Warm Breze from the Starboard Bow: a new Population of neutral Helium in the Heliosphere

We investigate the signals from neutral helium atoms observed in situ from Earth orbit in 2010 by the Interstellar Boundary Explorer (IBEX). The full helium 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 helium that we call the Warm Breeze. The Warm Breeze is approximately 2 times 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 ~19° from the inflow direction of interstellar gas. The Warm Breeze seems to be a long-term, perhaps permanent feature of the heliospheric environment. It has not been detected earlier because it is strongly ionized inside the heliosphere. This effect 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. We discuss possible sources for the Warm Breeze, including (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 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. Whatever the nature of the Warm Breeze, its discovery exposes a critical new feature of our heliospheric environment.

[Sun-tanned and still not healthy!]

We describe a case of a 10 years old girl, which presented to the emergency room with non-specific gastro-intestinal symptoms, fatigue and low blood pressure. The clinical signs and laboratory value supported the diagnosis of Addison crisis with hypovolaemic shock. The pathophysiology and the therapy of this entity are discussed. Importantly, in children the aetiology may differ depending on age and sex. Based on the family history of autoimmune disorders, in our patient presenting with autoimmune adrenalitis and celiac disease, the diagnosis of an autoimmune polyendocrinopathy was made. A therapy of mineralcorticoids and glucocorticoids was initiated and a special gluten-free diet was prescribed. On this treatment our patient recovered promptly.

Melan-a-positive "pseudomelanocytic nests": a pitfall in the histopathologic and immunohistochemical diagnosis of pigmented lesions on sun-damaged skin

We encountered recently 3 cases with a histopathologic diagnosis of melanoma in situ on sun-damaged skin (male = 2, female = 1; median age: 59 years; range: 52-60 years). The diagnosis was based mainly on the finding of actinic elastosis in the dermis and increased number of melanocytes in the epidermis and was confirmed by strong positivity for Melan-A in single cells and in small nests ("pseudomelanocytic nests"), located at the dermoepidermal junction. Indeed, examination of slides stained with hematoxylin and eosin revealed the presence of marked hyperpigmentation and small nests of partially pigmented cells at the dermoepidermal junction, positive for Melan-A. The histologic and especially the immunohistochemical features were indistinguishable from those of melanoma in situ on chronic sun-damaged skin. In addition, a variably dense lichenoid inflammation was present. Clinicopathologic correlation, however, showed, in all patients, the presence of a lichenoid dermatitis (phototoxic reaction, 1 case; lichen planus pigmentosus, 1 case; and pigmented lichenoid keratosis, 1 case). Our cases clearly show the histopathologic pitfalls represented by lichenoid reactions on chronic sun-damaged skin. Immunohistochemical investigations, especially if performed with Melan-A alone, may lead to confusing and potentially disastrous results. The unexpected staining pattern of Melan-A in cases like ours raises concern about the utility of this antibody in the setting of a lichenoid tissue reaction on chronic sun-damaged skin. It should be underlined that pigmented lesions represent a paradigmatic example of how immunohistochemical results should be interpreted carefully and always in conjunction with histologic and clinical features.

Assessment of detectability of neutral interstellar deuterium by IBEX observations

Context. The abundance of deuterium in the interstellar gas in front of the Sun gives insight into the processes of filtration of neutral interstellar species through the heliospheric interface and potentially into the chemical evolution of the Galactic gas. Aims: We investigate the possibility of detection of neutral interstellar deuterium at 1 AU from the Sun by direct sampling by the Interstellar Boundary Explorer (IBEX). Methods: Using both previous and the most recent determinations of the flow parameters of neutral gas in the local interstellar cloud (LIC) and an observation-based model of solar radiation pressure and ionization in the heliosphere, we simulated the flux of neutral interstellar D at IBEX for the actual measurement conditions. We assessed the number of interstellar D atom counts expected during the first three years of IBEX operation. We also simulated the observations expected during an epoch of high solar activity. In addition, we calculated the expected counts of D atoms from the thin terrestrial water layer covering the IBEX-Lo conversion surface, sputtered by neutral interstellar He atoms. Results: Most D counts registered by IBEX-Lo are expected to come from the water layer, exceeding the interstellar signal by 2 orders of magnitude. However, the sputtering should stop once the Earth leaves the portion of orbit traversed by interstellar He atoms. We identify seasons during the year when mostly the genuine interstellar D atoms are expected in the signal. During the first 3 years of IBEX operations about 2 detectable interstellar D atoms are expected. This number is comparable to the expected number of sputtered D atoms registered during the same time intervals. Conclusions: The most favorable conditions for the detection occur during low solar activity, in an interval including March and April each year. The detection chances could be improved by extending the instrument duty cycle, say, by making observations in the special deuterium mode of IBEX-Lo.

Imaging the Heliosphere using neutral Atoms from Solar Wind Energy down to 15 eV

We study the spatial and temporal distribution of hydrogen energetic neutral atoms (ENAs) from the heliosheath observed with the IBEX-Lo sensor of the Interstellar Boundary EXplorer (IBEX) from solar wind energies down to the lowest available energy (15 eV). All available IBEX-Lo data from 2009 January until 2013 June were included. The sky regions imaged when the spacecraft was outside of Earth's magnetosphere and when the Earth was moving toward the direction of observation offer a sufficient signal-to-noise ratio even at very low energies. We find that the ENA ribbon—a 20° wide region of high ENA intensities—is most prominent at solar wind energies whereas it fades at lower energies. The maximum emission in the ribbon is located near the poles for 2 keV and closer to the ecliptic plane for energies below 1 keV. This shift is an evidence that the ENA ribbon originates from the solar wind. Below 0.1 keV, the ribbon can no longer be identified against the globally distributed ENA signal. The ENA measurements in the downwind direction are affected by magnetospheric contamination below 0.5 keV, but a region of very low ENA intensities can be identified from 0.1 keV to 2 keV. The energy spectra of heliospheric ENAs follow a uniform power law down to 0.1 keV. Below this energy, they seem to become flatter, which is consistent with predictions. Due to the subtraction of local background, the ENA intensities measured with IBEX agree with the upper limit derived from Lyα observations.

Interstellar neutral helium in the heliosphere from Interstellar Boundary Explorer 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. (2015b), along with a sophisticated data correlation and uncertainty system and parameter fitting method, described in the companion paper by Swaczyna et al. 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 similar to 6 degrees, with the other parameters varying accordingly along the parameter tube, and the minimum chi(2) 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 degrees.8 +/- 0 degrees.5, beta(ISNHe) = 5 degrees.16 +/- 0 degrees.10, T-ISNHe = 7440 +/- 260 K, nu(SNHe) = 25.8 +/- 0.4 km s(-1), and M-ISNHe = 5.079 +/- 0.028, with uncertainties strongly correlated along the parameter tube.

Impact of Planetary Gravitation on High Precision Neutral Atom Measurements

Measurements of energetic neutral atoms (ENAs) have been extremely successful in providing very important information on the physical processes inside and outside of our heliosphere. For instance, recent Interstellar Boundary Explorer (IBEX) observations have provided new insights into the local interstellar environment and improved measurements of the interstellar He temperature, velocity, and direction of the interstellar flow vector. Since particle collisions are rare, and radiation pressure is negligible for these neutrals, gravitational forces mainly determine the trajectories of neutral He atoms. Depending on the distance of an ENA to the source of a gravitational field and its relative speed and direction, this can result in significant deflection and acceleration. In this paper, we investigate the impact of the gravitational effects of Earth, the Moon, and Jupiter on ENA measurements performed in Earth's orbit. The results show that current analysis of the interstellar neutral parameters by IBEX is not significantly affected by planetary gravitational effects. We further studied the possibility of whether or not the Helium focusing cone of the Sun and Jupiter could be measured by IBEX and whether or not these cones could be used as an independent measure of the temperature of interstellar Helium.

Dust measurements in the coma of comet 67P/Churyumov-Gerasimenko inbound to the Sun

Critical measurements for understanding accretion and the dust/gas ratio in the solar nebula, where planets were forming 4.5 billion years ago, are being obtained by the GIADA (Grain Impact Analyser and Dust Accumulator) experiment on the European Space Agency's Rosetta spacecraft orbiting comet 67P/Churyumov-Gerasimenko. Between 3.6 and 3.4 astronomical units inbound, GIADA and OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) detected 35 outflowing grains of mass 10(-10) to 10(-7) kilograms, and 48 grains of mass 10(-5) to 10(-2) kilograms, respectively. Combined with gas data from the MIRO (Microwave Instrument for the Rosetta Orbiter) and ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) instruments, we find a dust/gas mass ratio of 4 +/- 2 averaged over the sunlit nucleus surface. A cloud of larger grains also encircles the nucleus in bound orbits from the previous perihelion. The largest orbiting clumps are meter-sized, confirming the dust/gas ratio of 3 inferred at perihelion from models of dust comae and trails.

The Interstellar Neutral He haze in the heliosphere: what can we learn?

Neutral interstellar helium has been observed by the Interstellar Boundary Explorer (IBEX) since 2009, with a signal-to-noise ratio well above 1000. Because of the geometry of the observations, the signal observed from January to March each year is the easiest to identify. However, as we show via simulations, the portion of the signal in the range of intensities from 10(-3) to 10(-2) of the peak value, previously mostly left out from the analysis, may provide important information about the details of the distribution function of interstellar He gas in front of the heliosphere. In particular, these observations may inform us about possible departures of the parent interstellar He population from equilibrium. We compare the expected distribution of the signal for the canonical assumption of a single Maxwell-Boltzmann population with the distributions for a superposition of the Maxwell-Boltzmann primary population and the recently discovered Warm Breeze, and for a single primary population given by a kappa function. We identify the regions on the sky where the differences between those cases are expected to be the most visible against the background. We discuss the diagnostic potential of the fall peak of the interstellar signal, reduced by a factor of 50 due to the Compton-Getting effect but still above the detection limit of IBEX. We point out the strong energy dependence of the fall signal and suggest that searching for this signal in the data could bring an independent assessment of the low-energy measurement threshold of the IBEX-Lo sensor.