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  1. Abstract

    Geomagnetic storms are primarily driven by stream interaction regions (SIRs) and coronal mass ejections (CMEs). Since SIR and CME storms have different solar wind and magnetic field characteristics, the magnetospheric response may vary accordingly. Using FAST/TEAMS data, we investigate the variation of ionospheric O+and H+outflow as a function of geomagnetic storm phase during SIR and CME magnetic storms. The effects of storm size and solar EUV flux, including solar cycle and seasonal effects, on storm time ionospheric outflow, are also investigated. The results show that for both CME and SIR storms, the O+and H+fluences peak during the main phase, and then declines in the recovery phase. However, for CME storms, there is also significant increase during the initial phase. Because the outflow starts during the initial phase in CME storms, there is time for the O+to reach the plasma sheet before the start of the main phase. Since plasma is convected into the ring current from the plasma sheet during the main phase, this may explain why more O+is observed in the ring current during CME storms than during SIR storms. We also find that outflow fluence is higher for intense storms than moderate storms and is higher during solar maximum than solar minimum.

     
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  2. Abstract

    A number of interdependent conditions and processes contribute to ionospheric‐origin energetic (10 eV to several keV) ion outflows. Due to these interdependences and the associated observational challenges, energetic ion outflows remain a poorly understood facet of atmosphere‐ionosphere‐magnetosphere coupling. Here we demonstrate the relationship between east‐west magnetic field fluctuations () and energetic outflows in the magnetosphere‐ionosphere transition region. We use dayside cusp region FAST satellite observations made near apogee (4,180‐km altitude) near fall equinox and solstices in both hemispheres to derive statistical relationships between ion upflow andspectral power as a function of spacecraft frame frequency bands between 0 and 4 Hz. Identification of ionospheric‐origin energetic ion upflows is automated, and the spectral powerin each frequency band is obtained via integration ofpower spectral density. Derived relationships are of the formfor upward ion fluxat 130‐km altitude, withthe mapped upward ion flux for a nominal spectral power nT. The highest correlation coefficients are obtained for spacecraft frame frequencies0.1–0.5 Hz. Summer solstice and fall equinox observations yield power law indices0.9–1.3 and correlation coefficients, while winter solstice observations yield0.4–0.8 with. Mass spectrometer observations reveal that the oxygen/hydrogen ion composition ratio near summer solstice is much greater than the corresponding ratio near winter. These results reinforce the importance of ion composition in outflow models. If observedperturbations result from Doppler‐shifted wave structures with near‐zero frequencies, we show that spacecraft frame frequencies0.1–0.5 Hz correspond to perpendicular spatial scales of several to tens of kilometers.

     
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  3. Abstract

    Factors related to two sources of energy input to the ionosphere, the Poynting flux associated with both quasistatic fields (Sdc) and Alfvénic fluctuations (Sac), and the soft electron precipitation, are investigated to evaluate their correlations with the O+and the H+outflows in the dayside cusp region by using recalibrated FAST/Time‐of‐Flight Energy, Angle, and Mass Spectrograph (TEAMS) data during the 24–25 September 1998 geomagnetic storm studied by Strangeway et al. (2005,https://doi.org/10.1029/2004JA010829). The Poynting flux and the soft electron precipitation are well correlated with ion outflow flux in the dayside cusp region.Sdcshows the highest correlation with the O+outflows, while it is the electron number flux that correlates best with the H+outflows. The Alfvénic waves play an essential role in accelerating outflows. The averaged O+/H+flux ratio is 3.0 and is positively correlated to the Poynting flux, suggesting that the O+flux increases more strongly with the energy input.

     
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