Y.I. Logachev

Solar and Heliospheric Phenomena in October-November 2003: Causes and Effects

We present new observational data on the phenomena of extremely high activity on the Sun and in the heliosphere that took place in October–November 2003. A large variety of solar and heliospheric parameters give evidence that the interval under consideration is unique over the entire observation time. Based on these data, comparing them with similar situations in the past and using available theoretical concepts, we discuss possible cause-and-effect connections between the processes observed. The paper includes the first results and conclusions derived by the collaboration “Solar Extreme Events-2003” organized in Russia for detailed investigations of these events. As a result of our consideration, it is beyond question that the physical causes of solar and heliospheric phenomena in October–November 2003 are not exclusively local and do not belong only to the active regions and solar atmosphere above them. The energy reservoirs and driving forces of these processes have a more global nature. In general, they are hidden from an observer, since ultimately their sources lie in the subphotospheric layers of the Sun, where changes that are fast and difficult to predict can sometimes take place (and indeed they do). Solar flares can serve as sufficiently good tracers of these sudden changes and reconstructions on the Sun, although one can still find other diagnostic indicators among the parameters of magnetic fields, motions of matter, and emission characteristics.

Suprathermal ions at 1 AU in solar wind fluxes from near equatorial coronal holes in 2006-09

Ion energy spectra and abundance ratios are studied in 0.04-2 MeV/nucleon ion fluxes using ULEIS/ACE data during the solar minimum between solar cycles 23 and 24. The unique prolonged minimum of 2006-2009 permitted to select 35 quiet time periods when suprathermal ion fluxes originating from near-equatorial coronal holes (CH) were observed at 1 AU. The values of relative ion abundances indicate the presence of particle populations accelerated in different processes on the Sun and in the interplanetary space observed as suprathermal fluxes. The ratios of suprathermal C/O and Fe/O arising from coronal holes were found to correlate with their bulk solar wind ratios from CH (SWICS/ACE data) whereas 40-80 keV/nucleon 4 He/O ratios were about two times higher than their bulk wind values. The 3 He, 4 He, Fe, C, and O ion energy spectra showed that ion intensities depend on solar wind speed and the fluxes were higher inside fast wind streams. The results obtained suggest that the bulk solar wind described by Maxwellian distribution appears to be the source of ions further accelerated to suprathermal energies thus forming the high energy solar wind tail. The ion spectra obtained here were fitted by power-law functions or combined power-law/exponential which suggests different mechanisms of acceleration.