from both the fast, polar coronal hole wind and the low latitude, streamer-associated slow solar wind. Using a detailed analysis of ionic and elemental abundances, as well as solar wind dynamic properties, we conclude that there is a third quasi-stationary solar wind state, called the boundary wind. This boundary wind is characterized by a charge-state distribution that is similar to slow wind, but with an elemental composition that is coronal hole like. Based on these data, we present arguments for the location of the origin of this wind. We conclude that the boundary wind is a subset of the fast wind emanating from regions close to the boundaries of coronal holes and is accelerated by a similar process

Spatial Relationship of Signatures of Interplanetary Coronal Mass Ejections

Interplanetary coronal mass ejections (ICMEs) are characterized by a number of signatures. In particular, we examine the relationship between Fe charge states and other signatures during ICMEs in solar cycle 23. Though enhanced Fe charge states characterize many ICMEs, average charge states vary from event to event, are more likely to be enhanced in faster or flare‐related ICMEs, and do not appear to depend on whether the ICME is a magnetic cloud. © 2003 American Institute of PhysicsPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87650/2/681_1.pd