What is hidden within the variability of the elemental composition of the slow solar wind?

Abstract:

The solar wind is constantly emitted from the Sun. The properties of the solar wind reflect the conditions of the respective solar source
region modified by transport effects. Several solar wind parameters change with increasing distance to the Sun due to expansion,
wave-particle interactions and stream interactions. However, the charge state and heavy ion composition are thought to be sensitive tracers for the
respective solar source region of a specific solar wind stream and are less affected by transport. The slow solar wind is known to be highly
variable in its properties. Under these conditions, long-term averages are not necessarily representative for individual solar wind streams
and conclusions based on of long-term averages may be misleading. Therefore, we investigate whether the heavy ion composition of the solar wind is
better represented by the superposition of many different states in the slow solar wind or whether few and consistent subtypes of slow
solar wind can be identified by their elemental composition.

We complement this study by analyzing the elemental abundance of recurring solar wind streams. If the elemental composition of the
solar wind is indeed specific to individual solar wind streams, this can be utilized to identify the same solar wind stream with different instruments
by the elemental composition alone. Recurring solar wind streams observed at the solar activity minimum by the Solar Wind Ion
Spectrometer (SWICS) onboard the Advanced Composition Explorer (ACE) provide an opportunity to evaluate this assumption. We focus on heavy
ions (i.e. O, Fe, Mg, Si) and take advantage of the 12-minute time-resolution of ACE/SWICS. The same methods are applicable to the
Heavy Ion Sensor (HIS) onboard Solar Orbiter.