Space weather driven changes in lower atmosphere phenomena

• Exploits a characteristic signature of solar variability over a short timescale to identify coupling to the lower atmosphere.
• Analyses solar–terrestrial coupling using a new phase-locked technique.
• Demonstrates common changes occurring in the heliosphere and the lower atmosphere.
• Shows coupling between solar changes, the global electric circuit and cloud properties in the lower troposphere.
• Identifies a local surface temperature response highly unusual during a highly unusual period of solar variability.

During a period of heliospheric disturbance in 2007–9 associated with a co-rotating interaction region (CIR), a characteristic periodic variation becomes apparent in neutron monitor data. This variation is phase-locked to periodic heliospheric current sheet crossings. Phase-locked electrical variations are also seen in the terrestrial lower atmosphere in the southern UK, including an increase in the vertical conduction current density of fair weather atmospheric electricity during increases in galactic cosmic ray-induced neutron monitor count rate at the surface and energetic proton count rates measured by geosynchronous spacecraft. At the same time as the conduction current increases, changes in the cloud microphysical properties lead to an increase in the detected height of the cloud base at Lerwick Observatory, Shetland, with associated changes in surface meteorological quantities. As electrification is expected at the base of layer clouds, which can influence droplet properties, these observations of phase-locked thermodynamic, cloud, atmospheric electricity and solar sector changes are not inconsistent with a heliospheric disturbance driving lower troposphere changes.