Solar cycle variation of interstellar neutral He, Ne, O density and pick-up ions along the Earth's orbit

Abstract

We simulated the modulation of the interstellar neutral (ISN) He, Ne, and O density and pick-up ion (PUI) production rate and count rate along the Earth's orbit over the solar cycle from 2002 to 2013 to verify if solar cycle-related effects may modify the inferred ecliptic longitude of the ISN inflow direction. We adopted the classical PUI model with isotropic distribution function and adiabatic cooling, modified by time- and heliolatitude-dependent ionization rates and non-zero injection speed of PUIs. We found that the ionization losses have a noticeable effect on the derivation of the ISN inflow longitude based on the Gaussian fit to the crescent and cone peak locations. We conclude that the non-zero radial velocity of the ISN flow and the energy range of the PUI distribution function that is accumulated are of importance for a precise reproduction of the PUI count rate along the Earth orbit. However, the temporal and latitudinal variations of the ionization in the heliosphere, and particularly their variation on the solar cycle time-scale, may significantly modify the shape of PUI cone and crescent and also their peak positions from year to year and thus bias by a few degrees the derived longitude of the ISN gas inflow direction.

arXiv commentPublished in the Monthly Notices of the Royal Astronomical Society, vol. 458, Issue 4, pp 3691-3704, doi:10.1093/mnras/stw515

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Cited by in corpus (8)

• Sun-Heliosphere Observation-based Ionization Rates Model
• Interstellar Neutral Gas Species And Their Pickup Ions Inside The Heliospheric Termination Shock. Ionization Rates For H, O, Ne, And He
• The helium Warm Breeze in IBEX observations as a result of charge exchange collisions in the outer heliosheath
• Interstellar neutral helium in the heliosphere from IBEX observations. V. Observations in IBEX-Lo ESA steps 1, 2, & 3
• Interstellar Neutral Gas Species And Their Pickup Ions Inside The Heliospheric Termination Shock. The Large-scale Structures
• Helium Energetic Neutral Atoms from the Heliosphere: Perspectives for Future Observations
• Modeling Emission of Heavy Energetic Neutral Atoms from the Heliosphere
• Three dimensional He+ pickup ion velocity distribution functions observed with STEREO-A PLASTIC