Statistical Study of the Relationship Between Pi1/2‐Band Wave Powers and Firehose Instability Criterion During Fast Flows in the Magnetotail Plasma Sheet. Issue 11 (25th November 2022)

• Record Type: Journal Article
• Authors: Wei, Jiayun; Wang, Guoqiang; Zuo, Pingbing
• Is Part Of: Journal of geophysical research. Volume 127:Issue 11(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-11-25
• Subjects: magnetotail -- fast flows -- firehose instabilities -- ultralow frequency waves; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1029/2022JA030567
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: Fast flows play a significant role in the transport of magnetic flux, mass, and energy in the terrestrial plasma sheet. Abundant wave activities occur during fast flows, however, what determines their wave powers is not fully understood. Here, we statistically investigate the relation of Pi1‐band (10–40 s) and Pi2‐band (40–150 s) mean wave amplitudes (MWAs) to the threshold of firehose instabilities during fast flows based on observations of the Magnetospheric Multiscale mission. To reduce the effect of dipolarization processes on the MWAs, we only analyze the fast flows with an average BZ < 3 nT, where BZ is the Z component of the magnetic field in the geocentric solar magnetospheric coordinate system. The compressional and transverse components of the magnetic field fluctuations during fast flows are mostly comparable for each frequency range. The probability of reaching firehose unstable condition tends to be larger for the faster fast flow. The Pi1/2‐band MWAs tend to be larger as the probability of the firehose unstable condition near the neutral sheet is larger for the fast flows with a certain average velocity near the neutral sheet, although they have a weak relationship. Our results suggest that the firehose instability is a possible factor to affect the Pi1/2‐band MWAs during the fast flow in the magnetotail current sheet. Key Points: The probability of the firehose unstable condition near the neutral sheet (NS) during fast flows tends to be larger for the faster flow The Pi1/2‐band wave powers during fast flows are associated with the threshold of firehose instabilities as well as the fast flow velocity The firehose unstable condition might affect the Pi1/2‐band wave powers during fast flows with a certain average velocity near the NS