The mean ionic charge of silicon in 3HE-rich solar flares

Mean ionic charge of iron in 3He-rich solar flares and the average mean charge of Silicon for 23 #He-rich periods during the time interval from September 1978 to October 1979 were determined. It is indicated that the value of the mean charge state of Silicon is higher than the normal flare average by approximately 3 units and in perticular it is higher then the value predicted by resonant heating models for 3He-rich solar flares

Observation of pick-up ions in the solar wind: Evidence for the source of the anomalous cosmic ray component?

Singly ionized energetic helium has been observed in the solar wind by using the time of flight spectrometer SULEICA on the AMPTE/IRM satellite between September and December, 1984. The energy density spectrum shows a sharp cut off which is strongly correlated with the four fold solar wind bulk energy. The absolute flux of the He(+)ions of about 10000 ion/sq cm.s is present independent of the IPL magnetic field orientation. The most likely source is the neutral helium of the interstellar wind which is ionized by solar UV radiation. It is suggested that these particles represent the source of the anomalous cosmic ray component

Determining the ionization rates of interstellar neutral species using direct-sampling observations of their direct and indirect beams

A good understanding of the ionization rates of neutral species in the heliosphere is important for studies of the heliosphere and planetary atmospheres. So far, the intensities of the ionization reactions have been studied based on observations of the contributing phenomena, such as the solar spectral flux in the EUV band and the flux of the solar wind protons, alpha particles, and electrons. The results strongly depend on absolute calibration of these measurements, which, especially for the EUV measurements, is challenging. Here, we propose a novel method of determining the ionization rate of neutral species based on direct sampling of interstellar neutral gas from two locations in space distant to each other. In particular, we suggest performing observations from the vicinity of Earth's orbit and using ratios of fluxes of ISN He for the direct and indirect orbits of interstellar atoms. We identify the most favorable conditions and observations geometries, suitable for implementation on the forthcoming NASA mission Interstellar Mapping and Acceleration Probe.Comment: Accepted for ApJ

Warm Breeze from the starboard bow: a new population of neutral helium in the heliosphere

We investigate the signals from neutral He atoms observed from Earth orbit in 2010 by IBEX. The full He signal observed during the 2010 observation season can be explained as a superposition of pristine neutral interstellar He gas and an additional population of neutral He that we call the Warm Breeze. The Warm Breeze is approximately two-fold slower and 2.5 times warmer than the primary interstellar He population, and its density in front of the heliosphere is ~7% that of the neutral interstellar helium. The inflow direction of the Warm Breeze differs by ~19deg from the inflow direction of interstellar gas. The Warm Breeze seems a long-term feature of the heliospheric environment. It has not been detected earlier because it is strongly ionized inside the heliosphere, which brings it below the threshold of detection via pickup ion and heliospheric backscatter glow observations, as well as by the direct sampling of GAS/Ulysses. Possible sources for the Warm Breeze include (1) the secondary population of interstellar helium, created via charge exchange and perhaps elastic scattering of neutral interstellar He atoms on interstellar He+ ions in the outer heliosheath, or (2) a gust of interstellar He originating from a hypothetic wave train in the Local Interstellar Cloud. A secondary population is expected from models, but the characteristics of the Warm Breeze do not fully conform to modeling results. If, nevertheless, this is the explanation, IBEX-Lo observations of the Warm Breeze provide key insights into the physical state of plasma in the outer heliosheath. If the second hypothesis is true, the source is likely to be located within a few thousand of AU from the Sun, which is the propagation range of possible gusts of interstellar neutral helium with the Warm Breeze characteristics against dissipation via elastic scattering in the Local Cloud.Comment: submitted to ApJ

Effect of the heliospheric interface on the distribution of interstellar hydrogen atom inside the heliosphere

This paper deals with the modeling of the interstellar hydrogen atoms (H atoms) distribution in the heliosphere. We study influence of the heliospheric interface, that is the region of the interaction between solar wind and local interstellar medium, on the distribution of the hydrogen atoms in vicinity of the Sun. The distribution of H atoms obtained in the frame of the self-consistent kinetic-gasdynamic model of the heliospheric interface is compared with a simplified model which assumes Maxwellian distribution of H atoms at the termination shock and is called often as 'hot' model. This comparison shows that the distribution of H atoms is significantly affected by the heliospheric interface not only at large heliocentric distances, but also in vicinity of the Sun at 1-5 AU. Hence, for analysis of experimental data connected with direct or undirect measurements of the interstellar atoms one necessarily needs to take into account effects of the heliospheric interface. In this paper we propose a new model that is relatively simple but takes into account all major effects of the heliospheric interface. This model can be applied for analysis of backscattered Ly-alpha radiation data obtained on board of different spacecraft.Comment: published in Astronomy Letter

Interstellar neutral helium in the heliosphere from IBEX observations. III. Mach number of the flow, velocity vector, and temperature from the first six years of measurements

We analyzed observations of interstellar neutral helium (ISN~He) obtained from the Interstellar Boundary Explorer (IBEX) satellite during its first six years of operation. We used a refined version of the ISN~He simulation model, presented in the companion paper by Sokol_et al. 2015, and a sophisticated data correlation and uncertainty system and parameter fitting method, described in the companion paper by Swaczyna et al 2015. We analyzed the entire data set together and the yearly subsets, and found the temperature and velocity vector of ISN~He in front of the heliosphere. As seen in the previous studies, the allowable parameters are highly correlated and form a four-dimensional tube in the parameter space. The inflow longitudes obtained from the yearly data subsets show a spread of ~6 degree, with the other parameters varying accordingly along the parameter tube, and the minimum chi-square value is larger than expected. We found, however, that the Mach number of the ISN~He flow shows very little scatter and is thus very tightly constrained. It is in excellent agreement with the original analysis of ISN~He observations from IBEX and recent reanalyses of observations from Ulysses. We identify a possible inaccuracy in the Warm Breeze parameters as the likely cause of the scatter in the ISN~He parameters obtained from the yearly subsets, and we suppose that another component may exist in the signal, or a process that is not accounted for in the current physical model of ISN~He in front of the heliosphere. From our analysis, the inflow velocity vector, temperature, and Mach number of the flow are equal to lambda_ISNHe = 255.8 +/- 0.5 degree, beta_ISNHe = 5.16 +/- 0.10 degree, T_ISNHe = 7440 +/- 260 K, v_ISNHe = 25.8 +/- 0.4$ km/s, and M_ISNHe = 5.079 +/- 0.028, with uncertainties strongly correlated along the parameter tube.Comment: Updated reference

SOHO CTOF Observations of Interstellar He+ Pickup Ion Enhancements in Solar Wind Compression Regions

We present a recent analysis with 1996 SOHO CELIAS CTOF data, which reveals correlations of He+ pickup ion fluxes and spectra with the magnetic field strength and solar wind density. The motivation is to better understand the ubiquitous large variations in both pickup ion fluxes and their velocity distributions found in interstellar pickup ion datasets. We concentrate on time periods of that can be associated with compression regions in the solar wind. Along with enhancements of the overall pickup ion fluxes, adiabatic heating and acceleration of the pickup ions are also observed in these regions. Transport processes that lead to the observed compressions and related heating or acceleration are discussed. A shift in velocity space associated with traveling interplanetary compression regions is observed, and a simple model presented to explain this phenomenon based on the conserved magnetic adiabatic moment.Comment: 4 pages, 5 figures, Solar Wind 10 Conference Proceedings Pape