Figure 7 - available via license: Creative Commons Attribution 4.0 International
Content may be subject to copyright.
Silicon (Si 7+ /Si 8+ (top, left), Si 8+ /Si 9+ (top, right)), and sulfur (S 9+ /S 10+ (bottom, left), S 11+ /S 10+ (bottom, right)) charge state ratios solutions are shown in the same meridional plane as in Figures 5 and 6.
Source publication
The charge state composition of the solar wind carries information about the electron temperature, density, and velocity of plasma in the solar corona that cannot always be measured with remote sensing techniques, due to limitations in instrumental sensitivity and field of view as well as line-of-sight integration issues. However, in situ measureme...
Context in source publication
Context 1
... reached a (presumably) frozen-in state already at about 1.4 R e . Figure 15 shows the ratio between the charge state values and their frozen-in value along each flow line: results of the fast wind coronal holes centers are qualitatively similar to those obtained in 1D by Landi et al. (2012a Figure 7), using the fast wind from the coronal hole model of Cranmer et al. (2007). Plasma traveling along flow lines corresponding to open magnetic field freeze-in below 3 R e , although the precise height changes from ion to ion and flow line to flow line, with #1 freezing in already at 1.5 R e despite coming from a lowlatitude source region. ...
Citations
... described the physics within AWSoM in great detail, while van der Holst et al. (2022) discussed the recent improvement of the Alfvén wave turbulence cascade. AWSoM results have shown reasonable agreement with in situ and remote observations under different solar wind conditions (Jin et al. 2012; Oran et al. 2013; Sachdeva et al. 2019; van der Holst et al. 2019;Sachdeva et al. 2021;Szente et al. 2022;Huang et al. 2023;Szente et al. 2023;Shi et al. 2024) and were widely used in the community(Jian et al. 2016;Lloveras et al. 2020;Henadhira Arachchige et al. 2022). ...
A potential field solution is widely used to extrapolate the coronal magnetic field above the Sun’s surface to a certain height. This model applies the current-free approximation and assumes that the magnetic field is entirely radial beyond the source surface height, which is defined as the radial distance from the center of the Sun. Even though the source surface is commonly specified at 2.5 R s (solar radii), previous studies have suggested that this value is not optimal in all cases. In this study, we propose a novel approach to specify the source surface height by comparing the areas of the open magnetic field regions from the potential field solution with predictions made by a magnetohydrodynamic model, in our case the Alfvén Wave Solar atmosphere Model. We find that the adjusted source surface height is significantly less than 2.5 R s near solar minimum and slightly larger than 2.5 R s near solar maximum. We also report that the adjusted source surface height can provide a better open flux agreement with the observations near the solar minimum, while the comparison near the solar maximum is slightly worse.
... It is open-source on GitHub 1 and can also be accessed via the runs-on-request service provided by the Community Coordinated Modeling Center. AWSoM has been extensively validated with in situ and remote observations under different solar wind conditions (Jin et al. 2012;Oran et al. 2013;Sachdeva et al. 2021;Szente et al. 2022Szente et al. , 2023Huang et al. 2023), as well as at different heliocentric distances including Parker Solar Probe locations (van der Holst et al. 2019, 2022). ...
In a previous study, Huang et al. used the Alfvén Wave Solar atmosphere Model, one of the widely used solar wind models in the community, driven by ADAPT-GONG magnetograms to simulate the solar wind in the last solar cycle and found that the optimal Poynting flux parameter can be estimated from either the open field area or the average unsigned radial component of the magnetic field in the open field regions. It was also found that the average energy deposition rate (Poynting flux) in the open field regions is approximately constant. In the current study, we expand the previous work by using GONG magnetograms to simulate the solar wind for the same Carrington rotations and determine if the results are similar to the ones obtained with ADAPT-GONG magnetograms. Our results indicate that similar correlations can be obtained from the GONG maps. Moreover, we report that ADAPT-GONG magnetograms can consistently provide better comparisons with 1 au solar wind observations than GONG magnetograms, based on the best simulations selected by the minimum of the average curve distance for the solar wind speed and density.
... Multiple modules can be coupled with AWSoM to gain more insight into the underlying physics of the system. For example, spectroscopic images can be made with the SPECTRUM module (Szente et al. 2019;Shi et al. 2022) and the charge states' composition through the heliosphere can be modeled using the nonequilibrium ionization charge state calculations (Szente et al. 2022(Szente et al. , 2023. ...
We used the stream-aligned magnetohydrodynamics (SA-MHD) model to simulate Carrington rotation 2210, which contains Parker Solar Probe’s (PSP) first perihelion at 36.5 R ⊙ on 2018 November 6, to provide context to the in situ PSP observations by FIELDS and SWEAP. The SA-MHD model aligns the magnetic field with the velocity vector at each point, thereby allowing for clear connectivity between the spacecraft and the source regions on the Sun, without unphysical magnetic field structures. During this Carrington rotation, two stream interaction regions (SIRs) form, due to the deep solar minimum. We include the energy partitioning of the parallel and perpendicular ions and the isotropic electrons to investigate the temperature anisotropy through the compression regions to better understand the wave energy amplification and proton thermal energy partitioning in a global context. Overall, we found good agreement in all in situ plasma parameters between the SA-MHD results and the observations at PSP, STEREO-A, and Earth, including at PSP’s perihelion and through the compression region of the SIRs. In the typical solar wind, the parallel proton temperature is preferentially heated, except in the SIR, where there is an enhancement in the perpendicular proton temperature. This is further showcased in the ion cyclotron relaxation time, which shows a distinct decrease through the SIR compression regions. This work demonstrates the success of the Alfvén wave turbulence theory for predicting interplanetary magnetic turbulence levels, while self-consistently reproducing solar wind speeds, densities, and overall temperatures, including at small heliocentric distances and through SIR compression regions.
... This module has been tested in our hydrodynamic 1D, WTD wind code (Lionello et al. 2019). A similar time-dependent 3D model of charges states of minor ions is shown in Szente et al. (2022). ...
We describe, test, and apply a technique to incorporate full-Sun, surface flux evolution into an MHD model of the global solar corona. Requiring only maps of the evolving surface flux, our method is similar to that of Lionello et al., but we introduce two ways to correct the electric field at the lower boundary to mitigate spurious currents. We verify the accuracy of our procedures by comparing to a reference simulation, driven with known flows and electric fields. We then present a thermodynamic MHD calculation lasting one solar rotation driven by maps from the magnetic flux evolution model of Schrijver & DeRosa. The dynamic, time-dependent nature of the model corona is illustrated by examining the evolution of the open flux boundaries and forward-modeled EUV emission, which evolve in response to surface flows and the emergence and cancellation flux. Although our main goal is to present the method, we briefly investigate the relevance of this evolution to properties of the slow solar wind, examining the mapping of dipped field lines to the topological signatures of the “S-Web” and comparing charge state ratios computed in the time-dependently driven run to a steady-state equivalent. Interestingly, we find that driving on its own does not significantly improve the charge state ratios, at least in this modest resolution run that injects minimal helicity. Still, many aspects of the time-dependently driven model cannot be captured with traditional steady-state methods, and such a technique may be particularly relevant for the next generation of solar wind and coronal mass ejection models.
... In this paper, we carried out a global simulation using a magnetogram by the Global Oscillation Network Group (GONG; Harvey et al. 1996) with the radial magnetic field of CR 2063 (between 2007 November 7 and 2007 December 4). Szente et al. (2022) recently implemented in AWSoM the capability of calculating NEI for multiple ions self-consistently as part of the main simulation. The charge states are calculated throughout the three-dimensional domain of the solar corona and inner heliosphere by solving the set of continuity equations for ions X + m with number density N(X + m ): Here, T e is the electron temperature, N e is the electron density, and u is the solar wind bulk speed. ...
... The charge states are calculated using tables for the total ionization and recombination rates, C m (T e ) and R m (T e ), obtained from CHIANTI 10.0 (Dere et al. 1997;Del Zanna et al. 2021). The details of the implementation of charge-state calculations can be found in Szente et al. (2022). In this paper, we calculated the charge states of ions of C, N O, Ne, Mg, Si, S, and Fe, as these are the ions providing the bulk of the emission observed by current remote-sensing instrumentation working on the UV, EUV, and X-ray wavelength ranges; AWSoM can calculate charge states for all elements included in the CHIANTI database, namely, from H to Zn. ...
... We first studied how individual line intensities change when the assumption of EI is released, utilizing the same AWSoM model results used by Szente et al. (2022), which included the calculation of nonequilibrium charge states. This simulation used the GONG magnetogram of CR 2063 as a boundary condition (corresponding to the minimum of solar cycle 24 between 2007 November 4 and December 1), and provided, after evolving for 200,000 time steps, a realistic steady-state plasma solution in the 3D solar corona from 50,000 K (at 1 R ☉ ) out to 24 R ☉ . ...
In this work, we combined AWSoM’s nonequilibrium ionization (NEI) calculations from Szente et al. with the synthetic spectral computations of SPECTRUM to predict nonequilibrium line intensities across the entire domain of the AWSoM 3D global model. We find that the resulting spectra are strongly affected by nonequilibrium effects in the fast-wind regions and streamer edges and that these effects propagate to narrowband images from SoHO/EIT, SECCHI/EUVI, and SDO/AIA. The dependence shows a different nature for each line observed, resulting in significant changes in line intensity, which need to be accounted for during plasma diagnostics. However, we also find that these effects depend on the local plasma properties, and that no single correction can be developed to account for nonequilibrium effects in observed spectra and images. With a comparison to observational data, we saw that the changes due to NEI, while significant, are not sufficient to account for the differences between Hinode/EIS spectra and AWSoM/SPECTRUM predictions.
... Along with non-thermal particle distributions, large gradients in temperature, density, and outflow speed can lead to NEI conditions which affect the interpretation of the plasma properties inferred from their emission (Landi et al 2012, Gilly & Cranmer 2020. NEI develops for conditions where the thermodynamic state of plasma changes rapidly such that the ionization and recombination processes that establish ion abundances become unbalanced and lead to ion quantities that do not reflect the immediate plasma state (Shen et al 2017, Szente et al 2022. Figure 3, adapted from Rivera et al 2019, shows a comparison of synthetic intensities in select spectral lines of outflowing solar material for equilibrium (dashed magenta) and NEI (solid green) conditions indicating that a rapid deviation from the ionization equilibrium assumption can occur low in the corona. ...
... Previous work has indicated that the inclusion of time-dependent ionization and recombination of heavy ions can provide a useful observational constraint to models of the solar wind and transients through the comparison of both remote sensing, i.e. synthetic multi-wavelength emission, and in situ observations, i.e. simulated freeze-in charge state distributions, as shown through simulated intensities and particle abundances in the top and bottom of Figure 3, respectively (Oran et al 2015, Shen et al 2017, Lionello et al 2019, Szente et al 2022. For instance, simulations of heavy ion evolution in solar eruptions have provided critical insight to the energy deposition and non uniform heating experienced in coronal mass ejections (CMEs) essential to constraining the energy budget (Rakowski et al 2007, Lynch et al 2011, Gruesbeck et al 2011, 2012, Rivera et at 2019a as well as important in determining the source region and dynamic processes occurring during solar wind outflow (Ko et al 1997, Gilly & Cranmer 2020, Rivera et al 2020. ...
... Since there has been recent progress integrating aspects of heavy ion composition forward modeling into steady-state MHD solar wind calculations (e.g., Oran et al. 2015;Shen et al. 2017;Lionello et al. 2019;Szente et al. 2022), it would be extremely interesting to perform these calculations on dynamic, time-dependent MHD modeling of the formation and evolution of coherent magnetic structures generated under different reconnection scenarios. For example, the Aslanyan et al. (2022) calculation of the synthetic suprathermal electron PAD "time series" associated with PS interchange reconnection outflows shows excellent qualitative agreement with the observed broadening of the strahl for some of our PS intervals (#4, #6, and #7 in particular). ...
Connecting the solar wind observed throughout the heliosphere to its origins in the solar corona is one of the central aims of heliophysics. The variability in the magnetic field, bulk plasma, and heavy ion composition properties of the slow wind are thought to result from magnetic reconnection processes in the solar corona. We identify regions of enhanced variability and composition in the solar wind from 2003 April 15 to May 13 (Carrington Rotation 2002), observed by the Wind and Advanced Composition Explorer spacecraft, and demonstrate their relationship to the separatrix–web (hereafter, S-Web) structures describing the corona’s large-scale magnetic topology. There are four pseudostreamer (PS) wind intervals and two helmet streamer (HS) heliospheric current sheet/plasma sheet crossings (and an interplanetary coronal mass ejection), which all exhibit enhanced alpha-to-proton ratios and/or elevated ionic charge states of carbon, oxygen, and iron. We apply the magnetic helicity–partial variance of increments ( H m –PVI) procedure to identify coherent magnetic structures and quantify their properties during each interval. The mean duration of these structures are ∼1 hr in both the HS and PS wind. We find a modest enhancement above the power-law fit to the PVI waiting-time distribution in the HS-associated wind at the 1.5–2 hr timescales that is absent from the PS intervals. We discuss our results in the context of previous observations of the ∼90 minutes periodic density structures in the slow solar wind, further development of the dynamic S-Web model, and future Parker Solar Probe and Solar Orbiter joint observational campaigns.
... Along with non-thermal particle distributions, large gradients in temperature, density, and outflow speed can lead to NEI conditions which affect the interpretation of the plasma properties inferred from their emission (Landi et al 2012;Gilly & Cranmer 2020). NEI develops for conditions where the thermodynamic state of plasma changes rapidly such that the ionization and recombination processes that establish ion abundances become unbalanced and lead to ion quantities that do not reflect the immediate plasma state (Shen et al 2017;Szente et al 2022). Figure 2, adapted from Rivera et al 2019, shows a comparison of synthetic intensities in select spectral lines of outflowing solar material for equilibrium (dashed magenta) and NEI (solid green) conditions indicating that a rapid deviation from the ionization equilibrium assumption can occur low in the corona. ...
This paper outlines the necessity for the availability, accessibility, and expansion of atomic physics data and analysis tools for the meaningful interpretation of spectroscopic and polarimetric observations. As we move towards observing the Sun at higher spatio-temporal resolutions, and near-continuously at a range of wavelengths, it becomes critical to develop the appropriate atomic data and physics tools to facilitate scientific progress. We recommend the continued improvement and expansion of current databases to support the development of optically-thick/radiative transfer models, evaluate non-thermal and non-equilibrium ionization effects, and quantify uncertainties in atomic and molecular values. A critical long-term goal will require extending and strengthening collaborations across the atomic, solar/heliospheric, and laboratory plasma physics communities through the participation and training of early career scientists. We also recommend establishing funding for a centralized atomic physics resource made up of a comprehensive and user-oriented atomic database and modeling framework.
... The reconnection models can naturally explain the observed density fluctuations and some composition anomalies in the slow wind. Both models have some difficulty reproducing the ionization states measured in the heliosphere (Oran et al. 2015;Shen et al. 2017;Szente et al. 2022). We also note that while coronal mass ejections (CMEs) are basically driven by simple MHD forces, the ejected plasma continues to be heated after it leaves the Sun (Akmal et al. 2001;Lee et al. 2009;Rakowski et al. 2007Rakowski et al. , 2011Murphy et al. 2011;Wilson et al. 2022), but the nature of that heating is difficult to determine. ...
The SWICS instrument on board the ACE satellite has detected frequent intervals in the slow solar wind and interplanetary coronal mass ejections in which C ⁶⁺ and other fully stripped ions are strongly depleted, though the ionization states of elements such as Si and Fe indicate that those ions should be present. It has been suggested that these “outlier” or “dropout” events can be explained by the resonant cyclotron heating process, because these ions all have the same cyclotron frequency as He ²⁺ . We investigate the region in the corona where these outlier events form. It must be above the ionization freeze-in height and the transition to collisionless plasma conditions, but low enough that the wind still feels the effects of solar gravity. We suggest that the dropout events correspond to relatively dense blobs of gas in which the heating is reduced because local variations in the Alfvén speed change the reflection of Alfvén waves and the turbulent cascade. As a result, the wave power at the cyclotron frequency of the fully stripped ions is absorbed by He ²⁺ and may not be able to heat the other fully stripped ions enough to overcome solar gravity. If this picture is borne out, it may help to discriminate between resonant cyclotron heating and stochastic heating models of the solar wind.
