Policies to regulate severe surface ozone pollution in cities in India are challenging to develop, due to the complex dependence on precursor emissions of volatile organic compounds (VOCs) and nitrogen oxides (NOx), non-linear chemistry leading to ozone formation, and very limited spatial and temporal surface air quality monitoring. Ratios of space-based observations of formaldehyde (HCHO), an intermediate oxidation product of VOCs, and nitrogen dioxide (NO2) have been used to characterize the sensitivity of surface ozone production to precursor emissions of VOCs and NOx, but interpretation of these depends on the local oxidation regime. Here we develop an improved approach in which we discretize the data into background HCHO due to methane and other long-lived VOCs (regression intercept) and the local relationship (regression slope) between HCHO associated with reactive VOCs and NO2. We apply this to TROPOMI HCHO and NO2 tropospheric columns oversampled to higher spatial resolution than the native pixel resolution of the instrument over the ten most populous cities in India. We use GEOS-Chem to characterize the ozone production regimes and then apply this updated interpretation of the relationship between HCHO and NO2 to the oversampled TROPOMI columns to identify the most effective strategies for regulating ozone and whether these should vary seasonally and spatially.

The MHD with embedded PIC (MHD-EPIC) model makes it feasible to incorporate kinetic physics into a global simulation. Still, this requires a large enough box-shaped PIC domain to accommodate the movement and changes of the magnetic reconnection regions over time. This wastes computational resources on simulating regions with the expensive PIC model where MHD would be sufficient to describe the physics. We have developed a new MHD with Adaptively Embedded PIC (MHD-AEPIC) algorithm that couples the BATS-R-US MHD model with the new FLexible Exascale Kinetic Simulator (FLEKS) PIC code. In the new coupled model the PIC domains can move with the magnetic reconnection regions and adapt to them with an arbitrary shape. In this work, we will first introduce the algorithms for selecting the reconnection regions in the MHD model that need to be resolved with the kinetic PIC model. Then we will compare simulations obtained with MHD-EPIC using fixed PIC regions versus MHD-AEPIC employing adaptive PIC regions to verify that the new model generates reliable results. Finally, we will apply the MHD-AEPIC model to a global magnetic storm simulation and demonstrate the improved efficiency.

Recently, Anderson et al. (2012, https://doi.org/10.1126/science.1222978, 2017, https://doi. org/10.1073/pnas.1619318114) and Anderson and Clapp (2018, https://doi.org/10.1039/C7CP08331A) proposed that summertime convectively injected water vapor over North America could lead to stratospheric ozone depletion through halogenic catalytic reactions. Such ozone loss would reduce the ozone column and increase erythemal daily dose (EDD). Using 10 years of observations over the North American monsoon region from the Aura Ozone Monitoring Instrument, we find that the column ozone and EDD has a ~0.8–0.9 spatial correlation with lower stratospheric water vapor measured by the Aura Microwave Limb Sounder. We show that this correlation appears to be due to the elevation of the monsoonal tropopause and associated monsoonal convection. The increase in tropopause altitude reduces the ozone column and increases EDD. We see no apparent evidence of substantial heterogeneous chemical ozone loss in lower stratospheric ozone coincident with the stratospheric monsoonal water vapor enhancement.

Next year marks the 50th anniversary of the detection of Coronal Mass Ejections from space. The discovery and subsequent observations of thousands of events from a stream of coronagraph telescopes marked a paradigm shift of our view of the corona, from a physical system changing gradually over a solar cycle, to a system marked with explosive transient activity on timescales from seconds to days to months. Thanks to coronagraphs, and more recently EUV imagers, Space Weather forecasting and research have become strong research areas within the Heliophysics discipline. adding to that, the transients and even the more quiescent background wind can now be imaged directly in the inner heliosphere thanks to the advent of heliospheric imaging since the mid-2000s. The recent deployment of the Parker Solar Probe and Solar Orbiter missions ushers a new era of coronal/heliospheric imaging from widely varying vantage points along with future missions, such as PUNCH, and operational mission at the L1 and L5 point. It is, therefore, an appropriate time to take stock of the lessons learned from the decades of imaging of the solar wind, both quiescent and transient. In this talk, I review those lessons/learned and discuss where to go next.