Planet Mercury was located about 43◦ west of the Earth-Sun line at ∼ 0.46 AU distance from the Sun on 20–22 April 1998. A proton flare appeared at the Sun on 20 April (W 90◦, S 47◦, 9:38–11:19 UT) and Mercury was hit by energetic protons... more
Planet Mercury was located about 43◦ west of the Earth-Sun line at ∼ 0.46 AU distance from the Sun on 20–22 April 1998. A proton flare appeared at the Sun on 20 April (W 90◦, S 47◦, 9:38–11:19 UT) and Mercury was hit by energetic protons and α-particles which released probably pickup and sputter ions from the planetary surface. The WIND/SC, located in the libration point L1 in April 1998, was connected via the interplanetary magnetic field with Mercury. The SMS-experiment detected in the energy/charge ranges 0.5–9.5 and 6.5– 225 keV/e singly charged heavy ions above the solar cosmic ray background which we interprete partly as Mercury ions. However a contribution of pickup ions from the dust located near the Sun cannot be excluded.
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ABSTRACT From data collected with the MTOF sensor of the CELIAS instrument on board the SOHO spacecraft we derived the elemental abundance ratios for Si/O and Fe/O in the solar wind with high time resolution. Since Si and Fe are elements... more
ABSTRACT From data collected with the MTOF sensor of the CELIAS instrument on board the SOHO spacecraft we derived the elemental abundance ratios for Si/O and Fe/O in the solar wind with high time resolution. Since Si and Fe are elements with a low first ionization potential (FIP) and oxygen is a high FIP element, these abundance ratios are valuable diagnostic tools for the study of the FIP fractionation process. The abundance ratios we find for slow and fast solar wind are commensurate with published values for interstream and coronal hole type solar wind. Between these two extreme cases of solar wind flow we find a continuous decrease of the abundance ratios for increasing solar wind speed, from a high value indicative of solar wind originating from the streamer belt to low values associated with flow from coronal holes.
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ABSTRACT Although, substantial progress has been made in the understanding of particle injection and acceleration at shocks, the processes involved are not fully understood. Meanwhile numerical simulations have become powerful enough to... more
ABSTRACT Although, substantial progress has been made in the understanding of particle injection and acceleration at shocks, the processes involved are not fully understood. Meanwhile numerical simulations have become powerful enough to include different species, such as heavy ions and electrons, and observations are now more sensitive to resolve individual ion species and charge states even during less intense solar energetic particle events. As a consequence, the combination of theory, simulations, and observations provides the tools to study the physical processes at interplanetary discontinuities in detail. In this talk we will report on recent results using ACE/SEPICA and SOHO/CELIAS/STOF to observe interstellar pickup He+ as well as coronal and/or solar wind He2+ at interplanetary discontinuities. Apparently He+ is injected and accelerated with very high efficiency compared with He2+. Therefore, this pair, He+ and He2+, represents an ideal probe for the injection efficiency, because it comes from two well-defined sources with different velocity distributions. We will discuss the most recent findings as well as their implications on shock structure and acceleration in comparison with theory and numerical simulations.
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The Yohkoh soft X-ray telescope (SXT) has observed several largescale eruptive events per year for the first three years of observations (Aug. 1991 - Nov. 1994) Such events are most prominent at high latitudes, but resemble long-duration... more
The Yohkoh soft X-ray telescope (SXT) has observed several largescale eruptive events per year for the first three years of observations (Aug. 1991 - Nov. 1994) Such events are most prominent at high latitudes, but resemble long-duration flare events seen in active regions. Some of the high-latitude events have now been identified in the Ulysses/SWICS data base during the Ulysses south polar passage. There are puzzling examples of solar events with no interplanetary counterparts. A comparison of coronal and interplanetary events can lead to better models for mapping interplanetary disturbances back to their source location, especially by combining Yohkoh morphology with three-dimensional representations of the coronal magnetic field. In this paper we describe the parameters of the hot plasma seen by SXT. There is clear evidence for non radial motion in specific events. We present comparisons between the ionization temperature of the interplanetary plasma with that observed at the Su...
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The high-speed solar wind streaming from the southern coronal hole was remarkably uniform and steady and was confined by a sharp boundary that extended to the corona and chromosphere. Charge state measurements indicate that the electron... more
The high-speed solar wind streaming from the southern coronal hole was remarkably uniform and steady and was confined by a sharp boundary that extended to the corona and chromosphere. Charge state measurements indicate that the electron temperature in this coronal hole reached a maximum of about 1.5 million kelvin within 3 solar radii of the sun. This result, combined with the observed lack of depletion of heavy elements, suggests that an additional source of momentum is required to accelerate the polar wind.
Research Interests: Physics, Science, Medicine, Multidisciplinary, Elements, and 7 moreSolar Wind, Wind, Solar System, High Speed, Spectrum analysis, Spacecraft, and Ions
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ABSTRACT The ionic charge states of energetic C, O, Ne, Mg, and Fe have been observed in several co-rotating interaction regions (CIR) in 1999 and 2000 with ACE SEPICA. Except for a small contribution of Ne+, most likely from interstellar... more
ABSTRACT The ionic charge states of energetic C, O, Ne, Mg, and Fe have been observed in several co-rotating interaction regions (CIR) in 1999 and 2000 with ACE SEPICA. Except for a small contribution of Ne+, most likely from interstellar pickup ions, the mean charge states of all heavy ions appear to be consistent with those observed in CME related energetic particle events and in the solar wind. In the following, we compare the charge states of the energetic ions in the CIRs with the charge states of heavy solar wind ions in the adjacent solar wind, as observed with ACE SWICS. It has been argued that the energetic particles in CIRs are mainly produced at the reverse shock and/or in the related part of the compression region of the fast solar wind. The observed temporal flux profile and charge states of the energetic ions are consistent with an origin in the fast solar wind. No correlation of the event to event variation of the energetic charge states is found with the solar wind, which does not show significant charge state variations in the observed time periods. However, there is a consistent event to event variation of all species in the energetic population with a tendency towards higher charge states than in the fast solar wind. This observation seems to suggest occasional increases of the charge states during the acceleration, similar to those found by Klecker et al. (2000) in interplanetary shock accelerated particle events. Klecker, B., et al., In: Acceleration and Transport of Energetic Particles Observed in the Heliosphere; R.A. Mewaldt, et al. eds.; AIP Conf. Proc., 528, 135, 2000.
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ABSTRACT We have investigated several CME related SEP events with unusually high abundance in He+ in the energetic particle population which have been observed between 1998 and 2000 with ACE SEPICA and SOHO CELIAS. Usually the abundance... more
ABSTRACT We have investigated several CME related SEP events with unusually high abundance in He+ in the energetic particle population which have been observed between 1998 and 2000 with ACE SEPICA and SOHO CELIAS. Usually the abundance of He+ is below a few percent whereas at these times the He+/He2+ ratio can be closer to one. Possible sources for He+ are interstellar pickup ions or cold solar ejecta in CMEs. The temporal evolution and the energy spectra of these events have been investigated in detail. The maximum of the He+/He2+ ratio usually coincides with the arrival of the shock or a discontinuity. This seems to suggest local acceleration of these ions. The He+ enhancement does not seem to be associated with cold ejecta in the CME. Therefore, most probably interstellar pickup ions are the source for the He+ enhancement. Furthermore, the He+/He2+ ratio appears to be consistently lower at higher energies, and the observed temporal variability decreases with increasing energy. This seems to indicate two different populations for He+ and He2+ with different energy spectra.
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ABSTRACT The SEPICA instrument on the Advanced Composition Explorer (ACE) spacecraft has measured ionic charge states of solar energetic particles (SEPs) from late 1997 through 2000. Charge state measurements provide insights about the... more
ABSTRACT The SEPICA instrument on the Advanced Composition Explorer (ACE) spacecraft has measured ionic charge states of solar energetic particles (SEPs) from late 1997 through 2000. Charge state measurements provide insights about the acceleration and propa- gation history of SEPs. In impulsive events, SEP charge states provide information about the flare environment, where source heating and collisions are important. In in- terplanetary shock events, SEP charge states are diagnostics of the rigidity-dependent acceleration process and particle seed populations. For example, 3He enrichment has been observed in some events with a local shock passage (Desai et al., 2001). An en- hancement in high charge state Fe has also been observed in these events (Popecki et al., 2001). This suggests that the seed population for the interplanetary shock con- tained ions previously accelerated in flares. SEP charge states from impulsive events will be compared to those from events with a local shock passage (ESP events). In addition, the ESP events wil be separated into those with and without 3He enrichment. Results will be presented in the context of mission-integrated ionic charge state distributions for each species.
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Several important planetary investigations now underway as part of the Messenger, Venus Express, Mars Express and Cassini missions depend on a knowledge of the solar and local interplanetary conditions. For example: Messenger will resolve... more
Several important planetary investigations now underway as part of the Messenger, Venus Express, Mars Express and Cassini missions depend on a knowledge of the solar and local interplanetary conditions. For example: Messenger will resolve the question of whether Mercury's structured and variable sodium missions detected on the ground are a result of solar wind and interplanetary field control, Venus and
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... Stefano A. Livi, StefanoLivi@swri.edu, 210-522-3310 Antoinette Galvin, University of New Hampshire Lynn Kistler, University of New ... such as Hinode, STEREO, SOHO, RHESSI, and TRACE, advances in understanding of the 3D solar wind... more
... Stefano A. Livi, StefanoLivi@swri.edu, 210-522-3310 Antoinette Galvin, University of New Hampshire Lynn Kistler, University of New ... such as Hinode, STEREO, SOHO, RHESSI, and TRACE, advances in understanding of the 3D solar wind structure provided by Ulysses, and the ...
Solar Energetic Particle (SEP) events with unusually high abundance in He+ that have been observed between 1998 and 2000 with ACE/SEPICA have been investigated in detail. Usually He+/He2+ abundance ratio in the solar wind/corona is of the... more
Solar Energetic Particle (SEP) events with unusually high abundance in He+ that have been observed between 1998 and 2000 with ACE/SEPICA have been investigated in detail. Usually He+/He2+ abundance ratio in the solar wind/corona is of the order of 10e-4. However during SEP events the He+/He2+ ratio can be closer to one. This survey has shown that the increase of the He+/He2+ abundance ratio coincides with the arrival of the shock (either driven by a CME or associated with a CIR) or a discontinuity. The analysis strongly suggests local acceleration of these ions and it is also shown that interstellar pickup ions are the main source for the He+ enhancement. We have identified the types of discontinuities which are predominantly associated with an increase of the He+/He2+ ratio. A representative sample of CMEs, CME-related disturbances as well as corotating/transient streams has been examined in detail. We have investigated the observed temporal and energy dependence of the He+/He2+ ra...
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The solar wind quasi-invariant (QI) is defined as the ratio of the solar wind magnetic energy density to the plasma kinetic energy density (i.e., the inverse square of the Alfvén Mach number). Previous work has found this quantity to be a... more
The solar wind quasi-invariant (QI) is defined as the ratio of the solar wind magnetic energy density to the plasma kinetic energy density (i.e., the inverse square of the Alfvén Mach number). Previous work has found this quantity to be a good proxy for solar activity, correlating very well with the sunspot number at various heliospheric distances. It has the
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Recent observations with ACE/SEPICA and SOHO CELIAS STOF have shown that energetic He+ is after H+ and He2+ the third most abundant energetic particle population in the heliosphere. The He+/He2+ ratio in the energetic particle population... more
Recent observations with ACE/SEPICA and SOHO CELIAS STOF have shown that energetic He+ is after H+ and He2+ the third most abundant energetic particle population in the heliosphere. The He+/He2+ ratio in the energetic particle population can reach unusually high values; in the energy range of 250keV/n -800keV/n ratios close to unity. The major source of the energetic He+ has been identified to be interplanetary pickup ions that are preferentially accelerated at CIR's, TIR's, and interplanetary traveling shocks. Since, compared to solar wind ions pickup ions are already suprathermal, any accelerator can create an enhancement in the energetic He+/He2+ ratio. In our survey of energetic helium over three years (1998-2000) from STOF and SEPICA we have identified additional discontinuities and magnetic field signatures, such as current sheet crossings, flows, and enhanced magnetic turbulence, which are associated with an enhancement in He+/He2+ ratio.
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The CELIAS instrument is designed to study the composition of the Solar Wind (SW) and of solar and interplanetary accelerated energetic particles on SOHO (Solar and Heliospheric Observatory). It consists of three different sensors with... more
The CELIAS instrument is designed to study the composition of the Solar Wind (SW) and of solar and interplanetary accelerated energetic particles on SOHO (Solar and Heliospheric Observatory). It consists of three different sensors with associated electronics, which are optimized each for a particular aspect of ion composition. These aspects are the elemental, isotopic, and ionic charge compostion of SW or energetic ions emanating from the Sun. A fourth sensor, the Solar EUV Monitor (SEM) was included into CELIAS for monitoring the absolute EUV flux from the Sun.
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AB Galvin · LM Kistler · MA Popecki · CJ Farrugia · KDC Simunac · L. Ellis · E. Möbius · MA Lee · M. Boehm · J. Carroll · A. Crawshaw · M. Conti · P. Demaine · S. Ellis · JA Gaidos · J. Googins · M. Granoff · A. Gustafson · D. Heirtzler ·... more
AB Galvin · LM Kistler · MA Popecki · CJ Farrugia · KDC Simunac · L. Ellis · E. Möbius · MA Lee · M. Boehm · J. Carroll · A. Crawshaw · M. Conti · P. Demaine · S. Ellis · JA Gaidos · J. Googins · M. Granoff · A. Gustafson · D. Heirtzler · B. King · U. Knauss · J. Levasseur · S. Longworth ...
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The Solar Orbiter spacecraft, a collaborative mission between ESA and NASA, will be launched in 2017 and will include the Solar Wind Analyzer instrumentation suite. This space mission will allow for unprecedented data collection of... more
The Solar Orbiter spacecraft, a collaborative mission between ESA and NASA, will be launched in 2017 and will include the Solar Wind Analyzer instrumentation suite. This space mission will allow for unprecedented data collection of particle characteristics near the Sun at various heliolatitudes during both the quiet and active phases of the solar cycle. The close proximity will allow for determination of the source regions on the sun for the observed events. Of particular interest will be the study of the origins of and processes related to solar energetic particles. This mission will lead to a better understanding of the Sun and the interstellar medium in our solar system. The Solar Wind Analyzer (SWA) suite is composed by a comprehensive set of sensors to characterize the Solar Wind plasma: the Electron Analyzer System to determine the properties of solar wind electrons, the Proton and Alpha Sensor to measure at high cadence the distribution functions of protons and alphas, and the Heavy Ion Sensor to analyze the minor ion components of the solar wind. As a result of the measurements SWA will take, we will be able to: Identify interplanetary shocks and characterize their spatial and temporal evolution; characterize the power spectra of density and velocity fluctuations upstream and downstream of shocks; study the heating and dissipation mechanisms at shocks at various radial distances and latitudes; and identify the mechanisms that heat thermal solar wind ions near shocks and determine the energy partition at shocks.
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We inquire into how much information content is lost in using interplanetary field and plasma parameters to predict the Dst index from monitors in the inner heliosphere (distance R < 1 AU) and displaced from the Sun-Earth line. To this... more
We inquire into how much information content is lost in using interplanetary field and plasma parameters to predict the Dst index from monitors in the inner heliosphere (distance R < 1 AU) and displaced from the Sun-Earth line. To this end, we selected a period in March, 1979, during which 2 major geomagnetic storms (Dst < -100 nT) occurred. Data are from ISEE 3, in orbit around the L1 Lagrangian point, and from Helios 2 situated at R ~ 0.8 AU and at a substantial separation from the Sun-Earth line are used. Scaling factors with R are the same as those in Lindsay et al. (1999), irrespective of interplanetary configuration. Previous investigations have recorded good overall agreement between the measured Dst and that predicted from Burton et al.'s formula (1975). However, there are occasional large discrepancies even when input interplanetary parameters are from probes near the Sun-Earth line. In computing the Dst in this study we shall therefore contrast predictions using two approaches. One is based on Burton et al.'s formula; the other is based on a numerical simulation with our kinetic ring current model [3] driven by a magnetopsheric electric field derived from the Weimer [2001] model. The twofold aim of the work is thus to answer the two questions: (1) which part of the Dst is still predicted from off the Sun-Earth line and what are the corresponding interplanetary configurations?; (2) Is prediction improved when the model of Weimer (2001) is used?. This work is supported by NASA Living with a Star grant NAG5-10883. 1. Lindsay, G. M., et al., JGR, 104, 10,335, 1999. 2. Burton, R. K., et al., JGR, 80, 4204, 1975. 3. Jordanova, V. K., et al., JGR, 103, 79, 1998. 4. Weimer, D. R., JGR, 106, 407, 2001.