A SURVEY OF MAGNETIC WAVES EXCITED BY NEWBORN INTERSTELLAR He+ OBSERVED BY THE ACE SPACECRAFT AT 1 au
ABSTRACT 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+. Twenty-five events are studied. They possess the generally predicted attributes: sp...
Saved in:
Published in | The Astrophysical journal Vol. 830; no. 1; pp. 47 - 60 |
---|---|
Main Authors | , , , , , , , , , , , |
Format | Journal Article |
Language | English |
Published |
Philadelphia
The American Astronomical Society
10.10.2016
IOP Publishing Institute of Physics (IOP) |
Subjects | |
Online Access | Get full text |
Cover
Loading…
Summary: | ABSTRACT 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+. Twenty-five events are studied. They possess the generally predicted attributes: spacecraft-frame frequencies slightly greater than the He+ 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. |
---|---|
Bibliography: | AAS00599 The Sun and the Heliosphere LA-UR-17-27183 National Aeronautics and Space Administration (NASA) Polish National Science Centre (NCN) NSF SHINE AC52-06NA25396; NNX13AF97G; NNX13AH66G; AGS1358103; AGS1357893; 2015/18/M/ST9/00036 |
ISSN: | 0004-637X 1538-4357 1538-4357 |
DOI: | 10.3847/0004-637X/830/1/47 |