Possible wave amplitudes in shocks in the solar corona - Predictions for Solar Probe

Shocks and Alfven turbulence are frequently invoked as mechanisms to heat the solar corona and accelerate the solar wind. A primary objective of the Solar Probe Mission is to detect and characterize these nonthermal dissipation and energization processes. Although the solar wind in the corona is usually assumed to be sub-Alfvenic, temporal and spatial variability in the plasma parameters could lead to conditions under which weak, fast mode shocks might form. ISEE 3 data from the flanks of the Earth's bow shock show that even low Mach number, quasi-parallel shocks generate large-amplitude Alfven turbulence with δB/B of the order of 1, and intense high-frequency electrostatic plasma waves. Using a model of the corona and scaling parameters to those expected in the regions to be traversed by Solar Probe (r ≥ 4 Rs), we suggest it is possible that such shocks might produce Alfven turbulence with magnetic field amplitudes up to the order of 0.1 G and electric field amplitudes up to the order of 1 V/m; electrostatic waves near 100 kHz may have amplitudes of 0.1 V/m. Since the shock-generated Alfven waves would be Doppler shifted to frequencies of a few kilohertz because of the high spacecraft velocity at perihelion, detection of these waves imposes severe requirements on the designs of plasma wave and magnetic field sensors on Solar Probe.