A SURVEY OF MAGNETIC WAVES EXCITED BY NEWBORN INTERSTELLAR He{sup +} OBSERVED BY THE ACE SPACECRAFT AT 1 au

Journal Article · Mon Oct 10 00:00:00 EDT 2016 · Astrophysical Journal

DOI:https://doi.org/10.3847/0004-637X/830/1/47· OSTI ID:22667350

Fisher, Meghan K.; Argall, Matthew R.; others, and

We report observations of low-frequency waves at 1 au by the magnetic field instrument on the Advanced Composition Explorer ( ACE /MAG) and show evidence that they arise due to newborn interstellar pickup He{sup +}. Twenty-five events are studied. They possess the generally predicted attributes: spacecraft-frame frequencies slightly greater than the He{sup +} cyclotron frequency, left-hand polarization in the spacecraft frame, and transverse fluctuations with minimum variance directions that are quasi-parallel to the mean magnetic field. Their occurrence spans the first 18 years of ACE operations, with no more than 3 such observations in any given year. Thus, the events are relatively rare. As with past observations by the Ulysses and Voyager spacecraft, we argue that the waves are seen only when the background turbulence is sufficiently weak as to allow for the slow accumulation of wave energy over many hours.

• OSTI ID: 22667350
• Journal Information: Astrophysical Journal, Vol. 830, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
COSMIC GASES
CYCLOTRON FREQUENCY
CYCLOTRON RADIATION
FLUCTUATIONS
HELIOSPHERE
HELIUM IONS
INSTABILITY
INTERSTELLAR SPACE
MAGNETIC FIELDS
POLARIZATION
SOLAR WIND
SPACE VEHICLES
SUN
TURBULENCE