Exploring the Origin of Coronal Mass Ejection Plasma from In Situ Observations of Ionic Charge State Composition.

Solar wind ionic composition measurements are powerful tools in discriminating between different sources of solar wind as well as identifying interplanetary coronal mass ejections (ICMEs). First, we present a new charge state evolution model which estimates the coronal electron environment from in situ ionic composition measurements. The coronal electron profile is not well measured, as direct observations are difficult to obtain due to the extreme heat and radiation near the sun. Using this model, we show that the unique bi-modal charge states, observed in the iron charge state distribution, may be a direct result of the heating and expansion characteristics of a coronal mass ejection (CME). We next turn our attention to very cool charge states which are sometimes observed concurrently with hot charge states during ICMEs. We show that these observations are a result of simultaneous observations of hot plasma and the remnants of an embedded prominence within the same ICME. We then use the charge state distribution to explore the origin of suprathermal plasma observed during ICMEs. Suprathermal plasma is known to be an important seed population for solar energetic particles (SEPs) which are accelerated at the CME-driven shock, but the plasma which is being accelerated to the suprathermal energies is not well understood. Using in situ measurements from the Suprathermal Ion Composition Spectrometer (STICS) onboard the Wind spacecraft and the Solar Wind Ion Composition Spectrometer (SWICS) on the Advanced Composition Explorer (ACE), we compare the suprathermal ionic composition to the bulk solar wind plasma during ICMEs. We present a comparison of suprathermal iron and oxygen to the co-located bulk plasma distribution during ICMEs as well as the bulk plasma upstream of the CME-driven shock. This is one of the first studies to present the suprathermal composition of heavy ions observed in ICME plasma. We find that there is a strong correlation between the suprathermal plasma and the co-located bulk plasma and not with the upstream bulk plasma. This implies a local acceleration mechanism is energizing the local bulk plasma to suprathermal energies and not due to shock acceleration acting on the heliospheric plasma upstream of the ICME.PhDAtmospheric, Oceanic and Space SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/99920/1/jagruesb_1.pd

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

Constraints on CME 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 ICME plasma, between 2 - 5 R-solar. We find that the data can be fit only 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 reconnect ion 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 time-scales, 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

Making waves: Mirror Mode structures around Mars observed by the MAVEN spacecraft

We present an in-depth analysis of a time interval when quasi-linear mirror mode structures were detected by magnetic field and plasma measurements as observed by the NASA/Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft. We employ ion and electron spectrometers in tandem to support the magnetic field measurements and confirm that the signatures are indeed mirror modes. Wedged against the magnetic pile-up boundary, the low-frequency signatures last on average $\sim$10 s with corresponding sizes of the order of 15-30 upstream solar wind proton thermal gyroradii, or 10-20 proton gyroradii in the immediate wake of the quasi-perpendicular bow shock. Their peak-to-peak amplitudes are of the order of 30-35 nT with respect to the background field, and appear as a mixture of dips and peaks, suggesting that they may have been at different stages in their evolution. Situated in a marginally stable plasma with $\beta_{||}\sim$1, we hypothesise that these so-called magnetic bottles, containing a relatively higher energy and denser ion population with respect to the background plasma, are formed upstream of the spacecraft behind the quasi-perpendicular shock. These signatures are very reminiscent of magnetic bottles found at other unmagnetised objects such as Venus and comets, also interpreted as mirror modes. Our case study constitutes the first unmistakable identification and characterisation of mirror modes at Mars from the joint points of view of magnetic field, electron and ion measurements. Up until now, the lack of high-temporal resolution plasma measurements has prevented such an in-depth study.Comment: 37 pages, 11 figures, 1 tabl

CME Evolution in the Structured Heliosphere and Effects at Earth and Mars During Solar Minimum

The activity of the Sun alternates between a solar minimum and a solar maximum, the former corresponding to a period of "quieter" status of the heliosphere. During solar minimum, it is in principle more straightforward to follow eruptive events and solar wind structures from their birth at the Sun throughout their interplanetary journey. In this paper, we report analysis of the origin, evolution, and heliospheric impact of a series of solar transient events that took place during the second half of August 2018, i.e. in the midst of the late declining phase of Solar Cycle 24. In particular, we focus on two successive coronal mass ejections (CMEs) and a following high-speed stream (HSS) on their way towards Earth and Mars. We find that the first CME impacted both planets, whilst the second caused a strong magnetic storm at Earth and went on to miss Mars, which nevertheless experienced space weather effects from the stream interacting region (SIR) preceding the HSS. Analysis of remote-sensing and in-situ data supported by heliospheric modelling suggests that CME--HSS interaction resulted in the second CME rotating and deflecting in interplanetary space, highlighting that accurately reproducing the ambient solar wind is crucial even during "simpler" solar minimum periods. Lastly, we discuss the upstream solar wind conditions and transient structures responsible for driving space weather effects at Earth and Mars.Comment: 27 pages, 7 figures, 1 table, accepted for publication in Space Weathe

The Interplanetary Magnetic Field Observed by Juno Enroute to Jupiter

The Juno spacecraft was launched on 5 August 2011 and spent nearly 5 years traveling through the inner heliosphere on its way to Jupiter. The Magnetic Field Investigation was powered on shortly after launch and obtained vector measurements of the interplanetary magnetic field (IMF) at sample rates from 1 to 64 samples/second. The evolution of the magnetic field with radial distance from the Sun is compared to similar observations obtained by Voyager 1 and 2 and the Ulysses spacecraft, allowing a comparison of the radial evolution between prior solar cycles and the current depressed one. During the current solar cycle, the strength of the IMF has decreased throughout the inner heliosphere. A comparison of the variance of the normal component of the magnetic field shows that near Earth the variability of the IMF is similar during all three solar cycles but may be less at greater radial distances

Cross Shock Electrostatic Potentials at Mars Inferred From MAVEN Measurements

International audienceA bow shock is generated by the interaction of the solar wind with the planetary global dipole field (e.g., Earth), or with (mainly) the planetary ionosphere (e.g., Mars). The cross shock potential has been well studied at Earth but not yet for Mars. We infer and approximate the peak in the frame invariant de Hoffmann Teller shock potential profile at Mars (ϕ) with data from the Mars Atmospheric and Volatile EvolutioN (MAVEN) mission. We find that ϕ and its ratio to the solar wind ram ion energy (Eram) vary similarly against solar zenith angle (SZA, a proxy for the angle between the solar wind flow and the shock normal) and magnetic latitudes. Our results also reveal no significant dependence of the shock potential on parameters such as the angle between the upstream interplanetary magnetic field (IMF) and the shock normal and plasma beta of upstream solar wind. There is a somewhat positive correlation with the magnetosonic Mach number and the magnetic amplification ratio across the shock. We also find a solar cycle effect on the shock location, closer to the planet near the solar minimum, as expected. Lastly, similarities and differences of cross shock potentials at Mars and Earth are discussed. Characterizing electron energization and high altitude ion loss at Mars is influenced by the bow shock and thereby the work here

A Two-Spacecraft Study of Mars' Induced Magnetosphere's Response to Upstream Conditions

This is a two-spacecraft study, in which we investigate the effects of the upstream solar wind conditions on the Martian induced magnetosphere and upper ionosphere. We use Mars Express (MEX) magnetic field magnitude data together with interplanetary magnetic field (IMF), solar wind density, and velocity measurements from the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission, from November 2014 to November 2018. We compare simultaneous observations of the magnetic field magnitude in the induced magnetosphere of Mars (|B|(IM)) with the IMF magnitude (|B|(IMF)), and we examine variations in the ratio |B|(IM)/|B|(IMF) with solar wind dynamic pressure, speed and density. We find that the |B|(IM)/|B|(IMF) ratio in the induced magnetosphere generally decreases with increased dynamic pressure and that a more structured interaction is seen when comparing induced fields to the instantaneous IMF, where reductions in the relative fields at the magnetic pile up boundary (MPB) are more evident than in the field strength itself, along with enhancements in the immediate vicinity of the optical shadow of Mars. We interpret these results as evidence that while the induced magnetosphere is indeed compressed and induced field strengths are higher during periods of high dynamic pressure, a relatively larger amount of magnetic flux threads the region compared to that available from the unperturbed IMF during low dynamic pressure intervals

On the Growth and Development of Non‐Linear Kelvin–Helmholtz Instability at Mars: MAVEN Observations

In this study, we have analyzed Mars Atmosphere and Volatile EvolutioN (MAVEN) observations of fields and plasma signatures associated with an encounter of fully developed Kelvin–Helmholtz (K–H) vortices at the northern polar terminator along Mars’ induced magnetosphere boundary. The signatures of the K–H vortices event are: (a) quasi‐periodic, “bipolar‐like” sawtooth magnetic field perturbations, (b) corresponding density decrease, (c) tailward enhancement of plasma velocity for both protons and heavy ions, (d) co‐existence of magnetosheath and planetary plasma in the region prior to the sawtooth magnetic field signature (i.e., mixing region of the vortex structure), and (e) pressure enhancement (minimum) at the edge (center) of the sawtooth magnetic field signature. Our results strongly support the scenario for the non‐linear growth of K–H instability along Mars’ induced magnetosphere boundary, where a plasma flow difference between the magnetosheath and induced‐magnetospheric plasma is expected. Our findings are also in good agreement with 3‐dimensional local magnetohydrodynamics simulation results. MAVEN observations of protons with energies greater than 10 keV and results from the Walén analyses suggests the possibility of particle energization within the mixing region of the K–H vortex structure via magnetic reconnection, secondary instabilities or other turbulent processes. We estimate the lower limit on the K–H instability linear growth rate to be ∼5.84 × 10−3 s−1. For these vortices, we estimate the instantaneous atmospheric ion escape flux due to the detachment of plasma clouds during the late non‐linear stage of K–H instability to be ∼5.90 × 1026 particles/s. Extrapolation of loss rates integrated across time and space will require further work.Key PointsMars Atmosphere and Volatile EvolutioN (MAVEN) observed magnetic field and plasma signatures consistent with the encounter of fully developed Kelvin–Helmholtz (K–H) vortices along Mars’ induced magnetospheric boundary (IMB)Close agreement between 3‐D magnetohydrodynamics simulation result and MAVEN observation support the scenario for K–H instability occurrence along Mars’ IMBWe estimated the instantaneous atmospheric ion escape flux due to detachment of plasma clouds from K–H instability to be ∼5.9 × 1026 s−1Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/170215/1/jgra56662.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/170215/2/jgra56662_am.pd