Pc 1–2 and Pc 4–5 pulsations observed at a network of high‐latitude stations

Abstract

Analysis of magnetospheric Pc 1 and Pc 2 (in brief Pc 1–2) pulsations at a network of six northern hemisphere stations at latitudes 65°–76° CGM shows that their average frequency decreases with increasing latitude of the station. Their maximum occurrence is at L=6–9 and 1200–1600 LT. The ionospheric ducting is weak for f < 0.3 Hz. Occasionally the Pc 1 intensity at a station is modulated by a simultaneously arriving quasi‐periodic Pc 4–5 signal. A mechanism for generating micropulsations which is common to both high‐frequency and low‐frequency waves is presented and discussed, the proposed mechansim being that a broadband signal from the solar wind is amplified in the magnetosphere in the frequency bands of the field line resonance (Pc 4–5) and in the He+ cyclotron frequency (Pc 1–2) range.

High resolution observations of spectral width features associatedwith ULF wave signatures in artificial HF radar backscatter

“…It seems likely that the events presented in the current paper are best described by the action of long-period (Pc4/5) ULF waves on the ion-cyclotron wave source region in the magnetosphere, and that the current observations are related to those reported by Plyasova-Bakounina et al (1996), Mursula et al (1997Mursula et al ( , 1999Mursula et al ( , 2001) and Rasinkangas and Mursula (1998). This study presents multiple occurrences of Pc4 waves driven by wave-particle interactions in the magnetosphere, simultaneously with broadened spectral widths and increases in Pc1 activity.…”

“…There are ground-based (Plyasova-Bakounina et al, 1996) and combined ground-satellite (e.g. Mursula et al, 1997Mursula et al, , 1999Mursula et al, , 2001Rasinkangas and Mursula, 1998) observations supporting Pc1 growth by long-period ULF waves.…”

Satellite observations of Pc 1 pearl waves: The changing paradigm

“…This would naturally lead to repetitive wave packets at the ULF wave period (or twice the period in the case of an antisymmetric wave). During the last 10 years, an increasing amount of evidence has been reported by both ground observations (Plyasova-Bakounina et al, 1996) and by satellite observations (Fraser et al, 1992;Rasinkangas et al, 1994;Mursula et al, 1997;Rasinkangas and Mursula, 1998;Mursula et al, 2001) in favor of the simultaneous occurrence of Pc 1 pearls and ULF waves with period matching the pearl repetition period.…”

Recent progress in understanding Pc1 pearl formation

“…For such bouncing, a density gradient such as the plasmapause is significant (Mazur and Potapov, 1983;Dmitrienko and Mazur, 1985). Another suggested explanation for the pearl repetition, which recently gained popularity, is that it is due to the modulation of CI growth rate by field-line oscillations in the Pc3/4 ($0:01 Hz) frequency range (Lyatsky and Plyasova-Bakounina, 1986;Plyasova-Bakounina et al, 1996;Mursula et al, 1997).…”