title: Interstellar neutral hydrogen in the heliosphere: new horizons observations in the context of models

authors: Swaczyna, P

subjects: mathematics

abstract: Interstellar neutral (ISN) hydrogen is the most abundant species in the outer heliosheath and the very local interstellar medium (VLISM). Charge-exchange collisions in the outer heliosheath result in filtration, reducing the ISN hydrogen density inside the heliosphere. Additionally, these atoms are intensively ionized close to the Sun, resulting in a substantial reduction of their density within a few astronomical units from the Sun. The products of this ionization—pickup ions (PUIs)—are detected by charged particle detectors. The Solar Wind Around Pluto instrument on New Horizons provides, for the first time, PUI observations from the distant heliosphere. We analyze the observations collected between 22 and 52 au from the Sun to find the ISN hydrogen density profile and compare the results with predictions from global heliosphere models. We conclude that the density profile derived from the observations is inconsistent with steady-state model predictions. This discrepancy is not explained by time variations close to the Sun and thus may be related to the temporal evolution of the outer boundaries or VLISM conditions. Furthermore, we show that the cold and hot models of ISN hydrogen distribution are not a good approximation closer to the termination shock. Therefore, we recommend a new fiduciary point based on the available New Horizons observations at 40 au from the Sun, at ecliptic direction (285.°62, 1.°94), where the ISN hydrogen density is 0.11 cm−3. The continued operation of New Horizons should give better insight into the source of the discussed discrepancy.

text: Interstellar neutral hydrogen in the heliosphere: new horizons observations in the context of models Interstellar neutral (ISN) hydrogen is the most abundant species in the outer heliosheath and the very local interstellar medium (VLISM). Charge-exchange collisions in the outer heliosheath result in filtration, reducing the ISN hydrogen density inside the heliosphere. Additionally, these atoms are intensively ionized close to the Sun, resulting in a substantial reduction of their density within a few astronomical units from the Sun. The products of this ionization—pickup ions (PUIs)—are detected by charged particle detectors. The Solar Wind Around Pluto instrument on New Horizons provides, for the first time, PUI observations from the distant heliosphere. We analyze the observations collected between 22 and 52 au from the Sun to find the ISN hydrogen density profile and compare the results with predictions from global heliosphere models. We conclude that the density profile derived from the observations is inconsistent with steady-state model predictions. This discrepancy is not explained by time variations close to the Sun and thus may be related to the temporal evolution of the outer boundaries or VLISM conditions. Furthermore, we show that the cold and hot models of ISN hydrogen distribution are not a good approximation closer to the termination shock. Therefore, we recommend a new fiduciary point based on the available New Horizons observations at 40 au from the Sun, at ecliptic direction (285.°62, 1.°94), where the ISN hydrogen density is 0.11 cm−3. The continued operation of New Horizons should give better insight into the source of the discussed discrepancy.

year: 2024

title: Latent class count models of total visitation demands: days out hiking in the eastern Alps

authors: Scarpa, Riccardo

subjects: travel cost method

abstract: We report preliminary results on the investigation of the hypothesis of the existence of latent classes in the total demand for days out in a vast section of the Italian Eastern Alps. Finite mixing is informed by socioeconomic variables and it is limited to the demand portion of a hurdle model of visitation. Gradually more flexible count models are estimated moving from the Poisson to the Negative Binomial -1 and -2, to the generalized negative binomial. The implications for expected consumers surplus, predicted visitation and choke prices are discussed for a plausible 2 class model where years of experience play an important role in class membership.

text: Latent class count models of total visitation demands: days out hiking in the eastern Alps We report preliminary results on the investigation of the hypothesis of the existence of latent classes in the total demand for days out in a vast section of the Italian Eastern Alps. Finite mixing is informed by socioeconomic variables and it is limited to the demand portion of a hurdle model of visitation. Gradually more flexible count models are estimated moving from the Poisson to the Negative Binomial -1 and -2, to the generalized negative binomial. The implications for expected consumers surplus, predicted visitation and choke prices are discussed for a plausible 2 class model where years of experience play an important role in class membership.

year: 2007

title: The Digital Divide in New Zealand: The position of Māori and Pacific peoples

authors: Gibson, John

subjects: Māori digital access

abstract: Information and communication technology plays an ever-growing role in economic, political and social life and those who are unable to access such technologies are increasingly disadvantaged. Hence, what has come to be known as the ‘digital divide’ is of considerable significance. Here, indicators of that divide as it affects Māori and Pacific Islands peoples in Aotearoa/New Zealand are presented and discussed.

text: The Digital Divide in New Zealand: The position of Māori and Pacific peoples Information and communication technology plays an ever-growing role in economic, political and social life and those who are unable to access such technologies are increasingly disadvantaged. Hence, what has come to be known as the ‘digital divide’ is of considerable significance. Here, indicators of that divide as it affects Māori and Pacific Islands peoples in Aotearoa/New Zealand are presented and discussed.

year: 2002-09