Details

Autor(en) / Beteiligte

• Zhao, X. X.
• Zong, Q.‐G.
• Liu, J. J.
• Yue, Chao
• Zhou, X.‐Z.
• Hu, Z. J.
• Hu, H. Q.
• Liu, Z.‐Y.

Titel

A Conjunction of Pc5 ULF Waves From Spaceborne and Ground‐Based Observations

Ist Teil von

• Journal of geophysical research. Space physics, 2023-09, Vol.128 (9), p.n/a

Ort / Verlag

Washington: Blackwell Publishing Ltd

Erscheinungsjahr

2023

Quelle

Wiley-Blackwell Journals

Beschreibungen/Notizen

• Large scale (low wavenumber m) ultra‐low frequency (ULF) waves observed in the inner magnetosphere can propagate into the ionosphere and to the ground, which are recognized as magnetic pulsations by ground‐based magnetometers. We present the conjunctive observations of Pc5 ULF waves from Van Allen Probes (at ∼6MLT, earlier), GOES13 (at ∼1MLT, later), SuperDARN radar (at ∼6MLT), and ground magnetometers. The phase shifts of the waves observed by satellites at different MLTs indicate westward propagation from the noon sector. The traveling Alfven waves are thought to propagate along the field line and reflect mostly at the ionosphere, while a few wave energy leak from the ionosphere to the ground. Thus, we suppose that standing waves are observed by the spacecraft while traveling signals are observed by the ground‐based magnetometers in the form of electromagnetic waves. By mapping the ground magnetic pulsations to the magnetic equatorial plane (which depends on the total ionosphere conductivity from IRI and MSIS model), the expected ULF waves match well with the satellite observations. Besides, it suggests that the ionosphere conductivity can be estimated from the conjunctive ULF waves observed on the ground and in the magnetosphere. The calculated total conductivity is 15–30% higher than the model. Plain Language Summary The ultra‐low frequency (ULF, usually 1 mHz ∼ 1 Hz) waves can propagate along the magnetic field line as traveling Alfven waves in the magnetosphere. Most energy of the traveling Alfven waves would reflect at the ionosphere, while a few energy can spread to the ground as electromagnetic waves. In this study, we present the conjunctive observations of Pc5 ULF waves in the magnetosphere, the ionosphere, and on the ground, respectively. The expected ULF waves mapping from the ground magnetic pulsations coincide well with the waves observed by the spaceborne probe, suggesting that the ULF waves propagate from the magnetosphere to the ionosphere and then to the ground. Besides, the phase shifts of the ULF waves observed by satellites at different MLTs indicate that the ULF waves propagate westward from the noon sector, with an azimuthal wave number m of approximately −5. Our work demonstrates the localized ULF waves propagation in the magnetosphere‐ionosphere‐atmosphere system through the spaceborne and ground‐based observations, suggesting that standing Alfven waves can be observed in the magnetosphere while magnetic pulsations on the ground are the signals of traveling Alfven waves. The ionosphere conductivity can be estimated from the conjunctive ULF waves observed on the ground and in the magnetosphere. Key Points The ultra‐low frequency (ULF) wave propagation in the magnetosphere‐ionosphere‐atmosphere system is demonstrated through spaceborne and ground‐based observations The phase shifts in the ULF waves at different MLTs suggest westward propagation from the noon sector with an azimuthal wave number of −5 It is possible to estimate the ionosphere conductivity from conjunctive ULF wave observations on the ground and in the magnetosphere