| |
|
From B. Klecker et al., On the variability of Suprathermal He+ at 1 AU, 2001 |
This is a copy of the Venus Tail Rays poster created by M. Hilchenbach which includes data from Gruenwaldt et al., 1997. |
Halo CME of April 6, 2000 observed by SOHO/CELIAS/STOF (by M. Hilchenbach) |
Summed spectrum as recorded by CELIAS/MTOF during the interstream period from DOY 304-307, 1998. The solid line shows the result of the 17 parameter Maximum Likelihood Fit. |
Within the figure, the thin black line is the result of the raw data from MTOF, the thick black line is the maximum likelihood estimate, and the uncertainty bars have been plotted as well. The uncertainty, at this time, is based on the background counts, WAVE transmission, VMASS transmission efficiency. The preliminary value of 36Ar/38Ar is 5.7 ±0.8 and is determined with the ratio of the areas under the argon peaks from maximum likelihood fit. A fortunate result of this exercise is the clear observation of 35Cl and 37Cl (See the figure above). As far as this author is aware this is the first identification of chlorine within the solar wind. |
At the end of April a sequence of large CMEs was observed optically by e.g. SOHO/LASCO: On April 29 (DOY 119) a halo CME, on May 2 (DOY 122) a large CME, and on May 6 (DOY 126) another halo CME. With some delay these events were observed with spacecraft particle experiments of SOHO and ACE at L1. Using data from the CELIAS/STOF sensor onboard SOHO we can study for the first time the energy spectra and the charge state distribution of suprathermal particles in the energy range from 35 to 660 keV/e just above the solar wind distribution and below the low energy flare particle energies. From top to bottom: the energies of all particles measured by STOF, the energy spectra of He++ and He+ and the charge states of He and Fe for a period of 12 hours during the first CME. - Note that the fluxes are not yet fully calibrated. The He+/He++ ratio was strongly enhanced during the first halo CME (DOY 120). After a sudden rise it dropped successively to approximately zero. The May 2-3 CME (DOY 122 - 123) shows much less enrichment of He+ in the suprathermal particles. In contrast, in the CME-related solar wind of May 2-3, 1998, a significant enhancement of He+ for an interval of more than 24 hours was found. The mean charge state of Fe of the pre-CME time period is lower than during and after the May 2-3 CME. In the second halo CME (DOY 126 - 128) two kinds of material can be distinguished in time: One with higher charge states of Fe and one with lower. During the time periods with shocks (DOY 121 and 124) and the first halo CME (DOY 120) very hard spectra were observed with spectral indices of about 2 for He++. Simultaneously the SWICS and SWIMS instruments on the Advanced Composition Explorer (ACE) observed a most unusual elemental and charge state composition in the solar wind related to the May 2-3 CME: high and low charge states for all elements (e.g., Fe3+ to Fe16+), an enhanced 3He/4He ratio and a prolongued He+ enhancement. |
This graph displays the daily average of EUV flux from 260 Å to 340 Å as measured by the SEM sensor from 1996 to 1999. |
This CELIAS/MTOF spectrum was accumulated over a three day period (these valuesare uncorrected for efficiencies). The MTOF sensor was set in a mode that was optimized for observing solar wind species with masses above that of sulfur. This is why the peaks for Calcium (mass 40) and Iron (mass 56) are so dominant compared to, for example, Oxygen. In this color version of the figure, the peaks that are simply linedrawn are the elements commonly observed by insitu solar wind experiments: Carbon (mass 12 amu), Oxygen (mass 16 amu), Neon (mass 20), Magnesium (mass 24), Silicon (mass 28), and Iron (mass 56). The elements and isotopes for which SOHO MTOF has given the first in situ spacecraft solar wind observations are in red. These include the Silicon isotopes (masses 29, 30), the element Phosphorus (mass 31), a Sulfur isotope (mass 34), the element Chlorine (mass 35) and its isotope (mass 37), an Argon isotope (mass 38), the Calcium isotopes (masses 42 and 44), the element Titanium (mass 48), the element Chromium (mass 52) and its isotope (mass 53), the Iron isotope (mass 54, there is also a shoulder for mass 57), the element Manganese (mass 55), the element Nickel (mass 58) and its isotopes (masses 60, 62). [For all but Argon 38, these are the first in situ solar wind observations by any means. There was a measurement of Argon 38 in the Apollo foil experiments, but it had a large uncertainty, and is not frequently quoted by the foil experimenters themselves for solar wind abundance measurements.] The elements and isotopes that are shaded green are not observed routinely by conventional solar wind experiments. These include the element Nitrogen (mass 14), a Neon isotope (mass 22), the element Sodium (mass 23), the Magnesium isotopes (masses 25, 26), the element Aluminum (mass 27), the Sulfur element (mass 32), the Argon element (mass 36), and the Calcium element (mass 40). Measurements for Sulfur 32 have been made with the Ulysses SWICS experiment, by accumulating over several months of data, and using extensive fitting techniques (it is not really resolved from Iron and Magnesium). Neon 22 and Argon 36 were measured by the Apollo foil experiments. The remainder were first observed in the in situ solar wind by the MTOF prototype sensor, which was launched on WIND about 13 months before SOHO. However, MTOF has a major advantage over its prototype regarding temporal resolution, because of its higher collection power. |
On May 6 (DOY 126), 1998 an X-class flare was detected by SOHO/EIT at 0809 UT, and at 0829 UT a very wide and fast CME was seen by SOHO/LASCO. The corresponding suprathermal particle event exhibited a clear velocity dispersion at its onset. The measured energy of each He-particle detected by HSTOF is plotted versus the time of its detection. The corresponding velocity curve is also shown. For a non-relativistic particle of mass m and kinetic energy E, the travel time t along a magnetic field line of length s from near the Sun to L1 is given by t = s * (m/2E)1/2. We found s = 1.275 ± 0.25 AU. (From K. Bamert, et al., JGR, submitted, 2001). |
Solar wind iron isotopic abundances from SOHO/CELIAS/MTOF. From F.M. Ipavich et al., AIP conference proceedings, revised, 2001. See Abstract |
Chromium to Iron abundance ratio (as determined by MTOF) for 3 events corresponding to 3 different solar wind flow types. The lighter shaded region represents the 1-sigma range of the meteoritic abundance ratio reported by Grevesse and Sauval (1998). The darker shaded region is the analogous photospheric abundance ratio from the same paper. |
Time of Flight spectrum for 50 keV Fe (and contaminants) from the MTOF spare instrument in the MEFISTO accelerator. The peaks are labeled with species and charge state after the foil. |
Chromium to Iron Abundance Ratio from MTOF for 3 events corresponding to 3 different solar wind flow types and for the average of three 1-year periods as compared to Grevesse and Sauval (1998) |
Enrichment factors of solar wind elements as a function of the Firs Ionization Potential (FIP) |
This is an image of the CTOF sensor from the CELIAS Instrument. |
This is an image of the MTOF sensor from the CELIAS Instrument. |
This is an image of the STOF sensor from the CELIAS Instrument. |
This is an image of the SEM sensor from the CELIAS Instrument. |
This is the offical SOHO logo. |
This is the offical CELIAS Logo |
CELIAS team group photo from the 7th CELIAS Postlaunch Workshop. |
CELIAS team group photo from the 8th CELIAS Postlaunch Workshop. |
CELIAS team group photo from the 10th CELIAS Postlaunch Workshop. |
Ca/H Abundance |
Return to the CELIAS home page