The Solar Wind in the Outer Heliosphere and Heliosheath

NASA's New Horizons spacecraft flies past Pluto on 14 July 2015, carrying two instruments that detect charged particles. Pluto has a tenuous, extended atmosphere that is escaping the planet's weak gravity. The interaction of the solar wind with Pluto's escaping atmosphere depends on solar wind conditions as well as the vertical structure of Pluto's atmosphere. We have analyzed Voyager 2 particles and fields measurements between 25 and 39 AU and present their statistical variations. We have adjusted these predictions to allow for the Sun's declining activity and solar wind output. We summarize the range of SW conditions that can be expected at 33 AU and survey the range of scales of interaction that New Horizons might experience. Model estimates for the solar wind standoff distance vary from~7 to~1000 R P with our best estimate being around 40 R P (where we take Pluto's radius to be R P = 1184 km).

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“…Voyager observations of the outer heliosphere are reviewed by Richardson et al . [, ] and Richardson and Burlaga [].…”

Section: Voyager Datamentioning

confidence: 99%

Solar wind at 33 AU: Setting bounds on the Pluto interaction for New Horizons

et al. 2015

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“…The subject of a strong variability of the B-field in the HS along the trajectory of V2 has been mentioned already [12]. There they reported that HS plasma and magnetic field were highly variable on scales as small as ten minutes.…”

Section: Journey and Trajectory Of The Sc In The Hs/the Intervals Selmentioning

confidence: 84%

Survey of Compressions Observed in the Heliosheath with the Spacecraft Voyager

Berdichevsky¹

2021

AAST

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Examples of changes in the magnitude of the B-field after the heliosphere termination shock (TS) with both Voyager spacecraft (SC) are presented. The work focuses on similarities and differences in the observations at their in-situ measurements along divergent paths. The presented results were collected where the accuracy of the magnetometer is the highest. These locations are those wherein, four to seven times during the year, the SC performs about 330 minutes of slow rotations identified in the SC language as MAGROLs. They are next reviewed, with the understanding that after the TS, at MA-GROLs, the solar wind (SW) flows appear to be mostly sub-magnetosonic and compressional in this region, region named helio-sheath (HS). This is a preliminary survey that uses 48 sec B-field averages. The time-intervals in this work fill gaps in the currently available studies for longer time intervals. The present study reinforces the view that in the HS after the TS the SW is most likely strongly compressional. Further we discuss the fact that observed fluctuation intensity-modes of the B-field in our time-ranges appear to be much more pronounced at the Voyager 2 path than at the Voyager 1 path.

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“…Voyager 2 (V2) crossed the termination shock (TS) and entered the heliosheath in August 2007 during a time of decreasing solar activity [ Burlaga et al ., ]. Heliosheath observations of the plasma from 2007.7 to mid‐2010 and the magnetic field from 2007.7 to 2009.4 were reviewed by Richardson and Burlaga [].…”

Section: Introductionmentioning

confidence: 99%

Heliosheath magnetic field and plasma observed by Voyager 2 during 2011

2014

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We discuss magnetic field and plasma observations from Voyager 2 (V2) during 2011, when V2 was beginning to see the effects of increasing solar activity following the solar minimum in 2009. The magnetic field strength (B) profile showed large amplitude fluctuations that can be resolved into a linear increase of B with time and a sinusoidal variation of the period of 86.2 ± 0.8 days. Voyager 2 was in a unipolar region in which the magnetic polarity was directed away from the Sun along the Parker spiral 96% of the time, indicating that V2 was poleward of the heliospheric current sheet throughout most of 2011. The distribution of B was lognormal, but a Gaussian distribution was observed when the linear variation of B was subtracted from the data. The distribution of daily increments of B was a q-Gaussian distribution with q = 1.1 ± 0.1, which is less intermittent than normally observed in the heliosheath. However, the distribution of hourly increments of B was a q-Gaussian distribution with q = 1.5 ± 0.03. The density, temperature, and velocity increased linearly from the beginning of 2011 to approximately day 254. The magnetic and thermal pressure tended to increase throughout the year, but the magnetic pressure dominated most of the time. The counting rate of >70 MeV/nucleon particles increased rapidly during the first 250 days, but it leveled out during the rest of the year when B was stronger. The empirical CR-B relationship describes this behavior.

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The Solar Wind in the Outer Heliosphere and Heliosheath

Cited by 4 publications

References 58 publications

Solar wind at 33 AU: Setting bounds on the Pluto interaction for New Horizons

Solar wind at 33 AU: Setting bounds on the Pluto interaction for New Horizons

Survey of Compressions Observed in the Heliosheath with the Spacecraft Voyager

Heliosheath magnetic field and plasma observed by Voyager 2 during 2011

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