Study of the solar flare of December 16, 1988 on the basis of the 2.223-MeV γ line and initial characteristics of flare neutrons
The third burst of the solar flare of December 16, 1988 was investigated on the assumption of both Bessel and power spectra of the initial charged particles. Refined data on the flare-neutron-production cross sections were used and two different neutron source altitudes were considered. An increase in the solar plasma density under the flare region up 2 × 1017 cm−3 has been found throughout the photosphere; in some cases, the plasma density increased to (3–6) × 1017 cm−3 in the initial flare stages. The dynamics of the increase in the plasma density during γ emission has been traced. It is found that the particle spectrum changes from moderately hard to soft and then to hard during γ emission in both spectral representations.