Occurrence rate of earthward-propagating dipolarization fronts

• Published in: Geophysical research letters 2012-05, Vol.39 (10), p.L10101-n/a
• Main Authors: Fu, H. S., Khotyaintsev, Y. V., Vaivads, A., André, M., Huang, S. Y.
• Format: Article
• Language: English
• Subjects: Atmospheric sciences; Clusters; Current sheets; dipolarization front; Earth sciences; Earth, ocean, space; Electrocardiography; Environmental testing; Exact sciences and technology; Fittings; Geophysics; hyperbolic tangent function; Life support systems; Magnetic fields; Magnetic flux; Magnetism; occurrence rate; Physical examinations; reconnection; Simulation; statistical; substorm; Tangents
• ISSN: 0094-8276; 1944-8007; 1944-8007
• DOI: 10.1029/2012GL051784

The occurrence rate of earthward‐propagating dipolarization fronts (DFs) is investigated in this paper based on the 9 years (2001–2009) of Cluster 1 data. For the first time, we select the DF events by fitting the characteristic increase inBzusing a hyperbolic tangent function. 303 earthward‐propagating DFs are found; they have on average a duration of 4 s and aBz increase of 8 nT. DFs have the maximum occurrence at ZGSM ≈ 0 and r ≈ 15 RE with one event occurring every 3.9 hours, where r is the distance to the center of the Earth in the XYGSM plane. The maximum occurrence rate at ZGSM ≈ 0 can be explained by the steep and large increase of Bz near the central current sheet, which is consistent with previous simulations. Along the r direction, the occurrence rate increases gradually from r ≈ 20 to r ≈ 15 RE but decreases rapidly from r ≈ 15 to r ≈ 10 RE. This may be due to the increasing pileup of the magnetic flux from r ≈ 20 to r ≈ 15 RE and the strong background magnetic field at r