Title: Dispersion of time-to-maximum of solar particle events: Function of charge-to-mass of the suprathermal ions?

Authors: L.Simeonov, M.Hilchenbach, B.Klecker, R.Kallenbach, K.Bamert and D.McMullin.

Reference: Proc. of the 9th Conf. on contemporary problems of the solar-terrestrial influences. Sofia, 21-21.Nov. 2002, p.85-88.

The measurements with the STOF/STOF and HSTOF instrument of the CELIAS/SOHO sensor allow the determination of the energy, mass and ionic charge of suprathermal energetic particles of gradual and/or inpulsive solar particle events. The dynamics of an energetic solar particle event could be described by its time-profile, including the rising phase to the highest intensity or the "time to maximum", the maximum itself and the decaying phase of the event. The "time to maximum" in a solar event is found to be a function of the charge- to -mass ratio of the observed elements. In the case of Fe the onset phase could differ for single energetic events, being a function not only of the velocity of the ion, but also of its state of ionization, i.e on the extent of stripping. The question is whether some quantitative dependence between the "time to maximum" and the charge/mass for individual elements (for example, H, He, O, Fe) could be derived from the STOF/HSTOF data, thus providing additional evidence to the problematic of solar energetic events, especially concerning the diffusive propagation of particles. In the paper this problematic is discussed, featuring the gradual solar particle event, detected on 30 June 2000 or 181DoY2000. As an example, plots from HSTOF and ULEIS on ACE, concerning the time profiles of O and Fe, and especially the different ?time to maximum? of the elements are presented. Reference X-ray plot from GOES and a picture from LASCO/SOHO is used for additional identification of the chosen solar event.

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Last Update: 22 December 2002, Xuyu Wang