JOP 25 proposal:

Correlation between Energetic Particle Production and Solar Plasma Properties

J. Torsti, PI of ERNE

Spectrometers, particle instruments.

According to Parker's model, the interplanetary magnetic field line passing through the L1-point connects to ~60 deg west of the central meridian of the Sun if the solar wind speed is around 400 km/s. The neighbourhood of this nominal footpoint should be monitored to find out the possible correlation between energetic particle fluxes at L1 and the plasma properties (composition, temperature, magnetic field, density etc.) at different heights in the solar atmosphere. Measurements should be done both when this region is active and non-active.

We have performed a preliminary analysis of the energetic proton fluxes measured by IMP-8 during the quiet year 1986. The results suggest that there is a significant solar contribution to the >10 MeV proton flux for a few percent of the time. (In smaller energies, the solar contribution is even bigger). Also, some evidence of a 27-day periodicity in particle flux enhancement has been observed. Due to enhanced detection efficiency, the quiet time energetic solar proton component can be measured with higher accuracy than before. Heavier element and electron abundances can also be covered with a broad energy range.

We propose a joint observation program for spectrometers and particle instruments. An area of 60 x 60 deg around the nominal footpoint should be covered with the solar atmospheric plasma measurements (see figure). An optical scan should be taken along selected grid lines at least twice a day or every five hours. Complete energetic particle spectra (all species and maximal energy ranges) will be measured with CEPAC instruments (and possibly CELIAS) continuously.

Figure. A schematic picture of the Sun showing a possible grid of plasma measurements around the Parker spiral footpoint.