Sectors of homogeneity in the inner heliosphere
Abstract
We define the sectors of homogeneity in the inner heliosphere as regions where the characteristic time, τ , of the exponential decay of proton and electron SEP events (Ep few MeV, Ee few hundred keV), J = J0 exp (-t/τ ), J0 =10 -104 /(cm2 ssrM eV ) is nearly constant. It is pointed out that in many events τ = const for a period of 3-5 days, sometimes up to a week, which corresponds to the spread of the sector of homogeneity up to about 90° . Sometimes the interval of homogeneity may even extend to three or more successive SEP events with equal τ , which suggests spatial homogeneity over longer time intervals, sometimes two weeks and even longer (then the spread of the sector of homogeneity is > 180° ). This means that more than the half of near-Sun space displays quasi-stationary characteristics of magnetic field and its fluctuations, or satisfies the stability of convection and adiabatic deceleration conditions, governing particle motion and yielding the invariance of τ . Such widespread regions of homogeneity derived simultaneously from both p and decays are observed only in about 50% of all events. In many cases one can find quasi stable interplanetary medium either for p or e, which suggests that only those parts of the spectrum of magnetic field fluctuations are invariable which correspond either to high (e) or low (p) frequencies throughout these periods. All exponential SEP event p and decays are examined from this aspect using CPME instrument data aboard IMP-8 in 1974-2001.
- Publication:
-
38th COSPAR Scientific Assembly
- Pub Date:
- 2010
- Bibcode:
- 2010cosp...38.1686D