Genesis On-board Determination of the Solar Wind Flow Regime

Neugebauer, M.; Steinberg, J. T.; Tokar, R. L.; Barraclough, B. L.; Dors, E. E.; Wiens, R. C.; Gingerich, David E.; Luckey, D.; Whiteaker, D. B.

doi:10.1007/978-94-010-0241-7_6

Cited by 36 publications

(52 citation statements)

References 14 publications

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“…They also obtained functions to calculate the T exp . Later, Neugebauer et al [] and Elliott et al [] also found other functions to describe the relationship between T p and V p . In Démoulin [], the physics behind this relationship was discussed based on the momentum and the internal energy equations.…”

Section: Discussionmentioning

confidence: 99%

Small solar wind transients at 1 AU: STEREO observations (2007–2014) and comparison with near‐Earth wind results (1995–2014)

Farrugia

Galvin

et al. 2016

JGR Space Physics

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This paper discusses small solar wind transients (STs) from 1995 to 2014. Using STEREO data, we have more sites from which to study STs near 1 AU. STEREO measurements are compared with wind observations near the Sun‐Earth line. We examined statistically the dependence of ST occurrence frequency on (i) solar cycle phase, as monitored by the sunspot number (SSN), and (ii) solar wind speed. We find dependencies on both: an anticorrelation with SSN, an opposite trend to that of interplanetary coronal mass ejections (ICMEs), and correlation with slow solar wind (over 80% in the slow wind). We compare ST distributions during solar maximum year 2003, which had the lowest percentage of slow wind, and minimum year 2009, which had the highest percentage thereof, and show evidence of both dependencies. We give a statistical overview of ST parameters: field strength, B, Alfvén Mach number, MA, and proton beta, βp. They show the same temporal trends as the ambient solar wind but have twice (B) or one half (MA, βp) of its average values. In STs, the proton temperature is not below the temperature expected from corotating solar wind expansion. Non‐force free models should be used in solar minimum years where βplasma≈ 1, while the force free models could be used in solar maximum when βplasma<<1. We find that only ∼5% of STs show enhanced values of iron charge states. Our work further supports the two‐source origin of STs, i.e., the solar corona and the interplanetary medium.

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Section: Discussionmentioning

confidence: 99%

Small solar wind transients at 1 AU: STEREO observations (2007–2014) and comparison with near‐Earth wind results (1995–2014)

Farrugia

Galvin

et al. 2016

JGR Space Physics

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“…Borovsky, ), while almost all other solar wind variables are strongly affected by compression or rarefaction. The ratio T p / v sw is often used in classification algorithms for the different types of solar wind plasma originating from different types of regions on the solar surface (e.g., Borovsky & Steinberg, ; Camporeale et al, ; Elliott et al, ; Neugebauer et al, ; Neugebauer et al, ; Reisenfeld et al, ; Xu & Borovsky, ).…”

Section: Time‐integral Correlations With Fe12mentioning

confidence: 99%

Time‐Integral Correlations of Multiple Variables With the Relativistic‐Electron Flux at Geosynchronous Orbit: The Strong Roles of Substorm‐Injected Electrons and the Ion Plasma Sheet

Borovsky

2017

JGR Space Physics

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Time‐integral correlations are examined between the geosynchronous relativistic electron flux index Fe1.2 and 31 variables of the solar wind and magnetosphere. An “evolutionary algorithm” is used to maximize correlations. Time integrations (into the past) of the variables are found to be superior to time‐lagged variables for maximizing correlations with the radiation belt. Physical arguments are given as to why. Dominant correlations are found for the substorm‐injected electron flux at geosynchronous orbit and for the pressure of the ion plasma sheet. Different sets of variables are constructed and correlated with Fe1.2: some sets maximize the correlations, and some sets are based on purely solar wind variables. Examining known physical mechanisms that act on the radiation belt, sets of correlations are constructed (1) using magnetospheric variables that control those physical mechanisms and (2) using the solar wind variables that control those magnetospheric variables. Fe1.2‐increasing intervals are correlated separately from Fe1.2‐decreasing intervals, and the introduction of autoregression into the time‐integral correlations is explored. A great impediment to discerning physical cause and effect from the correlations is the fact that all solar wind variables are intercorrelated and carry much of the same information about the time sequence of the solar wind that drives the time sequence of the magnetosphere.

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“…The time resolution is 4 min for the magnetic field data and 64 s for V, Tp, and N α /Np. We also plot the expected solar wind proton temperature (Texp) from Lopez and Freeman [1986] and Neugebauer et al [2003]. From these plots, we identify the intervals of Tp depression with respect to Texp.…”

Section: Shocks Of Solar Cycle 23mentioning

confidence: 99%

“…From these plots, we identify the intervals of Tp depression with respect to Texp. Ejecta intervals are those with Tp/Texp < 0.5 [ Cane and Richardson , 2003; Neugebauer et al , 2003; Elliott et al , 2005]. We also use N α /Np > 0.08 as a secondary criterion to cross check the Tp depression.…”

Section: Shocks Of Solar Cycle 23mentioning

confidence: 99%

CME interactions with coronal holes and their interplanetary consequences

et al. 2009

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[1] A significant number of interplanetary shocks ($17%) during cycle 23 were not followed by drivers. The number of such ''driverless'' shocks steadily increased with the solar cycle with 15%, 33%, and 52% occurring in the rise, maximum, and declining phase of the solar cycle. The solar sources of 15% of the driverless shocks were very close the central meridian of the Sun (within $15°), which is quite unexpected. More interestingly, all the driverless shocks with their solar sources near the solar disk center occurred during the declining phase of solar cycle 23. When we investigated the coronal environment of the source regions of driverless shocks, we found that in each case there was at least one coronal hole nearby, suggesting that the coronal holes might have deflected the associated coronal mass ejections (CMEs) away from the Sun-Earth line. The presence of abundant low-latitude coronal holes during the declining phase further explains why CMEs originating close to the disk center mimic the limb CMEs, which normally lead to driverless shocks due to purely geometrical reasons. We also examined the solar source regions of shocks with drivers. For these, the coronal holes were located such that they either had no influence on the CME trajectories, or they deflected the CMEs toward the Sun-Earth line. We also obtained the open magnetic field distribution on the Sun by performing a potential field source surface extrapolation to the corona. It was found that the CMEs generally move away from the open magnetic field regions. The CME-coronal hole interaction must be widespread in the declining phase and may have a significant impact on the geoeffectiveness of CMEs.

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Genesis On-board Determination of the Solar Wind Flow Regime

Cited by 36 publications

References 14 publications

Small solar wind transients at 1 AU: STEREO observations (2007–2014) and comparison with near‐Earth wind results (1995–2014)

Small solar wind transients at 1 AU: STEREO observations (2007–2014) and comparison with near‐Earth wind results (1995–2014)

Time‐Integral Correlations of Multiple Variables With the Relativistic‐Electron Flux at Geosynchronous Orbit: The Strong Roles of Substorm‐Injected Electrons and the Ion Plasma Sheet

CME interactions with coronal holes and their interplanetary consequences

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