Spatial distribution of mid‐latitude sporadic E scintillations in summer daytime

Authors:
  • TOTadahiko Ogawa
    Tadahiko Ogawa
  • ASAkira Suzuki
    Akira Suzuki
  • MKManabu Kunitake
    Manabu Kunitake
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Abstract
In the summer of 1986, 150‐MHz transmissions from six U.S. Navy Navigation Satellite System satellites were received at Kokubunji, Japan, to investigate daytime scintillations due to mid‐latitude sporadic E layers. From analysis of 145 satellite passes accompanied by Es scintillations, it is found that the diurnal variation of the scintillation occurrence ratio has two maxima, one before noon (1100 JST) and the other around evening (1800 JST), consistent with the diurnal variation of the occurrence probability of ƒoEs exceeding 8 MHz. Some of the Es layers are not accompanied by scintillations, suggesting that they are insusceptible to the plasma instability giving rise to the irregularities. Horizontal, nearly north‐south scale lengths of the scintillation regions range from 20 to 600 km with a predominant peak around 50 km and have a distribution approximated by a form of L−0.8 (L, scale length) for L ≥ 40 km. These scale lengths may represent the extents of wind shear regions producing sporadic E layers. An important finding is that of the north‐south asymmetry of scintillation occurrences. A tilted irregularity layer model is hypothesized to account for this asymmetry.

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