Premium
Ultra‐low‐frequency wave power in the magnetotail lobes 1. Relation to substorm Onsets and the auroral electrojet index
Author(s) -
Smith R. A.,
Goldstein M. L.,
Sands M. R.,
Lepping R. P.,
Goertz C. K.,
Harrold B. G.,
Fitch C. A.,
Shan L.H.
Publication year - 1990
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl017i011p01845
Subject(s) - substorm , electrojet , physics , expansive , phase (matter) , geophysics , astrophysics , magnetic field , magnetosphere , earth's magnetic field , quantum mechanics , compressive strength , thermodynamics
Time series observations of the magnetotail lobe magnetic field have been Fourier analyzed to compute the frequency‐weighted energy density P fz in the range 1–30 mHz. P fz is generally observed in the range 10 −4 – 10 −2 γ 2 – Hz, with a mean value of 1.2 × 10 −3 γ 2 – Hz during substorm phases and 1.0 × 10 −3 γ 2 – Hz in the comparison intervals. No strong correlation of P fz is found with AE in set of intervals, but during substorm growth phases P fz may vary by an order of magnitude over time scales of 30 min, with a tendency for higher power levels to occur later in the growth phase. Increases in P fz are seen to precede by ∼ 10 min localized expansive phase activity observed in individual magnetograms. The observed levels of P fz during growth phase are in general accord with the requirements of the thermal catastrophe substorm model.