Received: 29 Aug 2018 – Accepted for review: 05 Sep 2018 – Discussion started: 06 Sep 2018
Abstract. The Semiannual Variation (SAV) is an annual pattern characterized by maxima around the equinoxes and minima near solstices observed in many space weather parameters. Several authors have studied this variation in the electron fluxes of the magnetosphere, focusing only in a few energy levels. In this investigation, Van Allen probes data are processed to extend SAV studies in electron fluxes of a wider energy range. A superposed epoch analysis was applied to data of the REPT and MagEIS instruments obtaining a clear semiannual pattern in the superposed year for L-shell values between 2.5 and 6.5. The Day Of Year (DOY) at which the highest electron flux values are detected near the September equinox coincide with the Russel & McPherron prediction. However, the DOY of the maximum expected close the March equinox occurs with a one month lag from the prediction of the accepted models. In addition, integrating over L-shell the annual DOY-L data with the semiannual pattern resulted in temporal curves that enabled to determine the energy range for which the SAV can be detected: from MeV to tens MeV energy values. Finally, an additional analysis of the fluxes of the Ring Current principal components (H+ and O+ ions) was performed, obtaining no evidence of a SAV on them. This result could indicate that the widely recognized semiannual pattern in the geomagnetic activity is related to a different current system.
How to cite. Poblet, F. L. and Azpilicueta, F.: Semiannual Variation in radiation belts particle fluxes: Van Allen probes observations, Ann. Geophys. Discuss. [preprint], https://doi.org/10.5194/angeo-2018-98, 2018.
In this article, the Semiannual Variation is recognized in electron fluxes of the outer radiation belt using Van Allen Probes data. The maxima near the equinoxes are clearly seen but the the maximum of the March equinox appears delayed one month from the theories prediction. Also, the Semiannual Variation is detected only in a narrow energy range: electron fluxes with energies between the MeV to tens MeV.
In this article, the Semiannual Variation is recognized in electron fluxes of the outer...