Comparison at the time of Orbiter:

The Alfvén radius is linked to the solar wind mass and magnetic flux. The wind magnetisation parameter (~ratio of mag/mass flux), is used to understand this dependence. Our results follow the trends from MHD wind simulations, but had an offset that is likely due to 3D effects and turbulence. (5/8)

Towards maximum activity, the heliospheric current sheet became complex and the solar wind sources moved towards the active latitudes. So, for example, an encounter of PSP that spends more time in the solar wind near current sheets will have a smaller Alfvén radii on average. (7/8)

A very dipolar magnetic field became inclined to the rotation axis. (6/8)

The heliospheric current sheet became warped by the emergence of active regions. (5/8)

The evolution of the coronal magnetic field during the solar cycle, strongly influenced the magnetic connectivity of PSP. Each encounter is different, which obscures our perception of the average Alfvén radius. Near minimum, the wind measured by PSP originated closer to the Sun's poles. (4/8)

We mapped the wind back to its source using the Parker spiral and a potential field source surface model. The Alfvén surface was modulated by structure in the corona. Smaller near current sheets and pseudo-streamers, larger near the dipole axis and expanding magnetic field. (3/8)

Using hourly measurements from the SWEAP and FIELDS suites, we mapped PSP to the Alfvén surface with a Parker spiral. Each encounter had a distribution of radii. The longitudinal-average reduced the bias from individual wind streams, the average grew from 10-16 solar radii. (2/8)

3D view of this plot:

Approaching perihelion (16th Sept.), the structure of the coronal magnetic field is similar to our prediction from July. The Sun's dipole field remains fully inclined with nested active regions influencing the heliospheric current sheet. Solar Orbiter will be mostly connnected to active latitudes.

Looking at this swirling feature in the solar atmosphere, revealed that the viscous heating along the swirl boundary was connected with the breakdown of coherent oscillations in the swirl. The MSF/W method provides a new pathway to investigate wave activity in the solar atmosphere. (4/4)

Using this approach, horizontal slices of a realistic solar atmosphere were decomposed into their most significant frequencies. A biproduct of this method, the highest frequency bin highlights dissipation/shocks. This is especially clear at swirl boundaries. (3/4)

The MSF/W method uses discrete Fourier transforms to move variables into frequency/wavenumber space and identify the most significant contribution to that variable at a given time/place. An example of a signal decomposed into the most and 2nd most significant wavenumbers. (2/4)