Sharp Alfvenic Impulses in the Near-Sun Solar Wind: Properties and Possible Origins

Parker Solar Probe has revealed the presence of large numbers of discrete Alfvenic impulses in the near-Sun solar wind with an anti-Sunward sense of propagation. These are similar to those previously observed near 1 AU and in high speed streams over the Sun's poles and at 60 solar radii. At 35 solar radii, however, they are typically shorter and sharper than seen elsewhere. In addition, these spikes occur in "patches" and there are also clear periods within the same stream when they do not occur. While the velocity fluctuations associated with these spikes are typically under 100 km/s due to the rather low Alfven speeds in the streams observed by Probe to date, these are still associated with large angular deflections of the magnetic field - and these deflections are not isotropic. We discuss the scales, amplitudes and orientations of these structures and their links to other properties measured by Probe, such as the bulk plasma flow. We also discuss how these new observations, combined with those from earlier missions, provide evidence for the possible origins of these events and in particular whether they are the long-sought interplanetary signature of discrete reconnection jets in the solar corona.