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7 Result(s)

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  1. No Access

    Article

    New model for auroral acceleration: O-shaped potential structure cooperating with waves

    There are recent observational indications (lack of convergent electric field signatures above the auroral oval at 4 R E altitude) that the U-shaped potential drop model for aur...

    P. Janhunen, A. Olsson in Annales Geophysicae (2000)

  2. No Access

    Article

    Characteristics of a stable are based on FAST and MIRACLE observations

    A stable evening sector are is studied using observations from the FAST satellite at 1250 km altitude and the MIRACLE ground-based network, which contains all-sky cameras, coherent radars (STARE), and magnetom...

    P. Janhunen, A. Olsson, O. Amm, K. Kauristie in Annales Geophysicae (2000)

  3. No Access

    Article

    How does the U-shaped potential close above the acceleration region? A study using Polar data

    We present a statistical study of Polar electric field observations using auroral oval passes over Scandinavia above the acceleration region. We are especially interested in seeing whether we can find large pe...

    P. Janhunen, A. Olsson, F. S. Mozer, H. Laakso in Annales Geophysicae (1999)

  4. No Access

    Article

    A case study of electron precipitation in the late substorm growth phase on and nearby a preonset arc

    We follow the electron precipitation characteristics on and nearby a preonset arc using the high resolution Freja TESP instrument. Our data coverage extends from about 10 min before onset up to 1 min before on...

    A. Olsson, P. Janhunen in Annales Geophysicae (1998)

  5. No Access

    Article

    The current-voltage relationship revisited: exact and approximate formulas with almost general validity for hot magnetospheric electrons for bi-Maxwellian and kappa distributions

    We derive the current-voltage relationship in the auroral region taking into account magnetospheric electrons for the bi-Maxwellian and kappa source plasma distribution functions. The current-voltage formulas ...

    P. Janhunen, A. Olsson in Annales Geophysicae (1998)

  6. No Access

    Article

    Field-aligned conductance values estimated from Maxwellian and kappa distributions in quiet and disturbed events using Freja electron data

    We study the question of what difference it makes for the derived field-aligned conductance (K) values if one uses Maxwellian or kappa distributions for the fitting of low-orbiting satellite electron flux spectra...

    A. Olsson, P. Janhunen in Annales Geophysicae (1998)

  7. No Access

    Article

    On the current-voltage relationship in auroral breakups and westwards-travelling surges

    Auroral precipitating electrons pass through an acceleration region before entering the atmosphere. Regardless of what produces it, a parallel electric field is assumed to cause the acceleration. It is well kn...

    A. Olsson, A. I. Eriksson, P. Janhunen in Annales Geophysicae (1997)